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Sample records for amorphous carbon films

  1. Nanostructural characterization of amorphous diamondlike carbon films

    Energy Technology Data Exchange (ETDEWEB)

    SIEGAL,MICHAEL P.; TALLANT,DAVID R.; MARTINEZ-MIRANDA,L.J.; BARBOUR,J. CHARLES; SIMPSON,REGINA L.; OVERMYER,DONALD L.

    2000-01-27

    Nanostructural characterization of amorphous diamondlike carbon (a-C) films grown on silicon using pulsed-laser deposition (PLD) is correlated to both growth energetic and film thickness. Raman spectroscopy and x-ray reflectivity probe both the topological nature of 3- and 4-fold coordinated carbon atom bonding and the topographical clustering of their distributions within a given film. In general, increasing the energetic of PLD growth results in films becoming more ``diamondlike'', i.e. increasing mass density and decreasing optical absorbance. However, these same properties decrease appreciably with thickness. The topology of carbon atom bonding is different for material near the substrate interface compared to material within the bulk portion of an a-C film. A simple model balancing the energy of residual stress and the free energies of resulting carbon topologies is proposed to provide an explanation of the evolution of topographical bonding clusters in a growing a-C film.

  2. Structural morphology of amorphous conducting carbon film

    Indian Academy of Sciences (India)

    P N Vishwakarma; V Prasad; S V Subramanyam; V Ganesan

    2005-10-01

    Amorphous conducting carbon films deposited over quartz substrates were analysed using X-ray diffraction and AFM technique. X-ray diffraction data reveal disorder and roughness in the plane of graphene sheet as compared to that of graphite. This roughness increases with decrease in preparation temperature. The AFM data shows surface roughness of carbon films depending on preparation temperatures. The surface roughness increases with decrease in preparation temperature. Also some nucleating islands were seen on the samples prepared at 900°C, which are not present on the films prepared at 700°C. Detailed analysis of these islands reveals distorted graphitic lattice arrangement. So we believe these islands to be nucleating graphitic. Power spectrum density (PSD) analysis of the carbon surface indicates a transition from the nonlinear growth mode to linear surface-diffusion dominated growth mode resulting in a relatively smoother surface as one moves from low preparation temperature to high preparation temperature. The amorphous carbon films deposited over a rough quartz substrate reveal nucleating diamond like structures. The density of these nucleating diamond like structures was found to be independent of substrate temperature (700–900°C).

  3. Buckling instability in amorphous carbon films

    Science.gov (United States)

    Zhu, X. D.; Narumi, K.; Naramoto, H.

    2007-06-01

    In this paper, we report the buckling instability in amorphous carbon films on mirror-polished sapphire (0001) wafers deposited by ion beam assisted deposition at various growth temperatures. For the films deposited at 150 °C, many interesting stress relief patterns are found, which include networks, blisters, sinusoidal patterns with π-shape, and highly ordered sinusoidal waves on a large scale. Starting at irregular buckling in the centre, the latter propagate towards the outer buckling region. The maximum length of these ordered patterns reaches 396 µm with a height of ~500 nm and a wavelength of ~8.2 µm. However, the length decreases dramatically to 70 µm as the deposition temperature is increased to 550 °C. The delamination of the film appears instead of sinusoidal waves with a further increase of the deposition temperature. This experimental observation is correlated with the theoretic work of Crosby (1999 Phys. Rev. E 59 R2542).

  4. ENHANCING ADHESION OF TETRAHEDRAL AMORPHOUS CARBON FILMS

    Institute of Scientific and Technical Information of China (English)

    Zhao Yuqing; Lin Yi; Wang Xiaoyan; Wang Yanwu; Wei Xinyu

    2005-01-01

    Objective The high energy ion bombardment technique is applied to enhancing the adhesion of the tetrahedral amorphous carbon (TAC) films deposited by the filtered cathode vacuum arc (FCVA). Methods The abrasion method, scratch method, heating and shaking method as well as boiling salt solution method is used to test the adhesion of the TAC films on various material substrates. Results The test results show that the adhesion is increased as the ion bombardment energy increases. However, if the bombardment energy were over the corresponding optimum value, the adhesion would be enhanced very slowly for the harder material substrates and drops quickly, for the softer ones. Conclusion The optimum values of the ion bombardment energy are larger for the harder materials than that for the softer ones.

  5. Coaxial carbon plasma gun deposition of amorphous carbon films

    Science.gov (United States)

    Sater, D. M.; Gulino, D. A.; Rutledge, S. K.

    1984-01-01

    A unique plasma gun employing coaxial carbon electrodes was used in an attempt to deposit thin films of amorphous diamond-like carbon. A number of different structural, compositional, and electrical characterization techniques were used to characterize these films. These included scanning electron microscopy, scanning transmission electron microscopy, X ray diffraction and absorption, spectrographic analysis, energy dispersive spectroscopy, and selected area electron diffraction. Optical absorption and electrical resistivity measurements were also performed. The films were determined to be primarily amorphous, with poor adhesion to fused silica substrates. Many inclusions of particulates were found to be present as well. Analysis of these particulates revealed the presence of trace impurities, such as Fe and Cu, which were also found in the graphite electrode material. The electrodes were the source of these impurities. No evidence of diamond-like crystallite structure was found in any of the film samples. Details of the apparatus, experimental procedure, and film characteristics are presented.

  6. Angular magnetoresistance in semiconducting undoped amorphous carbon thin films

    Energy Technology Data Exchange (ETDEWEB)

    Sagar, Rizwan Ur Rehman; Saleemi, Awais Siddique; Zhang, Xiaozhong, E-mail: xzzhang@tsinghua.edu.cn [Key Laboratory of Advanced Materials (MOE), School of Materials Science and Engineering, Tsinghua University, Beijing 100084, People' s Republic of China and Beijing National Center for Electron Microscopy, Beijing 100084 (China)

    2015-05-07

    Thin films of undoped amorphous carbon thin film were fabricated by using Chemical Vapor Deposition and their structure was investigated by using High Resolution Transmission Electron Microscopy and Raman Spectroscopy. Angular magnetoresistance (MR) has been observed for the first time in these undoped amorphous carbon thin films in temperature range of 2 ∼ 40 K. The maximum magnitude of angular MR was in the range of 9.5% ∼ 1.5% in 2 ∼ 40 K. The origin of this angular MR was also discussed.

  7. Raman spectra of amorphous carbon films deposited by SWP

    Science.gov (United States)

    Xu, Junqi; Liu, Weiguo; Hang, Lingxia; Su, Junhong; Fan, Huiqing

    2010-10-01

    Amorphous carbon film is one of the most important anti-reflection protective films coated on infrared optical components. In this paper, hydrogen-free amorphous carbon films were deposited by new type surface-wave-sustained plasma (SWP) source with a graphite target at various experiment parameters. The laser Raman spectroscopy at wavelength of 514 nm was used to investigate the structure and bonding of these carbon films. The results showed consanguineous correlations between the intensity ratio ID/IG and the experiment parameters such as microwave power, target voltage and gas pressure applied to the SWP source. Raman spectra proved the structure of these carbon films prepared by SWP technique is typical diamond-like carbon (DLC). The analysis on G peak position and intensity ratio ID/IG indicated that Raman shifts moves to low wavenumber and ID/IG decreases with the increasing of microwave power from 150 W to 330 W. These results means the formation of sp3 bond prefers higher microwave power. DLC films prepared at target voltage of -200 V have higher sp3 content than that of -350 V, moreover, an increase of gas pressure during experiments yields higher sp3 content at the microwave power below 270 W, whereas the change of sp3 content is slight with the various conditions when microwave power exceeds 270 W.

  8. Sputtering deposition and characterization of ultrathin amorphous carbon films

    Science.gov (United States)

    Lu, Wei

    1999-11-01

    This dissertation focuses on experimental investigations of ultrathin, ultrasmooth amorphous carbon (a-C) films deposited on Si(100) substrates by radio frequency (RF) sputtering and characterization of the nanomechanical and nanotribological properties and thermal stability of the films. Ultrathin a-C films of thickness 5--100 nm and typical root-mean-square roughness of 0.15--1 nm were deposited on ultrasmooth Si(100) substrates using pure argon as the sputtering gas. A low-pressure RF argon discharge model was used to analyze the plasma parameters in the film growth environment. These plasma parameters correlate the deposition conditions with the film growth processes. Atomic force microscopy (AFM) and surface force microscopy (SFM) were used to characterize the nanomechanical and nanotribological properties of the a-C films. X-ray photoelectron spectroscopy (XPS) was used to investigate the compositions and microstructures of the films. Sputter-etching measurements of the a-C films by energetic argon ion bombardment were used to study the surface binding energy of carbon atoms in a-C films deposited under different conditions. The dependence of film properties on deposition conditions was studied, and relations between nanomechanical and nanotribological properties were discussed in terms of a modified deformation index. The deformation and nanotribology mechanisms of the a-C films were compared with those of other films, such as TiC and Cr films (both 100 nm thick), and bulk Si(100). Reactive RF sputtering of nitrogenated amorphous carbon (a-CNx) films was investigated by introducing nitrogen into the a-C films during film growth by using an argon-nitrogen gas mixture as the sputtering gas. The alloying effect of nitrogen on the film growth and properties, such as hardness and surface energy, was studied and interpreted in terms of the changes in the plasma environment induced due to differences in the composition of the sputtering gas mixture. The thermal

  9. Infrared analysis of thin films amorphous, hydrogenated carbon on silicon

    CERN Document Server

    Jacob, W; Schwarz-Selinger, T

    2000-01-01

    The infrared analysis of thin films on a thick substrate is discussed using the example of plasma-deposited, amorphous, hydrogenated carbon layers (a-C:H) on silicon substrates. The framework for the optical analysis of thin films is presented. The main characteristic of thin film optics is the occurrence of interference effects due to the coherent superposition of light multiply reflected at the various internal and external interfaces of the optical system. These interference effects lead to a sinusoidal variation of the transmitted and reflected intensity. As a consequence, the Lambert-Beer law is not applicable for the determination of the absorption coefficient of thin films. Furthermore, observable changes of the transmission and reflection spectra occur in the vicinity of strong absorption bands due to the Kramers-Kronig relation. For a sound data evaluation these effects have to be included in the analysis. To be able to extract the full information contained in a measured optical thin film spectrum, ...

  10. Amorphous carbon buffer layers for separating free gallium nitride films

    Science.gov (United States)

    Altakhov, A. S.; Gorbunov, R. I.; Kasharina, L. A.; Latyshev, F. E.; Tarala, V. A.; Shreter, Yu. G.

    2016-11-01

    The possibility of using amorphous diamond-like carbon (DLC) films for self-separation of gallium nitride (GaN) layers grown by hydride vapor-phase epitaxy has been analyzed. DLC films have been synthesized by plasma-enhanced chemical vapor deposition under low pressure on sapphire (Al2O3) substrates with a (0001) crystallographic orientation. The samples have been studied by the methods of Raman scattering and X-ray diffraction analysis. It is shown that thin DLC films affect only slightly the processes of nucleation and growth of gallium nitride films. Notably, the strength of the "GaN film-Al2O3" substrate interface decreases, which facilitates separation of the GaN layers.

  11. Oxidation of fluorinated amorphous carbon (a-CF(x)) films.

    Science.gov (United States)

    Yun, Yang; Broitman, Esteban; Gellman, Andrew J

    2010-01-19

    Amorphous fluorinated carbon (a-CF(x)) films have a variety of potential technological applications. In most such applications these films are exposed to air and undergo partial surface oxidation. X-ray photoemission spectroscopy has been used to study the oxidation of fresh a-CF(x) films deposited by magnetron sputtering. The oxygen sticking coefficient measured by exposure to low pressures (<10(-3) Torr) of oxygen at room temperature is on the order of S approximately 10(-6), indicating that the surfaces of these films are relatively inert to oxidation when compared with most metals. The X-ray photoemission spectra indicate that the initial stages of oxygen exposure (<10(7) langmuirs) result in the preferential oxidation of the carbon atoms with zero or one fluorine atom, perhaps because these carbon atoms are more likely to be found in configurations with unsaturated double bonds and radicals than carbon atoms with two or three fluorine atoms. Exposure of the a-CF(x) film to atmospheric pressures of air (effective exposure of 10(12) langmuirs to O(2)) results in lower levels of oxygen uptake than the low pressure exposures (<10(7) langmuirs). It is suggested that this is the result of oxidative etching of the most reactive carbon atoms, leaving a relatively inert surface. Finally, low pressure exposures to air result in the adsorption of both nitrogen and oxygen onto the surface. Some of the nitrogen adsorbed on the surface at low pressures is in a reversibly adsorbed state in the sense that subsequent exposure to low pressures of O(2) results in the displacement of nitrogen by oxygen. Similarly, when an a-CF(x) film oxidized in pure O(2) is exposed to low pressures of air, some of the adsorbed oxygen is displaced by nitrogen. It is suggested that these forms of nitrogen and oxygen are bound to free radical sites in the film.

  12. Transport properties of low-dimensional amorphous carbon films

    Energy Technology Data Exchange (ETDEWEB)

    Bhattacharyya, Somnath [Nano-Electronics Centre, Advanced Technology Institute, School of Electronics and Physical Sciences, University of Surrey (United Kingdom)]. E-mail: s.bhattacharyya@surrey.ac.uk; Silva, S.R.P. [Nano-Electronics Centre, Advanced Technology Institute, School of Electronics and Physical Sciences, University of Surrey (United Kingdom)

    2005-06-22

    Research on amorphous carbon (a-C) to date has focused on the distinction between the sp{sup 2} and sp{sup 3} phases and understanding the properties on the basis of the sp{sup 2}-C bonded component. Recently, sufficient information on the sp{sup 2}-bonded clusters and nanoforms of carbon has helped to identify the importance of sp{sup 2}-C over sp{sup 3}-C, especially in transport properties and encouraged many groups to exploit this knowledge for device design. However, at present, few studies dedicated purely to understanding the transport properties and electronic structure of the family of a-C films as a whole is available. In this paper, we try to identify the key issues in using a-C as an unconventional semiconducting material and try to elaborate on how to overcome these hurdles in order to utilize this extremely versatile material for active device fabrication.

  13. Silicon and aluminum doping effects on the microstructure and properties of polymeric amorphous carbon films

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Xiaoqiang, E-mail: lxq_suse@sina.com [Material Corrosion and Protection Key Laboratory of Sichuan province, Sichuan University of Science and Engineering, Zigong 643000 (China); Hao, Junying, E-mail: jyhao@licp.cas.cn [State Key Laboratory of Solid Lubrication, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, Lanzhou 730000 (China); Xie, Yuntao [Material Corrosion and Protection Key Laboratory of Sichuan province, Sichuan University of Science and Engineering, Zigong 643000 (China)

    2016-08-30

    Highlights: • Evolution of nanostructure and properties of the polymeric amorphous carbon films were firstly studied. • Si doping enhanced polymerization of the hydrocarbon chains and Al doping resulted in increase in the ordered carbon clusters of polymeric amorphous carbon films. • Soft polymeric amorphous carbon films exhibited an unconventional frictional behaviors with a superior wear resistance. • The mechanical and vacuum tribological properties of the polymeric amorphous carbon films were significantly improved by Si and Al co-doping. - Abstract: Polymeric amorphous carbon films were prepared by radio frequency (R.F. 13.56 MHz) magnetron sputtering deposition. The microstructure evolution of the deposited polymeric films induced by silicon (Si) and aluminum(Al) doping were scrutinized through infrared spectroscopy, multi-wavelength Raman spectroscopy, scanning electron microscopy (SEM) and high resolution transmission electron microscopy (HRTEM). The comparative results show that Si doping can enhance polymerization and Al doping results in an increase in the ordered carbon clusters. Si and Al co-doping into polymeric films leads to the formation of an unusual dual nanostructure consisting of cross-linked polymer-like hydrocarbon chains and fullerene-like carbon clusters. The super-high elasticity and super-low friction coefficients (<0.002) under a high vacuum were obtained through Si and Al co-doping into the films. Unconventionally, the co-doped polymeric films exhibited a superior wear resistance even though they were very soft. The relationship between the microstructure and properties of the polymeric amorphous carbon films with different elements doping are also discussed in detail.

  14. Hardness and stress of amorphous carbon film deposited by glow discharge and ion beam assisting deposition

    CERN Document Server

    Marques, F C

    2000-01-01

    The hardness and stress of amorphous carbon films prepared by glow discharge and by ion beam assisting deposition are investigated. Relatively hard and almost stress free amorphous carbon films were deposited by the glow discharge technique. On the other hand, by using the ion beam assisting deposition, hard films were also obtained with a stress of the same order of those found in tetrahedral amorphous carbon films. A structural analysis indicates that all films are composed of a sp sup 2 -rich network. These results contradict the currently accepted concept that both stress and hardness are only related to the concentration of sp sup 3 sites. Furthermore, the same results also indicate that the sp sup 2 sites may also contribute to the hardness of the films.

  15. Nano-structural Modification of Amorphous Carbon Thin Films by Low-energy Electron Beam Irradiation

    Institute of Scientific and Technical Information of China (English)

    EijiIwamura; MasanoriYamaguchi

    2004-01-01

    A new approach using a low-energy electron beam radiation system was investigated to synthesize carbon hybrid structures in amorphous carbon thin films. Two types of amorphous carbon films, which were 15at% iron containing film and with column/inter-column structures, were deposited onto Si substrates by a sputtering technique and subsequently exposed to an electron shower of which the energy and dose rate were much smaller compared to an intense electron beam used in a transmission electron microscopy. As a result of the low-energy and low-dose electron irradiation process, graphitic structures formed in amorphous matrix at a relatively low temperature up to 450 K. Hybrid carbon thin films containing onion-like structures in an amorphous carbon matrix were synthesized by dynamic structural modification of iron containing amorphous carbon thin films. It was found that the graphitization progressed more in the electron irradiation than in annealing at 773K, and it was attributed to thermal and catalytic effects which are strongly related to grain growth of metal clusters. On the other hand, a reversal of TEM image contrast was observed in a-C films with column/inter-column structures. It is presumed that preferable graphitization occurred in the inter-column regions induced by electron irradiation.

  16. Nano-structural Modification of Amorphous Carbon Thin Films by Low-energy Electron Beam Irradiation

    Institute of Scientific and Technical Information of China (English)

    Eiji Iwamura; Masanori Yamaguchi

    2004-01-01

    A new approach using a low-energy electron beam radiation system was investigated to synthesize carbon hybrid structures in amorphous carbon thin films. Two types of amorphous carbon films, which were 15at% iron containing film and with column/inter-column structures, were deposited onto Si substrates by a sputtering technique and subsequently exposed to an electron shower of which the energy and dose rate were much smaller compared to an intense electron beam used in a transmission electron microscopy. As a result of the low-energy and low-dose electron irradiation process,graphitic structures formed in amorphous matrix at a relatively low temperature up to 450 K. Hybrid carbon thin films containing onion-like structures in an amorphous carbon matrix were synthesized by dynamic structural modification of iron containing amorphous carbon thin films. It was found that the graphitization progressed more in the electron irradiation than in annealing at 773K, and it was attributed to thermal and catalytic effects which are strongly related to grain growth of metal clusters. On the other hand, a reversal of TEM image contrast was observed in a-C films with column/inter-column structures. It is presumed that preferable graphitization occurred in the inter-column regions induced by electron irradiation.

  17. Irradiation of the amorphous carbon films by picosecond laser pulses

    Energy Technology Data Exchange (ETDEWEB)

    Marcinauskas, L., E-mail: liutauras.marcinauskas@ktu.lt [Kaunas University of Technology, Studentu 50, LT-51368 Kaunas (Lithuania); Grigonis, A. [Kaunas University of Technology, Studentu 50, LT-51368 Kaunas (Lithuania); Račiukaitis, G.; Gedvilas, M. [Center for Physical Sciences and Technology, Savanoriu Ave. 231, LT-02300 Vilnius (Lithuania); Vinciūnaitė, V. [Kaunas University of Technology, Studentu 50, LT-51368 Kaunas (Lithuania)

    2015-10-30

    The effect of a picosecond laser irradiation on structure modification of diamond-like carbon (DLC) and graphite-like carbon (GLC) films was analyzed in this work. The DLC films were irradiated by Nd:YVO{sub 4} laser operating at the 532 nm wavelength with the picosecond (10 ps) pulse duration at the fluence in the range of (0.08–0.76) J/cm{sup 2}. The GLC films were irradiated only at the fluence of 0.76 J/cm{sup 2}. The different pulse number (1, 10, and 100) was used for irradiation the films. The micro-Raman spectroscopy measurements indicated that the laser irradiation led to rearrangement of the sp{sup 3} C–C bonds to the sp{sup 2} C=C bonds in the DLC films. The formation of silicon carbide (SiC) was found in the irradiated spot after 10 and 100 pulses. Modifications in the structure of the DLC film took place even in the areas with low intensity of the Gaussian beam wings (heat affected areas). The increase in the oxygen concentration up to ten times was detected in the heat affected areas after 100 pulses. Opposite to that, the laser irradiation decreased the oxygen concentration and smoothened the surface microrelief of the GLC films. The bonding type remained unchanged in the GLC films even after irradiation with 100 pulses per spot. - Highlights: • The picosecond laser irradiation led to the rearrangement of sp{sup 3} C-C to the sp{sup 2} C = C bonds in the diamond-like carbon film. • The ps-laser irradiation of the DLC films stipulates appearance of the aromatic carbon structures. • The bonding type of the graphite-like carbon films remained unchanged even after ps laser irradiation with 100 pulses.

  18. Self-lubricated Array Film of Amorphous Carbon Nanorods on an Aluminum Substrate

    Institute of Scientific and Technical Information of China (English)

    JIANGChun-xi; TUJiang-ping; GUOShao-yi; FUMing-fu; ZHAOXin-bing

    2004-01-01

    A self-lubricated array film of amorphous carbon nanorods was prepared by chemical catalytic pyrolysis of acetylene on the anodic aluminum oxide membrane fabricated by two-step anodization of aluminum. The tribological properties of the array film of amorphous carbon nanorods in ambient air were investigated using a ball-on-disk tester at applied loads range from 245 mN to 1960 mN at a sliding velocity of 0.2 m/s. The self-lubricated array film exhibited a small value of the friction coefficient as well as good wear resistance. The friction coefficient of array film of amorphous carbon nanorods decreased gradually with increasing the applied load. The approach proposed demonstrated a new efficient route towards enhanced the friction and wear performances of aluminum.

  19. Low-energy electron irradiation induced top-surface nanocrystallization of amorphous carbon film

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Cheng [Institute of Nanosurface Science and Engineering (INSE), Shenzhen University, Shenzhen 518060 (China); Key Laboratory of Optoelectronic Devices and Systems of Ministry of Education and Guangdong Province, College of Optoelectronic Engineering, Shenzhen University, Shenzhen 518060 (China); Fan, Xue, E-mail: fanx@szu.edu.cn [Institute of Nanosurface Science and Engineering (INSE), Shenzhen University, Shenzhen 518060 (China); Diao, Dongfeng, E-mail: dfdiao@szu.edu.cn [Institute of Nanosurface Science and Engineering (INSE), Shenzhen University, Shenzhen 518060 (China)

    2016-10-30

    Graphical abstract: Low-energy electron irradiation was proposed to nanocrystallize the top-surface of the as-deposited amorphous carbon film, and sp{sup 2} nanocrystallites formed in the film top-surface within 4 nm thickness. Display Omitted - Abstract: We report a low-energy electron irradiation method to nanocrystallize the top-surface of amorphous carbon film in electron cyclotron resonance plasma system. The nanostructure evolution of the carbon film as a function of electron irradiation density and time was examined by transmission electron microscope (TEM) and Raman spectroscopy. The results showed that the electron irradiation gave rise to the formation of sp{sup 2} nanocrystallites in the film top-surface within 4 nm thickness. The formation of sp{sup 2} nanocrystallite was ascribed to the inelastic electron scattering in the top-surface of carbon film. The frictional property of low-energy electron irradiated film was measured by a pin-on-disk tribometer. The sp{sup 2} nanocrystallized top-surface induced a lower friction coefficient than that of the original pure amorphous film. This method enables a convenient nanocrystallization of amorphous surface.

  20. Facile fabrication of boron nitride nanosheets-amorphous carbon hybrid film for optoelectronic applications

    KAUST Repository

    Wan, Shanhong

    2015-01-01

    A novel boron nitride nanosheets (BNNSs)-amorphous carbon (a-C) hybrid film has been deposited successfully on silicon substrates by simultaneous electrochemical deposition, and showed a good integrity of this B-C-N composite film by the interfacial bonding. This synthesis can potentially provide the facile control of the B-C-N composite film for the potential optoelectronic devices. This journal is

  1. Characterization and Electrochemical Properties of Oxygenated Amorphous Carbon (a-C) Films

    OpenAIRE

    Palomäki, Tommi; Wester, Niklas; Johansson, Leena-Sisko; Laitinen, Mikko; Jiang, Hua; Arstila, Kai; Sajavaara, Timo; Han, Jeon G.; Koskinen, Jari; Laurila, Tomi

    2016-01-01

    Amorphous carbon (a-C) films with varying oxygen content were deposited by closed-field unbalanced magnetron sputtering with the aim to understand the effect of oxygen on the structural and physical properties of the films and subsequently correlate these changes with electrochemical properties. The a-C films were characterized by transmission electron microscopy, helium-ion microscopy, atomic force microscopy, Raman spectroscopy, X-ray photoelectron spectroscopy and time-of-flight elastic re...

  2. Carbon-Incorporated Amorphous Indium Zinc Oxide Thin-Film Transistors

    Science.gov (United States)

    Parthiban, S.; Park, K.; Kim, H.-J.; Yang, S.; Kwon, J.-Y.

    2014-11-01

    We propose the use of amorphous-carbon indium zinc oxide (a-CIZO) as a channel material for thin-film transistor (TFT) fabrication. This study chose a carbon dopant as a carrier suppressor and strong oxygen binder in amorphous-indium zinc oxide (a-IZO) channel material. a-CIZO thin films were deposited using radiofrequency (RF) sputtering and postannealed at 150°C. X-ray diffraction and transmission electron microscopy analysis revealed that the film remained amorphous even after postannealing. The a-CIZO TFT postannealed at 150°C exhibited saturation field-effect mobility of 16.5 cm2 V-1 s-1 and on-off current ratio of ˜4.3 × 107.

  3. Structural and mechanical properties of amorphous carbon films deposited by the dual plasma technique

    Institute of Scientific and Technical Information of China (English)

    Yaohui Wang; Xu Zhang; Xianying Wu; Huixing Zhang; Xiaoji Zhang

    2008-01-01

    Direct current metal filtered cathodic vacuum are (FCVA) and acetylene gas (C2H2) were wielded to synthesize Ti-containing amorphous carbon films on Si (100). The influence of substrate bias voltage and acetylene gas on the microstructure and mechanical properties of the films were investigated. The results show that the phase of TiC in the (111) preferential crystallo-graphic orientation exists in the film, and rite main existing pattern of carbon is sp2. With increasing the acetylene flow rate, the con-tents of Ti and TiC phase of the film gradually reduce; however, the thickness of the film increases. When the substrate bias voltage reaches -600 V, the internal stress of the film reaches 1.6 GPa. The micro-hardness and elastic modulus of the film can reach 33.9 and 237.6 GPa, respectively, and the friction coefficient of the film is 0.25.

  4. Effect of Substrate Bias on Microstructure and Properties of Tetrahedral Amorphous Carbon Films

    Institute of Scientific and Technical Information of China (English)

    Jiaqi ZHU; Jiecai HAN; Songhe MENG; Qiang LI; Manlin TAN

    2003-01-01

    The microstructure and properties of tetrahedral amorphous carbon (ta-C) films deposited by the filtered cathodic vacuum arc technology has been investigated by visible Raman spectroscopy, AFM and Nano-indentor. The Raman spectra have been fitted with a s

  5. Electron emission degradation of nano-structured sp2-bonded amorphous carbon films

    Institute of Scientific and Technical Information of China (English)

    Lu Zhan-Ling; Wang Chang-Qing; Jia Yu; Zhang Bing-Lin; Yao Ning

    2007-01-01

    The initial field electron emission degradation behaviour of original nano-structured sp2-bonded amorphous carbon films has been observed.which can be attributed to the increase of the work function of the film in the field emission process analysed using a Fowler-Nordheim plot.The possible re.on for the change of work function is suggested to be the desorption of hydrogen from the original hydrogen termination film surface due to field emission current-induced local heating.For the explanation of the emission degradation behaviour of the nano-structured sp2-bonded amorphous carbon film,a cluster model with a series of graphite(0001) basal surfaces has been presented,and the theoretical calculations have been performed to investigate work functions of graphite(0001) surfaces with different hydrogen atom and ion chemisorption sites by using first principles method based on density functional theory-local density approximation.

  6. Composition and Microstructure of Magnetron Sputtering Deposited Ti-containing Amorphous Carbon Films

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    Ti-containing carbon films were deposited by using magnetron sputtering deposition. The composition and microstructure of the carbon films were characterized in detail by combining the techniques of Rutherford backscattering spectrometry (RBS), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) and transmission electron microscopy (TEM). It is found that carbon films contain Ti 18 at pct; after Ti incorporation, the films consist of titanium carbide; C1s peak appears at 283.4 eV and it could be divided into 283.29 and 284.55 eV, representing sp2 and sp3, respectively, and sp2 is superior to sp3. This Ti-containing film with dominating sp2 bonds is nanocomposites with nanocrystalline TiC clusters embedded in an amorphous carbon matrix, which could be proved by XRD and TEM.

  7. Amorphous carbon film deposition on inner surface of tubes using atmospheric pressure pulsed filamentary plasma source

    CERN Document Server

    Pothiraja, Ramasamy; Awakowicz, Peter

    2011-01-01

    Uniform amorphous carbon film is deposited on the inner surface of quartz tube having the inner diameter of 6 mm and the outer diameter of 8 mm. A pulsed filamentary plasma source is used for the deposition. Long plasma filaments (~ 140 mm) as a positive discharge are generated inside the tube in argon with methane admixture. FTIR-ATR, XRD, SEM, LSM and XPS analyses give the conclusion that deposited film is amorphous composed of non-hydrogenated sp2 carbon and hydrogenated sp3 carbon. Plasma is characterized using optical emission spectroscopy, voltage-current measurement, microphotography and numerical simulation. On the basis of observed plasma parameters, the kinetics of the film deposition process is discussed.

  8. Photoluminescence of amorphous carbon films fabricated by layer-by-layer hydrogen plasma chemical annealing method

    Institute of Scientific and Technical Information of China (English)

    徐骏; 黄晓辉; 李伟; 王立; 陈坤基

    2002-01-01

    A method in which nanometre-thick film deposition was alternated with hydrogen plasma annealing (layer-by-layermethod) was applied to fabricate hydrogenated amorphous carbon films in a conventional plasma-enhanced chemicalvapour deposition system. It was found that the hydrogen plasma treatment could decrease the hydrogen concentrationin the films and change the sp2/sp3 ratio to some extent by chemical etching. Blue photoluminescence was observed atroom temperature, as a result of the reduction of sp2 clusters in the films.

  9. Platinum containing amorphous hydrogenated carbon (a-C:H/Pt) thin films as selective solar absorbers

    Energy Technology Data Exchange (ETDEWEB)

    Lan, Yung-Hsiang; Brahma, Sanjaya [Department of Materials Science and Engineering, National Cheng Kung University, Tainan 701, Taiwan (China); Tzeng, Y.H. [Department of Electrical Engineering, National Cheng Kung University, Tainan 701, Taiwan (China); Ting, Jyh-Ming, E-mail: jting@mail.ncku.edu.tw [Department of Materials Science and Engineering, National Cheng Kung University, Tainan 701, Taiwan (China); Research Center for Energy Technology and Strategy, National Cheng Kung University, Tainan 701, Taiwan (China)

    2014-10-15

    We have investigated a double-cermet structured thin film in which an a-C:H thin film was used as an anti-reflective (AR) layer and two platinum-containing amorphous hydrogenated carbon (a-C:H/Pt) thin films were used as the double cermet layers. A reactive co-sputter deposition method was used to prepare both the anti-reflective and cermet layers. Effects of the target power and heat treatment were studied. The obtained films were characterized using X-ray diffraction, scanning electron microscopy, high-resolution transmission electron microscopy. The optical absorptance and emittance of the as deposited and annealed films were determined using UV–vis-NIR spectroscopy. We show that the optical absorptance of the resulting double-cermet structured thin film is as high as 96% and remains to be 91% after heat treatment at 400 °C, indicating the thermal stability of the film.

  10. Electron field emission from 2-induced insulating to metallic behaviour of amorphous carbon (-C) films

    Indian Academy of Sciences (India)

    Pitamber Mahanandia; P N Viswakarma; Prasad Vishnu Bhotla; S V Subramanyam; Karuna Kar Nanda

    2010-06-01

    The influence of concentration and size of 2 cluster on the transport properties and electron field emissions of amorphous carbon films have been investigated. The observed insulating to metallic behaviour from reduced activation energy derived from transport measurement and threshold field for electron emission of -C films can be explained in terms of improvements in the connectivity between 2 clusters. The connectivity is resulted by the cluster concentration and size. The concentration and size of 2 content cluster is regulated by the coalescence of carbon globules into clusters, which evolves with deposition conditions.

  11. Amorphous hydrogenated carbon films treated by SF{sub 6} plasma

    Energy Technology Data Exchange (ETDEWEB)

    Marins, N M S; Mota, R P; Santos, D C R; Honda, R Y; Kayama, M E; Kostov, K G; Algatti, M A [Laboratorio de Plasma, Faculdade de Engenharia, UNESP, Av. Dr. Ariberto Pereira da Cunha-333, 12516-410, Guaratingueta, SP (Brazil); Cruz, N C; Rangel, E C, E-mail: nazir@feg.unesp.b [Laboratorio de Plasmas Tecnologicos, Unidade Diferenciada Sorocaba/Ipero, UNESP, Av. Tres de Marco-511, 18085-180, Sorocaba, SP (Brazil)

    2009-05-01

    This work was performed to verify the chemical structure, mechanical and hydrophilic properties of amorphous hydrogenated carbon films prepared by plasma enhanced chemical vapor deposition, using acetylene/argon mixture as monomer. Films were prepared in a cylindrical quartz reactor, fed by 13.56 MHz radiofrequency. The films were grown during 5 min, for power varying from 25 to 125 W at a fixed pressure of 9.5 Pa. After deposition, all samples were treated by SF{sub 6} plasma with the aim of changing their hydrophilic character. Film chemical structure investigated by Raman spectroscopy, revealed the increase of sp{sup 3} hybridized carbon bonds as the plasma power increases. Hardness measurements performed by the nanoindentation technique showed an improvement from 5 GPa to 14 GPa following the increase discharge power. The untreated films presented a hydrophilic character, which slightly diminished after SF{sub 6} plasma treatment.

  12. Amorphous Carbon Gold Nanocomposite Thin Films: Structural and Spectro-ellipsometric Analysis

    Energy Technology Data Exchange (ETDEWEB)

    Montiel-Gonzalez, Z., E-mail: zeuzmontiel@hotmail.com [Instituto de Investigaciones en Materiales, Universidad Nacional Autonoma de Mexico, Circuito exterior s/n, Ciudad Universitaria, Coyoacan 04510, Mexico D.F (Mexico); Rodil, S.E.; Muhl, S. [Instituto de Investigaciones en Materiales, Universidad Nacional Autonoma de Mexico, Circuito exterior s/n, Ciudad Universitaria, Coyoacan 04510, Mexico D.F (Mexico); Mendoza-Galvan, A. [Centro de Investigacion y de Estudios Avanzados del Instituto Politecnico Nacional, Unidad Queretaro, 76010 Queretaro, Queretaro (Mexico); Rodriguez-Fernandez, L. [Instituto de Fisica, Universidad Nacional Autonoma de Mexico, Circuito de la Investigacion Cientifica, Ciudad Universitaria, 04510, Mexico D.F (Mexico)

    2011-07-01

    Spectroscopic Ellipsometry was used to determine the optical and structural properties of amorphous carbon:gold nanocomposite thin films deposited by dc magnetron co-sputtering at different deposition power. The incorporation of gold as small particles distributed in the amorphous carbon matrix was confirmed by X-ray Diffraction, Rutherford Backscattering measurements and High Resolution Transmission Electron Microscopy. Based on these results, an optical model for the films was developed using the Maxwell-Garnett effective medium with the Drude-Lorentz model representing the optical response of gold and the Tauc-Lorentz model for the amorphous carbon. The gold volume fraction and particle size obtained from the fitting processes were comparable to those from the physical characterization. The analysis of the ellipsometric spectra for all the samples showed strong changes in the optical properties of the carbon films as a consequence of the gold incorporation. These changes were correlated to the structural modification observed by Raman Spectroscopy, which indicated a clustering of the sp{sup 2} phase with a subsequent decrease in the optical gap. Finally, measurements of Reflection and Transmission Spectroscopy were carried out and Transmission Electron Microscopy images were obtained in order to support the ellipsometric model results.

  13. Properties of amorphous carbon

    CERN Document Server

    2003-01-01

    Amorphous carbon has a wide range of properties that are primarily controlled by the different bond hydridisations possible in such materials. This allows for the growth of an extensive range of thin films that can be tailored for specific applications. Films can range from those with high transparency and are hard diamond-like, through to those which are opaque, soft and graphitic-like. Films with a high degree of sp3 bonding giving the diamond-like properties are used widely by industry for hard coatings. Application areas including field emission cathodes, MEMS, electronic devices, medical and optical coatings are now close to market. Experts in amorphous carbon have been drawn together to produce this comprehensive commentary on the current state and future prospects of this highly functional material.

  14. Electrical and Electrochemical Properties of Nitrogen-Containing Tetrahedral Amorphous Carbon (ta-C) Thin Films

    Science.gov (United States)

    Yang, Xingyi

    Tetrahedral amorphous carbon (ta-C) is a diamond-like carbon (DLC) material comprised of a mixture of sp2 (˜40%) and sp3-bonded (˜60%) carbon domains. The physicochemical structure and electrochemical properties depend strongly on the sp2/sp3 bonding ratio as well as the incorporation of impurities, such as hydrogen or nitrogen. The ability to grow ta-C films at lower temperatures (25-100 °C) on a wider variety of substrates is a potential advantage of these materials as compared with diamond films. In this project, the basic structural and electrochemical properties of nitrogen-incorporated ta-C thin films will be discussed. The major goal of this work was to determine if the ta-C:N films exhibit electrochemical properties more closely aligned with those of boron-doped diamond (sp 3 carbon) or glassy carbon (amorphous sp2 carbon). Much like diamond, ta-C:N thin-film electrodes are characterized by a low background voltammetric current, a wide working potential window, relatively rapid electron-transfer kinetics for aqueous redox systems, such as Fe(CN) 6-3/-4 and Ru(NH3)6+3/+2 , and weak adsorption of polar molecules from solution. For example, negligible adsorption of methylene blue was found on the ta-C:N films in contrast to glassy carbon; a surface on which this molecule strongly adsorbs. The film microstructure was studied with x-ray photoelectron microscopy (XPS), visible Raman spectroscopy and electron-energy loss spectroscopy (EELS); all of which revealed the sp2-bonded carbon content increased with increasing nitrogen. The electrical properties of ta-C:N films were studied by four-point probe resistance measurement and conductive-probe AFM (CP-AFM). The incorporation of nitrogen into ta-C films increased the electrical conductivity primarily by increasing the sp2-bonded carbon content. CP-AFM showed the distribution of the conductive sp2-carbon on the film surface was not uniform. These films have potential to be used in field emission area. The

  15. A Low-Stress, Elastic, and Improved Hardness Hydrogenated Amorphous Carbon Film

    Directory of Open Access Journals (Sweden)

    Qi Wang

    2015-01-01

    Full Text Available The evolution of hydrogenated amorphous carbon films with fullerene-like microstructure was investigated with a different proportion of hydrogen supply in deposition. The results showed at hydrogen flow rate of 50 sccm, the deposited films showed a lower compressive stress (lower 48.6%, higher elastic recovery (higher 19.6%, near elastic recovery rate 90%, and higher hardness (higher 7.4% compared with the films deposited without hydrogen introduction. Structural analysis showed that the films with relatively high sp2 content and low bonded hydrogen content possessed high hardness, elastic recovery rate, and low compressive stress. It was attributed to the curved graphite microstructure, which can form three-dimensional covalently bonded network.

  16. Inprovement of Field Emission Properties of PBS Thin Films by Amorphous Carbon Coating

    Directory of Open Access Journals (Sweden)

    S. Jana

    2011-01-01

    Full Text Available Lead sulfide (PbS nanocrystalline thin films were synthesized at room temperature via chemical bath deposition on both silicon and glass substrates and coated with amorphous carbon of different thickness by varying deposition time in plasma enhanced chemical vapor deposition technique. The as prepared samples were characterized by X-ray diffraction (XRD, field emission scanning electron microscope (FESEM and atomic force microscope (AFM. XRD study reveals that coating of amorphous carbon does not change the crystal structure of PbS. From FESEM images it is seen that the average size of PbS nanoparticle does not exceed 100 nm, though sometomes small cubic particles agglomerated to form bigger particles. The coating of amorphous carbon can be clearly visible by the FESEM as well as from AFM micrographs. Field emission study show a significant betterment for the carbon coated sample as compared to the pure PbS. The effect of inter-electrode distance on the field emission characteristics of best field emitting sample has been studied for three different inter-electrode distances.

  17. Superior tribological properties of an amorphous carbon film with a graphite-like structure

    Institute of Scientific and Technical Information of China (English)

    Wang Yong-Jun; Li Hong-Xuan; Ji Li; Liu Xiao-Hong; Wu Yan-Xia; Zhou Hui-Di; Chen Jian-Min

    2012-01-01

    Amorphous carbon films with high sp2 concentrations are deposited by unbalanced magnetron sputtering with a narrow range of substrate bias voltage. Field emission scanning electron microscopes (FESEMs),high resolution transmission electron microscopes (HRTEMs),atomic force microscopes (AFMs),the Raman spectrometers,nanoindentation,and tribometers are subsequently used to characterize the microstructures and the properties of the resulting films.It is found that the present films are dominated by the sp2 sites.However,the films demonstrate a moderate hardness together with a low internal stress.The high hardness of the deposited film originates from the crosslinking of the sp2 clusters by the sp3 sites.The presence of the graphite-like clusters in the film structure may be responsible for the low internal stress.What is more important is that the resulting films show excellent tribological properties with high load capacity and excellent wear resistance in humid atmospheres.The relationship between the microstructure determined by the deposition condition and the film characteristic is discussed in detail.

  18. Spectroscopic studies of low dielectric constant fluorinated amorphous carbon films for ULSI integrated circuits

    Energy Technology Data Exchange (ETDEWEB)

    Ma, Y.; Yang, H. [Sharp Microelectronics Technology, Camas, WA (United States); Guo, J.; Sathe, C.; Agui, A.; Nordgren, J. [Uppsala Univ. (Sweden). Physics Dept.

    1998-12-31

    Performance of future generations of integrated circuits will be limited by the RC delay caused by on-chip interconnections. Overcoming this limitation requires the deployment of new high conductivity metals such as copper and low dielectric constant intermetal dielectrics (IMD). Fluorinated amorphous carbon (a-CFx) is a promising candidate for replacing SiO{sub 2} as the IMD. In this paper the authors investigated the structure and electronic properties of a-CFx thin films using high-resolution x-ray absorption, emission, and photoelectron spectroscopy. The composition and local bonding information were obtained and correlated with deposition conditions. The data suggest that the structure of the a-CFx is mostly of carbon rings and CF{sub 2} chains cross-linked with C atoms. The effects of growth temperature on the structure and the thermal stability of the film are discussed.

  19. Formation of Ultrananocrystalline Diamond/Amorphous Carbon Composite Films in Vacuum Using Coaxial Arc Plasma Gun

    Science.gov (United States)

    Hanada, Kenji; Yoshida, Tomohiro; Nakagawa, You; Yoshitake, Tsuyoshi

    2010-12-01

    Ultrananocrystalline diamond (UNCD)/nonhydrogenated amorphous carbon (a-C) composite films were grown in vacuum using a coaxial arc plasma gun. From the X-ray diffraction measurement, the UNCD crystallite size was estimated to be 1.6 nm. This size is dramatically reduced from that (2.3 nm) of UNCD/hydrogenated amorphous carbon (a-C:H) composite films grown in a hydrogen atmosphere. The sp3/(sp3 + sp2) value, which was estimated from the X-ray photoemission spectrum, was also reduced to be 41%. A reason for it might be the reduction in the UNCD crystallite size. From the near-edge X-ray absorption fine-structure (NEXAFS) spectrum, it was found that the π*C=C and π*C≡C bonds are preferentially formed instead of the σ*C-H bonds in the UNCD/a-C:H films. Since the extremely small UNCD crystallites (1.6 nm) correspond to the nuclei of diamond, we consider that UNCD crystallite formation should be due predominantly to nucleation. The supersaturated condition required for nucleation is expected to be realized in the deposition using the coaxial arc plasma gun.

  20. Optical properties of plasma deposited amorphous carbon nitride films on polymer substrates

    Energy Technology Data Exchange (ETDEWEB)

    Mohamed, S.H., E-mail: abo_95@yahoo.co [Physics Department, Faculty of Science, Sohag University, 82524 Sohag (Egypt); El-Hossary, F.M. [Physics Department, Faculty of Science, Sohag University, 82524 Sohag (Egypt); Gamal, G.A.; Kahlid, M.M. [Physics Department, Faculty of Science, South Valley University, 83523 Qena (Egypt)

    2010-01-01

    Amorphous carbon nitride thin films were deposited on polymer substrates using radio frequency (rf) plasma in a mixture of nitrogen (N{sub 2}) and acetylene (C{sub 2}H{sub 2}) gasses. The samples were prepared at different rf plasma power (350, 400, 450, 500, and 550 W), at constant plasma exposure time of 10 min, and constant N{sub 2}/C{sub 2}H{sub 2} ratio of 50%. The crystal structure and surface morphology of the prepared samples were examined using X-ray diffraction and atomic force microscopy analysis, respectively. The absence of the carbon nitride diffraction peaks confirms the amorphous nature of these films. The root mean square roughness of the films increased from 3.77 to 25.22 nm as the power increased from 350 to 550 W. The thickness and the deposition rate were found to increase with increasing plasma power. Over the whole studied wavelength range, from 200 to 2500 nm, the transmittance decreased with increasing plasma power. A shift in the onset of absorption towards higher wavelengths with increasing plasma power, indicating a decrease in the optical band gap, has been observed. The refractive index values were found to decrease while the extinction coefficient increased with increasing plasma power.

  1. Controlled fluoridation of amorphous carbon films deposited at reactive plasma conditions

    Directory of Open Access Journals (Sweden)

    Yoffe Alexander

    2015-09-01

    Full Text Available A study of the correlations between plasma parameters, gas ratios, and deposited amorphous carbon film properties is presented. The injection of a C4F8/Ar/N2 mixture of gases was successfully used in an inductively coupled plasma system for the preparation of amorphous carbon films with different fluoride doping at room-temperature, using silicon as a substrate. This coating was formed at low-pressure and low-energy using an inductively coupled plasma process. A strong dependence between the ratios of gases during deposition and the composition of the substrate compounds was shown. The values of ratios between Ar (or Ar+N2 and C4F8 - 1:1 and between N2 and Ar - 1:2 in the N2/Ar/C4F8 mixture were found as the best for low fluoridated coatings. In addition, an example of improving the etch-passivation in the Bosch procedure was described. Scanning electron microscopy with energy dispersive spectroscopy options, X-ray diffraction, and X-ray reflectivity were used for quantitative analysis of the deposited films.

  2. Amorphous Hydrogenated Carbon-Nitrogen Alloy Thin Films for Solar Cell Application

    Institute of Scientific and Technical Information of China (English)

    ZHOU Zhi-Bin; DING Zheng-Ming; PANG Qian-Jun; CUI Rong-Qiang

    2001-01-01

    Amorphous hydrogenated carbon-nitrogen alloy (a-CNx :H) thin films have been deposited on silicon substratesby improved dc magnetron sputtering from a graphite target in nitrogen and hydrogen gas discharging. Thefilms are investigated by using Raman spectroscopy, x-ray photoelectron spectroscopy, spectral ellipsometer and electron spin resonance techniques. The optimized process condition for solar cell application is discussed. Thephotovoltaic property of a-CNx:H/silicon heterojunctions can be improved by the adjustment of the pressureratio of hydrogen to nitrogen and unbalanced magnetic field intensity. Open-circuit voltage and short-circuitcurrent reach 300mV and 5.52 Ma/cm2, respectively.

  3. Dependence of Structure and Haemocompatibility of Amorphous Carbon Films on Substrate Bias Voltage

    Institute of Scientific and Technical Information of China (English)

    GUO Yang-Ming; MO Dang; LI Zhe-Yi; LIU Yi; HE Zhen-Hui; CHEN Di-Hu

    2004-01-01

    @@ Tetrahedral amorphous hydrogenated carbon (ta-C:H) films on Si(100) substrates were prepared by using a magnetic-field-filter plasma stream deposition system. Samples with different ratios of spa-bond to sp2-bond were obtained by changing the bias voltage applied to the substrates. The ellipsometric spectra of various carbon films in the photon energy range of 1.9-5.4eV were measured. The refractive index n and the relative sp3 C ratio of these films were obtained by simulating their ellipsometric spectra using the Forouhi-Bloomer model and by using the Bruggeman effective medium approximation, respectively. The haemocompatibility of these ta-C:H films was analysed by observation of platelet adhesion and measurement of kinetic clotting time. The results show that the sp3 C fraction is dependent on the substrate bias voltage, and the haemocompatibility is dependent on the ratio of sp3-bond to sp2-bond. A good haemocompatibility material of ta-C:H films with a suitable sp3 C fraction can be prepared by changing the substrate bias voltage.

  4. Structural and Electrical Properties of Amorphous Hydrogen Carbon-Nitrogen Films

    Institute of Scientific and Technical Information of China (English)

    SUO Da-Cheng; LIU Yi-Chun; LIU Yan; QI Xiu-Ying; ZHONG Dian-Qiang

    2004-01-01

    @@ Amorphous hydrogenated carbon-nitrogen (a-C:H:(N)) films with different nitrogen contents have been deposited by using rf-sputtering of a high purity graphite target in an Ar-H2-N2 atmosphere. Transmittance and reflectance spectra are used to characterize the Tauc gap and absorption coefficients in the wavelength range 0.185-3.2μm.The temperature dependence of conductivity demonstrates a hopping mechanism of the Fermi level in the temperature range of 77-300K. The density of state at the Fermi level is derived from the direct current conductivity.The photoluminescence properties of a-C:H:N films were investigated. The photoluminescence peak has a blue shift with increasing excitation energy. These results are discussed on the basis of a model in which the different sp2 clusters dispersed in sp3 matrices.

  5. Characterization of amorphous hydrogenated carbon films deposited by MFPUMST at different ratios of mixed gases

    Indian Academy of Sciences (India)

    Haiyang Dai; Changyong Zhan; Hui Jiang; Ningkang Huang

    2012-12-01

    Amorphous hydrogenated carbon films (-C:H) on -type (100) silicon wafers were prepared with a middle frequency pulsed unbalanced magnetron sputtering technique (MFPUMST) at different ratios of methane–argon gases. The band characteristics, mechanical properties as well as refractive index were measured by Raman spectra, X-ray photoelectron spectroscopy (XPS), nano-indentation tests and spectroscopic ellipsometry. It is found that the 3 fraction increases with increasing Ar concentration in the range of 17–50%, and then decreases when Ar concentration exceeds 50%. The nano-indentation tests reveal that nano-hardness and elastic modulus of the films increase with increasing Ar concentration in the range of 17–50%, while decreases with increasing Ar concentration from 50% to 86%. The variations in the nano-hardness and the elastic modulus could be interpreted due to different 3 fractions in the prepared -C:H films. The variation of refractive index with wavelength have the same tendency for the -C:H films prepared at different Ar concentrations, they decrease with increasing wavelength from 600 to 1700 nm. For certain wavelengths within 600–1700 nm, refractive index has the highest value at the Ar concentration of 50%, and it is smaller at the Ar concentration of 86% than at 17%. The results given above indicate that ratio of mixed gases has a strong influence on bonding configuration and properties of -C:H films during deposition. The related mechanism is discussed in this paper.

  6. The multilayered structure of ultrathin amorphous carbon films synthesized by filtered cathodic vacuum arc deposition

    KAUST Repository

    Wang, Na

    2013-08-01

    The structure of ultrathin amorphous carbon (a-C) films synthesized by filtered cathodic vacuum arc (FCVA) deposition was investigated by high-resolution transmission electron microscopy, electron energy loss spectroscopy, and x-ray photoelectron spectroscopy. Results of the plasmon excitation energy shift and through-thickness elemental concentration show a multilayered a-C film structure comprising an interface layer consisting of C, Si, and, possibly, SiC, a buffer layer with continuously increasing sp 3 fraction, a relatively thicker layer (bulk film) of constant sp 3 content, and an ultrathin surface layer rich in sp 2 hybridization. A detailed study of the C K-edge spectrum indicates that the buffer layer between the interface layer and the bulk film is due to the partial backscattering of C+ ions interacting with the heavy atoms of the silicon substrate. The results of this study provide insight into the minimum thickness of a-C films deposited by FCVA under optimum substrate bias conditions. Copyright © 2013 Materials Research Society.

  7. Application of nitrogen-doped ultrananocrystalline diamond/hydrogenated amorphous carbon composite films for ultraviolet detection

    Science.gov (United States)

    Zkria, Abdelrahman; Gima, Hiroki; Yoshitake, Tsuyoshi

    2017-03-01

    Nitrogen-doped ultrananocrystalline diamond/hydrogenated amorphous carbon (UNCD/a-C:H) films were grown by coaxial arc plasma deposition in the ambient of nitrogen and hydrogen mixed gases. Synthesized films were structurally investigated by X-ray photoemission and near-edge X-ray absorption fine structure spectroscopies. A heterojunction with p-type Si substrate was fabricated to study the ultraviolet photodetection properties of the film. Capacitance-voltage measurements assure the expansion of a depletion region into the film side. Current-voltage curves in the dark showed a good rectifying behaviour in the bias voltages range between ±5 V. Under 254 nm monochromatic light, the heterojunction shows a capability of deep ultraviolet light detection, which can be attribute to the existence of UNCD grains. As the diode was cooled from 300 K down to 150 K, the detectivity has a notable enhancement from 1.94 × 105 cm Hz1/2 W-1 at 300 K to 5.11 × 1010 cm Hz1/2 W-1 at 150 K, which is mainly due to a remarkable reduction in the leakage current at low temperatures. It was experimentally demonstrated that nitrogen-doped UNCD/a-C:H film works as ultraviolet-range photovoltaic material.

  8. A study of the chemical, mechanical, and surface properties of thin films of hydrogenated amorphous carbon

    Energy Technology Data Exchange (ETDEWEB)

    Vandentop, G.J.

    1990-07-01

    Amorphous hydrogenated carbon (a-C:H) films were studied with the objective of elucidating the nucleation and growth mechanisms, and the origin of their unique physical properties. The films were deposited onto Si(100) substrates both on the powered (negatively self-biased) and on the grounded electrodes from methane in an rf plasma (13.56 MHz) at 65 mTorr and 300 to 370 K. The films produced at the powered electrode exhibited superior mechanical properties, such as high hardness. A mass spectrometer was used to identify neutral species and positive ions incident on the electrodes from the plasma, and also to measure ion energies. The effect of varying ion energy flux on the properties of a-C:H films was investigated using a novel pulsed biasing technique. It was demonstrated that ions were not the dominant deposition species as the total ion flux measured was insufficient to account for the observed deposition rate. The interface between thin films of a-C:H and silicon substrates was investigated using angle resolved x-ray photoelectron spectroscopy. A silicon carbide layer was detected at the interface of a hard a-C:H film formed at the powered electrode. At the grounded electrode, where the kinetic energy is low, no interfacial carbide layer was observed. Scanning tunneling microscopy and high energy electron energy loss spectroscopy was used to investigate the initial stages of growth of a-C:H films. On graphite substrates, films formed at the powered electrode were observed to nucleate in clusters approximately 50 {Angstrom} in diameter, while at the grounded electrode no cluster formation was observed. 58 figs.

  9. Friction properties of amorphous carbon ultrathin films deposited by filtered cathodic vacuum arc and radio-frequency sputtering

    Energy Technology Data Exchange (ETDEWEB)

    Matlak, J.; Komvopoulos, K., E-mail: kyriakos@me.berkeley.edu

    2015-03-31

    The friction properties of ultrathin films of amorphous carbon (a-C) deposited on Si(100) substrates by filtered cathodic vacuum arc and radio-frequency sputtering were investigated by surface force microscopy. Deposition parameters yielding a-C films with high sp{sup 3} content were used to deposit films of thickness between 5 and 35 nm. The coefficient of friction of both types of a-C films was measured with a 1-μm-radius conical diamond tip and normal loads in the range of 20–640 μN. The results show a strong dependence of the friction properties on the surface roughness, thickness, and structure of the a-C films, which are influenced by the intricacies of the deposition method. The dependence of the coefficient of friction on normal load and the dominance of adhesion and plowing friction mechanisms are interpreted in terms of the through-thickness variation of carbon atom hybridization of the a-C films. - Highlights: • Comparison of nanoscale friction properties of ultrathin amorphous carbon films. • Friction dependence on film roughness, thickness, and structure (hybridization). • Effect of through-thickness changes in carbon atom hybridization on film friction. • Explanation of film friction trends in terms of competing friction mechanisms.

  10. Electronic structure and conductivity of nanocomposite metal (Au,Ag,Cu,Mo)-containing amorphous carbon films

    Energy Technology Data Exchange (ETDEWEB)

    Endrino, Jose L.; Horwat, David; Gago, Raul; Andersson, Joakim; Liu, Y.S.; Guo, Jinghua; Anders, Andre

    2008-05-14

    In this work, we study the influence of the incorporation of different metals (Me = Au, Ag, Cu, Mo) on the electronic structure of amorphous carbon (a-C:Me) films. The films were produced at room temperature using a novel pulsed dual-cathode arc deposition technique. Compositional analysis was performed with secondary neutral mass spectroscopy whereas X-ray diffraction was used to identify the formation of metal nanoclusters in the carbon matrix. The metal content incorporated in the nanocomposite films induces a drastic increase in the conductivity, in parallel with a decrease in the band gap corrected from Urbach energy. The electronic structure as a function of the Me content has been monitored by x-ray absorption near edge structure (XANES) at the C K-edge. XANES showed that the C host matrix has a dominant graphitic character and that it is not affected significantly by the incorporation of metal impurities, except for the case of Mo, where the modifications in the lineshape spectra indicated the formation of a carbide phase. Subtle modifications of the spectral lineshape are discussed in terms of nanocomposite formation.

  11. Strength and Fracture Resistance of Amorphous Diamond-Like Carbon Films for MEMS

    Directory of Open Access Journals (Sweden)

    K. N. Jonnalagadda

    2009-01-01

    Full Text Available The mechanical strength and mixed mode I/II fracture toughness of hydrogen-free tetrahedral amorphous diamond-like carbon (ta-C films, grown by pulsed laser deposition, are discussed in connection to material flaws and its microstructure. The failure properties of ta-C were obtained from films with thicknesses 0.5–3 μm and specimen widths 10–20 μm. The smallest test samples with 10 μm gage section averaged a strength of 7.3 ± 1.2 GPa, while the strength of 20-μm specimens with thicknesses 0.5–3 μm varied between 2.2–5.7 GPa. The scaling of the mechanical strength with specimen thickness and dimensions was owed to deposition-induced surface flaws, and, only in the smallest specimens, RIE patterning generated specimen sidewall flaws. The mode I fracture toughness of ta-C films is KIc=4.4±0.4 MPam, while the results from mixed mode I/II fracture experiments with cracks arbitrarily oriented in the plane of the film compared very well with theoretical predictions.

  12. Hydrogen pumping in amorphous deutered carbon films irradiated by swift heavy ions

    Science.gov (United States)

    Pawlak, F.; Balanzat, E.; Dufour, Ch.; Laurent, A.; Paumier, E.; Perriere, J.; Stoquert, J. P.; Toulemonde, M.

    1997-02-01

    Deutered amorphous carbon films have been irradiated at GANIL using 5 to 10 MeV/u sulfur beam with an electronic stopping power from 1 to 1.4 keV/nm. Such films have been deposited on silicon substrates by decomposition of CD 4 gas containing 10% of CH 4 in a dc multipolar plasma. After irradiation, they were analyzed firstly using absorption infrared spectroscopy to determine the number of CD and CH bonds. Secondly, deuterium, hydroge and carbon areal density were determined by ERDA and RBS. The results analysis shows a decrease of the atomic ratio ( {D}/{C}) as well as CD bonds down to a minimum value versus the fluence without a threshold fluence and in the same time an increase of the atomic ratio ( {H}/{C}) as well as CH bonds to a maximum value. So we may conclude that the hydrogen pumped after the irradiation is stabilized on broken (or unpaired) bonds.

  13. Amorphous iron (II) carbonate

    DEFF Research Database (Denmark)

    Sel, Ozlem; Radha, A.V.; Dideriksen, Knud;

    2012-01-01

    exothermic than that of amorphous calcium carbonate (ACC). This suggests that enthalpy of crystallization in carbonate systems is ionic-size controlled, which may have significant implications in a wide variety of conditions, including geological sequestration of anthropogenic carbon dioxide.......Abstract The synthesis, characterization and crystallization energetics of amorphous iron (II) carbonate (AFC) are reported. AFC may form as a precursor for siderite (FeCO3). The enthalpy of crystallization (DHcrys) of AFC is similar to that of amorphous magnesium carbonate (AMC) and more...

  14. The effect of substrate bias on titanium carbide/amorphous carbon nanocomposite films deposited by filtered cathodic vacuum arc

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Xu, E-mail: zhangxu@bnu.edu.cn [Key Laboratory of Beam Technology and Material Modification of Ministry of Education, College of Nuclear Science and Technology, Beijing Normal University (China); Liang, Hong [Key Laboratory of Beam Technology and Material Modification of Ministry of Education, College of Nuclear Science and Technology, Beijing Normal University (China); Wu, Zhenglong [Analytical and Testing Center, Beijing Normal University (China); Wu, Xiangying; Zhang, Huixing [Key Laboratory of Beam Technology and Material Modification of Ministry of Education, College of Nuclear Science and Technology, Beijing Normal University (China)

    2013-07-15

    The titanium carbide/amorphous carbon nanocomposite films have been deposited on silicon substrate by filtered cathodic vacuum arc (FCVA) technology, the effects of substrate bias on composition, structures and mechanical properties of the films are studied by scanning electron spectroscopy, X-ray diffraction and X-ray photoelectron spectroscopy and nano-indentation. The results show that the Ti content, deposition rate and hardness at first increase and then decrease with increasing the substrate bias. Maximum hardness of the titanium carbide/amorphous carbon nanocomposite film is 51 Gpa prepared at −400 V. The hardness enhancement may be attributed to the compressive stress and the fraction of crystalline TiC phase due to ion bombardment.

  15. Surface Functionalization of Plasma Treated Ultrananocrystalline Diamond/Amorphous Carbon Composite Films

    Science.gov (United States)

    Koch, Hermann; Popov, Cyril; Kulisch, Wilhelm; Spassov, G.; Reithmaier, Johann Peter

    Diamond possesses a number of outstanding properties which make it a perspective material as platform for preparation of biosensors. The diamond surface needs to be activated before the chemical attachment of crosslinkers with which biomolecules can interact. In the current work we have investigated the modification of ultrananocrystalline diamond/amorphous carbon (UNCD/a-C) films by oxygen and ammonia plasmas. Afterwards the layers were functionalized in a further step to obtain thiol-active maleimide groups on the surface. We studied the possibility for direct binding of maleimide to terminal OH-groups on the UNCD surface and for silanization with 3-aminopropyltriethoxysilane (APTES) to obtain NH2-groups for the following attachment of sulfosuccinimidyl 4-(N-maleimidomethyl)-cyclohexane-1-carboxylate (SSMCC). The thiol-bearing fluorescein-related dye 5-((2-(and-3)-S-(acetylmercapto) succinoyl) amino) fluorescein (SAMSA) was immobilized as an model biomolecule to evaluate the achieved thiol-activity by fluorescence microscopy. The results of the above mentioned surface modification and functionalization steps were investigated by Auger electron spectroscopy (AES) and contact angle measurements.

  16. Ab Initio Investigation on Cu/Cr Codoped Amorphous Carbon Nanocomposite Films with Giant Residual Stress Reduction.

    Science.gov (United States)

    Li, Xiaowei; Guo, Peng; Sun, Lili; Wang, Aiying; Ke, Peiling

    2015-12-23

    Amorphous carbon films (a-C) codoped by two metal elements exhibit the desirable combination of tribological and mechanical properties for widely potential applications, but are also prone to catastrophic failure due to the inevitable residual compressive stress. Thus far, the residual stress reduction mechanism remains unclear due to the insufficient understanding of the structure from the atomic and electronic scale. In this paper, using ab initio calculations, we first designed a novel Cu/Cr codoped a-C film and demonstrated that compared with pure and Cu/Cr monodoped cases, the residual stress in Cu/Cr codoped a-C films could be reduced by 93.6% remarkably. Atomic bond structure analysis revealed that the addition of Cu and Cr impurities in amorphous carbon structure resulted in the critical and significant relaxation of distorted C-C bond lengths. On the other hand, electronic structure calculation indicated a weak bonding interaction between the Cr and C atoms, while the antibonding interaction was observed for the Cu-C bonds, which would play a pivot site for the release of strain energy. Those interactions combined with the structural evolution could account for the drastic residual stress reduction caused by Cu/Cr codoping. Our results provide the theoretical guidance and desirable strategy to design and fabricate a new nanocomposite a-C films with combined properties for renewed applications.

  17. Swift heavy ion irradiation of metal containing tetrahedral amorphous carbon films

    Energy Technology Data Exchange (ETDEWEB)

    Karaseov, P.A., E-mail: platon.karaseov@spbstu.ru [Peter the Great St. Petersburg Polytechnic University, St. Petersburg (Russian Federation); Protopopova, V.S. [Aalto University, Espoo (Finland); Karabeshkin, K.V.; Shubina, E.N.; Mishin, M.V. [Peter the Great St. Petersburg Polytechnic University, St. Petersburg (Russian Federation); Koskinen, J. [Aalto University, Espoo (Finland); Mohapatra, S. [Guru Gobind Singh Indraprastha University, New Delhi (India); Tripathi, A. [Inter University Accelerator Center, New Delhi (India); Avasthi, D.K. [Amity University, Noida 201313, Uttar Pradesh (India); Titov, A.I. [Peter the Great St. Petersburg Polytechnic University, St. Petersburg (Russian Federation)

    2016-07-15

    Highlights: • ta-C films with Ni and Cu doping were grown using dual cathode filtered vacuum arc deposition. • Conductive channels were found in the films by C-AFM after irradiation with 100 MeV Ag ions. • SEM contrast found after irradiation strongly depends on kind of metal impurity in the film. • Different chemical effect of Ni and Cu on transformation of carbon matrix under irradiation was revealed. - Abstract: Thin carbon films were grown at room temperature on (0 0 1) n-Si substrate using dual cathode filtered vacuum arc deposition system. Graphite was used as a source of carbon atoms and separate metallic electrode was simultaneously utilized to introduce Ni or Cu atoms. Films were irradiated by 100 MeV Ag{sup 7+} ions to fluences in the range 1 × 10{sup 10}–3 × 10{sup 11} cm{sup −2}. Rutherford backscattering spectroscopy, Raman scattering, scanning electron microscopy and atomic force microscopy in conductive mode were used to investigate film properties and structure change under irradiation. Some conductive channels having metallic conductivity type were found in the films. Number of such channels is less than number of impinged ions. Presence of Ni and Cu atoms increases conductivity of those conductive channels. Fluence dependence of all properties studied suggests different mechanisms of swift heavy ion irradiation-induced transformation of carbon matrix due to different chemical effect of nickel and copper atoms.

  18. Swift heavy ion irradiation of metal containing tetrahedral amorphous carbon films

    Science.gov (United States)

    Karaseov, P. A.; Protopopova, V. S.; Karabeshkin, K. V.; Shubina, E. N.; Mishin, M. V.; Koskinen, J.; Mohapatra, S.; Tripathi, A.; Avasthi, D. K.; Titov, A. I.

    2016-07-01

    Thin carbon films were grown at room temperature on (0 0 1) n-Si substrate using dual cathode filtered vacuum arc deposition system. Graphite was used as a source of carbon atoms and separate metallic electrode was simultaneously utilized to introduce Ni or Cu atoms. Films were irradiated by 100 MeV Ag7+ ions to fluences in the range 1 × 1010-3 × 1011 cm-2. Rutherford backscattering spectroscopy, Raman scattering, scanning electron microscopy and atomic force microscopy in conductive mode were used to investigate film properties and structure change under irradiation. Some conductive channels having metallic conductivity type were found in the films. Number of such channels is less than number of impinged ions. Presence of Ni and Cu atoms increases conductivity of those conductive channels. Fluence dependence of all properties studied suggests different mechanisms of swift heavy ion irradiation-induced transformation of carbon matrix due to different chemical effect of nickel and copper atoms.

  19. Removal of a hydrogenated amorphous carbon film from the tip of a micropipette electrode using direct current corona discharge.

    Science.gov (United States)

    Kakuta, Naoto; Okuyama, Naoki; Yamada, Yukio

    2010-02-01

    Micropipette electrodes are fabricated by coating glass micropipettes first with metal and then with hydrogenated amorphous carbon (a-C:H) as an electrical insulator. Furthermore, at the tip of the micropipette electrode, the deposited a-C:H film needs to be removed to expose the metal-coated surface and hollow for the purposes of electrical measurement and injection. This paper describes a convenient and reliable method for removing the a-C:H film using direct current corona discharge in atmospheric air. The initial film removal occurred at an applied voltage of 1.5-2.0 kV, accompanied by an abrupt increase in the discharge current. The discharge current then became stable at a microampere level in the glow corona mode, and the removed area gradually extended.

  20. Structural and Physical Characteristics of Ultrananocrystalline Diamond/Hydrogenated Amorphous Carbon Composite Films Deposited Using a Coaxial Arc Plasma Gun

    Science.gov (United States)

    Yoshitake, Tsuyoshi; Nakagawa, You; Nagano, Akira; Ohtani, Ryota; Setoyama, Hiroyuki; Kobayashi, Eiichi; Sumitani, Kazushi; Agawa, Yoshiaki; Nagayama, Kunihito

    2010-01-01

    Ultrananocrystalline diamond (UNCD)/hydrogenated amorphous carbon (a-C:H) films were formed without initial nucleation using a coaxial arc plasma gun. The UNCD crystallite diameters estimated from the X-ray diffraction peaks were approximately 2 nm. The Fourier transform infrared absorption spectrum exhibited an intense sp3-CH peak that might originate from the grain boundaries between UNCD crystallites whose dangling bonds are terminated with hydrogen atoms. A narrow sp3 peak in the photoemission spectrum implied that the film comprises a large number of UNCD crystallites. Large optical absorption coefficients at photon energies larger than 3 eV that might be due to the grain boundaries are specific to the UNCD/a-C:H films.

  1. Amorphous silicon carbon films prepared by hybrid plasma enhanced chemical vapor/sputtering deposition system: Effects of r.f. power

    Energy Technology Data Exchange (ETDEWEB)

    Rashid, Nur Maisarah Abdul, E-mail: nurmaisarahrashid@gmail.com [Low Dimensional Materials Research Centre, Department of Physics, University of Malaya, 50603 Kuala Lumpur (Malaysia); Ritikos, Richard; Othman, Maisara; Khanis, Noor Hamizah; Gani, Siti Meriam Ab. [Low Dimensional Materials Research Centre, Department of Physics, University of Malaya, 50603 Kuala Lumpur (Malaysia); Muhamad, Muhamad Rasat [Chancellery Office, Multimedia University, Jalan Multimedia, 63100 Cyberjaya, Selangor (Malaysia); Rahman, Saadah Abdul, E-mail: saadah@um.edu.my [Low Dimensional Materials Research Centre, Department of Physics, University of Malaya, 50603 Kuala Lumpur (Malaysia); Chancellery Office, Multimedia University, Jalan Multimedia, 63100 Cyberjaya, Selangor (Malaysia)

    2013-02-01

    Silicon carbon films were deposited using a hybrid radio frequency (r.f.) plasma enhanced chemical vapor deposition (PECVD)/sputtering deposition system at different r.f. powers. This deposition system combines the advantages of r.f. PECVD and sputtering techniques for the deposition of silicon carbon films with the added advantage of eliminating the use of highly toxic silane gas in the deposition process. Silicon (Si) atoms were sputtered from a pure amorphous silicon (a-Si) target by argon (Ar) ions and carbon (C) atoms were incorporated into the film from C based growth radicals generated through the discharge of methane (CH{sub 4}) gas. The effects of r.f. powers of 60, 80, 100, 120 and 150 W applied during the deposition process on the structural and optical properties of the films were investigated. Raman spectroscopic studies showed that the silicon carbon films contain amorphous silicon carbide (SiC) and amorphous carbon (a-C) phases. The r.f. power showed significant influence on the C incorporation in the film structure. The a-C phases became more ordered in films with high C incorporation in the film structure. These films also produced high photoluminescence emission intensity at around 600 nm wavelength as a result of quantum confinement effects from the presence of sp{sup 2} C clusters embedded in the a-SiC and a-C phases in the films. - Highlights: ► Effects of radio frequency (r.f.) power on silicon carbon (SiC) films were studied. ► Hybrid plasma enhanced chemical vapor deposition/sputtering technique was used. ► r.f. power influences C incorporation in the film structure. ► High C incorporation results in higher ordering of the amorphous C phase. ► These films produced high photoluminescence emission intensity.

  2. Correlation of photothermal conversion on the photo-induced deformation of amorphous carbon nitride films prepared by reactive sputtering

    Energy Technology Data Exchange (ETDEWEB)

    Harata, T.; Aono, M., E-mail: aono@nda.ac.jp; Kitazawa, N.; Watanabe, Y. [Department of Materials Science and Engineering, National Defense Academy, 1-10-20 Hashirimizu, Yokosuka, Kanagawa 239-8686 (Japan)

    2014-08-04

    The photo-induced deformation of hydrogen-free amorphous carbon nitride (a-CN{sub x}) films was investigated under visible-light illumination. The films gave rise to photothermal conversion by irradiation. In this study, we investigated the effects of thermal energy generated by irradiation on the deformation of a-CN{sub x}/ultrathin substrate bimorph specimens. The films were prepared on both ultrathin Si and SiO{sub 2} substrates by reactive radio-frequency magnetron sputtering from a graphite target in the presence of pure nitrogen gas. The temperature of the film on the SiO{sub 2} substrate increased as the optical band-gap of the a-CN{sub x} was decreased. For the film on Si, the temperature remained constant. The deformation degree of the films on Si and SiO{sub 2} substrates were approximately the same. Thus, the deformation of a-CN{sub x} films primarily induced by photon energy directly.

  3. Effect of substrate bias in nitrogen incorporated amorphous carbon films with embedded nanoparticles deposited by filtered cathodic jet carbon arc technique

    Energy Technology Data Exchange (ETDEWEB)

    Panwar, O.S., E-mail: ospanwar@mail.nplindia.ernet.in [Amorphous and Microcrystalline Silicon Solar Cell Group, Physics of Energy Harvesting Division, National Physical Laboratory (C.S.I.R.), Dr. K.S. Krishnan Road, New Delhi-110012 (India); Kumar, Sushil; Ishpal,; Srivastava, A.K.; Chouksey, Abhilasha; Tripathi, R.K.; Basu, A. [Amorphous and Microcrystalline Silicon Solar Cell Group, Physics of Energy Harvesting Division, National Physical Laboratory (C.S.I.R.), Dr. K.S. Krishnan Road, New Delhi-110012 (India)

    2012-02-15

    Highlights: Black-Right-Pointing-Pointer a-C: N films having nanoparticles were deposited by filtered cathodic jet carbon arc (FCJCA) technique. Black-Right-Pointing-Pointer The effect of negative substrate bias on the properties of a-C: N films embedded with nanoparticles have been studied. Black-Right-Pointing-Pointer The properties of a-C: N films deposited by FCJCA technique have been compared with ta-C: N films deposited by FCVA process. - Abstract: The properties of nitrogen incorporated amorphous carbon (a-C: N) films with embedded nanoparticles, deposited using a filtered cathodic jet carbon arc technique, are reported. X-ray diffraction, high resolution transmission electron microscope and Raman spectroscopy measurements reveal an amorphous structure, but on closer examination the presence of clusters of nanocarbon single crystals with d-spacing close to diamond cubic-phase have also been identified. The effect of substrate bias on the microstructure, conductivity, activation energy, optical band gap, optical constants, residual stress, hardness, elastic modulus, plastic index parameter, percentage elastic recovery and density of states of a-C: N films have been studied and the properties obtained are found to depend on the substrate bias.

  4. Fabrication of periodical surface structures by picosecond laser irradiation of carbon thin films: transformation of amorphous carbon in nanographite

    Science.gov (United States)

    Popescu, C.; Dorcioman, G.; Bita, B.; Besleaga, C.; Zgura, I.; Himcinschi, C.; Popescu, A. C.

    2016-12-01

    Thin films of carbon were synthesized by ns pulsed laser deposition in vacuum on silicon substrates, starting from graphite targets. Further on, the films were irradiated with a picosecond laser source emitting in visible at 532 nm. After tuning of laser parameters, we obtained a film surface covered by laser induced periodical surface structures (LIPSS). They were investigated by optical, scanning electron and atomic force microscopy. It was observed that changing the irradiation angle influences the LIPSS covered area. At high magnification it was revealed that the LIPSS pattern was quite complex, being composed of other small LIPSS islands, interconnected by bridges of nanoparticles. Raman spectra for the non-irradiated carbon films were typical for a-C type of diamond-like carbon, while the LIPSS spectra were characteristic to nano-graphite. The pristine carbon film was hydrophilic, while the LIPSS covered film surface was hydrophobic.

  5. Effect of high substrate bias and hydrogen and nitrogen incorporation on filtered cathodic vacuum arc deposited tetrahedral amorphous carbon films

    Energy Technology Data Exchange (ETDEWEB)

    Panwar, O.S. [Plasma Processed Materials Group, National Physical Laboratory, Dr. K.S. Krishnan Road, New Delhi-110 012 (India)], E-mail: ospanwar@mail.nplindia.ernet.in; Khan, Mohd. Alim [Plasma Processed Materials Group, National Physical Laboratory, Dr. K.S. Krishnan Road, New Delhi-110 012 (India); Kumar, Mahesh; Shivaprasad, S.M. [Surface Physics and Nanostructures Group, National Physical Laboratory, Dr. K.S. Krishnan Road, New Delhi-110 012 (India); Satyanarayana, B.S. [MIT Innovation Centre and Electronics and Communication Department, Manipal Institute of Technology, Manipal-579104 (India); Dixit, P.N. [Plasma Processed Materials Group, National Physical Laboratory, Dr. K.S. Krishnan Road, New Delhi-110 012 (India); Bhattacharyya, R. [Emeritus Scientist, National Physical Laboratory, New Delhi-110012 (India); Khan, M.Y. [Department of Physics, Jamia Millia Islamia, Central University, New Delhi-110025 (India)

    2008-02-29

    The application of a sufficiently high negative substrate bias, during the growth of tetrahedral amorphous carbon (ta-C), is usually associated with low sp{sup 3} bonding configuration and stressed films. However, in an effort to understand and utilize the higher pseudo thermo dynamical conditions during the film growth, at high negative substrate bias (- 300 V), reported here is a study on ta-C films grown under different hydrogen and nitrogen concentration. As grown ta-C films were studied under different negative substrate bias conditions. The variation of the sp{sup 3} content and sp{sup 3}/sp{sup 2} ratio in the ta-C films exhibits a trend similar to those reported in literature, with a subtle variation in this report being the substrate bias voltage, which was observed to be around - 200 V, for obtaining the highest sp{sup 3} (80%) bonding and sp{sup 3}/sp{sup 2} (3.95) ratio. The hydrogen and nitrogen incorporated ta-C films studied, at a bias of - 300 V, show an increase in sp{sup 3} (87-91%) bonding and sp{sup 3}/sp{sup 2} (7-10) ratio in the range of studies reported. The inference is drawn on the basis of the set of data obtained from measurements carried out using X-ray photoelectron spectroscopy, X-ray induced Auger electron spectroscopy and Raman spectroscopy of as grown and hydrogen and nitrogen incorporated ta-C films deposited using an S bend filtered cathodic vacuum arc system. The study indicates the possibility of further tailoring ta-C film properties and also extending capabilities of the cathodic arc system for developing carbon based films for electronics and tribological applications.

  6. Stress relief patterns of hydrogenated amorphous carbon films grown by dc-pulse plasma chemical vapor deposition

    Science.gov (United States)

    Wang, Qi; Wang, Chengbing; Wang, Zhou; Zhang, Junyan; He, Deyan

    2008-12-01

    Hydrogenated amorphous carbon films were prepared on Si (1 0 0) substrates by dc-pulse plasma chemical vapor deposition. The nature of the deposited films was characterized by Raman spectra and the stress relief patterns were observed by scanning electron microscope. Besides the well-known sinusoidal type and flower type patterns, etc., two different stress relief patterns, ring type and peg-top shape with exiguous tine on the top, were observed. The ring type in this paper was a clear ridge-cracked buckle and unusual. Two competing buckle delamination morphologies ring and sinusoidal buckling coexist. The ridge-cracked buckle in ring type was narrower than the sinusoidal buckling. Meanwhile peg-top shape with exiguous tine on the top in this paper was unusual. These different patterns supported the approach in which the stress relief forms have been analyzed using the theory of plate buckling.

  7. Controllable Electrochemical Activities by Oxidative Treatment toward Inner-Sphere Redox Systems at N-Doped Hydrogenated Amorphous Carbon Films

    Directory of Open Access Journals (Sweden)

    Yoriko Tanaka

    2012-01-01

    Full Text Available The electrochemical activity of the surface of Nitrogen-doped hydrogenated amorphous carbon thin films (a-CNH, N-doped DLC toward the inner sphere redox species is controllable by modifying the surface termination. At the oxygen plasma treated N-doped DLC surface (O-DLC, the surface functional groups containing carbon doubly bonded to oxygen (C=O, which improves adsorption of polar molecules, were generated. By oxidative treatment, the electron-transfer rate for dopamine (DA positively charged inner-sphere redox analyte could be improved at the N-doped DLC surface. For redox reaction of 2,4-dichlorophenol, which induces an inevitable fouling of the anode surface by forming passivating films, the DLC surfaces exhibited remarkably higher stability and reproducibility of the electrode performance. This is due to the electrochemical decomposition of the passive films without the interference of oxygen evolution by applying higher potential. The N-doped DLC film can offer benefits as the polarizable electrode surface with the higher reactivity and higher stability toward inner-sphere redox species. By making use of these controllable electrochemical reactivity at the O-DLC surface, the selective detection of DA in the mixed solution of DA and uric acid could be achieved.

  8. Incidence Angle Effect of Energetic Carbon Ions on Deposition Rate, Topography, and Structure of Ultrathin Amorphous Carbon Films Deposited by Filtered Cathodic Vacuum Arc

    KAUST Repository

    Wang, N.

    2012-07-01

    The effect of the incidence angle of energetic carbon ions on the thickness, topography, and structure of ultrathin amorphous carbon (a-C) films synthesized by filtered cathodic vacuum arc (FCVA) was examined in the context of numerical and experimental results. The thickness of a-C films deposited at different incidence angles was investigated in the light of Monte Carlo simulations, and the calculated depth profiles were compared with those obtained from high-resolution transmission electron microscopy (TEM). The topography and structure of the a-C films were studied by atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS), respectively. The film thickness decreased with the increase of the incidence angle, while the surface roughness increased and the content of tetrahedral carbon hybridization (sp 3) decreased significantly with the increase of the incidence angle above 45° , measured from the surface normal. TEM, AFM, and XPS results indicate that the smoothest and thinnest a-C films with the highest content of sp 3 carbon bonding were produced for an incidence angle of 45°. The findings of this study have direct implications in ultrahigh-density magnetic recording, where ultrathin and smooth a-C films with high sp 3 contents are of critical importance. © 2012 IEEE.

  9. Molecular-scale tribology of amorphous carbon coatings: effects of film thickness, adhesion, and long-range interactions.

    Science.gov (United States)

    Gao, G T; Mikulski, Paul T; Harrison, Judith A

    2002-06-19

    Classical molecular dynamics simulations have been conducted to investigate the atomic-scale friction and wear when hydrogen-terminated diamond (111) counterfaces are in sliding contact with diamond (111) surfaces coated with amorphous, hydrogen-free carbon films. Two films, with approximately the same ratio of sp(3)-to-sp(2) carbon, but different thicknesses, have been examined. Both systems give a similar average friction in the load range examined. Above a critical load, a series of tribochemical reactions occur resulting in a significant restructuring of the film. This restructuring is analogous to the "run-in" observed in macroscopic friction experiments and reduces the friction. The contribution of adhesion between the probe (counterface) and the sample to friction was examined by varying the saturation of the counterface. Decreasing the degree of counterface saturation, by reducing the hydrogen termination, increases the friction. Finally, the contribution of long-range interactions to friction was examined by using two potential energy functions that differ only in their long-range forces to examine friction in the same system.

  10. Properties of boron and phosphorous incorporated tetrahedral amorphous carbon films grown using filtered cathodic vacuum arc process

    Energy Technology Data Exchange (ETDEWEB)

    Panwar, O.S., E-mail: ospanwar@mail.nplindia.ernet.in [Plasma Processed Materials Group, National Physical Laboratory (CSIR), Dr. K.S. Krishnan Road, New Delhi 110012 (India); Khan, Mohd Alim [Plasma Processed Materials Group, National Physical Laboratory (CSIR), Dr. K.S. Krishnan Road, New Delhi 110012 (India); Satyanarayana, B.S. [40, Sreeniketan, NDSE 24, New Delhi 110096 (India); Kumar, Sushil; Ishpal [Plasma Processed Materials Group, National Physical Laboratory (CSIR), Dr. K.S. Krishnan Road, New Delhi 110012 (India)

    2010-04-15

    This paper reports the electrical, mechanical, structural and field emission properties of as grown and also boron and phosphorous incorporated tetrahedral amorphous carbon (ta-C) films, deposited using a filtered cathodic vacuum arc process. The effect of varying boron and phosphorous content (up to 2.0 at.% in to ta-C) on the conductivity ({sigma}{sub D}), activation energy ({Delta}E{sub 1}), hardness, microstructure, emission threshold (E{sub turn-ON}) and emission current density (J) at 12.5 V/{mu}m of ta-C: B and ta-C: P films deposited at a high negative substrate bias of -300 V are reported. It is observed that both boron and phosphorous incorporation leads to a nearly an order increase in {sigma}{sub D} and corresponding decrease in {Delta}E{sub 1} and a slight increase in hardness as compared to as grown ta-C films. In the case of field assisted electron emission, it is observed that E{sub turn-ON} increases and J decreases. The changes are attributed to the changes in the sp{sup 3}/sp{sup 2} ratio of the films due to boron and phosphorous incorporation. The effect of boron on ta-C is to give a p-type effect whereas the effect of phosphorous gives n-type doping effect.

  11. Physical properties of ultrafast deposited micro- and nanothickness amorphous hydrogenated carbon films for medical devices and prostheses.

    Science.gov (United States)

    Zaharia, T; Sullivan, I L; Saied, S O; Bosch, R C; Bijker, M D

    2007-02-01

    Hydrogenated amorphous carbon films with diamond-like structures have been formed on different substrates at very low energies and temperatures by a plasma-enhanced chemical vapour deposition (PECVD) process employing acetylene as the precursor gas. The plasma source was of a cascaded arc type with argon as the carrier gas. The films grown at very high deposition rates were found to have a practical thickness limit of approximately 1.5 microm, above which delamination from the substrate occurred. Deposition on silicon (100), glass, and plastic substrates has been studied and the films characterized in terms of sp3 content, roughness, hardness, adhesion, and optical properties. Deposition rates of up to 20 nm/s have been achieved at substrate temperatures below 100 degrees C. A typical sp3 content of 60-75 per cent in the films was determined by X-ray-generated Auger electron spectroscopy (XAES). The hardness, reduced modulus, and adhesion of the films were measured using a MicroMaterials NanoTest indenter/scratch tester. Hardness was found to vary from 4 to 13 GPa depending on the admixed acetylene flow and substrate temperature. The adhesion of the film to the substrate was significantly influenced by the substrate temperature and whether an in situ d.c. cleaning was employed prior to the deposition process. The hydrogen content in the film was measured by a combination of the Fourier transformation infrared (FTIR) spectroscopy and Rutherford backscattering (RBS) techniques. From the results it is concluded that the films formed by the process described here are ideal for the coating of long-term implantable medical devices, such as prostheses, stents, invasive probes, catheters, biosensors, etc. The properties reported in this publication are comparable with good-quality films deposited by other PECVD methods. The advantages of these films are the low ion energy and temperature of deposition, ensuring that no damage is done to sensitive substrates, very high

  12. Thermal conductivity of carbon doped GeTe thin films in amorphous and crystalline state measured by modulated photo thermal radiometry

    Science.gov (United States)

    Kusiak, Andrzej; Battaglia, Jean-Luc; Noé, Pierre; Sousa, Véronique; Fillot, F.

    2016-09-01

    The thermal conductivity and thermal boundary resistance of GeTe and carbon doped GeTe thin films, designed for phase change memory (PCM) applications, were investigated by modulated photo thermal radiometry. It was found that C doping has no significant effect on the thermal conductivity of these chalcogenides in amorphous state. The thermal boundary resistance between the amorphous films and SiO2 substrate is also not affected by C doping. The films were then crystallized by an annealing at 450°C as confirmed by optical reflectivity analysis. The thermal conductivity of non-doped GeTe significantly increases after crystallization annealing. But, surprisingly the thermal conductivity of the crystallized C doped GeTe was found to be similar from that of the amorphous state and independent of C concentration. As for the amorphous phase, C doping does not affect the thermal boundary resistance between the crystalline GeTe films and SiO2 substrate. This behaviour is discussed thanks to XRD and FTIR analysis. In particular, XRD shows a decrease of crystalline grain size in crystalline films as C concentration is increased. FTIR analysis of the film before and after crystallization evidenced that this evolution could be attributed to the disappearing of Ge-C bonds and migration of C atoms out of the GeTe phase upon crystallization, limiting then the growth of GeTe crystallites in C-doped films.

  13. Deposit of thin films of nitrided amorphous carbon using the laser ablation technique; Deposito de peliculas delgadas de carbono amorfo nitrurado utilizando la tecnica de ablacion laser

    Energy Technology Data Exchange (ETDEWEB)

    Rebollo, P.B.; Escobar A, L.; Camps C, E. [Departamento de Fisica, Instituto Nacional de Investigaciones Nucleares, C.P. 52045 Salazar, Estado de Mexico (Mexico); Haro P, E.; Camacho L, M.A. [Departamento de Fisica, Universidad Autonoma Metropolitana Iztapalapa (Mexico); Muhl S, S. [Instituto de Investigacion en Materiales, UNAM (Mexico)

    2000-07-01

    It is reported the synthesis and characterization of thin films of amorphous carbon (a-C) nitrided, deposited by laser ablation in a nitrogen atmosphere at pressures which are from 4.5 x 10 {sup -4} Torr until 7.5 x 10 {sup -2} Torr. The structural properties of the films are studied by Raman spectroscopy obtaining similar spectra at the reported for carbon films type diamond. The study of behavior of the energy gap and the ratio nitrogen/carbon (N/C) in the films, shows that the energy gap is reduced when the nitrogen incorporation is increased. It is showed that the refraction index of the thin films diminish as nitrogen pressure is increased, indicating the formation of graphitic material. (Author)

  14. Flexible amorphous metal films with high stability

    Science.gov (United States)

    Liu, M.; Cao, C. R.; Lu, Y. M.; Wang, W. H.; Bai, H. Y.

    2017-01-01

    We report the formation of amorphous Cu50Zr50 films with a large-area of more than 100 cm2. The films were fabricated by ion beam assisted deposition with a slow deposition rate at moderate temperature. The amorphous films have markedly enhanced thermal stability, excellent flexibility, and high reflectivity with atomic level smoothness. The multifunctional properties of the amorphous films are favorites in the promising applications of smart skin or wearable devices. The method of preparing highly stable amorphous metal films by tuning the deposition rate instead of deposition temperature could pave a way for exploring amorphous metal films with unique properties.

  15. Light emission in forward and reverse bias operation in OLED with amorphous silicon carbon nitride thin films

    Energy Technology Data Exchange (ETDEWEB)

    Reyes, R [Facultad de Ingenieria Quimica y Textil, Universidad Nacional de Ingenieria, Av. Tupac Amaru SN, Lima (Peru); Cremona, M [Departamento de Fisica, PontifIcia Universidade Catolica de Rio de Janeiro, PUC-Rio, Cx. Postal 38071, Rio de Janeiro, RJ, CEP 22453-970 (Brazil); Achete, C A, E-mail: rreyes@uni.edu.pe [Departamento de Engenheria Metalurgica e de Materiais, Universidade Federal do Rio de Janeiro, Cx. Postal 68505, Rio de Janeiro, RJ, CEP 21945-970 (Brazil)

    2011-01-01

    Amorphous silicon carbon nitride (a-SiC:N) thin films deposited by magnetron sputtering were used in the structure of an organic light emitting diode (OLED), obtaining an OLED operating in forward and reverse bias mode. The device consist of the heterojunction structure ITO/a-SiC:N/Hole Transport Layer (HTL)/ Electron Transport Layer (ETL)/a-SiC:N/Al. As hole transporting layer was used a thin film of 1-(3-methylphenyl)-1,2,3,4 tetrahydroquinoline - 6 - carboxyaldehyde - 1,1'- diphenylhydrazone (MTCD), while the tris(8-hydroxyquinoline aluminum) (Alq{sub 3}) is used as electron transport and emitting layer. A significant increase in the voltage operation compared to the conventional ITO/MTCD/Alq{sub 3}/Al structure was observed, so the onset of electroluminescence occurs at about 22 V in the forward and reverse bias mode of operation. The electroluminescence spectra is similar in both cases, only slightly shifted 0.14 eV to lower energies in relation to the conventional device.

  16. Surface morphology and grain analysis of successively industrially grown amorphous hydrogenated carbon films (a-C:H) on silicon

    Energy Technology Data Exchange (ETDEWEB)

    Catena, Alberto [Department of Physics, University of Koblenz-Landau, 56070 Koblenz (Germany); McJunkin, Thomas [Department of Physics, The Ohio State University, 43210 Columbus, Ohio (United States); Agnello, Simonpietro; Gelardi, Franco M. [Department of Physics and Chemistry, University of Palermo, 90100 Palermo (Italy); Wehner, Stefan [Department of Physics, University of Koblenz-Landau, 56070 Koblenz (Germany); Fischer, Christian B., E-mail: chrbfischer@uni-koblenz.de [Department of Physics, University of Koblenz-Landau, 56070 Koblenz (Germany)

    2015-08-30

    Graphical abstract: - Highlights: • Two different a-C:H coatings in various thicknesses on Si (1 0 0) have been studied. • For both types no significant difference in surface morphology is detectable. • The grain number with respect to their height appears randomly distributed. • In average no grain higher than 14 nm and larger than 0.05 μm{sup 2} was observed. • A height to area correlation confines all detected grains to a limited region. - Abstract: Silicon (1 0 0) has been gradually covered by amorphous hydrogenated carbon (a-C:H) films via an industrial process. Two types of these diamond-like carbon (DLC) coatings, one more flexible (f-DLC) and one more robust (r-DLC), have been investigated. Both types have been grown by a radio frequency plasma-enhanced chemical vapor deposition (RF-PECVD) technique with acetylene plasma. Surface morphologies have been studied in detail by atomic force microscopy (AFM) and Raman spectroscopy has been used to investigate the DLC structure. Both types appeared to have very similar morphology and sp{sup 2} carbon arrangement. The average height and area for single grains have been analyzed for all depositions. A random distribution of grain heights was found for both types. The individual grain structures between the f- and r-type revealed differences: the shape for the f-DLC grains is steeper than for the r-DLC grains. By correlating the average grain heights to the average grain areas for all depositions a limited region is identified, suggesting a certain regularity during the DLC deposition mechanisms that confines both values. A growth of the sp{sup 2} carbon entities for high r-DLC depositions is revealed and connected to a structural rearrangement of carbon atom hybridizations and hydrogen content in the DLC structure.

  17. Time-Resolved Observation of Deposition Process of Ultrananocrystalline Diamond/Hydrogenated Amorphous Carbon Composite Films in Pulsed Laser Deposition

    Directory of Open Access Journals (Sweden)

    Kenji Hanada

    2009-01-01

    Full Text Available Optical emission spectroscopy was used to study pulsed laser ablation of graphite in a hydrogen atmosphere wherein ultrananocrystalline diamond (UNCD/hydrogenated amorphous carbon (a-C:H composite films were grown on heated substrates. Time-resolved photographs of a plume that expanded from a laser-irradiation spot toward a substrate were taken using a high-speed ICCD camera equipped with narrow-bandpass filters. While the emissions from C atoms and C2 dimers lasted above the laser-irradiation spot on the target, the emission from C+ ions lasted above the substrate surface for approximately 7 microseconds, although the emission lifetime of species is generally approximately 10 nanoseconds. This implies that C+ ions actively collided with each other above the substrate surface for such a long time. We believe that the keys to UNCD growth in PLD are the supply of highly energetic carbon species at a high density to the substrate and existence of atomic hydrogen during the growth.

  18. Study of Synchrotron Radiation Near-Edge X-Ray Absorption Fine-Structure of Amorphous Hydrogenated Carbon Films at Various Thicknesses

    Directory of Open Access Journals (Sweden)

    Sarayut Tunmee

    2015-01-01

    Full Text Available The compositions and bonding states of the amorphous hydrogenated carbon films at various thicknesses were evaluated via near-edge X-ray absorption fine-structure (NEXAFS and elastic recoil detection analysis combined with Rutherford backscattering spectrometry. The absolute carbon sp2 contents were determined to decrease to 65% from 73%, while the hydrogen contents increase from 26 to 33 at.% as the film thickness increases. In addition, as the film thickness increases, the π⁎ (C=C, σ⁎ (C–H, σ⁎ (C=C, and σ⁎ (C≡C bonding states were found to increase, whereas the π⁎ (C≡C and σ⁎ (C–C bonding states were observed to decrease in the NEXAFS spectra. Consequently, the film thickness is a key factor to evaluate the composition and bonding state of the films.

  19. Synthesis and characterization of thin films of nitrided amorphous carbon deposited by laser ablation; Sintesis y caracterizacion de peliculas delgadas de carbono amorfo nitrurado, depositadas por ablacion laser

    Energy Technology Data Exchange (ETDEWEB)

    Rebollo P, B

    2001-07-01

    The objective of this work is the synthesis and characterization of thin films of amorphous carbon (a-C) and thin films of nitrided amorphous carbon (a-C-N) using the laser ablation technique for their deposit. For this purpose, the physical properties of the obtained films were studied as function of diverse parameters of deposit such as: nitrogen pressure, power density, substrate temperature and substrate-target distance. For the characterization of the properties of the deposited thin films the following techniques were used: a) Raman spectroscopy which has demonstrated being a sensitive technique to the sp{sup 2} and sp{sup 3} bonds content, b) Energy Dispersive Spectroscopy which allows to know semi-quantitatively way the presence of the elements which make up the deposited films, c) Spectrophotometry, for obtaining the absorption spectra and subsequently the optical energy gap of the deposited material, d) Ellipsometry for determining the refraction index, e) Scanning Electron Microscopy for studying the surface morphology of thin films and, f) Profilemetry, which allows the determination the thickness of the deposited thin films. (Author)

  20. Amorphous MoSx thin-film-coated carbon fiber paper as a 3D electrode for long cycle life symmetric supercapacitors

    Science.gov (United States)

    Balasingam, Suresh Kannan; Thirumurugan, Arun; Lee, Jae Sung; Jun, Yongseok

    2016-06-01

    Amorphous MoSx thin-film-coated carbon fiber paper as a binder-free 3D electrode was synthesized by a facile hydrothermal method. The maximum specific capacitance of a single electrode was 83.9 mF cm-2, while it was 41.9 mF cm-2 for the symmetric device. Up to 600% capacitance retention was observed for 4750 cycles.Amorphous MoSx thin-film-coated carbon fiber paper as a binder-free 3D electrode was synthesized by a facile hydrothermal method. The maximum specific capacitance of a single electrode was 83.9 mF cm-2, while it was 41.9 mF cm-2 for the symmetric device. Up to 600% capacitance retention was observed for 4750 cycles. Electronic supplementary information (ESI) available. See DOI: 10.1039/C6NR01200K

  1. Near-Edge X-Ray Absorption Fine Structure of Ultrananocrystalline Diamond/Hydrogenated Amorphous Carbon Films Prepared by Pulsed Laser Deposition

    Directory of Open Access Journals (Sweden)

    Shinya Ohmagari

    2009-01-01

    Full Text Available The atomic bonding configuration of ultrananocrystalline diamond (UNCD/hydrogenated amorphous carbon (a-C:H films prepared by pulsed laser ablation of graphite in a hydrogen atmosphere was examined by near-edge X-ray absorption fine structure spectroscopy. The measured spectra were decomposed with simple component spectra, and they were analyzed in detail. As compared to the a-C:H films deposited at room substrate-temperature, the UNCD/a-C:H and nonhydrogenated amorphous carbon (a-C films deposited at a substrate-temperature of 550∘C exhibited enhanced ∗ and ∗C≡C peaks. At the elevated substrate-temperature, the ∗ and ∗C≡C bonds formation is enhanced while the ∗C–H and ∗C–C bonds formation is suppressed. The UNCD/a-C:H film showed a larger ∗C–C peak than the a-C film deposited at the same elevated substrate-temperature in vacuum. We believe that the intense ∗C–C peak is evidently responsible for UNCD crystallites existence in the film.

  2. The effect of deposition energy of energetic atoms on the growth and structure of ultrathin amorphous carbon films studied by molecular dynamics simulations

    KAUST Repository

    Wang, N

    2014-05-16

    The growth and structure of ultrathin amorphous carbon films was investigated by molecular dynamics simulations. The second-generation reactive-empirical-bond-order potential was used to model atomic interactions. Films with different structures were simulated by varying the deposition energy of carbon atoms in the range of 1-120 eV. Intrinsic film characteristics (e.g. density and internal stress) were determined after the system reached equilibrium. Short- and intermediate-range carbon atom ordering is examined in the context of atomic hybridization and ring connectivity simulation results. It is shown that relatively high deposition energy (i.e., 80 eV) yields a multilayer film structure consisting of an intermixing layer, bulk film and surface layer, consistent with the classical subplantation model. The highest film density (3.3 g cm-3), sp3 fraction (∼43%), and intermediate-range carbon atom ordering correspond to a deposition energy of ∼80 eV, which is in good agreement with experimental findings. © 2014 IOP Publishing Ltd.

  3. Endothelialization of TiO2 Nanorods Coated with Ultrathin Amorphous Carbon Films

    Science.gov (United States)

    Chen, Hongpeng; Tang, Nan; Chen, Min; Chen, Dihu

    2016-03-01

    Carbon plasma nanocoatings with controlled fraction of sp3-C bonding were deposited on TiO2 nanorod arrays (TNAs) by DC magnetic-filtered cathodic vacuum arc deposition (FCVAD). The cytocompatibility of TNA/carbon nanocomposites was systematically investigated. Human umbilical vein endothelial cells (HUVECs) were cultured on the nanocomposites for 4, 24, and 72 h in vitro. It was found that plasma-treated TNAs exhibited excellent cell viability as compared to the untreated. Importantly, our results show that cellular responses positively correlate with the sp3-C content. The cells cultured on high sp3-C-contented substrates exhibit better attachment, shape configuration, and proliferation. These findings indicate that the nanocomposites with high sp3-C content possessed superior cytocompatibility. Notably, the nanocomposites drastically reduced platelet adhesion and activation in our previous studies. Taken together, these findings suggest the TNA/carbon scaffold may serve as a guide for the design of multi-functionality devices that promotes endothelialization and improves hemocompatibility.

  4. Deposition of amorphous carbon-silver composites

    Energy Technology Data Exchange (ETDEWEB)

    Garcia-Zarco, O. [Instituto de Investigaciones en Materiales, Universidad Nacional Autonoma de Mexico, Circuito Exterior s/n, Ciudad Universitaria. 04510, Mexico D. F. Mexico (Mexico); Rodil, S.E., E-mail: ser42@iim.unam.m [Instituto de Investigaciones en Materiales, Universidad Nacional Autonoma de Mexico, Circuito Exterior s/n, Ciudad Universitaria. 04510, Mexico D. F. Mexico (Mexico); Camacho-Lopez, M.A. [Facultad de Quimica, Universidad Autonoma del Estado de Mexico, Tollocan s/n, esq. Paseo Colon, Toluca, Estado de Mexico, 50110 (Mexico)

    2009-12-31

    Composites of amorphous carbon films and silver were deposited by co-sputtering, where the target (10 cm diameter) was of pure graphite with small inclusion of pure silver (less than 1 cm{sup 2}). The films were deposited under different powers, from 40 to 250 W, and different target-substrate distances. The substrate was earthed and rotated in order to obtain a uniform distribution of the silver content. The addition of the Ag piece into the target increased the deposition rate of the carbon films, which could be related to the higher sputter yield of the silver, but there seems to be also a contribution from a larger emission of secondary electrons from the Ag that enhances the plasma and therefore the sputtering process becomes more efficient. Scanning electron micrographs acquired using backscattered electrons showed that the silver was segregated from the carbon matrix, forming nanoparticles or larger clusters as the power was increased. The X-ray diffraction pattern showed that the silver was crystalline and the carbon matrix remained amorphous, although for certain conditions a peak attributed to fullerene-like structures was obtained. Finally, we used Raman spectroscopy to understand the bonding characteristics of the carbon-silver composites, finding that there are variations in the D/G ratio, which can be correlated to the observed structure and X-ray diffraction results.

  5. PHOTO- AND ELECTRO-LUMINESCENCE FROM HYDROGENATED AMORPHOUS SILICON CARBIDE FILMS PREPARED BY USING ORGANIC CARBON SOURCE

    Institute of Scientific and Technical Information of China (English)

    Xu Jun; Ma Tian-fu; Li Wei; Chen Kun-ji; Li Zhi-feng; Lu Wei

    2000-01-01

    Hydrogenated amorphous silicon carbide (a-SiC:H) films were grown byusing an organic source, xylene (C8H{10), instead of methane(CH4) in a conventional plasma enhanced chemical vapor depositionsystem. The optical band gap of these samples was increased gradually bychanging the gas ratio of C8H10 to SiH4. The film with highoptical band gap was soft and polymer-like and intense photoluminescencewere obtained. Room temperature electro-luminescence was also achievedwith peak energy at 2.05 eV (600 nm) for the a-SiC:H film withoptical band gap of 3.2 eV.1.8mm

  6. The influence of methane/argon plasma composition on the formation of the hydrogenated amorphous carbon films

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Hsin-Hung [Department of Materials Science and Engineering, National Cheng Kung University, No. 1, University Road, Tainan 70101, Taiwan (China); Liao, Jiunn-Der, E-mail: jdliao@mail.ncku.edu.t [Department of Materials Science and Engineering, National Cheng Kung University, No. 1, University Road, Tainan 70101, Taiwan (China); Weng, Chih-Chiang; Hsieh, Jui-Fu; Chang, Chia-Wei [Department of Materials Science and Engineering, National Cheng Kung University, No. 1, University Road, Tainan 70101, Taiwan (China); Lin, Chao-Hsien; Cho, Ting-Pin [Metal Industries Development and Research Centre, 1001 Kaonan Highway, Kaohsiung 811, Taiwan (China)

    2011-01-03

    The quality of the a-C:H films was particularly correlated with the mixed ratio of methane/argon plasma. For a constant supply of energy and flowing rate, the optical emission from H{sub {alpha}} intensity linearly increased with the addition of methane in argon plasma, while that from intensities of radiation of diatmoic radicals (CH*and C{sub 2}*) exponentially decreased. For the a-C:H films, the added methane in argon plasma tended to raise the quantity of hydrogenated carbon or sp{sup 3} C-H structure, which exponentially decreased the nano-hardness and friction coefficient of the films. In contrast, the electric resistance of the films enlarged dramatically with the increase of the methane content in argon plasma. It is therefore advantageous to balance the mechanical properties and electrical resistance of the a-C:H film by adjusting plasma composition in the course of the film-growing process.

  7. Low-temperature growth of low friction wear-resistant amorphous carbon nitride thin films by mid-frequency, high power impulse, and direct current magnetron sputtering

    Energy Technology Data Exchange (ETDEWEB)

    Bakoglidis, Konstantinos D., E-mail: konba@ifm.liu.se; Schmidt, Susann; Garbrecht, Magnus; Ivanov, Ivan G.; Jensen, Jens; Greczynski, Grzegorz; Hultman, Lars [Department of Physics, Chemistry and Biology (IFM), Linköping University, SE-581 83 Linköping (Sweden)

    2015-09-15

    The potential of different magnetron sputtering techniques for the synthesis of low friction and wear resistant amorphous carbon nitride (a-CN{sub x}) thin films onto temperature-sensitive AISI52100 bearing steel, but also Si(001) substrates was studied. Hence, a substrate temperature of 150 °C was chosen for the film synthesis. The a-CN{sub x} films were deposited using mid-frequency magnetron sputtering (MFMS) with an MF bias voltage, high power impulse magnetron sputtering (HiPIMS) with a synchronized HiPIMS bias voltage, and direct current magnetron sputtering (DCMS) with a DC bias voltage. The films were deposited using a N{sub 2}/Ar flow ratio of 0.16 at the total pressure of 400 mPa. The negative bias voltage, V{sub s}, was varied from 20 to 120 V in each of the three deposition modes. The microstructure of the films was characterized by high-resolution transmission electron microscopy and selected area electron diffraction, while the film morphology was investigated by scanning electron microscopy. All films possessed an amorphous microstructure, while the film morphology changed with the bias voltage. Layers grown applying the lowest substrate bias of 20 V exhibited pronounced intercolumnar porosity, independent of the sputter technique. Voids closed and dense films are formed at V{sub s} ≥ 60 V, V{sub s} ≥ 100 V, and V{sub s} = 120 V for MFMS, DCMS, and HiPIMS, respectively. X-ray photoelectron spectroscopy revealed that the nitrogen-to-carbon ratio, N/C, of the films ranged between 0.2 and 0.24. Elastic recoil detection analysis showed that Ar content varied between 0 and 0.8 at. % and increased as a function of V{sub s} for all deposition techniques. All films exhibited compressive residual stress, σ, which depends on the growth method; HiPIMS produces the least stressed films with values ranging between −0.4 and −1.2 GPa for all V{sub s}, while CN{sub x} films deposited by MFMS showed residual stresses up to −4.2

  8. Ultrahard carbon nanocomposite films

    Energy Technology Data Exchange (ETDEWEB)

    SIEGAL,MICHAEL P.; TALLANT,DAVID R.; PROVENCIO,PAULA P.; OVERMYER,DONALD L.; SIMPSON,REGINA L.; MARTINEZ-MIRANDA,L.J.

    2000-01-27

    Modest thermal annealing to 600 C of diamondlike amorphous-carbon (a-C) films grown at room temperature results in the formation of carbon nanocomposites with hardness similar to diamond. These nanocomposite films consist of nanometer-sized regions of high density a-C embedded in an a-C matrix with a reduced density of 5--10%. The authors report on the evolution of density and bonding topologies as a function of annealing temperature. Despite a decrease in density, film hardness actually increases {approximately} 15% due to the development of the nanocomposite structure.

  9. Ultrahard carbon nanocomposite films

    Energy Technology Data Exchange (ETDEWEB)

    Siegal, M. P. [Sandia National Laboratories, Albuquerque, New Mexico 87185-1421 (United States); Tallant, D. R. [Sandia National Laboratories, Albuquerque, New Mexico 87185-1421 (United States); Provencio, P. N. [Sandia National Laboratories, Albuquerque, New Mexico 87185-1421 (United States); Overmyer, D. L. [Sandia National Laboratories, Albuquerque, New Mexico 87185-1421 (United States); Simpson, R. L. [Sandia National Laboratories, Albuquerque, New Mexico 87185-1421 (United States); Martinez-Miranda, L. J. [Department of Materials and Nuclear Engineering, University of Maryland, College Park, Maryland 20742 (United States)

    2000-05-22

    Modest thermal annealing to 600 degree sign C of diamondlike amorphous-carbon (a-C) films grown at room temperature results in the formation of carbon nanocomposites with hardness similar to diamond. These nanocomposite films consist of nanometer-sized regions of high density a-C embedded in an a-C matrix with a reduced density of 5%-10%. We report on the evolution of density and bonding topologies as a function of annealing temperature. Despite a decrease in density, film hardness actually increases {approx}15% due to the development of the nanocomposite structure. (c) 2000 American Institute of Physics.

  10. Heavy-ion induced desorption yields of amorphous carbon films bombarded with 4.2 MeV/u lead ions

    CERN Document Server

    Mahner, E; Küchler, D; Scrivens, R; Costa Pinto, P; Yin Vallgren, C; Bender, M

    2011-01-01

    During the past decade, intense experimental studies on the heavy-ion induced molecular desorption were performed in several particle accelerator laboratories worldwide in order to understand and overcome large dynamic pressure rises caused by lost beam ions. Different target materials and various coatings were studied for desorption and mitigation techniques were applied to heavy-ion accelerators. For the upgrade of the CERN injector complex, a coating of the Super Proton Synchrotron (SPS) vacuum system with a thin film of amorphous carbon is under study to mitigate the electron cloud effect observed during SPS operation with the nominal proton beam for the Large Hadron Collider (LHC). Since the SPS is also part of the heavy-ion injector chain for LHC, dynamic vacuum studies of amorphous carbon films are important to determine their ion induced desorption yields. At the CERN Heavy Ion Accelerator (LINAC 3), carbon-coated accelerator-type stainless steel vacuum chambers were tested for desorption using 4.2 Me...

  11. Carbon Superatom Thin Films

    Energy Technology Data Exchange (ETDEWEB)

    Canning, A. [Cray Research, PSE, EPFL, 1015 Lausanne (Switzerland); Canning, A.; Galli, G. [Institut Romand de Recherche Numerique en Physique des Materiaux (IRRMA), IN-Ecublens, 1015 Lausanne (Switzerland); Kim, J. [Department of Physics, The Ohio State University, Columbus, Ohio 43210 (United States)

    1997-06-01

    We report on quantum molecular dynamics simulations of C{sub 28} deposition on a semiconducting surface. Our results show that under certain deposition conditions C{sub 28} {close_quote}s act as building blocks on a nanometer scale to form a thin film of nearly defect-free molecules. The C{sub 28} {close_quote}s behave as carbon superatoms, with the majority of them being threefold or fourfold coordinated, similar to carbon atoms in amorphous systems. The microscopic structure of the deposited film supports recent suggestions about the stability of a new form of carbon, the hyperdiamond solid. {copyright} {ital 1997} {ital The American Physical Society}

  12. Structural characteristics of copper/hydrogenated amorphous carbon composite films prepared by microwave plasma-assisted deposition processes from methane-argon and acetylene-argon gas mixtures

    Energy Technology Data Exchange (ETDEWEB)

    Thiery, F.; Pauleau, Y.; Grob, J.J.; Babonneau, D

    2004-11-01

    Copper/hydrogenated amorphous carbon (Cu/a-C:H) composite films have been deposited on silicon substrates by a hybrid technique combining microwave plasma-assisted chemical vapor deposition and sputter-deposition from methane-argon and acetylene-argon gas mixtures. The major objective of this work was to investigate the effect of the carbon gas precursor on the structural characteristics of Cu/a-C:H composite films deposited at ambient temperature. The major characteristics of CH{sub 4}-argon and C{sub 2}H{sub 2}-argon plasmas were analyzed by Langmuir probe measurements. The composition of films was determined by Rutherford backscattering spectroscopy, energy recoil detection analyses and nuclear reaction analyses. The carbon content in the films was observed to vary in the range 20-77 at.% and 7.5-99 at.% as the CH{sub 4} and C{sub 2}H{sub 2} concentrations in the gas phase increased from 10 to 100%, respectively. The atom number ratio H/C in the films was scattered approximately 0.4 whatever the carbon gas precursor used. The crystallographic structure and the size of copper crystallites incorporated in the a-C were determined by X-ray diffraction techniques. The copper crystallite size decreased from 20 nm in pure copper films to less than 5 nm in Cu/a-C:H films containing more than 40 at.% of carbon. Grazing incidence small angle X-ray scattering measurements were performed to investigate the size distribution and distance of copper crystallites as functions of the deposition parameters. The structural characteristics of copper crystallites were dependent on the hydrocarbon gas precursor used. The crystallite size and the width of the size distribution were homogeneous in films deposited from CH{sub 4}. Copper crystallites with an anisotropic shape were found in films deposited from C{sub 2}H{sub 2}. The major radicals formed in the plasma and condensed on the surface of growing films, namely CH and C{sub 2}H radicals for films produced from CH{sub 4} and C

  13. Dangling bond energetics in carbon nitride and phosphorus carbide thin films with fullerene-like and amorphous structure

    OpenAIRE

    Kostov Gueorguiev, Gueorgui; Broitman, E; Furlan, Andrej; Stafström, Sven; Hultman, Lars

    2009-01-01

    The energy cost for dangling bond formation in Fullerene-like Carbon Nitride (FL-CNx) and Phosphorus carbide (FL-CPx) as well as their amorphous counterparts: a-CNx, a-CPx, and a-C has been calculated within the framework of Density Functional Theory and compared with surface water adsorption measurements. The highest energy cost is found in the FL-CNx ( about 1.37 eV) followed by FL-CPx compounds (0.62-1.04 eV). (C) 2009 Elsevier B. V. All rights reserved. Original Publication:Gueorgui K...

  14. Film adhesion in amorphous silicon solar cells

    Indian Academy of Sciences (India)

    A R M Yusoff; M N Syahrul; K Henkel

    2007-08-01

    A major issue encountered during fabrication of triple junction -Si solar cells on polyimide substrates is the adhesion of the solar cell thin films to the substrates. Here, we present our study of film adhesion in amorphous silicon solar cells made on different polyimide substrates (Kapton VN, Upilex-S and Gouldflex), and the effect of tie coats on film adhesion.

  15. Time-Resolved Spectroscopic Observation of Deposition Processes of Ultrananocrystalline Diamond/Amorphous Carbon Composite Films by Using a Coaxial Arc Plasma Gun

    Science.gov (United States)

    Hanada, Kenji; Yoshitake, Tsuyoshi; Nishiyama, Takashi; Nagayama, Kunihito

    2010-08-01

    The deposition of ultrananocrystalline diamond (UNCD)/amorphous carbon composite films using a coaxial arc plasma gun in vacuum and, for comparison, in a 53.3 Pa hydrogen atmosphere was spectroscopically observed using a high-speed camera equipped with narrow-band-pass filters. UNCD crystallites with diameters of approximately 1.6 nm were formed even in vacuum. These extremely small crystallites imply that the formation is predominantly due to nucleation without the subsequent growth. Even in vacuum, emissions from C+ ions, C atoms, and C2 dimers lasted for approximately 100 µs, although the emission lifetimes of these species are generally 10 ns. We consider that the nucleation is due to the supersaturated environment containing excited carbon species with large number densities.

  16. Biological characteristics of the MG-63 human osteosarcoma cells on composite tantalum carbide/amorphous carbon films.

    Directory of Open Access Journals (Sweden)

    Yin-Yu Chang

    Full Text Available Tantalum (Ta is a promising metal for biomedical implants or implant coating for orthopedic and dental applications because of its excellent corrosion resistance, fracture toughness, and biocompatibility. This study synthesizes biocompatible tantalum carbide (TaC and TaC/amorphous carbon (a-C coatings with different carbon contents by using a twin-gun magnetron sputtering system to improve their biological properties and explore potential surgical implant or device applications. The carbon content in the deposited coatings was regulated by controlling the magnetron power ratio of the pure graphite and Ta cathodes. The deposited TaC and TaC/a-C coatings exhibited better cell viability of human osteosarcoma cell line MG-63 than the uncoated Ti and Ta-coated samples. Inverted optical and confocal imaging was used to demonstrate the cell adhesion, distribution, and proliferation of each sample at different time points during the whole culture period. The results show that the TaC/a-C coating, which contained two metastable phases (TaC and a-C, was more biocompatible with MG-63 cells compared to the pure Ta coating. This suggests that the TaC/a-C coatings exhibit a better biocompatible performance for MG-63 cells, and they may improve implant osseointegration in clinics.

  17. Dynamic optical properties of amorphous diamond-like carbon nanocomposite films doped with Cu and Ag nanoparticles

    Science.gov (United States)

    Tamulevičius, Tomas; Peckus, Domantas; Tamulevičiene, Asta; Vasiliauskas, Andrius; Čiegis, Arvydas; Meškinis, Šarūnas; Tamulevičius, Sigitas

    2014-09-01

    The investigation of relaxation processes in noble metal nanoparticles upon ultrafast excitations by femtosecond laser pulses is useful to understand the origin and the enhancement mechanism of the nonlinear optical properties for metaldielectric nanocomposites. In the current work we analyze diamond like carbon (DLC) film based copper and silver nanocomposites with different metal content synthesized employing unbalanced magnetron sputtering of metal targets with argon ions in acetylene gas atmosphere. Surface morphology and nanoparticle sizes were analyzed employing scanning electron and atomic force microscopy. Optical properties of the nanocomposite films were analyzed employing UV-VIS-NIR spectrometry. Transient absorption measurements were obtained employing Yb:KGW femtosecond laser spectroscopic system (HARPIA, Light Conversion Ltd.). Energy relaxation dynamics in Cu nanoparticles showed some significant differences from Ag nanoparticles. The increase of excitation intensity hasn't show additional nonlinear effects for the excited state relaxation dynamics for both kinds of samples.

  18. Chemical bonding structural analysis of nitrogen-doped ultrananocrystalline diamond/hydrogenated amorphous carbon composite films prepared by coaxial arc plasma deposition

    Science.gov (United States)

    Gima, Hiroki; Zkria, Abdelrahman; Katamune, Yūki; Ohtani, Ryota; Koizumi, Satoshi; Yoshitake, Tsuyoshi

    2017-01-01

    Nitrogen-doped ultra-nanocrystalline diamond/hydrogenated amorphous carbon composite films prepared in hydrogen and nitrogen mixed-gas atmospheres by coaxial arc plasma deposition with graphite targets were studied electrically and chemical-bonding-structurally. The electrical conductivity was increased by nitrogen doping, accompanied by the production of n-type conduction. From X-ray photoemission, near-edge X-ray absorption fine-structure, hydrogen forward-scattering, and Fourier transform infrared spectral results, it is expected that hydrogen atoms that terminate diamond grain boundaries will be partially replaced by nitrogen atoms and, consequently, π C–N and C=N bonds that easily generate free electrons will be formed at grain boundaries.

  19. Growth, characterisation and electronic applications of amorphous hydrogenated carbon

    CERN Document Server

    Paul, S

    2000-01-01

    temperature on GaAs, has been studied and concluded to be satisfactory on the basis of good adherence and low leakage currents. Such a structure was motivated by the applicability in Metal Insulator Semiconductor Field Effect Transistors (MISFET). My thesis proposes solutions to a number of riddles associated with the material, hydrogenated amorphous carbon, (a-C:H). This material has lately generated interest in the electronic engineering community, owing to some remarkable properties. The characterisation of amorphous carbon films, grown by radio frequency plasma enhanced chemical vapour deposition has been reported. The coexistence of multiple phases in the same a-C:H film manifests itself in the inconsistent electrical behaviour of different parts of the film, thus rendering it difficult to predict the nature of films. For the first time, in this thesis, a reliable prediction of Schottky contact formation on a-C:H films is reported. A novel and simple development on a Scanning Electron Microscope, configu...

  20. Anomalous hopping conduction in nanocrystalline/amorphous composites and amorphous semiconductor thin films

    Science.gov (United States)

    Kakalios, James; Bodurtha, Kent

    Composite nanostructured materials consisting of nanocrystals (nc) embedded within a thin film amorphous matrix can exhibit novel opto-electronic properties. Composite films are synthesized in a dual-chamber co-deposition PECVD system capable of producing nanocrystals of material A and embedding then within a thin film matrix of material B. Electronic conduction in composite thin films of hydrogenated amorphous silicon (a-Si:H) containing nc-germanium or nc-silicon inclusions, as well as in undoped a-Si:H, does not follow an Arrhenius temperature dependence, but rather is better described by an anomalous hopping expression (exp[-(To/T)3/4) , as determined from the ``reduced activation energy'' proposed by Zabrodskii and Shlimak. This temperature dependence has been observed in other thin film resistive materials, such as ultra-thin disordered films of Ag, Bi, Pb and Pd; carbon-black polymer composites; and weakly coupled Au and ZnO quantum dot arrays. There is presently no accepted theoretical understanding of this expression. The concept of a mobility edge, accepted for over four decades, appears to not be necessary to account for charge transport in amorphous semiconductors. Supported by NSF-DMR and the Minnesota Nano Center.

  1. Synthesis of amorphous carbon nitride by ion implantation

    Institute of Scientific and Technical Information of China (English)

    ChenZ.; OlofinjanaA.; BellJ

    2001-01-01

    N2+ were implanted into diamondlike carbon (DLC) films in an attempt to synthesizeamorphous carbon nitride. The DLC films were previously deposited on steel substrate by using anion beam sputtering deposition (IBSD) where a single Kaufman type ion gun with argon sourcewas used to sputter a graphite target and simultaneously bombard the growing film. Parallel to theion implantation route, amorphous carbon nitride films were also synthesized by directly using thereactive ion beam sputtering deposition (RIBSD) with nitrogen source to incorporate nitrogen intothe film. The structure and properties of the films were determined by using Raman spectroscopy,XPS and nano-indentation. The implantation of N2+ into a-C films offers a higher hardness thanthat directly synthesized by RIBSD, probably through an increase in sp3/sp2 ratio and in the pro-portion of nitrogen atoms chemically bonding to carbon atoms. The results show that althoughthere are differences in film composition, structure and properties between these two processes,both methods can be used for synthesis of nitrogen-containing amorphous DLC thin films whichsignificantly modify the substrate surface.

  2. Amorphous silicon for thin-film transistors

    NARCIS (Netherlands)

    Schropp, Rudolf Emmanuel Isidore

    1987-01-01

    Hydrogenated amorphous silicon (a-Si:H) has considerable potential as a semiconducting material for large-area photoelectric and photovoltaic applications. Moreover, a-Si:H thin-film transistors (TFT’s) are very well suited as switching devices in addressable liquid crystal display panels and addres

  3. On the crystallization of amorphous germanium films

    Science.gov (United States)

    Edelman, F.; Komem, Y.; Bendayan, M.; Beserman, R.

    1993-06-01

    The incubation time for crystallization of amorphous Ge (a-Ge) films, deposited by e-gun, was studied as a function of temperature between 150 and 500°C by means of both in situ transmission electron microscopy and Raman scattering spectroscopy. The temperature dependence of t0 follows an Arrhenius curve with an activation energy of 2.0 eV for free-sustained a-Ge films. In the case where the a-Ge films were on Si 3N 4 substrate, the activation energy of the incubation process was 1.3 eV.

  4. Large-scale and patternable graphene: direct transformation of amorphous carbon film into graphene/graphite on insulators via Cu mediation engineering and its application to all-carbon based devices.

    Science.gov (United States)

    Chen, Yu-Ze; Medina, Henry; Lin, Hung-Chiao; Tsai, Hung-Wei; Su, Teng-Yu; Chueh, Yu-Lun

    2015-02-07

    Chemical vapour deposition of graphene was the preferred way to synthesize graphene for multiple applications. However, several problems related to transfer processes, such as wrinkles, cleanness and scratches, have limited its application at the industrial scale. Intense research was triggered into developing alternative synthesis methods to directly deposit graphene on insulators at low cost with high uniformity and large area. In this work, we demonstrate a new concept to directly achieve growth of graphene on non-metal substrates. By exposing an amorphous carbon (a-C) film in Cu gaseous molecules after annealing at 850 °C, the carbon (a-C) film surprisingly undergoes a noticeable transformation to crystalline graphene. Furthermore, the thickness of graphene could be controlled, depending on the thickness of the pre-deposited a-C film. The transformation mechanism was investigated and explained in detail. This approach enables development of a one-step process to fabricate electrical devices made of all carbon material, highlighting the uniqueness of the novel approach for developing graphene electronic devices. Interestingly, the carbon electrodes made directly on the graphene layer by our approach offer a good ohmic contact compared with the Schottky barriers usually observed on graphene devices using metals as electrodes.

  5. Amorphous Carbon-Boron Nitride Nanotube Hybrids

    Science.gov (United States)

    Kim, Jae Woo (Inventor); Siochi, Emilie J. (Inventor); Wise, Kristopher E. (Inventor); Lin, Yi (Inventor); Connell, John (Inventor)

    2016-01-01

    A method for joining or repairing boron nitride nanotubes (BNNTs). In joining BNNTs, the nanotube structure is modified with amorphous carbon deposited by controlled electron beam irradiation to form well bonded hybrid a-C/BNNT structures. In repairing BNNTs, the damaged site of the nanotube structure is modified with amorphous carbon deposited by controlled electron beam irradiation to form well bonded hybrid a-C/BNNT structures at the damage site.

  6. Revealing the 1 nm/s Extensibility of Nanoscale Amorphous Carbon in a Scanning Electron Microscope

    DEFF Research Database (Denmark)

    Zhang, Wei

    2013-01-01

    In an ultra-high vacuum scanning electron microscope, the edged branches of amorphous carbon film (∼10 nm thickness) can be continuously extended with an eye-identifying speed (on the order of ∼1 nm/s) under electron beam. Such unusual mobility of amorphous carbon may be associated with deformation...

  7. Damage-free back channel wet-etch process in amorphous indium-zinc-oxide thin-film transistors using a carbon-nanofilm barrier layer.

    Science.gov (United States)

    Luo, Dongxiang; Zhao, Mingjie; Xu, Miao; Li, Min; Chen, Zikai; Wang, Lang; Zou, Jianhua; Tao, Hong; Wang, Lei; Peng, Junbiao

    2014-07-23

    Amorphous indium-zinc-oxide thin film transistors (IZO-TFTs) with damage-free back channel wet-etch (BCE) process were investigated. A carbon (C) nanofilm was inserted into the interface between IZO layer and source/drain (S/D) electrodes as a barrier layer. Transmittance electron microscope images revealed that the 3 nm-thick C nanofilm exhibited a good corrosion resistance to a commonly used H3PO4-based etchant and could be easily eliminated. The TFT device with a 3 nm-thick C barrier layer showed a saturated field effect mobility of 14.4 cm(2) V(-1) s(-1), a subthreshold swing of 0.21 V/decade, an on-to-off current ratio of 8.3 × 10(10), and a threshold voltage of 2.0 V. The favorable electrical performance of this kind of IZO-TFTs was due to the protection of the inserted C to IZO layer in the back-channel-etch process. Moreover, the low contact resistance of the devices was proved to be due to the graphitization of the C nanofilms after annealing. In addition, the hysteresis and thermal stress testing confirmed that the usage of C barrier nanofilms is an effective method to fabricate the damage-free BCE-type devices with high reliability.

  8. Amorphous molybdenum silicon superconducting thin films

    Directory of Open Access Journals (Sweden)

    D. Bosworth

    2015-08-01

    Full Text Available Amorphous superconductors have become attractive candidate materials for superconducting nanowire single-photon detectors due to their ease of growth, homogeneity and competitive superconducting properties. To date the majority of devices have been fabricated using WxSi1−x, though other amorphous superconductors such as molybdenum silicide (MoxSi1−x offer increased transition temperature. This study focuses on the properties of MoSi thin films grown by magnetron sputtering. We examine how the composition and growth conditions affect film properties. For 100 nm film thickness, we report that the superconducting transition temperature (Tc reaches a maximum of 7.6 K at a composition of Mo83Si17. The transition temperature and amorphous character can be improved by cooling of the substrate during growth which inhibits formation of a crystalline phase. X-ray diffraction and transmission electron microscopy studies confirm the absence of long range order. We observe that for a range of 6 common substrates (silicon, thermally oxidized silicon, R- and C-plane sapphire, x-plane lithium niobate and quartz, there is no variation in superconducting transition temperature, making MoSi an excellent candidate material for SNSPDs.

  9. Apatite Formation from Amorphous Calcium Phosphate and Mixed Amorphous Calcium Phosphate/Amorphous Calcium Carbonate.

    Science.gov (United States)

    Ibsen, Casper J S; Chernyshov, Dmitry; Birkedal, Henrik

    2016-08-22

    Crystallization from amorphous phases is an emerging pathway for making advanced materials. Biology has made use of amorphous precursor phases for eons and used them to produce structures with remarkable properties. Herein, we show how the design of the amorphous phase greatly influences the nanocrystals formed therefrom. We investigate the transformation of mixed amorphous calcium phosphate/amorphous calcium carbonate phases into bone-like nanocrystalline apatite using in situ synchrotron X-ray diffraction and IR spectroscopy. The speciation of phosphate was controlled by pH to favor HPO4 (2-) . In a carbonate free system, the reaction produces anisotropic apatite crystallites with large aspect ratios. The first formed crystallites are highly calcium deficient and hydrogen phosphate rich, consistent with thin octacalcium phosphate (OCP)-like needles. During growth, the crystallites become increasingly stoichiometric, which indicates that the crystallites grow through addition of near-stoichiometric apatite to the OCP-like initial crystals through a process that involves either crystallite fusion/aggregation or Ostwald ripening. The mixed amorphous phases were found to be more stable against phase transformations, hence, the crystallization was inhibited. The resulting crystallites were smaller and less anisotropic. This is rationalized by the idea that a local phosphate-depletion zone formed around the growing crystal until it was surrounded by amorphous calcium carbonate, which stopped the crystallization.

  10. Tunable plasticity in amorphous silicon carbide films.

    Science.gov (United States)

    Matsuda, Yusuke; Kim, Namjun; King, Sean W; Bielefeld, Jeff; Stebbins, Jonathan F; Dauskardt, Reinhold H

    2013-08-28

    Plasticity plays a crucial role in the mechanical behavior of engineering materials. For instance, energy dissipation during plastic deformation is vital to the sufficient fracture resistance of engineering materials. Thus, the lack of plasticity in brittle hybrid organic-inorganic glasses (hybrid glasses) often results in a low fracture resistance and has been a significant challenge for their integration and applications. Here, we demonstrate that hydrogenated amorphous silicon carbide films, a class of hybrid glasses, can exhibit a plasticity that is even tunable by controlling their molecular structure and thereby leads to an increased and adjustable fracture resistance in the films. We decouple the plasticity contribution from the fracture resistance of the films by estimating the "work-of-fracture" using a mean-field approach, which provides some insight into a potential connection between the onset of plasticity in the films and the well-known rigidity percolation threshold.

  11. Influence of source and drain contacts on the properties of indium-gallium-zinc-oxide thin-film transistors based on amorphous carbon nanofilm as barrier layer.

    Science.gov (United States)

    Luo, Dongxiang; Xu, Hua; Zhao, Mingjie; Li, Min; Xu, Miao; Zou, Jianhua; Tao, Hong; Wang, Lei; Peng, Junbiao

    2015-02-18

    Amorphous indium-gallium-zinc-oxide thin film transistors (α-IGZO TFTs) with damage-free back channel wet-etch (BCE) process were achieved by introducing a carbon nanofilm as a barrier layer. We investigate the effects of different source-and-drain (S/D) materials on TFT performance. We find the TFT with Ti/C S/D electrodes exhibits a superior performance with higher output current, lower threshold voltage, and higher effective electron mobility compared to that of Mo/C S/D electrodes. Transmittance electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS) are employed to analysis the interfacial interaction between S/D metal/C/α-IGZO layers. The results indicate that the better performance of TFTs with Ti/C electrodes should be attributed to the formations of Ti-C and Ti-O at the Ti/C-contact regions, which lead to a lower contact resistance, whereas Mo film is relatively stable and does not react easily with C nanofilm, resulting in a nonohmic contact behavior between Mo/C and α-IGZO layer. However, both kinds of α-IGZO TFTs show good stability under thermal bias stress, indicating that the inserted C nanofilms could avoid the impact on the α-IGZO channel regions during S/D electrodes formation. Finally, we successfully fabricated a high-definition active-matrix organic lighting emitting diode prototype driven by α-IGZO TFTs with Ti/C electrodes in a pilot line.

  12. Amorphous microcellular polytetrafluoroethylene foam film

    Science.gov (United States)

    Tang, Chongzheng

    1991-11-01

    We report herein the preparation of novel low-density ultramicrocellular fluorocarbon foams and their application. These fluorocarbon foams are of interest for the biochemistry arena in numerous applications including foodstuff, pharmacy, wine making, beer brewery, fermentation medical laboratory, and other processing factories. All of those require good quality processing programs in which, after eliminating bacterium and virus, compressed air is needed. Ordinarily, compressed air contains bacterium and virus, its size is 0.01 - 2 micrometers fluorocarbon foam films. Having average porous diameter 0.04 - 0.1 micrometers , these are stable to high temperature (280 degree(s)C) and chemical environments, and generally have good engineering and mechanical properties (e.g., low coefficient of thermal expansion, high modulus, and good dimensional stability). Our new process for preparing low density fluorocarbon foams provides materials with unique properties. As such, they offer the possibility for being superior to earlier materials for a number of the filter applications mentioned.

  13. Growth Induced Magnetic Anisotropy in Crystalline and Amorphous Thin Films

    Energy Technology Data Exchange (ETDEWEB)

    Hellman, Frances

    1998-10-03

    OAK B204 Growth Induced Magnetic Anisotropy in Crystalline and Amorphous Thin Films. The work in the past 6 months has involved three areas of magnetic thin films: (1) amorphous rare earth-transition metal alloys, (2) epitaxial Co-Pt and hTi-Pt alloy thin films, and (3) collaborative work on heat capacity measurements of magnetic thin films, including nanoparticles and CMR materials.

  14. POROUS AMORPHOUS FLUOROPOLYMER FILMS WITH ULTRALOW DIELECTRIC CONSTANT

    Institute of Scientific and Technical Information of China (English)

    DING SHI-JIN; WANG PENG-FEI; ZHANG WEI; WANG JI-TAO; WEI WILLIAM LEE; ZHANG YE-WEN; KIA ZHONG-FU

    2000-01-01

    With the development of ultralarge scale integrated circuit, new interlayer dielectrics with low dielectric constant for multilevel interconnections are required, instead of conventional SiO2 films. For the sake of seeking perfect dielectrics, amorphous fluoropolymer (AF) thin film with a thickness of about 0.9μm has been prepared by spin-coating method, following the principle of phase separation. By capacitance-voltage (C-V) measurements the dielectric constant of the thin film is equal to 1.57 at 1 MHz, which is attributed to numerous pores contained in the film matrix. X-ray photoelectron spectroscopy (XPS) spectra show that after annealing, about 71% CFa groups in the AF film have decomposed into CF2, CF, etc. This leads to the increase of CF2 groups by three times and CF groups by 8% in the AF film. In a word, compared with the film without being annealed, about 25% carbon, 7% fluorine and 12% oxygen atoms will be lost after annealing at 400℃ for 30min.

  15. Pyrolyzed thin film carbon

    Science.gov (United States)

    Tai, Yu-Chong (Inventor); Liger, Matthieu (Inventor); Harder, Theodore (Inventor); Konishi, Satoshi (Inventor); Miserendino, Scott (Inventor)

    2010-01-01

    A method of making carbon thin films comprises depositing a catalyst on a substrate, depositing a hydrocarbon in contact with the catalyst and pyrolyzing the hydrocarbon. A method of controlling a carbon thin film density comprises etching a cavity into a substrate, depositing a hydrocarbon into the cavity, and pyrolyzing the hydrocarbon while in the cavity to form a carbon thin film. Controlling a carbon thin film density is achieved by changing the volume of the cavity. Methods of making carbon containing patterned structures are also provided. Carbon thin films and carbon containing patterned structures can be used in NEMS, MEMS, liquid chromatography, and sensor devices.

  16. Methane Flow Rate Effects On The Optical Properties of Amorphous Silicon Carbon (a-SiC:H Films Deposited By DC Sputtering Methods

    Directory of Open Access Journals (Sweden)

    Rosari Saleh

    2002-04-01

    Full Text Available We have investigated the refractive index (n and the optical absorption coeffi cient (α from refl ection and transmission measurements on hydrogenated amorphous silicon carbon (a-SiC:H fi lms. The a-SiC:H fi lms were prepared by dc sputtering method using silicon target in argon and methane gas mixtures. The refractive index (n decreases as the methane fl ow rate increase. The optical absorption coeffi cient (α shifts to higher energy with increasing methane fl ow rate. At higher methane fl ow rate, the fi lms tend to be more disorder and have wider optical gap. The relation of the optical properties and the disorder amorphous network with the compositional properties will be discussed.

  17. Recent progress in the synthesis and characterization of amorphous and crystalline carbon nitride coatings

    CERN Document Server

    Widlow, I

    2000-01-01

    This review summarizes our most recent findings in the structure and properties of amorphous and crystalline carbon nitride coatings, synthesized by reactive magnetron sputtering. By careful control of the plasma conditions via proper choice of process parameters such as substrate bias, target power and gas pressure, one can precisely control film structure and properties. With this approach, we were able to produce amorphous carbon nitride films with controlled hardness and surface roughness. In particular, we can synthesize ultrathin (1 nm thick) amorphous carbon nitride films to be sufficiently dense and uniform that they provide adequate corrosion protection for hard disk applications. We demonstrated the strong correlation between ZrN (111) texture and hardness in CN sub x /ZrN superlattice coatings. Raman spectroscopy and near-edge X-ray absorption show the predominance of sp sup 3 -bonded carbon in these superlattice coatings.

  18. Silicon nanocrystals on amorphous silicon carbide alloy thin films: Control of film properties and nanocrystals growth

    Energy Technology Data Exchange (ETDEWEB)

    Barbe, Jeremy, E-mail: jeremy.barbe@hotmail.com [CEA, Liten, 17 rue des Martyrs, 38054 Grenoble Cedex 9 (France); Universite de Toulouse, UPS, INPT, LAPLACE (Laboratoire Plasma et Conversion d' Energie), 118 route de Narbonne, 31062 Toulouse (France); Xie, Ling; Leifer, Klaus [Department of Engineering Sciences, Uppsala University, Box 534, S-751 21 Uppsala (Sweden); Faucherand, Pascal; Morin, Christine; Rapisarda, Dario; De Vito, Eric [CEA, Liten, 17 rue des Martyrs, 38054 Grenoble Cedex 9 (France); Makasheva, Kremena; Despax, Bernard [Universite de Toulouse, UPS, INPT, LAPLACE (Laboratoire Plasma et Conversion d' Energie), 118 route de Narbonne, 31062 Toulouse (France); CNRS, LAPLACE, F-31062 Toulouse (France); Perraud, Simon [CEA, Liten, 17 rue des Martyrs, 38054 Grenoble Cedex 9 (France)

    2012-11-01

    The present study demonstrates the growth of silicon nanocrystals on amorphous silicon carbide alloy thin films. Amorphous silicon carbide films [a-Si{sub 1-x}C{sub x}:H (with x < 0.3)] were obtained by plasma enhanced chemical vapor deposition from a mixture of silane and methane diluted in hydrogen. The effect of varying the precursor gas-flow ratio on the film properties was investigated. In particular, a wide optical band gap (2.3 eV) was reached by using a high methane-to-silane flow ratio during the deposition of the a-Si{sub 1-x}C{sub x}:H layer. The effect of short-time annealing at 700 Degree-Sign C on the composition and properties of the layer was studied by X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy. It was observed that the silicon-to-carbon ratio in the layer remains unchanged after short-time annealing, but the reorganization of the film due to a large dehydrogenation leads to a higher density of SiC bonds. Moreover, the film remains amorphous after the performed short-time annealing. In a second part, it was shown that a high density (1 Multiplication-Sign 10{sup 12} cm{sup -2}) of silicon nanocrystals can be grown by low pressure chemical vapor deposition on a-Si{sub 0.8}C{sub 0.2} surfaces at 700 Degree-Sign C, from silane diluted in hydrogen. The influence of growth time and silane partial pressure on nanocrystals size and density was studied. It was also found that amorphous silicon carbide surfaces enhance silicon nanocrystal nucleation with respect to SiO{sub 2}, due to the differences in surface chemical properties. - Highlights: Black-Right-Pointing-Pointer Silicon nanocrystals (Si-NC) growth on amorphous silicon carbide alloy thin films Black-Right-Pointing-Pointer Plasma deposited amorphous silicon carbide films with well-controlled properties Black-Right-Pointing-Pointer Study on the thermal effect of 700 Degree-Sign C short-time annealing on the layer properties Black-Right-Pointing-Pointer Low pressure

  19. Thin films of hydrogenated amorphous carbon (a-C:H) obtained through chemical vapor deposition assisted by plasma; Peliculas delgadas de carbono amorfo hidrogenado (a-C:H) obtenidas mediante deposito quimico de vapores asistido por plasma

    Energy Technology Data Exchange (ETDEWEB)

    Mejia H, J.A.; Camps C, E.E.; Escobar A, L.; Romero H, S.; Chirino O, S. [ININ, 52045 Ocoyoacac, Estado de Mexico (Mexico); Muhl S, S. [IIM-UNAM, 04510 Mexico D.F. (Mexico)

    2004-07-01

    Films of hydrogenated amorphous carbon (a-C:H) were deposited using one source of microwave plasma with magnetic field (type ECR), using mixtures of H{sub 2}/CH{sub 4} in relationship of 80/20 and 95/05 as precursory gases, with work pressures of 4X10{sup -4} to 6x10{sup -4} Torr and an incident power of the discharge of microwaves with a constant value of 400 W. It was analyzed the influence among the properties of the films, as the deposit rate, the composition and the bonding types, and the deposit conditions, such as the flow rates of the precursory gases and the polarization voltage of the sample holders. (Author)

  20. Growth induced magnetic anisotropy in crystalline and amorphous thin films

    Energy Technology Data Exchange (ETDEWEB)

    Hellman, F.

    1998-07-20

    The work in the past 6 months has involved three areas of magnetic thin films: (1) amorphous rare earth-transition metal alloys, (2) epitaxial Co-Pt and Ni-Pt alloy thin films, and (3) collaborative work on heat capacity measurements of magnetic thin films, including nanoparticles and CMR materials. A brief summary of work done in each area is given.

  1. Microstructural analyses of amorphic diamond, i-C, and amorphous carbon

    DEFF Research Database (Denmark)

    Collins, C. B.; Davanloo, F.; Jander, D.R.;

    1992-01-01

    Recent experiments have identified the microstructure of amorphic diamond with a model of packed nodules of amorphous diamond expected theoretically. However, this success has left in doubt the relationship of amorphic diamond to other noncrystalline forms of carbon. This work reports...... the comparative examinations of the microstructures of samples of amorphic diamond, i-C, and amorphous carbon. Four distinct morphologies were found that correlated closely with the energy densities used in preparing the different materials. Journal of Applied Physics is copyrighted by The American Institute...

  2. Raman and ellipsometric characterization of hydrogenated amorphous silicon thin films

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    Hydrogenated amorphous silicon (a-Si:H) thin films were deposited by plasma-enhanced vapor deposition (PECVD) at different silane temperatures (Tg) before glow-discharge. The effect of Tg on the amorphous network and optoelectronic properties of the films has been investigated by Raman scattering spectra, ellipsometric transmittance spectra, and dark conductivity measurement, respectively. The results show that the increase in Tg leads to an improved ordering of amorphous network on the short and intermediate scales and an increase of both refractive index and absorption coefficient in a-Si:H thin films. It is indicated that the dark conductivity increases by two orders of magnitude when Tg is raised from room temperature (RT) to 433 K. The continuous ordering of amorphous network of a-Si:H thin films deposited at a higher Tg is the main cause for the increase of dark conductivity.

  3. Protolytic carbon film technology

    Energy Technology Data Exchange (ETDEWEB)

    Renschler, C.L.; White, C.A.

    1996-04-01

    This paper presents a technique for the deposition of polyacrylonitrile (PAN) on virtually any surface allowing carbon film formation with only the caveat that the substrate must withstand carbonization temperatures of at least 600 degrees centigrade. The influence of processing conditions upon the structure and properties of the carbonized film is discussed. Electrical conductivity, microstructure, and morphology control are also described.

  4. Electrochromic study on amorphous tungsten oxide films by sputtering

    Energy Technology Data Exchange (ETDEWEB)

    Li, Chuan, E-mail: cli10@yahoo.com [Department of Biomedical Engineering, National Yang Ming University, Taipei 11221, Taiwan (China); Department of Mechanical Engineering, National Central University, Jhongli, Taoyuan 32001, Taiwan (China); Hsieh, J.H. [Department of Materials Engineering, Ming Chi University of Technology, Taishan, Taipei 24301, Taiwan (China); Hung, Ming-Tsung [Department of Mechanical Engineering, National Central University, Jhongli, Taoyuan 32001, Taiwan (China); Huang, B.Q. [Department of Biomedical Engineering, National Yang Ming University, Taipei 11221, Taiwan (China)

    2015-07-31

    Tungsten oxide films under different oxygen flow rates are deposited by DC sputtering. The voltage change at target and analyses for the deposited films by X-ray diffraction, scanning electronic microscope, X-ray photoelectron spectroscopy and ultraviolet–visible-near infrared spectroscopy consistently indicate that low oxygen flow rate (5 sccm) only creates metal-rich tungsten oxide films, while higher oxygen flow rate (10–20 sccm) assures the deposition of amorphous WO{sub 3} films. To explore the electrochromic function of deposited WO{sub 3} films, we use electrochemical tests to perform the insertion of lithium ions and electrons into films. The WO{sub 3} films switch between color and bleach states effectively by both potentiostat and cyclic voltammetry. Quantitative evaluation on electrochemical tests indicates that WO{sub 3} film with composition close to its stoichiometry is an optimal choice for electrochromic function. - Highlights: • Amorphous WO{sub 3} films are deposited by DC sputtering under different O{sub 2} flow rates. • Higher oxygen flow rate (> 10 sccm) assures the deposition of amorphous WO{sub 3} films. • Both potentiostat and cyclic voltammetry make WO{sub 3} films switch its color. • An optimal electrochromic WO{sub 3} is to make films close to its stoichiometry.

  5. Molecular simulation of freestanding amorphous nickel thin films

    Energy Technology Data Exchange (ETDEWEB)

    Dong, T.Q. [Université Paris-Est, Laboratoire Modélisation et Simulation Multi Echelle, UMR 8208 CNRS, 5 Boulevard Descartes, 77454 Marne-la-Vallée, Cedex 2 (France); Hoang, V.V., E-mail: vvhoang2002@yahoo.com [Department of Physics, Institute of Technology, National University of Ho Chi Minh City, 268 Ly Thuong Kiet Street, District 10, Ho Chi Minh City (Viet Nam); Lauriat, G. [Université Paris-Est, Laboratoire Modélisation et Simulation Multi Echelle, UMR 8208 CNRS, 5 Boulevard Descartes, 77454 Marne-la-Vallée, Cedex 2 (France)

    2013-10-31

    Size effects on glass formation in freestanding Ni thin films have been studied via molecular dynamics simulation with the n-body Gupta interatomic potential. Atomic mechanism of glass formation in the films is determined via analysis of the spatio-temporal arrangements of solid-like atoms occurred upon cooling from the melt. Solid-like atoms are detected via the Lindemann ratio. We find that solid-like atoms initiate and grow mainly in the interior of the film and grow outward. Their number increases with decreasing temperature and at a glass transition temperature they dominate in the system to form a relatively rigid glassy state of a thin film shape. We find the existence of a mobile surface layer in both liquid and glassy states which can play an important role in various surface properties of amorphous Ni thin films. We find that glass formation is size independent for models containing 4000 to 108,000 atoms. Moreover, structure of amorphous Ni thin films has been studied in details via coordination number, Honeycutt–Andersen analysis, and density profile which reveal that amorphous thin films exhibit two different parts: interior and surface layer. The former exhibits almost the same structure like that found for the bulk while the latter behaves a more porous structure containing a large amount of undercoordinated sites which are the origin of various surface behaviors of the amorphous Ni or Ni-based thin films found in practice. - Highlights: • Glass formation is analyzed via spatio-temporal arrangements of solid-like atoms. • Amorphous Ni thin film exhibits two different parts: surface and interior. • Mobile surface layer enhances various surface properties of the amorphous Ni thin films. • Undercoordinated sites play an important role in various surface activities.

  6. A new carbon structure in annealed film coatings of the carbon-lead system

    Science.gov (United States)

    Volodin, V. N.; Tuleushev, Yu. Zh.; Zhakanbaev, E. A.; Tsai, K. V.; Rofman, O. V.

    2017-01-01

    Carbon-lead solid solutions coexisting with amorphous carbon have been obtained for the first time in a film coating deposited by ion-plasma sputtering. During subsequent vacuum annealing of carbon-lead films containing more than 68.5 at % Pb, this element almost completely evaporates to leave an amorphous carbon coating on a substrate. During annealing at 1100°C, this amorphous carbon crystallizes into a new hexagonal lattice with unit cell parameters a = 0.7603 nm and c = 0.8168 nm. Characteristic X-ray diffraction data for the identification of this phase are determined.

  7. Amorphous carbon interlayers for gold on elastomer stretchable conductors

    Science.gov (United States)

    Manzoor, M. U.; Tuinea-Bobe, C. L.; McKavanagh, F.; Byrne, C. P.; Dixon, D.; Maguire, P. D.; Lemoine, P.

    2011-06-01

    Gold on polydimethylsiloxane (PDMS) stretchable conductors were prepared using a novel approach by interlacing an hydrogenated amorphous carbon (a-C : H) layer between the deposited metal layer and the elastomer. AFM analysis of the a-C : H film surface before gold deposition shows nanoscale buckling, the corresponding increase in specific surface area corresponds to a strain compensation for the first 4-6% of bi-axial tensile loading. Without this interlayer, the deposited gold films show much smaller and uni-directional ripples as well as more cracks and delaminations. With a-C : H interlayer, the initial electrical resistivity of the metal film decreases markedly (280-fold decrease to 8 × 10-6 Ω cm). This is not due to conduction within the carbon interlayer; both a-C : H/PDMS and PDMS substrates are electrically insulating. Upon cyclic tensile loading, both films become more resistive, but return to their initial state after 20 tensile cycles up to 60% strain. Profiling experiments using secondary ion mass spectroscopy and x-ray photoelectron spectroscopy indicate that the a-C : H layer intermixes with the PDMS, resulting in a graded layer of decreasing stiffness. We believe that both this graded layer and the surface buckling contribute to the observed improvement in the electrical performance of these stretchable conductors.

  8. Blood-compatibility of La2O3 Doped Amorphous Carbon Film%氧化镧掺杂非晶碳薄膜的血液相容性

    Institute of Scientific and Technical Information of China (English)

    张麟; 陈弟虎; 于凤梅; 黄展云; 潘仕荣

    2009-01-01

    La2O3doped amorphous carbon(a-C) films were deposited on silicon substrates using a Radio-Frequency magnetron sputtering. The effect of doped rare earth on the microstructure,composition, surface morphology and hydrophilicity of a-C films were studied using Raman spectra and XPS, respectively. Results show that rare earth addition has a suppressive effect on the ratio of sp3-bond to sp2- bond in the a-C films and the hydrophobicity of rare earth doped a-C films is increased. The observation of platelet adhesion shows that the anti-cruor of a-C films can be improved by rare earth doped and the sample added appropriate rare earth shows the best blood compatibility. The mechanism of haemocompatibility of a-C films doped rare earth is discussed.%采用射频磁控溅射方法制备了氧化镧掺杂的非晶碳薄膜.利用拉曼光谱,光电子能谱等方法, 研究了氧化镧掺杂对非晶碳薄膜的微结构、成分、形貌及亲水性的影响.结果表明:在非晶碳薄膜中掺入氧化镧后,薄膜中sp3/sp2的比率发生显著变化,薄膜的疏水性明显提高.血小板粘附实验表明,掺杂氧化镧有利于提高非晶碳薄膜的抗凝血性能,适当的掺杂量能使薄膜的血液相容性得到优化.并分析了氧化镧对材料的血液相容性能的影响机制.

  9. Structure-property relations in amorphous carbon for photovoltaics

    Energy Technology Data Exchange (ETDEWEB)

    Risplendi, Francesca; Cicero, Giancarlo [Dipartimento di Scienza Applicata e Tecnologia, Politecnico di Torino, 10129 Torino (Italy); Bernardi, Marco [Department of Physics, University of California, Berkeley, California 94720 (United States); Grossman, Jeffrey C., E-mail: jcg@mit.edu [Department of Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States)

    2014-07-28

    Carbon is emerging as a material with great potential for photovoltaics (PV). However, the amorphous form (a-C) has not been studied in detail as a PV material, even though it holds similarities with amorphous Silicon (a-Si) that is widely employed in efficient solar cells. In this work, we correlate the structure, bonding, stoichiometry, and hydrogen content of a-C with properties linked to PV performance such as the electronic structure and optical absorption. We employ first-principles molecular dynamics and density functional theory calculations to generate and analyze a set of a-C structures with a range of densities and hydrogen concentrations. We demonstrate that optical and electronic properties of interest in PV can be widely tuned by varying the density and hydrogen content. For example, sunlight absorption in a-C films can significantly exceed that of a same thickness of a-Si for a range of densities and H contents in a-C. Our results highlight promising features of a-C as the active layer material of thin-film solar cells.

  10. Chemical vapor deposition of amorphous ruthenium-phosphorus alloy films

    Energy Technology Data Exchange (ETDEWEB)

    Shin Jinhong [Texas Materials Institute, University of Texas at Austin, Austin, TX 78750 (United States); Waheed, Abdul [Department of Chemistry and Biochemistry, University of Texas at Austin, Austin, TX 78712 (United States); Winkenwerder, Wyatt A. [Department of Chemical Engineering, University of Texas at Austin, Austin, TX 78712 (United States); Kim, Hyun-Woo [Department of Chemical Engineering, University of Texas at Austin, Austin, TX 78712 (United States); Agapiou, Kyriacos [Department of Chemistry and Biochemistry, University of Texas at Austin, Austin, TX 78712 (United States); Jones, Richard A. [Department of Chemistry and Biochemistry, University of Texas at Austin, Austin, TX 78712 (United States); Hwang, Gyeong S. [Department of Chemical Engineering, University of Texas at Austin, Austin, TX 78712 (United States); Ekerdt, John G. [Department of Chemical Engineering, University of Texas at Austin, Austin, TX 78712 (United States)]. E-mail: ekerdt@che.utexas.edu

    2007-05-07

    Chemical vapor deposition growth of amorphous ruthenium-phosphorus films on SiO{sub 2} containing {approx} 15% phosphorus is reported. cis-Ruthenium(II)dihydridotetrakis-(trimethylphosphine), cis-RuH{sub 2}(PMe{sub 3}){sub 4} (Me = CH{sub 3}) was used at growth temperatures ranging from 525 to 575 K. Both Ru and P are zero-valent. The films are metastable, becoming increasingly more polycrystalline upon annealing to 775 and 975 K. Surface studies illustrate that demethylation is quite efficient near 560 K. Precursor adsorption at 135 K or 210 K and heating reveal the precursor undergoes a complex decomposition process in which the hydride and trimethylphosphine ligands are lost at temperatures as low at 280 K. Phosphorus and its manner of incorporation appear responsible for the amorphous-like character. Molecular dynamics simulations are presented to suggest the local structure in the films and the causes for phosphorus stabilizing the amorphous phase.

  11. Preparation and Thermal Characterization of Diamond-Like Carbon Films

    Institute of Scientific and Technical Information of China (English)

    BAI Su-Yuan; TANG Zhen-An; HUANG Zheng-Xing; Yu Jun; WANG Jing; LIU Gui-Chang

    2009-01-01

    Diamond-like carbon (DLC) films are prepared on silicon substrates by microwave electron cyclotron resonance plasma enhanced chemical vapor deposition. Raman spectroscopy indicates that the films have an amorphous structure and typical characteristics. The topographies of the films are presented by AFM images. Effective thermal conductivities of the films are measured using a nanosecond pulsed photothermal reflectance method. The results show that thermal conductivity is dominated by the microstructure of the films.

  12. Electrodeposition of amorphous gold alloy films

    Energy Technology Data Exchange (ETDEWEB)

    Kato, Masaru; Senda, Kazutaka [Central Research Laboratory, Kanto Chemical Co., Inc., Saitama 340-0003 (Japan); Advanced Research Institute for Science and Engineering, Waseda University, Tokyo 169-8555 (Japan); Musha, Yuta [Department of Applied Chemistry, School of Science and Engineering, Waseda University, Tokyo 169-8555 (Japan); Sasano, Junji [Kagami Memorial Laboratory for Materials Science and Technology, Waseda University, Tokyo 169-0051 (Japan); Okinaka, Yutaka [Advanced Research Institute for Science and Engineering, Waseda University, Tokyo 169-8555 (Japan); Osaka, Tetsuya [Department of Applied Chemistry, School of Science and Engineering, Waseda University, Tokyo 169-8555 (Japan); Kagami Memorial Laboratory for Materials Science and Technology, Waseda University, Tokyo 169-0051 (Japan); Advanced Research Institute for Science and Engineering, Waseda University, Tokyo 169-8555 (Japan)], E-mail: osakatet@waseda.jp

    2007-11-20

    The process for electroplating amorphous gold-nickel-tungsten alloy that we developed previously based on the addition of a gold salt to a known amorphous Ni-W electroplating solution was investigated further using the X-ray diffraction (XRD) method for the purpose of quickly surveying the effects of various experimental variables on the microstructure of the alloy. In this system the gold concentration in the plating bath was found to be critical; i.e., when it is either very low or very high, the deposit becomes crystalline to XRD. The deposit composition varies linearly with the mole ratio of Au to Ni in solution, and the alloy deposit is amorphous to XRD when the atomic ratio of Au/Ni in the deposit is between 0.5 and 1.5. At suitable concentrations of the metal ions, the deposit contains essentially no tungsten. By extending the work on the Au-Ni-W system, an amorphous Au-Co alloy plating process was also developed.

  13. Substrate temperature influence on the trombogenicity in amorphous carbon nitride thin coatings

    Energy Technology Data Exchange (ETDEWEB)

    Galeano-Osorio, D.S.; Vargas, S.; Lopez-Cordoba, L.M.; Ospina, R. [Laboratorio de Fisica del Plasma, Universidad Nacional de Colombia Sede Manizales, Km. 9 via al Magdalena, Manizales (Colombia); Restrepo-Parra, E., E-mail: erestrepopa@unal.edu.co [Laboratorio de Fisica del Plasma, Universidad Nacional de Colombia Sede Manizales, Km. 9 via al Magdalena, Manizales (Colombia); Arango, P.J. [Laboratorio de Fisica del Plasma, Universidad Nacional de Colombia Sede Manizales, Km. 9 via al Magdalena, Manizales (Colombia)

    2010-10-01

    Carbon nitride thin films were obtained through plasma assisted physical vapor deposition technique by pulsed arc, varying the substrate temperature and investigating the influence of this parameter on the films hemocompatibility. For obtaining approaches of blood compatibility, environmental scanning electron microscopy (ESEM) was used in order to study the platelets adherence and their morphology. Moreover, the elemental chemical composition was determined by using energy dispersive spectroscopy (EDS), finding C, N and O. The coatings hemocompatibility was evaluated by in vitro thrombogenicity test, whose results were correlated with the microstructure and roughness of the films obtained. During the films growth process, the substrate temperature was varied, obtaining coatings under different temperatures, room temperature (T{sub room}), 100 deg. C, 150 deg. C and 200 deg. C. Parameters as interelectrodic distance, voltage, work pressure and number of discharges, were remained constant. By EDS, carbon and nitrogen were found in the films. Visible Raman spectroscopy was used, and it revealed an amorphous lattice, with graphitic process as the substrate temperature was increased. However, at a critical temperature of 150 deg. C, this tendency was broken, and the film became more amorphous. This film showed the lowest roughness, 2 {+-} 1 nm. This last characteristic favored the films hemocompatibility. Also, it was demonstrated that the blood compatibility of carbon nitride films obtained were affected by the I{sub D}/I{sub G} or sp{sup 3}/sp{sup 2} ratio and not by the absolute sp{sup 3} or sp{sup 2} concentration.

  14. Influence of dc bias on amorphous carbon deposited by pulse laser ablation

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    Amorphous carbon films were deposited on single-crystalline silicon and K9 glass by pulse laser ablation using different negative substrate bias. Scanning electron microscope (SEM) was used to observe morphology of the surface. Thickness and refractive index of the film deposited on K9 glass were measured by ellipsometry. Micro-hardness of films was measured relatively to single crystal silicon. All films deposited on silicon were analyzed by Raman spectra. All spectra were deconvoluted to three peaks. Line-width ratios varied similarly with bias voltage when the laser energy was kept invariant.

  15. Thermal decomposition of fullerene nanowhiskers protected by amorphous carbon mask

    Science.gov (United States)

    Guo, Hongxuan; Wang, Chengxiang; Miyazawa, Kun’Ichi; Wang, Hongxin; Masuda, Hideki; Fujita, Daisuke

    2016-12-01

    Fullerene nanostructures are well known for their unique morphology, physical and mechanical properties. The thermal stability of fullerene nanostructures, such as their sublimation at high temperature is also very important for studying their structures and applications. In this work, We observed fullerene nanowhiskers (FNWs) in situ with scanning helium ion microscopy (HIM) at elevated temperatures. The FNWs exhibited different stabilities with different thermal histories during the observation. The pristine FNWs were decomposed at the temperatures higher than 300 °C in a vacuum environment. Other FNWs were protected from decomposition with an amorphous carbon (aC) film deposited on the surface. Based on high spacial resolution, aC film with periodic structure was deposited by helium ion beam induced deposition (IBID) on the surface of FNWs. Annealed at the high temperature, the fullerene molecules were selectively sublimated from the FNWs. The periodic structure was formed on the surface of FNWs and observed by HIM. Monte Carlo simulation and Raman characterization proved that the morphology of the FNWs was changed by helium IBID at high temperature. This work provides a new method of fabricating artificial structure on the surface of FNWs with periodic aC film as a mask.

  16. Transparent amorphous zinc oxide thin films for NLO applications

    Science.gov (United States)

    Zawadzka, A.; Płóciennik, P.; Strzelecki, J.; Sahraoui, B.

    2014-11-01

    This review focuses on the growth and optical properties of amorphous zinc oxide (ZnO) thin films. A high quality ZnO films fabricated by dip-coating (sol-gel) method were grown on quartz and glass substrates at temperature equal to 350 K. The amorphous nature of the films was verified by X-ray diffraction. Atomic Force Microscopy was used to evaluate the surface morphology of the films. The optical characteristics of amorphous thin films have been investigated in the spectral range 190-1100 nm. Measurement of the polarized optical properties was shows a high transmissivity (80-99%) and low absorptivity (<5%) in the visible and near infrared regions at different angles of incidence. Linear optical properties were investigated by classic and Time-Resolved Photoluminescence (TRPL) measurements. Photoluminescence spectrum exhibits a strong ultraviolet emission while the visible emission is very weak. An innovative TRPL technique has enabled the measurement of the photoluminescence decay time as a function of temperature. TRPL measurements reveal a multiexponential decay behavior typical for amorphous thin films. Second and third harmonic generation measurements were performed by means of the rotational Maker fringe technique using Nd:YAG laser at 1064 nm in picosecond regime for investigations of the nonlinear optical properties. The obtained values of second and third order nonlinear susceptibilities were found to be high enough for the potential applications in the optical switching devices based on refractive index changes. Presented spectra confirm high structural and optical quality of the investigated zinc oxide thin films.

  17. Amorphous hafnium-indium-zinc oxide semiconductor thin film transistors

    Science.gov (United States)

    Kim, Chang-Jung; Kim, Sangwook; Lee, Je-Hun; Park, Jin-Seong; Kim, Sunil; Park, Jaechul; Lee, Eunha; Lee, Jaechul; Park, Youngsoo; Kim, Joo Han; Shin, Sung Tae; Chung, U.-In

    2009-12-01

    We developed amorphous hafnium-indium-zinc oxide (HIZO) thin films as oxide semiconductors and investigated the films electrically and physically. Adding of hafnium (Hf) element can suppress growing the columnar structure and drastically decrease the carrier concentration and hall mobility in HIZO films. The thin film transistors (TFTs) with amorphous HIZO active channel exhibit good electrical properties with field effect mobility of around 10 cm2/Vs, S of 0.23 V/decade, and high Ion/off ratio of over 108, enough to operate the next electronic devices. In particular, under bias-temperature stress test, the HIZO TFTs with 0.3 mol % (Hf content) showed only 0.46 V shift in threshold voltage, compared with 3.25 V shift in HIZO TFT (0.1 mol %). The Hf ions may play a key role to improve the instability of TFTs due to high oxygen bonding ability. Therefore, the amorphous HIZO semiconductor will be a prominent candidate as an operation device for large area electronic applications.

  18. Pyrolytic transformation from polydihydrosilane to hydrogenated amorphous silicon film

    Energy Technology Data Exchange (ETDEWEB)

    Masuda, Takashi, E-mail: mtakashi@jaist.ac.jp [Japan Science and Technology Agency, ERATO, Shimoda Nano-Liquid Process Project, 2-13 Asahidai, Nomi, Ishikawa, 923-1211 (Japan); Matsuki, Yasuo [Japan Science and Technology Agency, ERATO, Shimoda Nano-Liquid Process Project, 2-13 Asahidai, Nomi, Ishikawa, 923-1211 (Japan); Yokkaichi Research Center, JSR Corporation, 100 Kawajiri-cho, Yokkaichi, Mie, 510-8552 (Japan); Shimoda, Tatsuya [Japan Science and Technology Agency, ERATO, Shimoda Nano-Liquid Process Project, 2-13 Asahidai, Nomi, Ishikawa, 923-1211 (Japan); School of Materials Science, Japan Advanced Institute of Science and Technology, 1-1 Asahidai, Nomi, Ishikawa, 923-1292 (Japan)

    2012-08-31

    The fabrication of thin film silicon devices based on solution processes rather than on conventional vacuum processes is of substantial interest since cost reductions may result. Using a solution process, we coated substrates with polydihydrosilane solution and studied the pyrolytic transformation of the material into hydrogenated amorphous silicon (a-Si:H). From thermal gravimetry and differential thermal analysis data a significant reduction in weight of the material and a construction of Si-Si bonds are concluded for the pyrolysis temperature T{sub p} = 270 to 360 Degree-Sign C. The appearance of amorphous silicon phonon bands in Raman spectra for films prepared at T{sub p} {>=} 330 Degree-Sign C suggests the construction of a three-dimensional amorphous silicon network. Films prepared at T{sub p} {>=} 360 Degree-Sign C exhibit a hydrogen content near 10 at.% and an optical gap near 1.6 eV similar to device-grade vacuum processed a-Si:H. However, the infrared microstructure factor, the spin density, and the photosensitivity require significant improvements. - Highlights: Black-Right-Pointing-Pointer We fabricate hydrogenated amorphous silicon (a-Si:H) films by a solution process. Black-Right-Pointing-Pointer The a-Si:H films are prepared by pyrolytic transformation in polysilane solution. Black-Right-Pointing-Pointer We investigate basic properties in relation to the pyrolysis temperature. Black-Right-Pointing-Pointer Raman spectra, hydrogen content, and optical gap are similar to device-grade a-Si:H. Black-Right-Pointing-Pointer Microstructure factor, spin density, and photoconductivity show poor quality.

  19. Amorphous Dielectric Thin Films with Extremely Low Mechanical Loss

    Directory of Open Access Journals (Sweden)

    Liu X.

    2015-04-01

    Full Text Available The ubiquitous low-energy excitations are one of the universal phenomena of amorphous solids. These excitations dominate the acoustic, dielectric, and thermal properties of structurally disordered solids. One exception has been a type of hydrogenated amorphous silicon (a-Si:H with 1 at.% H. Using low temperature elastic and thermal measurements of electron-beam evap-orated amorphous silicon (a-Si, we show that TLS can be eliminated in this system as the films become denser and more structurally ordered under certain deposition conditions. Our results demonstrate that TLS are not intrinsic to the glassy state but instead reside in low density regions of the amorphous network. This work obviates the role hydrogen was previously thought to play in removing TLS in a-Si:H and favors an ideal four-fold covalently bonded amorphous structure as the cause for the disappearance of TLS. Our result supports the notion that a-Si can be made a “perfect glass” with “crystal-like” properties, thus offering an encouraging opportunity to use it as a simple crystal dielectric alternative in applications, such as in modern quantum devices where TLS are the source of dissipation, decoherence and 1/f noise.

  20. Amorphous Hafnium-Indium-Zinc Oxide Semiconductor Thin Film Transistors

    Directory of Open Access Journals (Sweden)

    Sheng-Po Chang

    2012-01-01

    Full Text Available We reported on the performance and electrical properties of co-sputtering-processed amorphous hafnium-indium-zinc oxide (α-HfIZO thin film transistors (TFTs. Co-sputtering-processed α-HfIZO thin films have shown an amorphous phase in nature. We could modulate the In, Hf, and Zn components by changing the co-sputtering power. Additionally, the chemical composition of α-HfIZO had a significant effect on reliability, hysteresis, field-effect mobility (μFE, carrier concentration, and subthreshold swing (S of the device. Our results indicated that we could successfully and easily fabricate α-HfIZO TFTs with excellent performance by the co-sputtering process. Co-sputtering-processed α-HfIZO TFTs were fabricated with an on/off current ratio of ~106, higher mobility, and a subthreshold slope as steep as 0.55 V/dec.

  1. Elastic properties of amorphous thin films studied by Rayleigh waves

    Energy Technology Data Exchange (ETDEWEB)

    Schwarz, R.B.; Rubin, J.B.

    1993-08-01

    Physical vapor deposition in ultra-high vacuum was used to co-deposit nickel and zirconium onto quartz single crystals and grow amorphous Ni{sub 1-x}Zr{sub x} (0.1 < x < 0.87) thin film. A high-resolution surface acoustic wave technique was developed for in situ measurement of film shear moduli. The modulus has narrow maxima at x = 0. 17, 0.22, 0.43, 0.5, 0.63, and 0.72, reflecting short-range ordering and formation of aggregates in amorphous phase. It is proposed that the aggregates correspond to polytetrahedral atom arrangements limited in size by geometrical frustration.

  2. Crystallization of amorphous Co-Nb-Zr sputtered films

    Energy Technology Data Exchange (ETDEWEB)

    Battezzati, L.; Baricco, M.; Attina, P.

    1986-08-01

    Thermal analysis results obtained with some sputtered Co-Nb-Zr alloys are presented. Microstructural determinations at some stages of the crystallization process were made with transmission electron microscopy and the results given. Crystallization occurs over a wider temperature range than for binary Co/sub 90/Zr/sub 10/ ribbons. Binary Co-Nb films crystallize in the range 750-800K, some 10 degrees below ternary films. The presence of zirconium enhances the stability of the amorphous phase. An explanation of the results is given.

  3. Characterization of amorphous and nanocomposite Nb–Si–C thin films deposited by DC magnetron sputtering

    Energy Technology Data Exchange (ETDEWEB)

    Nedfors, Nils, E-mail: nils.nedfors@kemi.uu.se [Department of Chemistry, The Ångström Laboratory, Uppsala University, SE-751 21 Uppsala (Sweden); Tengstrand, Olof [Thin Film Physics Division, Department of Physics, Chemistry and Biology (IFM), Linköping University, SE-581 83 Linköping (Sweden); Flink, Axel [Thin Film Physics Division, Department of Physics, Chemistry and Biology (IFM), Linköping University, SE-581 83 Linköping (Sweden); Impact Coatings AB, Westmansgatan 29, SE-582-16 Linköping (Sweden); Eklund, Per; Hultman, Lars [Thin Film Physics Division, Department of Physics, Chemistry and Biology (IFM), Linköping University, SE-581 83 Linköping (Sweden); Jansson, Ulf [Department of Chemistry, The Ångström Laboratory, Uppsala University, SE-751 21 Uppsala (Sweden)

    2013-10-31

    Two series of Nb–Si–C thin films of different composition have been deposited using DC magnetron sputtering. In the first series the carbon content was kept at about 55 at.% while the Si/Nb ratio was varied and in the second series the C/Nb ratio was varied instead while the Si content was kept at about 45 at.%. The microstructure is strongly dependent on Si content and Nb–Si–C films containing more than 25 at.% Si exhibit an amorphous structure as determined by X-ray diffraction. Transmission electron microscopy, however, induces crystallisation during analysis, thus obstructing a more detailed analysis of the amorphous structure. X-ray photo-electron spectroscopy suggests that the amorphous films consist of a mixture of chemical bonds such as Nb–Si, Nb–C, and Si–C. The addition of Si results in a hardness decrease from 22 GPa for the binary Nb–C film to 18 – 19 GPa for the Si-containing films, while film resistivity increases from 211 μΩcm to 3215 μΩcm. Comparison with recently published results on DC magnetron sputtered Zr–Si–C films, deposited in the same system using the same Ar-plasma pressure, bias, and a slightly lower substrate temperature (300 °C instead of 350 °C), shows that hardness is primarily dependent on the amount of Si–C bonds rather than type of transition metal. The reduced elastic modulus on the other hand shows a dependency on the type of transition metal for the films. These trends for the mechanical properties suggest that high wear resistant (high H/E and H{sup 3}/E{sup 2} ratio) Me–Si–C films can be achieved by appropriate choice of film composition and transition metal. - Highlights: • Si reduces crystallinity, amorphous structure for films containing > 25 at.% Si. • Electron beam induced crystallization during transmission electron microscopy. • Hardness and resistivity are primarily dependent on the relative amount of C–Si bonds.

  4. Fracture of Carbon Nanotube - Amorphous Carbon Composites: Molecular Modeling

    Science.gov (United States)

    Jensen, Benjamin D.; Wise, Kristopher E.; Odegard, Gregory M.

    2015-01-01

    Carbon nanotubes (CNTs) are promising candidates for use as reinforcements in next generation structural composite materials because of their extremely high specific stiffness and strength. They cannot, however, be viewed as simple replacements for carbon fibers because there are key differences between these materials in areas such as handling, processing, and matrix design. It is impossible to know for certain that CNT composites will represent a significant advance over carbon fiber composites before these various factors have been optimized, which is an extremely costly and time intensive process. This work attempts to place an upper bound on CNT composite mechanical properties by performing molecular dynamics simulations on idealized model systems with a reactive forcefield that permits modeling of both elastic deformations and fracture. Amorphous carbon (AC) was chosen for the matrix material in this work because of its structural simplicity and physical compatibility with the CNT fillers. It is also much stiffer and stronger than typical engineering polymer matrices. Three different arrangements of CNTs in the simulation cell have been investigated: a single-wall nanotube (SWNT) array, a multi-wall nanotube (MWNT) array, and a SWNT bundle system. The SWNT and MWNT array systems are clearly idealizations, but the SWNT bundle system is a step closer to real systems in which individual tubes aggregate into large assemblies. The effect of chemical crosslinking on composite properties is modeled by adding bonds between the CNTs and AC. The balance between weakening the CNTs and improving fiber-matrix load transfer is explored by systematically varying the extent of crosslinking. It is, of course, impossible to capture the full range of deformation and fracture processes that occur in real materials with even the largest atomistic molecular dynamics simulations. With this limitation in mind, the simulation results reported here provide a plausible upper limit on

  5. Crystallization and Transport Properties of Amorphous Cr-Si Thin Film Thermoelectrics

    Science.gov (United States)

    Novikov, S. V.; Burkov, A. T.; Schumann, J.

    2014-06-01

    We studied the thermoelectric properties, crystallization, and stability of amorphous and nanocrystalline states in Cr-Si composite films. Amorphous films, prepared by magnetron sputtering, were transformed into the nanocrystalline state by annealing with in situ thermopower and electrical resistivity measurements. We have found that the amorphous state is stable in these film composites to about 550 K. Prior to crystallization, the amorphous films undergo a structural relaxation, detected by peculiarities in the temperature dependences of the transport properties, but not visible in x-ray or electron diffraction. The magnitude and temperature dependences of electrical conductivity and thermopower indicate that electron transport in the amorphous films is through extended states. The amorphous films are crystallized at annealing temperatures above 550 K into a nanocrystalline composite with an average grain size of 10-20 nm.

  6. Determination of Chemical Bond of Tetrahedral Amorphous Carbon Films by Ellipsometry Approach%椭偏法表征四面体非晶碳薄膜的化学键结构

    Institute of Scientific and Technical Information of China (English)

    李晓伟; 周毅; 孙丽丽; 汪爱英

    2012-01-01

    Tetrahedral amorphous carbon (ta-C) films under different substrate negative bias are prepared by a home developed filtered cathodic vacuum arc (FCVA) technology with double bend shape. The film thickness is measured by a combined spectrophotometry and spectroscopic ellipsometry (SE) approach; the chemical bonds including sp2C and sp3C are gained by the fitted ellipsometry method. Furthermore,the accuracy of ellipsometry results is evaluated by comparing with those of X-ray photoelectron spectroscopy (XPS) and Raman spectra. The results indicate that the minimum thickness of ta-C film of 33. 9 nm is obtained when the bias voltage is -100 V; with the increase of bias voltage,the optical gaps and the content of sp3C atomic bond decrease,while the sp2C content increases correspondingly. By comparison with the results of XPS and Raman spectra,it is found that when the optical constants of sp2C model are represented by the glassy carbon and the fitting wavelength ranges are chosen from 250 to 1700 nm,the best fitting result of atomic bonds of ta-C films can be deduced by the ellipsometry method. Therefore,it could be said that the elliposometry method is a quite promising method to characterize the atomic bonds of ta-C films including sp2C and sp3C,as a new nondestructive,fast,quantitative and easy way.%采用自主研制的双弯曲磁过滤阴极真空电弧(FCVA)技术,在不同衬底负偏压下制备了四面体非晶碳(ta-C)薄膜.通过分光光度计和椭偏(SE)联用技术精确测量了薄膜厚度,重点采用椭偏法对不同偏压下制备的ta-C薄膜sp3C键和sp2C键结构进行了拟合表征,并与X射线光电子能谱(XPS)和拉曼光谱的实验结果相对比,分析了非晶碳结构的椭偏拟合新方法可靠性.结果表明,在-100 V偏压时薄膜厚度最小,为33.9 nm;随着偏压的增加,薄膜中的sp2C含量增加,sp3C含量减小,光学带隙下降.对比结果发现,椭偏法作为一种无损、简易、快速的表征

  7. Thermally reduced graphenes exhibiting a close relationship to amorphous carbon

    Science.gov (United States)

    An Wong, Colin Hong; Ambrosi, Adriano; Pumera, Martin

    2012-07-01

    Graphene is an important material for sensing and energy storage applications. Since the vast majority of sensing and energy storage chemical and electrochemical systems require bulk quantities of graphene, thermally reduced graphene oxide (TRGO) is commonly employed instead of pristine graphene. The sp2 planar structure of TRGO is heavily damaged, consisting of a very short sp2 crystallite size of nanometre length and with areas of sp3 hybridized carbon. Such a structure of TRGO is reminiscent of the key characteristic of the structure of amorphous carbon, which is defined as a material without long-range crystalline order consisting of both sp2 and sp3 hybridized carbons. Herein, we describe the characterization of TRGO, its parent graphite material and carbon black (a form of amorphous carbon) via transmission electron microscopy, Raman spectroscopy, X-ray photoelectron spectroscopy (XPS) and cyclic voltammetry experiments. We used the data obtained as well as consideration of practical factors to perform a comparative assessment of the relative electrochemical performances of TRGO against amorphous carbon. We found out that TRGO and amorphous carbon exhibit almost identical characteristics in terms of density of defects in the sp2 lattice and a similar crystallite size as determined by Raman spectroscopy. These two materials also exhibit similar amounts of oxygen containing groups as determined by XPS and nearly indistinguishable cyclic voltammetric response providing almost identical heterogeneous electron transfer constants. This leads us to conclude that for some sensing and energy storage electrochemical applications, the use of amorphous carbon might be a much more economical solution than the one requiring digestion of highly crystalline graphite with strong oxidants to graphite oxide and then thermally exfoliating it to thermally reduced graphene oxide.

  8. Structural properties of oxygenated amorphous cadmium telluride thin films

    Energy Technology Data Exchange (ETDEWEB)

    El Azhari, M.Y. [Laboratoire de Physique des Solides et des Couches Minces, Marakech (Morocco). Dept. de Physique; Azizan, M. [Laboratoire de Physique des Solides et des Couches Minces, Marakech (Morocco). Dept. de Physique; Bennouna, A. [Laboratoire de Physique des Solides et des Couches Minces, Marakech (Morocco). Dept. de Physique; Outzourhit, A. [Laboratoire de Physique des Solides et des Couches Minces, Marakech (Morocco). Dept. de Physique; Ameziane, E.L. [Laboratoire de Physique des Solides et des Couches Minces, Marakech (Morocco). Dept. de Physique; Brunel, M. [Laboratoire de Cristallographie, CNRS, Grenoble (France)

    1997-02-28

    Cadmium telluride (CdTe) thin films were prepared by diode radio-frequency sputtering from polycrystalline CdTe targets in an atmosphere of argon, nitrogen and oxygen. The layers prepared in the presence of nitrogen gas were amorphous and their oxygen contents increased with the partial pressure of nitrogen. The evolution of the composition of the layers as a function of the nitrogen partial pressure during deposition was followed by X-ray photoelectron spectroscopy. It is found that the oxygen is bound to both tellurium and cadmium atoms. The surface of the CdTe thin films was also studied as a function of their exposure time to a plasma containing a mixture of nitrogen and oxygen. It is found that the oxygen contents of the surface increases with increased exposure time. Also, this exposure resulted in an increase of the oxide thickness and a net decrease in the surface roughness of the films. (orig.)

  9. High thermal conductivity of a hydrogenated amorphous silicon film.

    Science.gov (United States)

    Liu, Xiao; Feldman, J L; Cahill, D G; Crandall, R S; Bernstein, N; Photiadis, D M; Mehl, M J; Papaconstantopoulos, D A

    2009-01-23

    We measured the thermal conductivity kappa of an 80 microm thick hydrogenated amorphous silicon film prepared by hot-wire chemical-vapor deposition with the 3omega (80-300 K) and the time-domain thermo-reflectance (300 K) methods. The kappa is higher than any of the previous temperature dependent measurements and shows a strong phonon mean free path dependence. We also applied a Kubo based theory using a tight-binding method on three 1000 atom continuous random network models. The theory gives higher kappa for more ordered models, but not high enough to explain our results, even after extrapolating to lower frequencies with a Boltzmann approach. Our results show that this material is more ordered than any amorphous silicon previously studied.

  10. Formation of single-crystalline aragonite tablets/films via an amorphous precursor.

    Science.gov (United States)

    Amos, Fairland F; Sharbaugh, Denise M; Talham, Daniel R; Gower, Laurie B; Fricke, Marc; Volkmer, Dirk

    2007-02-13

    Thin tablets and films of calcium carbonate have been grown at the air-water interface via an amorphous precursor route using soluble process-directing agents and a Langmuir monolayer based on resorcarene. By using appropriate concentrations of poly(acrylic acid-sodium salt) in combination with Mg2+ ion, an initially amorphous film is deposited on the monolayer template, which subsequently crystallizes into a mosaic film composed of a mixture of single-crystalline and spherulitic patches of calcite and aragonite. Of particular importance is the synthesis of single-crystalline "tablets" of aragonite (approximately 600 nm thick), because this phase generally forms needle-like polycrystalline aggregates when grown in vitro. To our knowledge, a tabular single-crystalline morphology of aragonite has only been observed in the nacreous layer of mollusk shells. Therefore, this in vitro system may serve as a useful model for examining mechanistic issues pertinent to biomineralization, such as the influence of organic templates on nucleation from an amorphous phase.

  11. Chromic mechanism in amorphous WO{sub 3} films

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, J G; Benson, D K; Tracy, C E; Deb, S K; Czanderna, A W [National Renewable Energy Lab., Golden, CO (United States); Bechinger, C [Universitaet Konstanz (Germany)

    1996-11-01

    The authors propose a new model for the chromic mechanism in amorphous tungsten oxide films (WO{sub 3{minus}y}{center_dot}nH{sub 2}O). This model not only explains a variety of seemingly conflicting experimental results reported in the literature that cannot be explained by existing models, it also has practical implications with respect to improving the coloring efficiency and durability of electrochromic devices. According to this model, a typical as-deposited tungsten oxide film has tungsten mainly in W{sup 6+} and W{sup 4+} states and can be represented as W{sub 1{minus}y}{sup 6+} W{sub y}{sup 4+}O{sub 3{minus}y}{center_dot}nH{sub 2}O. The proposed chromic mechanism is based on the small polaron transition between the charge-induced W{sup 5+} state and the original W{sup 4+} state instead of the W{sup 5+} and W{sup 6+} states as suggested in previous models. The correlation between the electrochromic and photochromic behavior in amorphous tungsten oxide films is also discussed.

  12. Modeling of amorphous carbon structures with arbitrary structural constraints.

    Science.gov (United States)

    Jornada, F H; Gava, V; Martinotto, A L; Cassol, L A; Perottoni, C A

    2010-10-06

    In this paper we describe a method to generate amorphous structures with arbitrary structural constraints. This method employs the simulated annealing algorithm to minimize a simple yet carefully tailored cost function (CF). The cost function is composed of two parts: a simple harmonic approximation for the energy-related terms and a cost that penalizes configurations that do not have atoms in the desired coordinations. Using this approach, we generated a set of amorphous carbon structures spawning nearly all the possible combinations of sp, sp(2) and sp(3) hybridizations. The bulk moduli of this set of amorphous carbons structures was calculated using Brenner's potential. The bulk modulus strongly depends on the mean coordination, following a power-law behavior with an exponent ν = 1.51 ± 0.17. A modified cost function that segregates carbon with different hybridizations is also presented, and another set of structures was generated. With this new set of amorphous materials, the correlation between the bulk modulus and the mean coordination weakens. The method proposed can be easily modified to explore the effects on the physical properties of the presence of hydrogen, dangling bonds, and structural features such as carbon rings.

  13. Machine learning based interatomic potential for amorphous carbon

    Science.gov (United States)

    Deringer, Volker L.; Csányi, Gábor

    2017-03-01

    We introduce a Gaussian approximation potential (GAP) for atomistic simulations of liquid and amorphous elemental carbon. Based on a machine learning representation of the density-functional theory (DFT) potential-energy surface, such interatomic potentials enable materials simulations with close-to DFT accuracy but at much lower computational cost. We first determine the maximum accuracy that any finite-range potential can achieve in carbon structures; then, using a hierarchical set of two-, three-, and many-body structural descriptors, we construct a GAP model that can indeed reach the target accuracy. The potential yields accurate energetic and structural properties over a wide range of densities; it also correctly captures the structure of the liquid phases, at variance with a state-of-the-art empirical potential. Exemplary applications of the GAP model to surfaces of "diamondlike" tetrahedral amorphous carbon (ta -C) are presented, including an estimate of the amorphous material's surface energy and simulations of high-temperature surface reconstructions ("graphitization"). The presented interatomic potential appears to be promising for realistic and accurate simulations of nanoscale amorphous carbon structures.

  14. First-principles studies of the vibrational properties of amorphous carbon nitrides

    Institute of Scientific and Technical Information of China (English)

    Niu Li; Wang Xuan-Zhang; Zhu Jia-Qi; Gao Wei

    2013-01-01

    Raman spectra of amorphous carbon nitride films (a-C:N) resemble those of typical amorphous carbon (a-C),and no specific features in the spectra are shown due to N doping.The present work provides a correlation between the microstructure and vibrational properties of a-C:N films from first principles.The six periodic model structures of 64 atoms with various mass densities and nitrogen contents are generated by the liquid-quench method using Car-Parinello molecular dynamics.By using Raman coupling tensors calculated with the finite electric field method,Raman spectra are obtained.The calculated results show that the vibrations of C=N could directly contribute to the Raman spectrum.The similarity of the Raman line shapes of N-doped and N-free amorphous carbons is due to the overlapping of C=N and C=C vibration bands.In addition,the origin of characteristic Raman peaks is also given.

  15. Selective-resputtering-induced perpendicular magnetic anisotropy in amorphous TbFe films.

    Science.gov (United States)

    Harris, V G; Pokhil, T

    2001-08-06

    Perpendicular magnetic anisotropy energy in rf magnetron sputtered amorphous TbFe films is measured to increase exponentially with pair-order anisotropy induced by the selective resputtering of surface adatoms during film growth.

  16. Nanostructured silicon carbon thin films grown by plasma enhanced chemical vapour deposition technique

    Energy Technology Data Exchange (ETDEWEB)

    Coscia, U. [Dipartimento di Fisica, Università di Napoli “Federico II” Complesso Universitario MSA, via Cinthia, 80126 Napoli (Italy); CNISM Unita' di Napoli, Complesso Universitario MSA, via Cinthia, 80126 Napoli (Italy); Ambrosone, G., E-mail: ambrosone@na.infn.it [Dipartimento di Fisica, Università di Napoli “Federico II” Complesso Universitario MSA, via Cinthia, 80126 Napoli (Italy); SPIN-CNR, Complesso Universitario MSA, via Cinthia, 80126 Napoli (Italy); Basa, D.K. [Department of Physics, Utkal University, Bhubaneswar 751004 (India); Rigato, V. [INFN Laboratori Nazionali Legnaro, 35020 Legnaro (Padova) (Italy); Ferrero, S.; Virga, A. [Dipartimento di Scienza Applicata e Tecnologia, Politecnico di Torino, C.so Duca degli Abruzzi 24, 10129 Torino (Italy)

    2013-09-30

    Nanostructured silicon carbon thin films, composed of Si nanocrystallites embedded in hydrogenated amorphous silicon carbon matrix, have been prepared by varying rf power in ultra high vacuum plasma enhanced chemical vapour deposition system using silane and methane gas mixtures diluted in hydrogen. In this paper we have studied the compositional, structural and electrical properties of these films as a function of rf power. It is shown that with increasing rf power the atomic densities of carbon and hydrogen increase while the atomic density of silicon decreases, resulting in a reduction in the mass density. Further, it is demonstrated that carbon is incorporated into amorphous matrix and it is mainly bonded to silicon. The study has also revealed that the crystalline volume fraction decreases with increase in rf power and that the films deposited with low rf power have a size distribution of large and small crystallites while the films deposited with relatively high power have only small crystallites. Finally, the enhanced transport properties of the nanostructured silicon carbon films, as compared to amorphous counterpart, have been attributed to the presence of Si nanocrystallites. - Highlights: • The mass density of silicon carbon films decreases from 2.3 to 2 g/cm{sup 3}. • Carbon is incorporated in the amorphous phase and it is mainly bonded to silicon. • Nanostructured silicon carbon films are deposited at rf power > 40 W. • Si nanocrystallites in amorphous silicon carbon enhance the electrical properties.

  17. Understanding the Structure of Amorphous Thin Film Hafnia - Final Paper

    Energy Technology Data Exchange (ETDEWEB)

    Miranda, Andre [SLAC National Accelerator Lab., Menlo Park, CA (United States)

    2015-08-27

    Hafnium Oxide (HfO2) amorphous thin films are being used as gate oxides in transistors because of their high dielectric constant (κ) over Silicon Dioxide. The present study looks to find the atomic structure of HfO2 thin films which hasn’t been done with the technique of this study. In this study, two HfO2 samples were studied. One sample was made with thermal atomic layer deposition (ALD) on top of a Chromium and Gold layer on a silicon wafer. The second sample was made with plasma ALD on top of a Chromium and Gold layer on a Silicon wafer. Both films were deposited at a thickness of 50nm. To obtain atomic structure information, Grazing Incidence X-ray diffraction (GIXRD) was carried out on the HfO2 samples. Because of this, absorption, footprint, polarization, and dead time corrections were applied to the scattering intensity data collected. The scattering curves displayed a difference in structure between the ALD processes. The plasma ALD sample showed the broad peak characteristic of an amorphous structure whereas the thermal ALD sample showed an amorphous structure with characteristics of crystalline materials. This appears to suggest that the thermal process results in a mostly amorphous material with crystallites within. Further, the scattering intensity data was used to calculate a pair distribution function (PDF) to show more atomic structure. The PDF showed atom distances in the plasma ALD sample had structure up to 10 Å, while the thermal ALD sample showed the same structure below 10 Å. This structure that shows up below 10 Å matches the bond distances of HfO2 published in literature. The PDF for the thermal ALD sample also showed peaks up to 20 Å, suggesting repeating atomic spacing outside the HfO2 molecule in the sample. This appears to suggest that there is some crystalline structure within the thermal ALD sample.

  18. atomic layer deposition of amorphous niobium carbide-based thin film superconductors.

    Energy Technology Data Exchange (ETDEWEB)

    Prolier, T.; Klug, J. A.; Elam, J. W.; Claus, H.; Becker, N. G.; Pellin, M. J. (Materials Science Division)

    2011-01-01

    Niobium carbide thin films were synthesized by atomic layer deposition (ALD) using trimethylaluminum (TMA), NbF{sub 5}, and NbCl{sub 5} precursors. In situ quartz crystal microbalance (QCM) measurements performed at 200 and 290 C revealed controlled, linear deposition with a high growth rate of 5.7 and 4.5 {angstrom}/cycle, respectively. The chemical composition, growth rate, structure, and electronic properties of the films were studied over the deposition temperature range 125-350 C. Varying amounts of impurities, including amorphous carbon (a-C), AlF{sub 3}, NbF{sub x}, and NbCl{sub x}, were found in all samples. A strong growth temperature dependence of film composition, growth rate, and room temperature DC resistivity was observed. Increasing film density, decreasing total impurity concentration, and decreasing resistivity were observed as a function of increasing deposition temperature for films grown with either NbF{sub 5} or NbCl{sub 5}. Superconducting quantum interference device (SQUID) magnetometry measurements down to 1.2 K revealed a superconducting transition at T{sub c} = 1.8 K in a 75 nm thick film grown at 350 C with TMA and NbF{sub 5}. The superconducting critical temperature could be increased up to 3.8 K with additional use of NH{sub 3} during ALD film growth.

  19. Atomic layer deposition of amorphous niobium carbide-based thin film superconductors.

    Energy Technology Data Exchange (ETDEWEB)

    Klug, J. A.; Prolier, T.; Elam, J. W.; Becker, N. G.; Pellin, M. J. (Energy Systems); ( HEP); ( MSD); (Illinois Inst. Tech.)

    2011-01-01

    Niobium carbide thin films were synthesized by atomic layer deposition (ALD) using trimethylaluminum (TMA), NbF{sub 5}, and NbCl{sub 5} precursors. In situ quartz crystal microbalance (QCM) measurements performed at 200 and 290 C revealed controlled, linear deposition with a high growth rate of 5.7 and 4.5 {angstrom}/cycle, respectively. The chemical composition, growth rate, structure, and electronic properties of the films were studied over the deposition temperature range 125-350 C. Varying amounts of impurities, including amorphous carbon (a-C), AlF{sub 3}, NbF{sub x}, and NbCl{sub x}, were found in all samples. A strong growth temperature dependence of film composition, growth rate, and room temperature DC resistivity was observed. Increasing film density, decreasing total impurity concentration, and decreasing resistivity were observed as a function of increasing deposition temperature for films grown with either NbF{sub 5} or NbCl{sub 5}. Superconducting quantum interference device (SQUID) magnetometry measurements down to 1.2 K revealed a superconducting transition at T{sub c} = 1.8 K in a 75 nm thick film grown at 350 C with TMA and NbF{sub 5}. The superconducting critical temperature could be increased up to 3.8 K with additional use of NH{sub 3} during ALD film growth.

  20. Ferroelectric-Like Properties of Amorphous Metal Oxide Thin Films Prepared by Sol-Gel Technique.

    Science.gov (United States)

    Xu, Yuhuan

    1995-01-01

    Advances in the field of both optical and electrical integrated circuit devices require new thin film materials. Ferroelectric materials have attractive properties such as hysteresis behavior, pyroelectricity, piezoelectricity and nonlinear optical properties. Many ferroelectric thin films have been successfully prepared from metal organic compounds via sol-gel processing. Thus far, research has concentrated upon polycrystalline or epitaxial ferroelectric films. For amorphous ferroelectric thin films, preliminary experimental results in our laboratory indicated that these amorphous films possessed good ferroelectric -like properties. The purpose of this research is (1) to fabricate amorphous metal oxide thin films by the sol-gel technique, (2) to determine whether these amorphous metal oxide thin films have ferroelectric-like properties and (3) to propose a theoretical model ("ferrons model") to explain the ferroelectric-like properties of amorphous thin films, which deals with a structure of permanent dipoles of "partially ordered clusters" (ferrons) in the amorphous films. The theoretical model is based on our experimental results of thin films of two amorphous materials (barium titanite and lead zirconate titanate). This research may provide a new functional material which could be useful for producing integrated electronic and electrooptic devices.

  1. Field electron emission enhancement of amorphous carbon through a niobium carbide buffer layer

    Science.gov (United States)

    Xu, L.; Wang, C.; Hu, C. Q.; Zhao, Z. D.; Yu, W. X.; Zheng, W. T.

    2009-01-01

    We investigate the field electron emission for amorphous carbon (a-C) films deposited on Si (100) substrates through a niobium carbide buffer layer with different structures and find that the niobium carbide buffer layer can substantially improve the electron field emission properties of a-C films, which can be attributed to an increase in the enhancement factor β on the surface of a-C films after the insertion of the niobium carbide layer in between a-C film and substrate. Moreover, a phase transition for niobium carbide layer from hexagonal (Nb2C) to cubic (NbC) structure, revealed by x-ray diffraction, further enhances the electron field emission. The first-principles calculated results show that the work function of NbC is lower than that of Nb2C, which is the reason why the electron emission of a-C is further enhanced.

  2. Electronic properties of intrinsic and doped amorphous silicon carbide films

    Energy Technology Data Exchange (ETDEWEB)

    Vetter, M. [Departament d' Enginyeria Electronica, Universitat Politecnica de Catalunya, Gran Capita s/n, Modul C4, E-08034 Barcelona (Spain)]. E-mail: mvetter@eel.upc.edu; Voz, C. [Departament d' Enginyeria Electronica, Universitat Politecnica de Catalunya, Gran Capita s/n, Modul C4, E-08034 Barcelona (Spain); Ferre, R. [Departament d' Enginyeria Electronica, Universitat Politecnica de Catalunya, Gran Capita s/n, Modul C4, E-08034 Barcelona (Spain); Martin, I. [Departament d' Enginyeria Electronica, Universitat Politecnica de Catalunya, Gran Capita s/n, Modul C4, E-08034 Barcelona (Spain); Orpella, A. [Departament d' Enginyeria Electronica, Universitat Politecnica de Catalunya, Gran Capita s/n, Modul C4, E-08034 Barcelona (Spain); Puigdollers, J. [Departament d' Enginyeria Electronica, Universitat Politecnica de Catalunya, Gran Capita s/n, Modul C4, E-08034 Barcelona (Spain); Andreu, J. [Departament de Fisica Aplicada i Optica, Universitat de Barcelona, Av. Diagonal 647, E-08028 Barcelona (Spain); Alcubilla, R. [Departament d' Enginyeria Electronica, Universitat Politecnica de Catalunya, Gran Capita s/n, Modul C4, E-08034 Barcelona (Spain)

    2006-07-26

    Hydrogenated amorphous silicon carbide (a-SiC{sub x} : H) films have shown excellent surface passivation of crystalline silicon. With the aim of large area deposition of these films the influence of the rf plasma power was investigated. It is found that homogenous deposition with effective surface recombination velocity lower than 100 cms{sup -1} is possible up to 6'' diameter in a simple parallel plate reactor by optimizing deposition parameters. For application in solar cell processes the conductivity of these a-SiC{sub x} : H films might become of importance since good surface passivation results from field-effect passivation which needs an insulating dielectric layer. Therefore, the temperature dependence of the dark dc conductivity of these films was investigated in the temperature range from - 20 to 260 deg. C. Two transition temperatures, T {sub s}{approx}80 deg. C and T {sub s}{approx}170 deg. C, were found where conductivity increases, resp. decreases over-exponential. From Arrhenius plots activation energy (E {sub a}) and conductivity pre-factor ({sigma} {sub 0}) were calculated for a large number of samples with different composition. A correlation between E {sub a} and {sigma} {sub 0} was found giving a Meyer-Neldel relation with a slope of 59 mV, corresponding to a material characteristic temperature T {sub m} = 400 deg. C, and an intercept at {sigma} {sub 00} = 0.1 {omega}{sup -1}cm{sup -1}.

  3. Nanotribological performance of fullerene-like carbon nitride films

    Energy Technology Data Exchange (ETDEWEB)

    Flores-Ruiz, Francisco Javier; Enriquez-Flores, Christian Ivan [Centro de Investigación y Estudios Avanzados (CINVESTAV) IPN, Unidad Querétaro, Lib. Norponiente 2000, Real de Juriquilla, C.P. 76230, Querétaro, Qro., México (Mexico); Chiñas-Castillo, Fernando, E-mail: fernandochinas@gmail.com [Department of Mechanical Engineering, Instituto Tecnológico de Oaxaca, Oaxaca, Oax. Calz. Tecnológico No. 125, CP. 68030, Oaxaca, Oax. (Mexico); Espinoza-Beltrán, Francisco Javier [Centro de Investigación y Estudios Avanzados (CINVESTAV) IPN, Unidad Querétaro, Lib. Norponiente 2000, Real de Juriquilla, C.P. 76230, Querétaro, Qro., México (Mexico)

    2014-09-30

    Highlights: • Fullerene-like CNx samples show an elastic recovery of 92.5% and 94.5% while amorphous CNx samples had only 75% elastic recovery. • Fullerene-like CNx films show an increment of 34.86% and 50.57% in fractions of C 1s and N 1s. • Fullerene-like CNx samples show a lower friction coefficient compared to amorphous CNx samples. • Friction reduction characteristics of fullerene-like CNx films are strongly related to the increase of sp{sup 3} CN bonds. - Abstract: Fullerene-like carbon nitride films exhibit high elastic modulus and low friction coefficient. In this study, thin CNx films were deposited on silicon substrate by DC magnetron sputtering and the tribological behavior at nanoscale was evaluated using an atomic force microscope. Results show that CNx films with fullerene-like structure have a friction coefficient (CoF ∼ 0.009–0.022) that is lower than amorphous CNx films (CoF ∼ 0.028–0.032). Analysis of specimens characterized by X-ray photoelectron spectroscopy shows that films with fullerene-like structure have a higher number of sp{sup 3} CN bonds and exhibit the best mechanical properties with high values of elastic modulus (E > 180 GPa) and hardness (H > 20 GPa). The elastic recovery determined on specimens with a fullerene-like CNx structure was of 95% while specimens of amorphous CNx structure had only 75% elastic recovery.

  4. Amorphous grain boundary layers in the ferromagnetic nanograined ZnO films

    Energy Technology Data Exchange (ETDEWEB)

    Straumal, B.B., E-mail: straumal@mf.mpg.de [National University of Science and Technology ' Moscow Institute of Steel and Alloys, MISiS' , Leninsky prospect 4, 119991 Moscow (Russian Federation); Institute of Solid State Physics, Russian Academy of Sciences, Chernogolovka, Moscow district, 142432 (Russian Federation); Karlsruher Institut fuer Technologie, Institut fuer Nanotechnologie, Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen (Germany); Mazilkin, A.A.; Protasova, S.G. [Institute of Solid State Physics, Russian Academy of Sciences, Chernogolovka, Moscow district, 142432 (Russian Federation); Max-Planck-Institut fuer Intelligente Systeme (former Institut fuer Metallforschung), Heisenbergstrasse 3, 70569 Stuttgart (Germany); Myatiev, A.A. [National University of Science and Technology ' Moscow Institute of Steel and Alloys, MISiS' , Leninsky prospect 4, 119991 Moscow (Russian Federation); Straumal, P.B. [National University of Science and Technology ' Moscow Institute of Steel and Alloys, MISiS' , Leninsky prospect 4, 119991 Moscow (Russian Federation); Institut fuer Materialphysik, Universitaet Muenster, Wilhelm-Klemm-Str. 10, D-48149 Muenster (Germany); Goering, E. [Max-Planck-Institut fuer Intelligente Systeme (former Institut fuer Metallforschung), Heisenbergstrasse 3, 70569 Stuttgart (Germany); and others

    2011-12-01

    Pure ZnO thin films were obtained by the wet chemistry ('liquid ceramics') method from the butanoate precursors. Films consist of dense equiaxial nanograins and reveal ferromagnetic behaviour. The structure of the ZnO films was studied by the high-resolution transmission electron microscopy. The intergranular regions in the nanograined ZnO films obtained by the 'liquid ceramics' method are amorphous. It looks like fine areas of the second amorphous phase which wets (covers) some of the ZnO/ZnO grain boundaries. Most probably these amorphous intergranular regions contain the defects which are responsible for the ferromagnetic behaviour.

  5. Mechanical properties of bismuth implanted amorphous Ge film

    Energy Technology Data Exchange (ETDEWEB)

    Juhasz, A.; Szommer, P.; Lendvai, J.; Vertesy, Z.; Peto, G. E-mail: peto@mfa.kfki.hu

    1999-01-02

    Mechanical properties of Bi ion implanted a-Ge film were studied by dynamic microhardness tests and compared to those of unimplanted a-Ge film. 400 nm thick films were evaporated in units of 30 nm thick layers and bombarded with Bi ions at 60 keV energy and 2 {mu}A/cm{sup 2} current. Cyclic load-unload indentation tests and indentation creep tests were performed to determine the hardness and ductility of the ion implanted and unimplanted specimens, respectively. The brittleness of the materials was characterised by scanning electron microscopic observation of crack formation around the Vickers indentations. The dynamic hardness was much larger, the ductility lower, the crack formation was significantly larger in the case of the unimplanted than in the ion bombarded specimens. The observed differences in the mechanical properties indicate structural differences between the two types of a-Ge are in agreement with the earlier reported formation of a new amorphous phase of Ge induced by ion implantation (G. Peto, J. Kanski, U. Sodervall, Phys. Lett. 124 (1987) 510)

  6. Mechanical properties of bismuth implanted amorphous Ge film

    Science.gov (United States)

    Juhász, A.; Szommer, P.; Lendvai, J.; Vértesy, Z.; Pető, G.

    1999-01-01

    Mechanical properties of Bi ion implanted a-Ge film were studied by dynamic microhardness tests and compared to those of unimplanted a-Ge film. 400 nm thick films were evaporated in units of 30 nm thick layers and bombarded with Bi ions at 60 keV energy and 2 μA/cm 2 current. Cyclic load-unload indentation tests and indentation creep tests were performed to determine the hardness and ductility of the ion implanted and unimplanted specimens, respectively. The brittleness of the materials was characterised by scanning electron microscopic observation of crack formation around the Vickers indentations. The dynamic hardness was much larger, the ductility lower, the crack formation was significantly larger in the case of the unimplanted than in the ion bombarded specimens. The observed differences in the mechanical properties indicate structural differences between the two types of a-Ge are in agreement with the earlier reported formation of a new amorphous phase of Ge induced by ion implantation (G. Pető, J. Kanski, U. Sodervall, Phys. Lett. 124 (1987) 510 [6]).

  7. ENHANCING ADHESION OF TETRAHEDRAL AMORPHOUS CARBON FILMS

    Institute of Scientific and Technical Information of China (English)

    赵玉清; 林毅; 王晓艳; 王炎武; 魏新宇

    2005-01-01

    TheperformanceoftheTACfilmsdeposited bytheFCVAisbetterthanthatofthediamond like carbonfilms[1,2],becausetheformerisofhigher hardnessandtransparency,smallerfriction coefficientandabsorbingtheultravioletraymore easily,etc.[3].Thesecharacteristicsaresimilarto thoseofthenaturaldiamond.Therefore,theTAC filmdepositedonawindowmaterialcanraisethe operatinglifegreatly.TheTACfilmisanideal protectivematerialforvariouskindsofwatch glassesandcameralenses. Metalandpotteryareoftenusedasthe substratesfordepositingtheTACfil...

  8. Simulation of swift boron clusters traversing amorphous carbon foils

    OpenAIRE

    Heredia Ávalos, Santiago; Abril Sánchez, Isabel; Denton Zanello, Cristian D.; García Molina, Rafael

    2007-01-01

    We use a simulation code to study the interaction of swift boron clusters (Bn+, n=2–6, 14) with amorphous carbon foils. We analyze different aspects of this interaction, such as the evolution of the cluster structure inside the target, the energy and angle distributions at the detector or the stopping power ratio. Our simulation code follows in detail the motion of the cluster fragments through the target and in the vacuum until reaching a detector, taking into account the following interacti...

  9. Amorphous IZO-based transparent thin film transistors

    Energy Technology Data Exchange (ETDEWEB)

    Paine, David C. [Division of Engineering, Brown University, Providence, RI 02912 (United States)], E-mail: David_Paine@Brown.edu; Yaglioglu, Burag; Beiley, Zach; Lee, Sunghwan [Division of Engineering, Brown University, Providence, RI 02912 (United States)

    2008-07-01

    Active electronics implemented on cheap flexible polymer substrates offer the promise of novel display technologies, wearable electronics, large area memory, and a multitude of other, as-yet-unthought-of applications that require low cost and high volume manufacturing. Thin film transistors (TFT's) fabricated on temperature-sensitive plastic substrates at low temperatures are the key to this technology. TFT's that use metal (In, Zn, Sn, Ga) oxide channels offer both high mobility (relative to amorphous Si) and the advantage of optical transparency in the visible regime. We report on the fabrication and performance of amorphous oxide transparent thin film transistors that use dc-magnetron sputter techniques to deposit IZO (In{sub 2}O{sub 3} - 10 wt.% ZnO) at low oxygen potential (0 vol.% O{sub 2}) for the source, drain, and gate-contact metallization and, at higher oxygen partial pressures (10 vol.% O{sub 2}), for the semi-conducting channel. The devices in this study were processed at room temperature except for a single 280 {sup o}C PECVD deposition step to deposit a 230 nm-thick SiO{sub x} gate dielectric. The devices are optically transparent and operate in depletion mode with a threshold voltage of - 5 V, mobility of 15 cm{sup 2}/V s, an on-off ratio of > 10{sup 6} and, a sub-threshold slope of 1.2 V/decade. In addition, we report persistent photo-conductivity in the channel region of these devices when exposed to UV illumination.

  10. Preparation and Properties of Amorphous NiFe/Cu/NiFe Thin Films

    Institute of Scientific and Technical Information of China (English)

    YE Yun; JIANG Ya-dong; HU Wen-cheng; ZENG Hong-juan

    2004-01-01

    The amorphous of Permalloy on the copper subtract was studied using composite electroplating method. A portion of hydrogen brings the counteraction on the surface of cathode leading nickel-iron alloys to be anomalous in the process of co-depositing. The results of X-ray diffraction (XRD) show that the Ni-Fe alloys layer is amorphous. The Giant Magneto -Impedance (GMI) effect of Ni-Fe alloys was obtained under the optimal conditions, dependence on the soft magnetic property of Ni-Fe amorphous thin film. As a result, the ratios△ Z/Z of NiFe/Cu/NiFe amorphous thin film are 30% at 40 kHz which is in low frequency. Furthermore, the GMI value of NiFe/Cu/NiFe amorphous thin film with a sandwich structure is higher than that of single-layer ferromagnetic films of the same thickness.

  11. HRTEM study of Popigai impact diamond: heterogeneous diamond nanostructures in native amorphous carbon matrix

    Science.gov (United States)

    Kis, Viktoria K.; Shumilova, Tatyana; Masaitis, Victor

    2016-07-01

    High-resolution transmission electron microscopy was applied for the detailed nanostructural investigation of Popigai impact diamonds with the aim of revealing the nature of the amorphous carbon of the matrix. The successful application of two complementary specimen preparation methods, focused ion beam (FIB) milling and mechanical cleavage, allowed direct imaging of nanotwinned nanodiamond crystals embedded in a native amorphous carbon matrix for the first time. Based on its stability under the electron beam, native amorphous carbon can be easily distinguished from the amorphous carbon layer produced by FIB milling during specimen preparation. Electron energy loss spectroscopy of the native amorphous carbon revealed the dominance of sp 2-bonded carbon and the presence of a small amount of oxygen. The heterogeneous size distribution and twin density of the nanodiamond crystals and the structural properties of the native amorphous carbon are presumably related to non-graphitic (organic) carbon precursor material.

  12. Property change during nanosecond pulse laser annealing of amorphous NiTi thin film

    Indian Academy of Sciences (India)

    S K Sadrnezhaad; Noushin Yasavol; Mansoureh Ganjali; Sohrab Sanjabi

    2012-06-01

    Nanosecond lasers of different intensities were pulsed into sputter-deposited amorphous thin films of near equiatomic Ni/Ti composition to produce partially crystallized highly sensitive -phase spots surrounded by amorphous regions. Scanning electron microscopy having secondary and back-scattered electrons, field emission scanning electron microscopy, optical microscopy and X-ray diffraction patterns were used to characterize the laser treated spots. Effect of nanosecond pulse lasering on microstructure, morphology, thermal diffusion and inclusion formation was investigated. Increasing beam intensity and laser pulse-number promoted amorphous to -phase transition. Lowering duration of the pulse incidence reduced local film oxidation and film/substrate interference.

  13. Catalytic acceleration of graphitisation of amorphous carbon during synthesis of tungsten carbide from tungsten and excess amorphous carbon in a solar furnace

    Energy Technology Data Exchange (ETDEWEB)

    Shohoji, N. [Inst. Nacional de Engenharia e Tecnologia Industrial, Lisbon (Portugal); Guerra Rosa, L.; Cruz Fernandes, J. [Instituto Superior Tecnico, Departamento de Engenharia de Materiais, Av. Rovisco Pais, 1049-001, Lisbon (Portugal); Martinez, D.; Rodriguez, J. [Plataforma Solar de Almeria, Centro Europeo de Ensayos de Energia Solar, Centro de Investigaciones Energeticas Medioambientales y Tecnologicas, P.O. Box 22, 04200, Tabernas (Spain)

    1999-03-25

    Amorphous carbon is one of the allotropes of carbon possessing carbon activity a(C) higher than that of graphite (standard state with a(C) = 1). Amorphous carbon is in a metastable state but, under normal circumstances, it takes several hours to be graphitised to an extent detectable by X-ray diffraction even at temperature higher than 1500 C. In the present work, we report the accelerated graphitisation of amorphous carbon induced apparently by the catalytic action of tungsten (W) or tungsten carbide (WC) during synthesis of WC started from W and active carbon in solar furnace under controlled atmosphere (Ar or N{sub 2}). This degree of graphitisation of amorphous carbon did not proceed by the similar reaction undertaken in the traditional laboratory furnace under the comparable conditions. (orig.) 14 refs.

  14. New Method of Depositing the Nanostructured Amorphous Carbon for Carbon Based Solar Cell Applications

    Directory of Open Access Journals (Sweden)

    A. N. Fadzilah

    2013-01-01

    Full Text Available Nanostructured amorphous carbon (a-C solar cells were successfully deposited via a self-designed aerosol-assisted chemical vapor deposition (AACVD. The fabricated solar cell with the configuration of Au/p-C/n-Si/Au achieved efficiency ( of % for device deposited at 500°C, % for 450°C, and % for 400°C. Photoresponse characteristic was highlighted under illumination (AM 1.5 illuminations: 100 mW/cm2, 25°C, where conductivity increased when the sample was being hit by light. Transmittance spectrum exhibits a large transmittance value (85% and absorption coefficient value of  cm−1 at the visible range from 390 to 790 nm. The nanostructured a-C thin film deposited at higher temperature possesses lower transmittance due to higher absorption as a result of the higher content of sp2-bonded carbon atoms. From Tauc’s plot, optical band gap ( was determined, and decreased as deposition temperature increased (1.2 eV, 1.0 eV, 0.7 eV. On the other hand, FESEM images exhibited a nanostructured sized a-C with the particle size less than 100 nm. To the best of our knowledge, the presence of nanostructured particle of a-C by a self-prepared AACVD has not frequently been reported.

  15. Exchange bias and bistable magneto-resistance states in amorphous TbFeCo thin films

    Energy Technology Data Exchange (ETDEWEB)

    Li, Xiaopu, E-mail: xl6ba@virginia.edu; Ma, Chung T.; Poon, S. Joseph, E-mail: sjp9x@virginia.edu [Department of Physics, University of Virginia, Charlottesville, Virginia 22904 (United States); Lu, Jiwei [Department of Materials Science and Engineering, University of Virginia, Charlottesville, Virginia 22904 (United States); Devaraj, Arun [Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory, Richland, Washington 99352 (United States); Spurgeon, Steven R.; Comes, Ryan B. [Physical and Computational Sciences Directorate, Pacific Northwest National Laboratory, Richland, Washington 99352 (United States)

    2016-01-04

    Amorphous TbFeCo thin films sputter deposited at room temperature on thermally oxidized Si substrate are found to exhibit strong perpendicular magnetic anisotropy. Atom probe tomography, scanning transmission electron microscopy, and energy dispersive X-ray spectroscopy mapping have revealed two nanoscale amorphous phases with different Tb atomic percentages distributed within the amorphous film. Exchange bias accompanied by bistable magneto-resistance states has been uncovered near room temperature by magnetization and magneto-transport measurements. The exchange anisotropy originates from the exchange interaction between the ferrimagnetic and ferromagnetic components corresponding to the two amorphous phases. This study provides a platform for exchange bias and magneto-resistance switching using single-layer amorphous ferrimagnetic thin films that require no epitaxial growth.

  16. Exchange bias and bistable magneto-resistance states in amorphous TbFeCo thin films

    Science.gov (United States)

    Li, Xiaopu; Ma, Chung T.; Lu, Jiwei; Devaraj, Arun; Spurgeon, Steven R.; Comes, Ryan B.; Poon, S. Joseph

    2016-01-01

    Amorphous TbFeCo thin films sputter deposited at room temperature on thermally oxidized Si substrate are found to exhibit strong perpendicular magnetic anisotropy. Atom probe tomography, scanning transmission electron microscopy, and energy dispersive X-ray spectroscopy mapping have revealed two nanoscale amorphous phases with different Tb atomic percentages distributed within the amorphous film. Exchange bias accompanied by bistable magneto-resistance states has been uncovered near room temperature by magnetization and magneto-transport measurements. The exchange anisotropy originates from the exchange interaction between the ferrimagnetic and ferromagnetic components corresponding to the two amorphous phases. This study provides a platform for exchange bias and magneto-resistance switching using single-layer amorphous ferrimagnetic thin films that require no epitaxial growth.

  17. Effect of substrate temperature on the structure of amorphous oxygenated hydrocarbon films grown with a pulsed supersonic methane plasma flow

    Energy Technology Data Exchange (ETDEWEB)

    Fedoseeva, Yu. V., E-mail: fedoseeva@niic.nsc.ru [Nikolaev Institute of Inorganic Chemistry SB RAS, Novosibirsk 630090 (Russian Federation); Novosibirsk State University, Novosibirsk 630090 (Russian Federation); Pozdnyakov, G.A. [Khristianovich Institute of Theoretical and Applied Mechanics, SB RAS, Novosibirsk 630090 (Russian Federation); Okotrub, A.V.; Kanygin, M.A. [Nikolaev Institute of Inorganic Chemistry SB RAS, Novosibirsk 630090 (Russian Federation); Novosibirsk State University, Novosibirsk 630090 (Russian Federation); Nastaushev, Yu. V. [Rzhanov Institute of Semiconductor Physics SB RAS, Novosibirsk 630090 (Russian Federation); Vilkov, O.Y. [St. Petersburg State University, St. Petersburg 198504 (Russian Federation); Bulusheva, L.G. [Nikolaev Institute of Inorganic Chemistry SB RAS, Novosibirsk 630090 (Russian Federation); Novosibirsk State University, Novosibirsk 630090 (Russian Federation)

    2016-11-01

    Highlights: • A deposition of supersonic methane plasma flow on silicon substrate produces amorphous oxygenated hydrocarbon (CO{sub x}H{sub y}) film. • The thickness, composition, and wettability of the film depend on the substrate temperature. • A rise of the substrate temperature from 500 to 700 °C promotes the sp{sup 3}-hybridization carbon formation. - Abstract: Since amorphous oxygenated hydrocarbon (CO{sub x}H{sub y}) films are promising engineering materials a study of the structure and composition of the films depending on the conditions of synthesis is important for controlling of their physicochemical properties. Here, we used the methods of scanning and transmission electron microscopy, X-ray photoelectron, near-edge X-ray absorption fine structure, Fourier transform infrared and Raman spectroscopy to reveal changes in the chemical connectivity of CO{sub x}H{sub y} films grown on silicon substrates heated to 300, 500, and 700 °C using a supersonic flow of methane plasma. It was found that the CO{sub x}H{sub y} films, deposited at 300 and 500 °C, were mainly composed of the sp{sup 2}-hybridized carbon areas with various oxygen species. A rise of the substrate temperature caused an increase of the portion of tetrahedral carbon atoms as well as carboxyl and hydroxyl groups. With growth of the substrate temperature, the film thickness reduced monotonically from 400 to 180 nm, while the film adhesion improved substantially. The films, deposited at lower temperatures, showed high hydrophilicity due to porosity and presence of oxygenated groups both at the surface and in the bulk.

  18. Epitaxial growth of amorphous Ge films deposited on single-crystal Ge

    OpenAIRE

    M. G. Grimaldi; Mäenpää, M. (Markus); Paine, B. M.; Nicolet, M-A.; Lau, S. S.; Tseng, W. F.

    1981-01-01

    The epitaxial growth of amorphous Ge films deposited onto 110 Ge substrate is demonstrated. Substrate cleaning prior to deposition involves only conventional chemical procedures. The growth appears to be a strong function of the interface cleanliness. Two different growth mechanisms are observed: (a) a direct transition from amorphous to single-crystalline layer and (b) the growth involving the transition of amorphous to polycrystals to single crystal.

  19. Fabrication of hydrogenated amorphous silicon carbide films by decomposition of hexamethyldisilane with microwave discharge flow of Ar

    Science.gov (United States)

    Ito, Haruhiko; Kumakura, Motoki; Suzuki, Tsuneo; Niibe, Masahito; Kanda, Kazuhiro; Saitoh, Hidetoshi

    2016-06-01

    Hydrogenated amorphous silicon carbide films have been fabricated by the decomposition of hexamethyldisilane with a microwave discharge flow of Ar. Mechanically hard films were obtained by applying radio-frequency (RF) bias voltages to the substrate. The atomic compositions of the films were analyzed by a combination of Rutherford backscattering and elastic recoil detection, X-ray photoelectron spectroscopy (XPS), and glow discharge optical emission spectroscopy. The chemical structure was analyzed by carbon-K near-edge X-ray absorption fine structure spectroscopy, high-resolution XPS, and Fourier transform infrared absorption spectroscopy. The structural changes upon the application of RF bias were investigated, and the concentration of O atoms near the film surface was found to play a key role in the mechanical hardness of the present films.

  20. Studies to Enhance Superconductivity in Thin Film Carbon

    Science.gov (United States)

    Pierce, Benjamin; Brunke, Lyle; Burke, Jack; Vier, David; Steckl, Andrew; Haugan, Timothy

    2012-02-01

    With research in the area of superconductivity growing, it is no surprise that new efforts are being made to induce superconductivity or increase transition temperatures (Tc) in carbon given its many allotropic forms. Promising results have been published for boron doping in diamond films, and phosphorus doping in highly oriented pyrolytic graphite (HOPG) films show hints of superconductivity.. Following these examples in the literature, we have begun studies to explore superconductivity in thin film carbon samples doped with different elements. Carbon thin films are prepared by pulsed laser deposition (PLD) on amorphous SiO2/Si and single-crystal substrates. Doping is achieved by depositing from (C1-xMx) single-targets with M = B4C and BN, and also by ion implantation into pure-carbon films. Previous research had indicated that Boron in HOPG did not elicit superconducting properties, but we aim to explore that also in thin film carbon and see if there needs to be a higher doping in the sample if trends were able to be seen in diamond films. Higher onset temperatures, Tc , and current densities, Jc, are hoped to be achieved with doping of the thin film carbon with different elements.

  1. Nanosized graphene crystallite induced strong magnetism in pure carbon films.

    Science.gov (United States)

    Wang, Chao; Zhang, Xi; Diao, Dongfeng

    2015-03-14

    We report strong magnetism in pure carbon films grown by electron irradiation assisted physical vapor deposition in electron cyclotron resonance plasma. The development of graphene nanocrystallites in the amorphous film matrix, and the dependence of the magnetic behavior on amorphous, nanocrystallite and graphite-like structures were investigated. Results were that the amorphous structure shows weak paramagnetism, graphene nanocrystallites lead to strong magnetization, and graphite-like structures corresponded with a lower magnetization. At a room temperature of 300 K, the highest saturation magnetization of 0.37 emu g(-1) was found in the nanosized graphene nanocrystallite structure. The origin of strong magnetism in nanocrystallites was ascribed to the spin magnetic moment at the graphene layer edges.

  2. Enhanced crystallization of amorphous silicon thin films using embedded silicon nanocrystals

    Science.gov (United States)

    Anderson, Curtis Michael

    This thesis is concerned with the production of silicon thin films for photovoltaic applications. Much research has been carried out to find a stable, more efficient alternative to amorphous silicon, resulting in a number of various amorphous/crystalline mixed-phase film structures with properties superior to amorphous silicon. This thesis work details a completely new approach to mixed-phase film deposition, focusing on the fast crystallization of these films. The deposition of amorphous silicon films with embedded nanocrystals was carried out via a dual-plasma system. It is known that plasma conditions to produce high quality films are much different from those to produce particles. Hence the experimental system used here involved two separate plasmas to allow the optimum production of the crystalline nanoparticles and the amorphous film. Both plasmas use 13.56 MHz excitation voltage with diluted silane as the silicon precursor. The nanoparticle production reactor is a flow-through device that can be altered to control the size of the particles from around 5--30 nm average diameter. The film production reactor is a parallel-plate capacitively-coupled plasma system, into which the aerosol-suspended nanoparticles were injected. The nanocrystals could either be "co-deposited" simultaneously with the amorphous film, or be deposited separately in a layer-by-layer technique; both approaches are discussed in detail. Measurements of the film conductivity provide for the first time unambiguous evidence that the presence of nanocrystallites above 5 nm in the amorphous film have a direct impact on the electronic properties of co-deposited films. Further measurements of the film structure by transmission electron microscopy (TEM) and Raman spectroscopy demonstrate clearly the effect of embedded nanocrystals on the annealed crystallization process; the immediate growth of the crystal seeds has been observed. Additionally, a newly discovered mechanism of film crystallization

  3. sp³ -linked amorphous carbon with sulfonic acid groups as a heterogeneous acid catalyst.

    Science.gov (United States)

    Suganuma, Satoshi; Nakajima, Kiyotaka; Kitano, Masaaki; Hayashi, Shigenobu; Hara, Michikazu

    2012-09-01

    SO₃H-bearing amorphous carbon prepared from polyvinyl chloride (PVC) is studied as a heterogeneous Brønsted acid catalyst. Sulfonation of partially carbonized PVC produces amorphous carbon consisting of small SO₃H-bearing carbon sheets linked by sp³ -based aliphatic hydrocarbons. This carbon material exhibits much higher catalytic performance in the hydrolysis of cellobiose than conventional heterogeneous Brønsted acid catalysts with SO₃H groups, including SO₃H-bearing amorphous carbon derived from cellulose. This can be attributed to a high density of SO₃H groups and the fast diffusion of reactants and products enabled by a flexible carbon network.

  4. Study of CVD diamond layers with amorphous carbon admixture by Raman scattering spectroscopy

    Directory of Open Access Journals (Sweden)

    Dychalska Anna

    2015-12-01

    Full Text Available Raman spectroscopy is a most often used standard technique for characterization of different carbon materials. In this work we present the Raman spectra of polycrystalline diamond layers of different quality, synthesized by Hot Filament Chemical Vapor Deposition method (HF CVD. We show how to use Raman spectroscopy for the analysis of the Raman bands to determine the structure of diamond films as well as the structure of amorphous carbon admixture. Raman spectroscopy has become an important technique for the analysis of CVD diamond films. The first-order diamond Raman peak at ca. 1332 cm−1 is an unambiguous evidence for the presence of diamond phase in the deposited layer. However, the existence of non-diamond carbon components in a CVD diamond layer produces several overlapping peaks in the same wavenumber region as the first order diamond peak. The intensities, wavenumber, full width at half maximum (FWHM of these bands are dependent on quality of diamond layer which is dependent on the deposition conditions. The aim of the present work is to relate the features of diamond Raman spectra to the features of Raman spectra of non-diamond phase admixture and occurrence of other carbon structures in the obtained diamond thin films.

  5. Femtosecond Laser Crystallization of Boron-doped Amorphous Hydrogenated Silicon Films

    Directory of Open Access Journals (Sweden)

    P.D. Rybalko

    2016-10-01

    Full Text Available Crystallization of amorphous hydrogenated silicon films with femtosecond laser pulses is one of the promising ways to produce nanocrystalline silicon for photovoltaics. The structure of laser treated films is the most important factor determining materials' electric and photoelectric properties. In this work we investigated the effect of femtosecond laser irradiation of boron doped amorphous hydrogenated silicon films with different fluences on crystalline volume fraction and electrical properties of this material. A sharp increase of conductivity and essential decrease of activation energy of conductivity temperature dependences accompany the crystallization process. The results obtained are explained by increase of boron doping efficiency in crystalline phase of modified silicon film.

  6. A Selective Metasurface Absorber with An Amorphous Carbon Interlayer for Solar Thermal Applications

    CERN Document Server

    Wan, Chenglong; Nunez-Sanchez, S; Chen, Lifeng; Lopez-Garcia, M; Pugh, J; Zhu, Bofeng; Selvaraj, P; Mallick, T; Senthilarasu, S; Cryan, M J

    2016-01-01

    This paper presents fabrication, measurement and modelling results for a metal-dielectric-metal metasurface absorber for solar thermal applications. The structure uses amorphous carbon as an inter-layer between thin gold films with the upper film patterned with a 2D periodic array using focused ion beam etching. The patterned has been optimised to give high absorptance from 400-1200nm and low absorptance above this wavelength range to minimise thermal radiation and hence obtain higher temperature performance. Wide angle absorptance results are shown and detailed modelling of a realistic nanostructured upper layer results in excellent agreement between measured and modelled results. The use of gold in this paper is a first step towards a high temperature metasurface where gold can be replaced by other refractory metals such as tungsten or chrome.

  7. Effect of crystalline/amorphous interfaces on thermal transport across confined thin films and superlattices

    Science.gov (United States)

    Giri, Ashutosh; Braun, Jeffrey L.; Hopkins, Patrick E.

    2016-06-01

    We report on the thermal boundary resistances across crystalline and amorphous confined thin films and the thermal conductivities of amorphous/crystalline superlattices for Si/Ge systems as determined via non-equilibrium molecular dynamics simulations. Thermal resistances across disordered Si or Ge thin films increase with increasing length of the interfacial thin films and in general demonstrate higher thermal boundary resistances in comparison to ordered films. However, for films ≲3 nm, the resistances are highly dependent on the spectral overlap of the density of states between the film and leads. Furthermore, the resistances at a single amorphous/crystalline interface in these structures are much lower than those at interfaces between the corresponding crystalline materials, suggesting that diffusive scattering at an interface could result in higher energy transmissions in these systems. We use these findings, together with the fact that high mass ratios between amorphous and crystalline materials can lead to higher thermal resistances across thin films, to design amorphous/crystalline superlattices with very low thermal conductivities. In this regard, we study the thermal conductivities of amorphous/crystalline superlattices and show that the thermal conductivities decrease monotonically with increasing interface densities above 0.1 nm-1. These thermal conductivities are lower than that of the homogeneous amorphous counterparts, which alludes to the fact that interfaces non-negligibly contribute to thermal resistance in these superlattices. Our results suggest that the thermal conductivity of superlattices can be reduced below the amorphous limit of its material constituent even when one of the materials remains crystalline.

  8. Surface bioactivity of plasma implanted silicon and amorphous carbon

    Institute of Scientific and Technical Information of China (English)

    Paul K CHU

    2004-01-01

    Plasma immersion ion implantation and deposition (PⅢ&D) has been shown to be an effective technique to enhance the surface bioactivity of materials. In this paper, recent progress made in our laboratory on plasma surface modification single-crystal silicon and amorphous carbon is reviewed. Silicon is the most important material in the integrated circuit industry but its surface biocompatibility has not been investigated in details. We have recently performed hydrogen PⅢ into silicon and observed the biomimetic growth of apatite on its surface in simulated body fluid. Diamond-like carbon (DLC) is widely used in the industry due to its excellent mechanical properties and chemical inertness. The use of this material in biomedical engineering has also attracted much attention. It has been observed in our laboratory that doping DLC with nitrogen by means of PⅢ can improve the surface blood compatibility. The properties as well as in vitro biological test results will be discussed in this article.

  9. Ultraviolet Spectroscopy of Matrix-isolated Amorphous Carbon Particles

    Science.gov (United States)

    Schnaiter, M.; Mutschke, H.; Henning, Th.; Lindackers, D.; Strecker, M.; Roth, P.

    1996-06-01

    In view of the interstellar 217.5 nm and the circumstellar 230--250 nm extinction features, the UV extinction behavior of small matrix-isolated amorphous carbon grains is investigated experimentally. The particles were produced in a flame by burning acetylene with oxygen at low pressure. To prevent coagulation, the condensing primary soot grains (average diameter ~6 nm) were extracted by a molecular beam technique into a high-vacuum chamber. There they were deposited into a layer of solid argon, isolated from each other. The particle mass and size were controlled using a particle mass spectrometer. The measured UV extinction of the matrix-isolated particles is compared with measurements on samples produced in the conventional way by collecting carbon smoke on substrate as well as with scattering calculations for small spheres and ellipsoides. The laboratory data give a good representation of the circumstellar extinction feature observed in the spectrum of V348 Sgr.

  10. Induced growth of high quality ZnO thin films by crystallized amorphous ZnO

    Institute of Scientific and Technical Information of China (English)

    Wang Zhi-Jun; Song Li-Jun; Li Shou-Chun; Lu You-Ming; Tian Yun-Xia; Liu Jia-Yi; Wang Lian-Yuan

    2006-01-01

    This paper reports the induced growth of high quality ZnO thin film by crystallized amorphous ZnO. Firstly amorphous ZnO was prepared by solid-state pyrolytic reaction, then by taking crystallized amorphous ZnO as seeds (buffer layer), ZnO thin films have been grown in diethyene glycol solution of zinc acetate at 80℃. X-ray Diffraction curve indicates that the films were preferentially oriented [001] out-of-plane direction of the ZnO. Atomic force microscopy and scanning electron microscopy were used to evaluate the surface morphology of the ZnO thin film. Photoluminescence spectrum exhibits a strong ultraviolet emission while the visible emission is very weak. The results indicate that high quality ZnO thin film was obtained.

  11. Amorphous Indium Selenide Thin Films Prepared by RF Sputtering: Thickness-Induced Characteristics.

    Science.gov (United States)

    Han, Myoung Yoo; Park, Yong Seob; Kim, Nam-Hoon

    2016-05-01

    The influence of indium composition, controlled by changing the film thickness, on the optical and electrical properties of amorphous indium selenide thin films was studied for the application of these materials as Cd-free buffer layers in CI(G)S solar cells. Indium selenide thin films were prepared using RF magnetron sputtering method. The indium composition of the amorphous indium selenide thin films was varied from 94.56 to 49.72 at% by increasing the film thickness from 30 to 70 nm. With a decrease in film thickness, the optical transmittance increased from 87.63% to 96.03% and Eg decreased from 3.048 to 2.875 eV. Carrier concentration and resistivity showed excellent values of ≥1015 cm(-3) and ≤ 10(4) Ω x cm, respectively. The conductivity type of the amorphous indium selenide thin films could be controlled by changing the film-thickness-induced amount of In. These results indicate the possibility of tuning the properties of amorphous indium selenide thin films by changing their composition for use as an alternate buffer layer material in CI(G)S solar cells.

  12. Chemical Structure of Carbon Nitride Films Prepared by MW-ECR Plasma Enhanced Magnetron Sputtering

    Institute of Scientific and Technical Information of China (English)

    XUJun,GAOPeng; DINGWan-yu; LIXin; DENGXin-lu; DONGChuang

    2004-01-01

    Amorphous carbon nitride thin films were prepared by plasma-enhanced DC magnetron sputtering using twinned microwave electron cyclotron resonance plasma sources. Chemical structure of deposited films was investigated using X-ray photoelectron spectroscopy and Fourier transtorm infrared spectroscopy. The results indicate that the deposition rate is strongly affected by direct current bias, and the films are mainly composed of a single amorphous carbon nitride phase with N/C ratio close to C3N4, and the bonding is predominantly of C-N type.

  13. Nanoindentation and AFM studies of PECVD DLC and reactively sputtered Ti containing carbon films

    Indian Academy of Sciences (India)

    A Pauschitz; J Schalko; T Koch; C Eisenmenger-Sittner; S Kvasnica; Manish Roy

    2003-10-01

    Amorphous carbon film, also known as DLC film, is a promising material for tribological application. It is noted that properties relevant to tribological application change significantly depending on the method of preparation of these films. These properties are also altered by the composition of the films. In view of this, the objective of the present work is to compare the nanoindentation and atomic force microscopy (AFM) study of diamond like carbon (DLC) film obtained by plasma enhanced chemical vapour deposition (PECVD) with the Ti containing amorphous carbon (Ti/-C : H) film obtained by unbalanced magnetron sputter deposition (UMSD). Towards that purpose, DLC and Ti/-C : H films are deposited on silicon substrate by PECVD and UMSD processes, respectively. The microstructural features and the mechanical properties of these films are evaluated by scanning electron microscopy (SEM), transmission electron microscopy (TEM), nanoindentation and by AFM. The results show that the PECVD DLC film has a higher elastic modulus, hardness and roughness than the UMSD Ti/-C : H film. It also has a lower pull off force than Ti containing amorphous carbon film.

  14. Thermal oxidation of Zr–Cu–Al–Ni amorphous metal thin films

    Energy Technology Data Exchange (ETDEWEB)

    Oleksak, R.P.; Hostetler, E.B.; Flynn, B.T. [School of Chemical, Biological and Environmental Engineering, Oregon State University, Corvallis, OR 97331 (United States); McGlone, J.M.; Landau, N.P.; Wager, J.F. [School of Electrical Engineering and Computer Science, Oregon State University, Corvallis, OR 97331 (United States); Stickle, W.F. [Hewlett-Packard Company, Corvallis, OR 97333 (United States); Herman, G.S., E-mail: greg.herman@oregonstate.edu [School of Chemical, Biological and Environmental Engineering, Oregon State University, Corvallis, OR 97331 (United States)

    2015-11-30

    The initial stages of thermal oxidation for Zr–Cu–Al–Ni amorphous metal thin films were investigated using X-ray photoelectron spectroscopy, transmission electron microscopy and energy dispersive X-ray spectroscopy. The as-deposited films had oxygen incorporated during sputter deposition, which helped to stabilize the amorphous phase. After annealing in air at 300 °C for short times (5 min) this oxygen was found to segregate to the surface or buried interface. Annealing at 300 °C for longer times leads to significant composition variation in both vertical and lateral directions, and formation of a surface oxide layer that consists primarily of Zr and Al oxides. Surface oxide formation was initially limited by back-diffusion of Cu and Ni (< 30 min), and then by outward diffusion of Zr (> 30 min). The oxidation properties are largely consistent with previous observations of Zr–Cu–Al–Ni metallic glasses, however some discrepancies were observed which could be explained by the unique sample geometry of the amorphous metal thin films. - Highlights: • Thermal oxidation of amorphous Zr–Cu–Al–Ni thin films was investigated. • Significant short-range inhomogeneities were observed in the amorphous films. • An accumulation of Cu and Ni occurs at the oxide/metal interface. • Diffusion of Zr was found to limit oxide film growth.

  15. Surface plasmon enhanced photoluminescence in amorphous silicon carbide films by adjusting Ag island film sizes

    Institute of Scientific and Technical Information of China (English)

    Yu Wei; Wang Xin-Zhan; Dai Wan-Lei; Lu Wan-Bing; Liu Yu-Mei; Fu Guang-Sheng

    2013-01-01

    Ag island films with different sizes are deposited on hydrogenated amorphous silicon carbide (α-SiC∶H) films,and the influences of Ag island films on the optical properties of the α-SiC∶H films are investigated.Atomic force microscope images show that Ag nanoislands are formed after Ag coating,and the size of the Ag islands increases with increasing Ag deposition time.The extinction spectra indicate that two resonance absorption peaks which correspond to out-of-plane and in-plane surface plasmon modes of the Ag island films are obtained,and the resonance peak shifts toward longer wavelength with increasing Ag island size.The photoluminescence (PL) enhancement or quenching depends on the size of Ag islands,and PL enhancement by 1.6 times on the main PL band is obtained when the sputtering time is 10 min.Analyses show that the influence of surface plasmons on the PL of α-SiC:H is determined by the competition between the scattering and absorption of Ag islands,and PL enhancement is obtained when scattering is the main interaction between the Ag islands and incident light.

  16. Effect of substrate temperature on the structure of amorphous oxygenated hydrocarbon films grown with a pulsed supersonic methane plasma flow

    Science.gov (United States)

    Fedoseeva, Yu. V.; Pozdnyakov, G. A.; Okotrub, A. V.; Kanygin, M. A.; Nastaushev, Yu. V.; Vilkov, O. Y.; Bulusheva, L. G.

    2016-11-01

    Since amorphous oxygenated hydrocarbon (COxHy) films are promising engineering materials a study of the structure and composition of the films depending on the conditions of synthesis is important for controlling of their physicochemical properties. Here, we used the methods of scanning and transmission electron microscopy, X-ray photoelectron, near-edge X-ray absorption fine structure, Fourier transform infrared and Raman spectroscopy to reveal changes in the chemical connectivity of COxHy films grown on silicon substrates heated to 300, 500, and 700 °C using a supersonic flow of methane plasma. It was found that the COxHy films, deposited at 300 and 500 °C, were mainly composed of the sp2-hybridized carbon areas with various oxygen species. A rise of the substrate temperature caused an increase of the portion of tetrahedral carbon atoms as well as carboxyl and hydroxyl groups. With growth of the substrate temperature, the film thickness reduced monotonically from 400 to 180 nm, while the film adhesion improved substantially. The films, deposited at lower temperatures, showed high hydrophilicity due to porosity and presence of oxygenated groups both at the surface and in the bulk.

  17. Room-temperature fabrication of light-emitting thin films based on amorphous oxide semiconductor

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Junghwan, E-mail: JH.KIM@lucid.msl.titech.ac.jp; Miyokawa, Norihiko; Ide, Keisuke [Materials and Structures Laboratory, Tokyo Institute of Technology, Mailbox R3-4, 4259 Nagatsuta, Midori-ku, Yokohama (Japan); Toda, Yoshitake [Materials Research Center for Element Strategy, Tokyo Institute of Technology, Mailbox SE-6, 4259 Nagatsuta, Midori-ku, Yokohama (Japan); Hiramatsu, Hidenori; Hosono, Hideo; Kamiya, Toshio [Materials and Structures Laboratory, Tokyo Institute of Technology, Mailbox R3-4, 4259 Nagatsuta, Midori-ku, Yokohama (Japan); Materials Research Center for Element Strategy, Tokyo Institute of Technology, Mailbox SE-6, 4259 Nagatsuta, Midori-ku, Yokohama (Japan)

    2016-01-15

    We propose a light-emitting thin film using an amorphous oxide semiconductor (AOS) because AOS has low defect density even fabricated at room temperature. Eu-doped amorphous In-Ga-Zn-O thin films fabricated at room temperature emitted intense red emission at 614 nm. It is achieved by precise control of oxygen pressure so as to suppress oxygen-deficiency/excess-related defects and free carriers. An electronic structure model is proposed, suggesting that non-radiative process is enhanced mainly by defects near the excited states. AOS would be a promising host for a thin film phosphor applicable to flexible displays as well as to light-emitting transistors.

  18. CW laser induced crystallization of thin amorphous silicon films deposited by EBE and PECVD

    Energy Technology Data Exchange (ETDEWEB)

    Said-Bacar, Z., E-mail: zabardjade@yahoo.fr [InESS (UMR 7163 CNRS-UDS), 23 rue de Loess, 67037 Strasbourg Cedex 2 (France); Prathap, P. [InESS (UMR 7163 CNRS-UDS), 23 rue de Loess, 67037 Strasbourg Cedex 2 (France); Cayron, C. [CEA, LITEN, DEHT, Minatec, 17 rue des Martyrs, 38054 Cedex 9 (France); Mermet, F. [IREPA LASER, Pole API - Parc d' Innovation, 67400 Illkirch (France); Leroy, Y.; Antoni, F.; Slaoui, A.; Fogarassy, E. [InESS (UMR 7163 CNRS-UDS), 23 rue de Loess, 67037 Strasbourg Cedex 2 (France)

    2012-09-15

    Highlights: Black-Right-Pointing-Pointer The effect of hydrogen in CW laser crystallization of hydrogenated amorphous silicon thin films has been investigated. Black-Right-Pointing-Pointer Large hydrogen content results in decohesion of the films due to hydrogen effusion. Black-Right-Pointing-Pointer Very low hydrogen content or hydrogen free amorphous silicon film are suitable for crystallization induced by CW laser. Black-Right-Pointing-Pointer Grains of size between 20 and 100 {mu}m in width and about 200 {mu}m in long in scanning direction are obtained with these latter films. - Abstract: This work presents the Continuous Wave (CW) laser crystallization of thin amorphous silicon (a-Si) films deposited by Plasma Enhanced Chemical Vapor Deposition (PECVD) and by Electron Beam Evaporation (EBE) on low cost glass substrate. The films are characterized by Elastic Recoil Detection Analysis (ERDA) and by Fourier-Transform Infrared (FTIR) spectroscopy to evaluate the hydrogen content. Analysis shows that the PECVD films contain a high hydrogen concentration ({approx}10 at.%) while the EBE films are almost hydrogen-free. It is found that the hydrogen is in a bonding configuration with the a-Si network and in a free form, requiring a long thermal annealing for exodiffusion before the laser treatment to avoid explosive effusion. The CW laser crystallization process of the amorphous silicon films was operated in liquid phase regime. We show by Electron Backscatter Diffraction (EBSD) that polysilicon films with large grains can be obtained with EBE as well as for the PECVD amorphous silicon provided that for the latest the hydrogen content is lower than 2 at.%.

  19. A Comparison of Photo-Induced Hysteresis Between Hydrogenated Amorphous Silicon and Amorphous IGZO Thin-Film Transistors.

    Science.gov (United States)

    Ha, Tae-Jun; Cho, Won-Ju; Chung, Hong-Bay; Koo, Sang-Mo

    2015-09-01

    We investigate photo-induced instability in thin-film transistors (TFTs) consisting of amorphous indium-gallium-zinc-oxide (a-IGZO) as active semiconducting layers by comparing with hydrogenated amorphous silicon (a-Si:H). An a-IGZO TFT exhibits a large hysteresis window in the illuminated measuring condition but no hysteresis window in the dark condition. On the contrary, a large hysteresis window measured in the dark condition in a-Si:H was not observed in the illuminated condition. Even though such materials possess the structure of amorphous phase, optical responses or photo instability in TFTs looks different from each other. Photo-induced hysteresis results from initially trapped charges at the interface between semiconductor and dielectric films or in the gate dielectric which possess absorption energy to interact with deep trap-states and affect the movement of Fermi energy level. In order to support our claim, we also perform CV characteristics in photo-induced hysteresis and demonstrate thermal-activated hysteresis. We believe that this work can provide important information to understand different material systems for optical engineering which includes charge transport and band transition.

  20. Mechanical dissipation at elevated temperatures in tetrahedral amorphous carbon.

    Energy Technology Data Exchange (ETDEWEB)

    Sullivan, John P.; Friedmann, Thomas Aquinas; Czaplewski, David A.; Wendt, Joel Robert

    2005-05-01

    We have measured the temperature dependence of mechanical dissipation in tetrahedral amorphous carbon flexural and torsional resonators over the temperature range from 300 to 1023 K. The mechanical dissipation was found to be controlled by defects within the material, and the magnitude and temperature dependence of the dissipation were found to depend on whether flexural or torsional vibrational modes were excited. The defects that were active under flexural stresses have a relatively flat concentration from 0.4 to 0.7 eV with an ever increasing defect concentration up to 1.9 eV. Under shear stresses (torsion), the defect activation energies increase immediately beginning at 0.4 eV, with increasing defect concentration at higher energies.

  1. Amorphous Silicon-Germanium Films with Embedded Nanocrystals for Thermal Detectors with Very High Sensitivity

    Directory of Open Access Journals (Sweden)

    Cesar Calleja

    2016-01-01

    Full Text Available We have optimized the deposition conditions of amorphous silicon-germanium films with embedded nanocrystals in a plasma enhanced chemical vapor deposition (PECVD reactor, working at a standard frequency of 13.56 MHz. The objective was to produce films with very large Temperature Coefficient of Resistance (TCR, which is a signature of the sensitivity in thermal detectors (microbolometers. Morphological, electrical, and optical characterization were performed in the films, and we found optimal conditions for obtaining films with very high values of thermal coefficient of resistance (TCR = 7.9% K−1. Our results show that amorphous silicon-germanium films with embedded nanocrystals can be used as thermosensitive films in high performance infrared focal plane arrays (IRFPAs used in commercial thermal cameras.

  2. Amorphous carbon-silicon heterojunctions by pulsed Nd:YAG laser deposition

    Energy Technology Data Exchange (ETDEWEB)

    Yap, Seong-Shan; Yow, Ho-Kwang [Faculty of Engineering, Multimedia University, Cyberjaya, Selangor 63100 (Malaysia); Tou, Teck-Yong, E-mail: tytou@mmu.edu.m [Faculty of Engineering, Multimedia University, Cyberjaya, Selangor 63100 (Malaysia)

    2009-07-31

    Amorphous carbon (a-C) films were deposited at 10{sup -4} Pa on n-Si (Si-111) and p-Si (Si-100) substrates using a pulsed Nd:YAG laser with fundamental, second- and third-harmonic outputs. These unhydrogenated and undoped a-C films were characterized by visible and UV Raman spectroscopy which indicated the presence of substantial amount of sp{sup 3} hybridized carbon network depending on the laser wavelength. The bulk resistivity in the Au/a-C/indium tin oxide structure varied between (10{sup 9}-10{sup 13}) {Omega} cm - the lowest resistivity was obtained for films deposited by the fundamental laser output at 1064 nm while the highest value was by the third-harmonic laser output at 355 nm. All the a-C/Si heterostructures exhibited a nonlinear current density-voltage characteristic. Under light illumination, by taking into consideration the fill factor of {approx} 0.2 for a-C/n-Si, the conversion efficiency at the highest photovoltage and photocurrent, at an illumination density of 0.175 mW/cm{sup 2} was estimated to be {approx} 0.28%.

  3. Low-temperature graphitization of amorphous carbon nanospheres

    Institute of Scientific and Technical Information of China (English)

    Katia Barbera; Leone Frusteri; Giuseppe Italiano; Lorenzo Spadaro; Francesco Frusteri; Siglinda Perathoner; Gabriele Centi

    2014-01-01

    The investigation by SEM/TEM, porosity, and X-ray diffraction measurements of the graphitization process starting from amorphous carbon nanospheres, prepared by glucose carbonization, is re-ported. Aspects studied are the annealing temperature in the 750-1000 °C range, the type of inert carrier gas, and time of treatment in the 2-6 h range. It is investigated how these parameters influ-ence the structural and morphological characteristics of the carbon materials obtained as well as their nanostructure. It is shown that it is possible to maintain after graphitization the round-shaped macro morphology, a high surface area and porosity, and especially a large structural disorder in the graphitic layers stacking, with the presence of rather small ordered domains. These are charac-teristics interesting for various catalytic applications. The key in obtaining these characteristics is the thermal treatment in a flow of N2. It was demonstrated that the use of He rather than N2 does not allow obtaining the same results. The effect is attributed to the presence of traces of oxygen, enough to create the presence of oxygen functional groups on the surface temperatures higher than 750 °C, when graphitization occurs. These oxygen functional groups favor the graphitization pro-cess.

  4. Transformation of amorphous calcium carbonate to rod-like single crystal calcite via "copying" collagen template.

    Science.gov (United States)

    Xue, Zhonghui; Hu, Binbin; Dai, Shuxi; Du, Zuliang

    2015-10-01

    Collagen Langmuir films were prepared by spreading the solution of collagen over deionized water, CaCl2 solution and Ca(HCO3)2 solution. Resultant collagen Langmuir monolayers were then compressed to a lateral pressure of 10 mN/m and held there for different duration, allowing the crystallization of CaCO3. The effect of crystallization time on the phase composition and microstructure of CaCO3 was investigated. It was found that amorphous calcium carbonate (ACC) was obtained at a crystallization time of 6 h. The amorphous CaCO3 was transformed to rod-like single crystal calcite crystals at an extended crystallization time of 12 h and 24 h, via "copying" the symmetry and dimensionalities of collagen fibers. Resultant calcite crystallites were well oriented along the longitudinal axis of collagen fibers. The ordered surface structure of collagen fibers and electrostatic interactions played key roles in tuning the oriented nucleation and growth of the calcite crystallites. The mineralized collagen possessing both desired mechanical properties of collagen fiber and good biocompatibility of calcium carbonate may be assembled into an ideal biomaterial for bone implants.

  5. Plasma deposition of diamond-like carbon and fluorinated amorphous carbon and the resultant properties and structure

    Science.gov (United States)

    Glew, Alexander David

    Researchers first created diamondlike carbon (DLC) 50 years ago, but it has only been the subject of intense research for the last decade. DLC is a highly stressed thin film that exists as a mixture of diamond like sp 3 and graphite like sp2 bonded carbon, with 0--50% H. Many believe that high intrinsic stress states are necessary to stabilize the carbon spa content responsible for the high hardness of DLC. This author's goals include fabricating high quality fluorinated amorphous carbon (FLAC) films by plasma enhanced chemical vapor deposition (PECVD), exploring the relationships between the processing parameters and the dielectric value, as well as the related material properties which limit the useful application of FLAC. An improved understanding of the fundamentals behind FLAC processing may allow workers to improve upon the properties limiting its use, such as intrinsic stress, thermal stability, and thermal conductivity. DLC and FLAC film hardness ranged from 14--16 GP and 16--18 GPa respectively. Their film stress ranged from 800 MPa to a 10 GPa. A study of the thickness dependent properties showed that only films thicker than 200 nm were able to achieve stresses greater than approximately 1.6 GPa, the room temperature transition pressure of graphite to diamond. X-ray photoelectron spectroscopy measurements also yielded different C sp3 contents for films of varying thickness deposited under the same conditions, helping to confirm a thickness dependence of film properties greater than 200 nm. Observation of the stress in real time during annealing of the films on Si wafers yielded activation energy values for the stress relief of DLC and FLAC as 0.11 and 0.24 eV respectively, and the CTE of DLC as 10.6 x 10-6 C-1. The stress relief mechanism consists of kinetically limited network arrangements that occur in highly stressed zones due heating, which are also the cause of the reduction in dielectric constant that occurs during rapid thermal annealing. Thermal

  6. Preparation of flat carbon support films

    NARCIS (Netherlands)

    Koning, RI; Oostergetel, GT; Brisson, A

    2003-01-01

    Wrinkling of carbon support films is known to limit the resolution of electron microscopy images of protein two-dimensional crystals. The origin of carbon wrinkling during preparation of the support films was investigated by reflected light microscopy. We observed that carbon films go through severa

  7. Grazing incidence X-ray absorption characterization of amorphous Zn-Sn-O thin film

    Science.gov (United States)

    Moffitt, S. L.; Ma, Q.; Buchholz, D. B.; Chang, R. P. H.; Bedzyk, M. J.; Mason, T. O.

    2016-05-01

    We report a surface structure study of an amorphous Zn-Sn-O (a-ZTO) transparent conducting film using the grazing incidence X-ray absorption spectroscopy technique. By setting the measuring angles far below the critical angle at which the total external reflection occurs, the details of the surface structure of a film or bulk can be successfully accessed. The results show that unlike in the film where Zn is severely under coordinated (N coordinated (N = 4) near the surface while the coordination number around Sn is slightly smaller near the surface than in the film. Despite a 30% Zn doping, the local structure in the film is rutile-like.

  8. Structure and magnetic properties of amorphous and polycrystalline Fe3O4 thin films

    Institute of Scientific and Technical Information of China (English)

    TANG Xiao-li; ZHANG Huai-wu; SU Hua; ZHONG Zhi-yong; JING Yu-lan

    2006-01-01

    Half-metallic Fe3O4 films prepared by DC magnetron reactive sputtering with a tantalum(Ta) buffer layer was investigated. Primary emphasis is placed on the structural impact on its magnetic properties. The experimental results show that the amorphous Fe3O4 films exhibit a superparamagnetic response at a large-scale from 20 nm to 150 nm,and the magnetoresistance (MR) isn't detected. By contrast,the polycrystalline Fe3O4 films possess large saturation magnetization Ms of 420 A/(kg-cm) and a clear magnetoresistance with a field of 40 kA/m. The unusual properties for the amorphous Fe3O4 film are attributed to the existing large density of the similar structure as anti-phase boundaries in the film.

  9. Nanodiamonds on tetrahedral amorphous carbon significantly enhance dopamine detection and cell viability.

    Science.gov (United States)

    Peltola, Emilia; Wester, Niklas; Holt, Katherine B; Johansson, Leena-Sisko; Koskinen, Jari; Myllymäki, Vesa; Laurila, Tomi

    2017-02-15

    We hypothesize that by using integrated carbon nanostructures on tetrahedral amorphous carbon (ta-C), it is possible to take the performance and characteristics of these bioelectrodes to a completely new level. The integrated carbon electrodes were realized by combining nanodiamonds (NDs) with ta-C thin films coated on Ti-coated Si-substrates. NDs were functionalized with mixture of carboxyl and amine groups NDandante or amine NDamine, carboxyl NDvox or hydroxyl groups NDH and drop-casted or spray-coated onto substrate. By utilizing these novel structures we show that (i) the detection limit for dopamine can be improved by two orders of magnitude [from 10µM to 50nM] in comparison to ta-C thin film electrodes and (ii) the coating method significantly affects electrochemical properties of NDs and (iii) the ND coatings selectively promote cell viability. NDandante and NDH showed most promising electrochemical properties. The viability of human mesenchymal stem cells and osteoblastic SaOS-2 cells was increased on all ND surfaces, whereas the viability of mouse neural stem cells and rat neuroblastic cells was improved on NDandante and NDH and reduced on NDamine and NDvox. The viability of C6 cells remained unchanged, indicating that these surfaces will not cause excess gliosis. In summary, we demonstrated here that by using functionalized NDs on ta-C thin films we can significantly improve sensitivity towards dopamine as well as selectively promote cell viability. Thus, these novel carbon nanostructures provide an interesting concept for development of various in vivo targeted sensor solutions.

  10. Immobilization of sericin molecules via amorphous carbon plasma modified-polystyrene dish for serum-free culture

    Energy Technology Data Exchange (ETDEWEB)

    Tunma, Somruthai [The Graduate School, Chiang Mai University, 239 Huay Kaew Road, Muang District, Chiang Mai 50200 (Thailand); Thailand Center of Excellence in Physics (ThEP), 239 Huay Kaew Road, Muang District, Chiang Mai 50200 (Thailand); Song, Doo-Hoon [Research Center for Orofacial Hard Tissue Regeneration, College of Dentistry, Yonsei University, 50 Yonsei-ro, Seodaemun-gu, Seoul 120-752 (Korea, Republic of); Kim, Si-Eun; Kim, Kyoung-Nam [Research Center for Orofacial Hard Tissue Regeneration, College of Dentistry, Yonsei University, 50 Yonsei-ro, Seodaemun-gu, Seoul 120-752 (Korea, Republic of); Department and Research Institute of Dental Biomaterials and Bioengineering, College of Dentistry, Yonsei University, 50 Yonsei-ro, Seodaemun-gu, Seoul 120-752 (Korea, Republic of); Han, Jeon-Geon [Center for Advanced Plasma Surface Technology, Sungkyunkwan University, 300 Chunchun-dong, Jangan-gu, Suwon 440-746 (Korea, Republic of); Boonyawan, Dheerawan, E-mail: dheerawan.b@cmu.ac.th [Thailand Center of Excellence in Physics (ThEP), 239 Huay Kaew Road, Muang District, Chiang Mai 50200 (Thailand); Department of Physics and Materials Science, Faculty of Science, Chiang Mai University, 239 Huay Kaew Road, Muang District, Chiang Mai 50200 (Thailand)

    2013-10-15

    In this study, we focused on sericin hydrolysates, originating from silkworm used in serum-free human bone marrow-derived mesenchymal stem cells (hBM-MSCs) culture. We reported the effect of a covalent linkage between a bioactive protein molecule and polystyrene dish surface via a carbon intermediate layer which can slow down the release rate of protein compounds into the phosphate buffer saline (PBS) solution. Films of amorphous carbon (a-C) and functionalized-carbon were deposited on PS culture dish surfaces by using a DC magnetron sputtering system and RF PECVD system. We found that a-C based-films can increase the hydrophilicity and biocompatibility of polystyrene (PS) dishes, especially a-C films and a-C:N{sub 2} films showed good attachment of hBM-MSCs at 24 h. However, in the case of silica surface (a-C:SiO{sub x} films), the cells showed a ragged and unattached boundary resulting from the presence of surface silanol groups. For the UV–vis absorbance, all carbon modified-PS dishes showed a lower release rate of sericin molecules into PBS solution than PS control. This revealed that the functionalized carbon could be enhanced by specific binding properties with given molecules. The carbon-coated PS dishes grafting with sericin protein were used in a serum-free condition. We also found that hBM-MSCs have higher percentage of proliferated cells at day 7 for the modified dishes with carbon films and coated with sericin than the PS control coated with sericin. The physical film properties were measured by atomic force microscopy (AFM), scanning electron microscope (SEM) and contact angle measurement. The presence of -NH{sub 2} groups of sericin compounds on the PS dish was revealed by Fourier transform infrared spectroscopy (FTIR). The stability of covalent bonds of sericin molecules after washing out ungrafted sericin was confirmed by X-ray photoelectron spectroscopy (XPS).

  11. Magnetic and microwave properties of amorphous FeCoNbBCu thin films

    Science.gov (United States)

    Bi, Mei; Wang, Xin; Lu, Haipeng; Deng, Longjiang; Sunday, Katie Jo; Taheri, Mitra L.; Harris, Vincent G.

    2016-01-01

    The soft magnetic and microwave properties of amorphous FeCoNbBCu thin films with thicknesses varying from 70 nm to 450 nm have been systematically investigated. Due to the amorphous structure, the coercivity is 1.5 Oe in thicker films. The thickness-dependent microwave characteristics of the films were measured over the range 0.5-6 GHz and analyzed using the Landau-Lifshitz-Gilbert equation. Without applying magnetic field during deposition and measurement, an in-plane uniaxial anisotropy in amorphous thin films was obtained, ranging from 21 to 45 Oe. The interface interaction between substrate and film is confirmed to be the origin of the induced anisotropy, whereas the volume anisotropy contribution is more pronounced with increasing film thickness. For films possessing an in-plane uniaxial anisotropy, the shift of resonance frequency with thickness is observed and verified by the Kittel equation. The demonstration of a controllable and tunable anisotropy suggests that the FeCoNbBCu thin films have potential application as magnetic materials for Spintronics-based microwave devices.

  12. Antibacterial efficacy of advanced silver-amorphous carbon coatings deposited using the pulsed dual cathodic arc technique

    Energy Technology Data Exchange (ETDEWEB)

    Endrino, J L; Anders, A; Albella, J M; Horton, J A; Horton, T H; Ayyalasomayajula, P R; Allen, M, E-mail: jlendrino@icmm.csic.es

    2010-11-01

    Amorphous carbon (a-C) also referred as diamond-like carbon (DLC) films are well known to be a biocompatible material with good chemical in ertness; this makes it a strong candidate to be used as a matrix that embeds metallic elements with an antimicrobial effect. We have deposited as et of a-C:Ag films using a dual-cathode pulsed filtered cathodic arc source, the arc pulse frequency of the silver and graphite cathodes was controlled in order to obtain samples with various silver contents. In this study, we show the deposition of silver and carbon ions using this technique and analyze the advantages of incorporating silver into a-C by studying the antimicrobial properties against staphylococcus of samples deposited on Ti{sub 6}Al{sub 4}V coupons and evaluated using 24-well tissue culture plates.

  13. Charge storage characteristics and tunneling mechanism of amorphous Ge-doped HfOx films

    Science.gov (United States)

    Qiu, X. Y.; Zhang, S. Y.; Zhang, T.; Wang, R. X.; Li, L. T.; Zhang, Y.; Dai, J. Y.

    2016-09-01

    Amorphous Ge-doped HfOx films have been deposited on p-Si(100) substrates by means of RF magnetron sputtering. Microstructural investigations reveal the partial oxidation of doped Ge atoms in the amorphous HfOx matrix and the existence of HfSiOx interfacial layer. Capacitance-voltage hysteresis of the Ag-/Ge-doped HfOx/Si/Ag memory capacitor exhibits a memory window of 3.15 V which can maintain for >5 × 104 cycles. Current-voltage characteristics reveal that Poole-Frenkel tunneling is responsible for electron transport in the Ge-doped HfOx film.

  14. Low temperature CVD growth of ultrathin carbon films

    Directory of Open Access Journals (Sweden)

    Chao Yang

    2016-05-01

    Full Text Available We demonstrate the low temperature, large area growth of ultrathin carbon films by chemical vapor deposition under atmospheric pressure on various substrates. In particularly, uniform and continuous carbon films with the thickness of 2-5 nm were successfully grown at a temperature as low as 500 oC on copper foils, as well as glass substrates coated with a 100 nm thick copper layer. The characterizations revealed that the low-temperature-grown carbon films consist on few short, curved graphene layers and thin amorphous carbon films. Particularly, the low-temperature grown samples exhibited over 90% transmittance at a wavelength range of 400-750 nm and comparable sheet resistance in contrast with the 1000oC-grown one. This low-temperature growth method may offer a facile way to directly prepare visible ultrathin carbon films on various substrate surfaces that are compatible with temperatures (500-600oC used in several device processing technologies.

  15. Gas and pressure effects on the synthesis of amorphous carbon nanotubes

    Institute of Scientific and Technical Information of China (English)

    ZHAO Tingkai; LIU Yongning; ZHU Jiewu

    2004-01-01

    The effects of gas, pressure and temperature on the production of amorphous carbon nanotubes were investigated using an arc discharging furnace at controlled temperature. Co/Ni alloy powder was used as catalyst.The discharge current was 80 A and voltage was 32 V. The optimal parameters were obtained: 600℃ temperature, hydrogen gas and 500 torr pressure. The productivity and purity of amorphous carbon nanotubes are 6.5 gram per hour and 80%, respectively. The diameter of the amorphous carbon nanotubes is about 7-20 nm.

  16. Dual ion beam deposition of carbon films with diamondlike properties

    Science.gov (United States)

    Mirtich, M. J.; Swec, D. M.; Angus, J. C.

    1984-01-01

    A single and dual ion beam system was used to generate amorphous carbon films with diamond like properties. A methane/argon mixture at a molar ratio of 0.28 was ionized in the low pressure discharge chamber of a 30-cm-diameter ion source. A second ion source, 8 cm in diameter was used to direct a beam of 600 eV Argon ions on the substrates (fused silica or silicon) while the deposition from the 30-cm ion source was taking place. Nuclear reaction and combustion analysis indicate H/C ratios for the films to be 1.00. This high value of H/C, it is felt, allowed the films to have good transmittance. The films were impervious to reagents which dissolve graphitic and polymeric carbon structures. Although the measured density of the films was approximately 1.8 gm/cu cm, a value lower than diamond, the films exhibited other properties that were relatively close to diamond. These films were compared with diamondlike films generated by sputtering a graphite target.

  17. Nanostructuring of GeTiO amorphous films by pulsed laser irradiation

    Directory of Open Access Journals (Sweden)

    Valentin S. Teodorescu

    2015-04-01

    Full Text Available Laser pulse processing of surfaces and thin films is a useful tool for amorphous thin films crystallization, surface nanostructuring, phase transformation and modification of physical properties of thin films. Here we show the effects of nanostructuring produced at the surface and under the surface of amorphous GeTiO films through laser pulses using fluences of 10–30 mJ/cm2. The GeTiO films were obtained by RF magnetron sputtering with 50:50 initial atomic ratio of Ge:TiO2. Laser irradiation was performed by using the fourth harmonic (266 nm of a Nd:YAG laser. The laser-induced nanostructuring results in two effects, the first one is the appearance of a wave-like topography at the film surface, with a periodicity of 200 nm and the second one is the structure modification of a layer under the film surface, at a depth that is related to the absorption length of the laser radiation. The periodicity of the wave-like relief is smaller than the laser wavelength. In the modified layer, the Ge atoms are segregated in spherical amorphous nanoparticles as a result of the fast diffusion of Ge atoms in the amorphous GeTiO matrix. The temperature estimation of the film surface during the laser pulses shows a maximum of about 500 °C, which is much lower than the melting temperature of the GeTiO matrix. GeO gas is formed at laser fluences higher than 20 mJ/cm2 and produces nanovoids in the laser-modified layer at the film surface. A glass transition at low temperatures could happen in the amorphous GeTiO film, which explains the formation of the wave-like topography. The very high Ge diffusivity during the laser pulse action, which is characteristic for liquids, cannot be reached in a viscous matrix. Our experiments show that the diffusivity of atomic and molecular species such as Ge and GeO is very much enhanced in the presence of the laser pulse field. Consequently, the fast diffusion drives the formation of amorphous Ge nanoparticles through the

  18. Anisotropies in magnetron sputtered carbon nitride thin films

    Science.gov (United States)

    Hellgren, Niklas; Johansson, Mats P.; Broitman, Esteban; Hultman, Lars; Sundgren, Jan-Eric

    2001-04-01

    Carbon nitride CNx (0⩽x⩽0.35) thin films, deposited by reactive dc magnetron sputtering in Ar/N2 discharges have been studied with respect to microstructure using electron microscopy, and elastic modulus using nanoindentation and surface acoustic wave analyses. For growth temperature of 100 °C, the films were amorphous, and with an isotropic Young's modulus of ˜170-200 GPa essentially unaffected by the nitrogen fraction. The films grown at elevated temperatures (350-550 °C) show anisotropic mechanical properties due to a textured microstructure with standing basal planes, as observed from measuring the Young's modulus in different directions. The modulus measured in the plane of the film was ˜60-80 GPa, while in the vertical direction the modulus increased considerably from ˜25 to ˜200 GPa as the nitrogen content was increased above ˜15 at. %.

  19. Density and localized states' impact on amorphous carbon electron transport mechanisms

    Science.gov (United States)

    Caicedo-Dávila, S.; Lopez-Acevedo, O.; Velasco-Medina, J.; Avila, A.

    2016-12-01

    This work discusses the electron transport mechanisms that we obtained as a function of the density of amorphous carbon (a-C) ultra-thin films. We calculated the density of states (total and projected), degree of electronic states' localization, and transmission function using the density functional theory and nonequilibrium Green's functions method. We generated 25 sample a-C structures using ab-initio molecular dynamics within the isothermal-isobaric ensemble. We identified three transport regimes as a function of the density, varying from semimetallic in low-density samples ( ≤2.4 g/cm3) to thermally activated in high-density ( ≥2.9 g/cm3) tetrahedral a-C. The middle-range densities (2.4 g/cm3 ≤ρ≤ 2.9 g/cm3) are characterized by resonant tunneling and hopping transport. Our findings offer a different perspective from the tight-binding model proposed by Katkov and Bhattacharyya [J. Appl. Phys. 113, 183712 (2013)], and agree with experimental observations in low-dimensional carbon systems [see S. Bhattacharyya, Appl. Phys. Lett. 91, 21 (2007)]. Identifying transport regimes is crucial to the process of understanding and applying a-C thin film in electronic devices and electrode coating in biosensors.

  20. Flexible amorphous oxide thin-film transistors on polyimide substrate for AMOLED

    Science.gov (United States)

    Xu, Zhiping; Li, Min; Xu, Miao; Zou, Jianhua; Gao, Zhuo; Pang, Jiawei; Guo, Ying; Zhou, Lei; Wang, Chunfu; Fu, Dong; Peng, Junbiao; Wang, Lei; Cao, Yong

    2014-10-01

    We report a flexible amorphous Lanthanide doped In-Zn-O (IZO) thin-film transistor (TFT) backplane on polyimide (PI) substrate. In order to de-bond the PI film from the glass carrier easily after the flexible AMOLED process, a special inorganic film is deposited on the glass before the PI film is coated. The TFT exhibited a field-effect mobility of 6.97 cm2V-1 s-1, a subthreshold swing of 0.248 V dec-1, and an Ion/Ioff ratio of 5.19×107, which is sufficient to drive the OLEDs.

  1. Investigation of crystallization and amorphization dynamics of phase-change thin films by subnanosecond laser pulses.

    Science.gov (United States)

    Kieu, Khanh; Narumi, Kenji; Mansuripur, Masud

    2006-10-20

    We report experimental results on amorphization and crystallization dynamics of reversible phase-change (PC) thin-film samples, GeSbTe and GeBiTe, for optical disk data storage. The investigation was conducted with subnanosecond laser pulses using a pump-and-probe configuration. Amorphization of the crystalline films could be achieved with a single subnanosecond laser pulse; the amorphization dynamics follow closely the temperature kinetics induced in the irradiated spot. As for crystallization of the samples initially in the amorphous state, a single subnanosecond pulse was found to be insufficient to fully crystallize the irradiated spot, but we could crystallize the PC film (in the area under the focused spot) by applying multiple short pulses. Our multipulse studies reveal that the GeSbTe crystallization is dominated by the growth of nuclei whose initial formation is slow but, once formed, their subsequent growth (under a sequence of subnanosecond pulses) happens quickly. In the case of GeBiTe samples, the crystalline nuclei appear to be present in the material initially, as they grow immediately upon illumination with laser pulses. Whereas our amorphous GeSbTe samples required approximately 200 pulses for full crystallization, for the GeBiTe samples approximately 15 pulses sufficed.

  2. Structural Changes of Amorphous GeTe2 Films by Annealing (Formation of Metastable Crystalline GeTe2 Films)

    Science.gov (United States)

    Fukumoto, Hirofumi; Tsunetomo, Keiji; Imura, Takeshi; Osaka, Yukio

    1987-01-01

    Amorphous GeTe2 films with the thickness ˜0.5 μm, prepared by sputtering technique, transform into the crystalline GeTe2 films with the isomorphic structure to β-cristobalite, cubic SiO2, at Ta(annealing temperature){=}200°C. The cubic phase of GeTe2 is metastable and decomposes into the mixed crystal of GeTe and Te at Ta{=}250°C.

  3. Research on high-efficiency, single-junction, monolithic, thin-film amorphous silicon solar cells

    Science.gov (United States)

    Wiesmann, H.; Dolan, J.; Fricano, G.; Danginis, V.

    1987-02-01

    A study was undertaken of the optoelectronic properties of amorphous silicon-hydrogen thin films deposited from disilane at high deposition rates. The information derived from this study was used to fabricate amorphous silicon solar cells with efficiencies exceeding 7%. The intrinsic layer of these solar cells was deposited at 15 angstroms/second. Material properties investigated included dark conductivity, photoconductivity, minority carrier diffusion length, and density of states. The solar cells properties characterized were absolute quantum yield and simulated global AM 1.5 efficiencies. Investigations were undertaken utilizing optical and infrared spectroscopy to optimize the microstructures of the intrinsic amorphous silicon. That work was sponsored by the New York State Energy Research and Development Authority. The information was used to optimize the intrinsic layer of amorphous silicon solar cells, resulting in AM 1.5 efficiencies exceeding 7%.

  4. Wake potential of swift ion in amorphous carbon target

    Science.gov (United States)

    Al-Bahnam, Nabil janan; Ahmad, Khalid A.; Aboo Al-Numan, Abdullah Ibrahim

    2017-02-01

    The wake potential and wake phenomena for swift proton in an amorphous carbon target were studied by utilising various dielectric function formalisms, including the Drude dielectric function, the Drude-Lorentz dielectric function and quantum dielectric function. The Drude model results exhibited a damped oscillatory behaviour in the longitudinal direction behind the projectile; the pattern of these oscillations decreases exponentially in the transverse direction. In addition, the wake potential extends slightly ahead of the projectile which also depends on the proton coordinate and velocity. The effect of electron binding on the wake potential, characterised by the ratio ωp2 / ω02 = 10 to 0.1, has been studied alongside the Drude-Lorentz dielectric function and quantum dielectric function formalisms; the results evidently show that the wake potential dip depth decreases with more oscillations when the electron density ratio ωp2 / ω02 decreases from 10 to 0.1. One of the primary objectives of the present work is to construct a reasonably realistic procedure for simulating the response of target to swift ions by combining an expression for the induced wake potential along with several important dielectric function models; the aim of this research is to reduce computational complexity without sacrificing accuracy. This is regarded as being an efficient strategy in that it creates suitable computer simulation procedures which are relevant to actual solids. After comparing this method with other models, the main differences and similarities have been noted while the end results have proved encouraging.

  5. Simulation of swift boron clusters traversing amorphous carbon foils

    Science.gov (United States)

    Heredia-Avalos, Santiago; Abril, Isabel; Denton, Cristian D.; Garcia-Molina, Rafael

    2007-01-01

    We use a simulation code to study the interaction of swift boron clusters ( Bn+ , n=2-6 , 14) with amorphous carbon foils. We analyze different aspects of this interaction, such as the evolution of the cluster structure inside the target, the energy and angle distributions at the detector or the stopping power ratio. Our simulation code follows in detail the motion of the cluster fragments through the target and in the vacuum until reaching a detector, taking into account the following interactions: (i) wake force, (ii) Coulomb repulsion among cluster fragments, (iii) stopping force, and (iv) elastic scattering with the target nuclei. Electron capture and loss by each fragment is also included in the code, affecting the above-mentioned interactions. The clusters size grows inside the foil due mainly to the Coulomb explosion but this increase is less pronounced in the plane transversal to the beam direction because of the alignment effect of the wake forces. We obtain an enhancement of the stopping power ratio that increases with the projectile energy and with the number of molecular constituents. Our results agree very well with the available experimental data for the thicker foils (≳10μg/cm2) and are compatible (within the experimental error bars) for the thinner foils.

  6. Spectroscopy and structural properties of amorphous and nanocrystalline silicon carbide thin films

    NARCIS (Netherlands)

    Halindintwali, Sylvain; Knoesen, D.; Julies, B.A.; Arendse, C.J.; Muller, T.; Gengler, Régis Y.N.; Rudolf, P.; Loosdrecht, P.H.M. van

    2011-01-01

    Amorphous SiC:H thin films were grown by hot wire chemical vapour deposition from a SiH4/CH4/H2 mixture at a substrate temperature below 400 °C. Thermal annealing in an argon environment up to 900 °C shows that the films crystallize as μc-Si:H and SiC with a porous microstructure that favours an oxi

  7. Electronic transport in mixed-phase hydrogenated amorphous/nanocrystalline silicon thin films

    Science.gov (United States)

    Wienkes, Lee Raymond

    Interest in mixed-phase silicon thin film materials, composed of an amorphous semiconductor matrix in which nanocrystalline inclusions are embedded, stems in part from potential technological applications, including photovoltaic and thin film transistor technologies. Conventional mixed-phase silicon films are produced in a single plasma reactor, where the conditions of the plasma must be precisely tuned, limiting the ability to adjust the film and nanoparticle parameters independently. The films presented in this thesis are deposited using a novel dual-plasma co-deposition approach in which the nanoparticles are produced separately in an upstream reactor and then injected into a secondary reactor where an amorphous silicon film is being grown. The degree of crystallinity and grain sizes of the films are evaluated using Raman spectroscopy and X-ray diffraction respectively. I describe detailed electronic measurements which reveal three distinct conduction mechanisms in n-type doped mixed-phase amorphous/nanocrystalline silicon thin films over a range of nanocrystallite concentrations and temperatures, covering the transition from fully amorphous to ~30% nanocrystalline. As the temperature is varied from 470 to 10 K, we observe activated conduction, multiphonon hopping (MPH) and Mott variable range hopping (VRH) as the nanocrystal content is increased. The transition from MPH to Mott-VRH hopping around 100K is ascribed to the freeze out of the phonon modes. A conduction model involving the parallel contributions of these three distinct conduction mechanisms is shown to describe both the conductivity and the reduced activation energy data to a high accuracy. Additional support is provided by measurements of thermal equilibration effects and noise spectroscopy, both done above room temperature (>300 K). This thesis provides a clear link between measurement and theory in these complex materials.

  8. Formation and structure of V-Zr amorphous alloy thin films

    KAUST Repository

    King, Daniel J M

    2015-01-01

    Although the equilibrium phase diagram predicts that alloys in the central part of the V-Zr system should consist of V2Zr Laves phase with partial segregation of one element, it is known that under non-equilibrium conditions these materials can form amorphous structures. Here we examine the structures and stabilities of thin film V-Zr alloys deposited at room temperature by magnetron sputtering. The films were characterized by X-ray diffraction, transmission electron microscopy and computational methods. Atomic-scale modelling was used to investigate the enthalpies of formation of the various competing structures. The calculations confirmed that an amorphous solid solution would be significantly more stable than a random body-centred solid solution of the elements, in agreement with the experimental results. In addition, the modelling effort provided insight into the probable atomic configurations of the amorphous structures allowing predictions of the average distance to the first and second nearest neighbours in the system.

  9. Effect of varying nitrogen flow rates on the optical properties of amorphous-SiCN thin films

    Science.gov (United States)

    Rahman, Mohd Azam Abdul; Tong, Goh Boon; Mahmood, Mohamad Rusop; Siong, Chiu Wee; Yian, Haw Choon; Rahman, Saadah Abdul

    2016-11-01

    Series of amorphous silicon carbon nitride (a-SiCN) films are synthesized using RF-PECVD technique on glass and silicon substrates from precursor gas of silane, methane and nitrogen. In this work, the change in nitrogen flow rate from 0 sccm to 50 sccm is a mean used to vary the elemental composition and bonding properties which lead to change in optical properties. The films thickness varies between 327 nm to 944 nm. The changes for the stated properties are discussed against the change in the stated nitrogen flow rate. The optical properties are investigated by means of UV-VIS spectroscopy in the wavelength range of 190 nm to 2500 nm. The transmittance of the films at ultra-violet wavelength is found to increases with increase in nitrogen flow rate. The index of refraction, n obtained for SiCN films from transmittance and reflectance measurements is lower compared to SiC films. The films optical band gap increases from 1.74 eV to 2.08 eV before it decreases to 1.89 eV as nitrogen flow rate increases from 0 to 50 sccm. The optical dispersion parameters were determined according to Wemple and Didomenico method.

  10. Transformation from amorphous to nano-crystalline SiC thin films prepared by HWCVD technique without hydrogen dilution

    Indian Academy of Sciences (India)

    F Shariatmadar Tehrani

    2015-09-01

    Silicon carbide (SiC) thin films were deposited on Si(111) by the hot wire chemical vapour deposition (HWCVD) technique using silane (SiH4) and methane (CH4) gases without hydrogen dilution. The effects of SiH4 to CH4 gas flow ratio (R) on the structural properties, chemical composition and photoluminescence (PL) properties of the films deposited at the different gas flow ratios were investigated and compared. X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectra revealed a structural transition from amorphous SiC to cubic nano-crystalline SiC films with the increase in the gas flow ratio. Raman scattering confirmed the multi-phased nature of the films. Auger electron spectroscopy showed that the carbon incorporation in the film structure was strongly dependent on the gas flow ratio. A similar broad visible room-temperature PL with two peaks was observed for all SiC films. The main PL emission was correlated to the band to band transition in uniform a-SiC phase and the other lower energy emission was related to the confined a-Si : H clusters in a-SiC matrix. SiC nano-crystallites exhibit no significant contribution to the radiative recombination.

  11. Energy-level density of amorphous carbon and its modification by the annealing

    CERN Document Server

    Ivanov-Omskij, V I; Tagliaferro, A; Fanchini, G

    2002-01-01

    Annealing influence on the modification of electron density states of amorphous carbon a-C and amorphous hydrogenated carbon a-C:H has been studied. Optical transmission spectra were studied in 1.5-5.6 eV range and ellipsometric angles were measured for He-Ne laser wavelength. The model was suggested of the optical response of amorphous carbon. This model was based on the hypothesis of size fluctuations of sp sup 2 -components of amorphous carbon. The size of the optical gap E sub g for both types of materials was explained in terms of availability of fluctuations of their allotropic content having critical values. The dependence of the density of states of electrons both in fundamental and excited bands on the energy experimental data using model parameters

  12. Depth profile study on Raman spectra of high-energy-electron-irradiated hydrogenated amorphous silicon films

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    According to the different penetration depths for the incident lights of 472 nm and 532 nm in hydrogenated amorphous silicon (a-Si:H) thin films, the depth profile study on Raman spectra of a-Si:H films was carried out. The network ordering evolution in the near surface and interior region of the unirradiated and irradiated a-Si:H films was investigated. The results show that there is a structural improvement in the shortand intermediate-range order towards the surface of the unirradiated a-Si:H films. The amorphous silicon network in the near and interior region becomes more disordered on the shortand intermediate-range scales after being irradiated with high energy electrons. However, the surface of the irradiated films becomes more disordered in comparison with their interior region, indicating that the created defects caused by electron irradiation are concentrated in the near surface of the irradiated films. Annealing eliminates the irradiation effects on a-Si:H thin films and the structural order of the irradiated films is similar to that of the unirradiated ones after being annealed. There exists a structural improvement in the shortand intermediate-range order towards the surface of the irradiated a-Si:H films after being annealed.

  13. Conduction mechanism in amorphous InGaZnO thin film transistors

    NARCIS (Netherlands)

    Bhoolokam, A.; Nag, M.; Steudel, S.; Genoe, J.; Gelinck, G.; Kadashchuk, A.; Groeseneken, G.; Heremans, P.

    2016-01-01

    We validate a model which is a combination of multiple trapping and release and percolation model for describing the conduction mechanism in amorphous indium gallium zinc oxide (a-IGZO) thin film transistors (TFT). We show that using just multiple trapping and release or percolation model is insuffi

  14. Charge transport in amorphous InGaZnO thin-film transistors

    NARCIS (Netherlands)

    Germs, W.C.; Adriaans, W.H.; Tripathi, A.K.; Roelofs, W.S.C.; Cobb, B.; Janssen, R.A.J.; Gelinck, G.H.; Kemerink, M.

    2012-01-01

    We investigate the mechanism of charge transport in indium gallium zinc oxide (a-IGZO), an amorphous metal-oxide semiconductor. We measured the field-effect mobility and the Seebeck coefficient (S=ΔV/ΔT) of a-IGZO in thin-film transistors as a function of charge-carrier density for different tempera

  15. Method of forming semiconducting amorphous silicon films from the thermal decomposition of fluorohydridodisilanes

    Science.gov (United States)

    Sharp, Kenneth G.; D'Errico, John J.

    1988-01-01

    The invention relates to a method of forming amorphous, photoconductive, and semiconductive silicon films on a substrate by the vapor phase thermal decomposition of a fluorohydridodisilane or a mixture of fluorohydridodisilanes. The invention is useful for the protection of surfaces including electronic devices.

  16. Photoconductivity studies on amorphous and crystalline TiO{sub 2} films doped with gold nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Valverde-Aguilar, G.; Garcia-Macedo, J.A. [Universidad Nacional Autonoma de Mexico, Departamento de Estado Solido, Instituto de Fisica, Mexico D.F. (Mexico); Renteria-Tapia, V. [Universidad de Guadalajara, Centro Universitario de los Valles, Departamento de Ciencias Naturales y Exactas, Ameca, Jalisco (Mexico); Aguilar-Franco, M. [Universidad Nacional Autonoma de Mexico, Departamento de Fisica Quimica, Instituto de Fisica, Mexico D.F. (Mexico)

    2011-06-15

    In this work, amorphous and crystalline TiO{sub 2} films were synthesized by the sol-gel process at room temperature. The TiO{sub 2} films were doped with gold nanoparticles. The films were spin-coated on glass wafers. The crystalline samples were annealed at 100 C for 30 minutes and sintered at 520 C for 2 h. All films were characterized using X-ray diffraction, transmission electronic microscopy and UV-Vis absorption spectroscopy. Two crystalline phases, anatase and rutile, were formed in the matrix TiO{sub 2} and TiO{sub 2}/Au. An absorption peak was located at 570 nm (amorphous) and 645 nm (anatase). Photoconductivity studies were performed on these films. The experimental data were fitted with straight lines at darkness and under illumination at 515 nm and 645 nm. This indicates an ohmic behavior. Crystalline TiO{sub 2}/Au films are more photoconductive than the amorphous ones. (orig.)

  17. Films Composed Of Diamond And Diamondlike Carbon

    Science.gov (United States)

    Shing, Yuh-Han

    1995-01-01

    Proposed films composed of diamond and diamondlike carbon useful as wear-resistant and self-lubricating protective and tribological coats at extreme temperatures and in corrosive and oxidizing environments. Films have wide variety of industrial applications.

  18. Deposition of diamond like carbon films by using a single ion gun with varying beam source

    Institute of Scientific and Technical Information of China (English)

    JIANG Jin-qiu; Chen Zhu-ping

    2001-01-01

    Diamond like carbon films have been successfully deposited on the steel substrate, by using a single ion gun with varying beam source. The films may appear blue, yellow and transparent in color, which was found related to contaminants from the sample holder and could be avoided. The thickness of the films ranges from tens up to 200 nanometers, and the hardness is in the range 20 to 30 GPa. Raman analytical results reveal the films are in amorphous structure. The effects of different beam source on the films structure are further discussed.

  19. Photocatalytic degradation characteristic of amorphous TiO2-W thin films deposited by magnetron sputtering

    Institute of Scientific and Technical Information of China (English)

    HUANG Jia-mu; LI Yue-xia; ZHAO Guo-dong; CAI Xiao-ping

    2006-01-01

    TiO2-W films were deposited on the slides by reactive magnetron sputtering. Properties of the films were analyzed via AFM,XRD,XPS,STS,UV-Vis and ellipse polarization apparatus. The results show that TiO2-W films are amorphous. The AFM map reveals that the surface of the film is tough and porous. The experiments of decomposing methylene blue indicate that the thickness threshold on these films is 141 nm,at which the rate of photodegradation is 90% in 2 h. And when the thickness is over 141 nm,the rate of photodegradation does not increase any more. This result is completely different from that of crystalloid TiO2 thin film.

  20. Magnetic Properties of Co-Fe-B Amorphous Films Thermomagnetically Treated with Different Field Directions

    Directory of Open Access Journals (Sweden)

    Zhe Liu

    2012-01-01

    Full Text Available Co-Fe-B films were prepared by electroless plating. As-deposited films were thermomagnetically treated in the applied magnetic field of 500 Oe with different field directions at 300°C for 1 hour. The effects of magnetic field direction of thermomagnetic treatment on the structure and magnetic properties of Co-Fe-B thin films were investigated. It is found that two phases existed in annealed Co-Fe-B films: one is weak crystallized CoFe phase, the other being amorphous phase. The surface morphologies of the treated films are found to be affected by the direction of thermomagnetic treatment field. The results also show that the magnetic properties of thermomagnetically treated films are influenced greatly by the treatment field direction.

  1. 石墨表层对四面体非晶炭膜中受激电子的石墨建序化作用%The role of a graphitic surface layer in electron-stimulated ordering in tetrahedral amorphous carbon films

    Institute of Scientific and Technical Information of China (English)

    梁士金; Tatsuya Banno; Yutaka Mera; Masahiro Kitajima; Kunie Ishioka; Yoshihisa Harada; Yoshinori Kitajima; Shik Shin; Koji Maeda

    2008-01-01

    对渗气阴极真空电弧法制备的四而体非晶炭(ta-c)膜实施氧等离子体刻蚀,消除其表面石墨层后,发现:原沉积膜中ta-C石墨表层的消除会影响其受激电子的石墨建序化.应用发射电子能耗谱,表面增强拉曼光谱和表面敏化X光吸收光谱等测量方法,测定了其表层的淌除(程度).样品的氧等离子体刻蚀阻迟了受激电子的石墨化作用,可能归因于多相成核过程中石墨晶核的缺失之故.%Electron-stimulated graphitic ordering in tetrahedral amorphous carbon (ta-C) films was found to be affected by the removal of the graphitic surface layer present in as-deposited films. To remove the graphitic layer on ta-C films fabricated by the filtered cathodic vacuum are method, the sample was etched with oxygen plasma. The removal of the surface layer was examined by transmission electron energy loss spectroscopy, surface-enhanced Raman spectroscopy,and surface-sensitive X-ray absorption spectroscopic measurements. The electron-stimulated graphitization was retarded in oxygen plasma etched samples presumably owing to the lack of graphitic nuclei for heterogeneous nucleation.

  2. Convective heat transfer enhancement using Carbon nanofibers (CNFs): influence of amorphous carbon layer on heat transfer performance

    NARCIS (Netherlands)

    Taha, T.J.; Lefferts, L.; Meer, van der T.H.

    2013-01-01

    In this work, an experimental heat transfer investigation was carried out to investigate the combined influence of both amorphous carbon (a-C) layer thickness and carbon nanofibers (CNFs) on the convective heat transfer behavior. Synthesis of these carbon nano structures was achieved using catalytic

  3. Helium release and amorphization resistance in ion irradiated nanochannel films

    Science.gov (United States)

    Hong, Mengqing; Wang, Yongqiang; Ren, Feng; Zhang, Hongxiu; Fu, Dejun; Yang, Bing; Xiao, Xiangheng; Jiang, Changzhong

    2014-04-01

    Volumetric swelling, surface blistering, exfoliation and embrittlement partially induced by the aggregation of gas bubbles are serious problems for materials in nuclear reactors. This letter demonstrates that the “vein-like” nanochannel films possess greater He management capability and radiation tolerance. For a given fluence, the He bubble size in the nanochannel film decreases with increasing the nanochannel density. For a given nanochannel density, the bubble size increases with increasing fluence initially but levels off to a maximum value of 0.8 nm after the ion fluence reaches 2\\times10^{17}\\ \\text{ions/cm}^{2} , corresponding to He release ratio of 79% in the irradiated CrN RT films. The abundant surfaces in the nanochannel films are perfect defect sinks and thereby large sized He bubbles and supersaturated defects are less likely to be developed in these high radiation tolerant materials.

  4. Structural and magnetic properties of FeNi thin films fabricated on amorphous substrates

    Energy Technology Data Exchange (ETDEWEB)

    Tashiro, T. Y.; Mizuguchi, M., E-mail: mizuguchi@imr.tohoku.ac.jp; Kojima, T.; Takanashi, K. [Institute for Materials Research, Tohoku University, Aoba-ku, Sendai 980-8577 (Japan); Koganezawa, T.; Kotsugi, M.; Ohtsuki, T. [Japan Synchrotron Radiation Research Institute (JASRI/SPring-8), Sayo, Hyogo 679-5198 (Japan)

    2015-05-07

    FeNi films were fabricated by sputtering and rapid thermal annealing on thermally amorphous substrates to realize the formation of an L1{sub 0}-FeNi phase by a simple method. Structural and magnetic properties of FeNi films were investigated by varying the annealing temperature. L1{sub 0}-FeNi superlattice peaks were not observed in X-ray diffraction patterns, indicating no formation of L1{sub 0}-ordered phase, however, the surface structure systematically changed with the annealing temperature. Magnetization curves also revealed a drastic change depending on the annealing temperature, which indicates the close relation between the morphology and magnetic properties of FeNi films fabricated on amorphous substrates.

  5. Al-induced Lateral Crystallization of Amorphous Si Thin Films by Microwave Annealing

    Institute of Scientific and Technical Information of China (English)

    RAO Rui; XU Zhong-yang; ZENG Xiang-bing

    2002-01-01

    Al-induced lateral crystallization of amorphous silicon thin films by microwave annealing is investigated. The crystallized Si films are examined by optical microscopy , Raman spectroscopy, transmission electron microscopy and transmission electron diffraction micrography. After microwave annealing at 480 ℃ for 50 min,the amorphous Si is completely crystallized with large grains of main ( 111 ) orientation. The rate of lateral crystallization is 0.04μm/min. This process, labeled MILC-MA, not only lowers the temperature but also reduces the time of crystallization. The crystallization mechanism during microwave annealing and the electrical properties of polycrystalline Si thin films are analyzed. This MILC-MA process has potential applications in large area electronics.

  6. Hall effect in semiconducting epitaxial and amorphous Y-Ba-Cu-O thin films

    Energy Technology Data Exchange (ETDEWEB)

    Shan, P.; Jahanzeb, A.; Butler, D.P.; Celik-Butler, Z. [Department of Electrical Engineering, Southern Methodist University, Dallas, Texas 75275 (United States); Kula, W.; Sobolewski, R. [Department of Electrical Engineering and Laboratory for Laser Energetics, University of Rochester, Rochester, New York 14627 (United States)

    1997-05-01

    An experimental study of the Hall effect in nonmetallic Y-Ba-Cu-O thin films is reported. Both epitaxial crystalline YBa{sub 2}Cu{sub 3}O{sub 6+x} (x{le}0.5) and multiphase/amorphous Y-Ba-Cu-O thin films were studied. The structure of the samples was measured by x-ray diffraction and Raman microprobe. The amorphous Y-Ba-Cu-O samples were found to have a grain size of about 100 {Angstrom}. The conduction properties were studied and analyzed for the two types of samples over a wide temperature range including room temperature. The Hall effect measurements showed positive charge carriers with a concentration ranging from 10{sup 17} to 10{sup 20} cm{sup {minus}3} at room temperature. The mobility was found to decrease with higher Hall carrier concentration. The empirical relationship for the mobility dependence on impurity concentration agreed with the relationship between mobility and the experimental Hall carrier concentration, suggesting that the same localized states were responsible for both providing the carriers and reducing the mobility through scattering. It was also observed that the mobility values for both amorphous and crystalline samples followed the same empirical curve, a result which showed that the conduction mechanisms in the epitaxial (tetragonal) and amorphous Y-Ba-Cu-O materials are very likely to be similar despite the differences in the composition and structure of the films. The similarity is consistent with other work that concludes that the conduction mechanism occurs along the copper oxide planes. Our work implies that the conduction mechanism operates over a short range, less than the 100 {Angstrom} grain size of the amorphous, such that the lack of order in the amorphous samples was essentially irrelevant to the charge transport. {copyright} {ital 1997 American Institute of Physics.}

  7. Hall effect in semiconducting epitaxial and amorphous Y-Ba-Cu-O thin films

    Science.gov (United States)

    Shan, Pao-Chuan; Jahanzeb, Agha; Butler, Donald P.; ćelik-Butler, Zeynep; Kula, Witold; Sobolewski, Roman

    1997-05-01

    An experimental study of the Hall effect in nonmetallic Y-Ba-Cu-O thin films is reported. Both epitaxial crystalline YBa2Cuoverflow="scroll">3O6+x (x⩽0.5) and multiphase/amorphous Y-Ba-Cu-O thin films were studied. The structure of the samples was measured by x-ray diffraction and Raman microprobe. The amorphous Y-Ba-Cu-O samples were found to have a grain size of about 100 Å. The conduction properties were studied and analyzed for the two types of samples over a wide temperature range including room temperature. The Hall effect measurements showed positive charge carriers with a concentration ranging from 1017 to 1020 cm-3 at room temperature. The mobility was found to decrease with higher Hall carrier concentration. The empirical relationship for the mobility dependence on impurity concentration agreed with the relationship between mobility and the experimental Hall carrier concentration, suggesting that the same localized states were responsible for both providing the carriers and reducing the mobility through scattering. It was also observed that the mobility values for both amorphous and crystalline samples followed the same empirical curve, a result which showed that the conduction mechanisms in the epitaxial (tetragonal) and amorphous Y-Ba-Cu-O materials are very likely to be similar despite the differences in the composition and structure of the films. The similarity is consistent with other work that concludes that the conduction mechanism occurs along the copper oxide planes. Our work implies that the conduction mechanism operates over a short range, less than the 100 Å grain size of the amorphous, such that the lack of order in the amorphous samples was essentially irrelevant to the charge transport.

  8. Microstructure and properties of hydrophobic films derived from Fe-W amorphous alloy

    Institute of Scientific and Technical Information of China (English)

    Song Wang; Yun-han Ling; Jun Zhang; Jian-jun Wang; Gui-ying Xu

    2014-01-01

    Amorphous metals are totally different from crystalline metals in regard to atom arrangement. Amorphous metals do not have grain boundaries and weak spots that crystalline materials contain, making them more resistant to wear and corrosion. In this study, amorphous Fe-W alloy films were first prepared by an electroplating method and were then made hydrophobic by modification with a water repellent (heptadecafluoro-1,1,2,2-tetradecyl) trimethoxysilane. Hierarchical micro-nano structures can be obtained by slightly oxidizing the as-deposited alloy, accompanied by phase transformation from amorphous to crystalline during heat treatment. The mi-cro-nano structures can trap air to form an extremely thin cushion of air between the water and the film, which is critical to producing hydrophobicity in the film. Results show that the average values of capacitance, roughness factor, and impedance for specific surface areas of a 600°C heat-treated sample are greater than those of a sample treated at 500°C. Importantly, the coating can be fabricated on various metal substrates to act as a corrosion retardant.

  9. Magnetoimpedance in amorphous/metal/amorphous sandwiched films at GHz frequencies

    Energy Technology Data Exchange (ETDEWEB)

    Correa, M.A. [Departamento de Fisica, CCNE, UFSM, 97105-900, Santa Maria, RS (Brazil)]. E-mail: mmacorrea@gmail.com; Viegas, A.D.C. [Departamento de Fisica, CCNE, UFSM, 97105-900, Santa Maria, RS (Brazil); Silva, R.B. da [Departamento de Fisica, CCNE, UFSM, 97105-900, Santa Maria, RS (Brazil); Andrade, A.M.H. de [Departamento de Fisica, CCNE, UFSM, 97105-900, Santa Maria, RS (Brazil); Sommer, R.L. [Centro Brasileiro de Pesquisas Fisicas, 22290-180, Rio de Janeiro, RJ (Brazil)

    2006-10-01

    In this work, we report a comparative study of the magnetoimpedance in sandwiched films with the structure FS/Cu/FS (SWS) and FM/Cu/FM (SWM) where FS=single-layer FeCuNbSiB and FM=multilayer FeCuNbSiB/Cu. Magnetoimpedance ratios of 250% were obtained for the real part of the impedance in the SWM sample, while variations of 100% were reached for the SWS sample.

  10. Structure and electronic properties features of amorphous chalhogenide semiconductor films prepared by ion-plasma spraying

    Energy Technology Data Exchange (ETDEWEB)

    Korobova, N., E-mail: korobova3@mail.ru; Timoshenkov, S. [Department of Microelectronics, National Research University of Electronic Technology (MIET), Zelenograd (Russian Federation); Almasov, N.; Prikhodko, O. [al-Farabi Kazakh National University, Almaty (Kazakhstan); Tsendin, K. [Ioffe Physical-Technical Institute, Russian Academy of Sciences, St. Petersburg (Russian Federation)

    2014-10-21

    Structure of amorphous chalcogenide semiconductor glassy As-S-Se films, obtained by high-frequency (HF) ion-plasma sputtering has been investigated. It was shown that the length of the atomic structure medium order and local structure were different from the films obtained by thermal vacuum evaporation. Temperature dependence of dark conductivity, as well as the dependence of the spectral transmittance has been studied. Conductivity value was determined at room temperature. Energy activation conductivity and films optical band gap have been calculated. Temperature and field dependence of the drift mobility of charge carriers in the HF As-S-Se films have been shown. Bipolarity of charge carriers drift mobility has been confirmed. Absence of deep traps for electrons in the As{sub 40}Se{sub 30}S{sub 30} spectrum of localized states for films obtained by HF plasma ion sputtering was determined. Bipolar drift of charge carriers was found in amorphous As{sub 40}Se{sub 30}S{sub 30} films obtained by ion-plasma sputtering of high-frequency, unlike the films of these materials obtained by thermal evaporation.

  11. Magnetic and Electric Properties of Amorphous Co40Fe40B20 Thin Films

    Directory of Open Access Journals (Sweden)

    Yuan-Tsung Chen

    2012-01-01

    Full Text Available C40Fe40B20 was deposited on a glass substrate to a thickness (tf of between 100 Å and 500 Å. X-ray diffraction patterns (XRD indicate that C40Fe40B20 films are in an amorphous state. The plane-view microstructures and grain size distributions of CoFeB thin films are observed under a high-resolution transmission electron microscope (HRTEM. The thicker CoFeB films have larger grain size distribution than thinner CoFeB films. The saturation magnetization (Ms exhibits a size effect, meaning that Ms increases as tf increases. The magnetic remanence magnetization (Mr of CoFeB thin films are sensitive to thinner CoFeB films, and the refined grain size of thinner CoFeB films can induce ferromagnetic stronger spin exchange-coupling behavior than thicker CoFeB films, resulting in higher remanence. The highest magnetic squareness ratio (Mr/Ms of the CoFeB films occurs at thickness of 100 Å, suggesting the 100 Å of the as-deposited CoFeB film is suitable for magnetic memory application. These results also demonstrate that coercivity (Hc is increased by an increase in the width of the distribution of grain sizes. The electrical resistivity (ρ of such a film is typically higher than normally exceeding 100 μΩ cm, revealing that the amorphous phase dominates. These results are consistent with the XRD results.

  12. Electrochemical preparation of lead-doped amorphous Se films and underpotential deposition of lead onto these films

    Science.gov (United States)

    Ivanov, Dmitry K.; Osipovich, Nikolay P.; Poznyak, Sergey K.; Streltsov, Eugene A.

    2003-06-01

    The process of the underpotential deposition (UPD) of Pb adatoms (Pb ad) onto Se was used to produce nanocomposite films consisting of amorphous Se and nanosized PbSe clusters distributed throughout the film bulk. It was found that doping lead into Se films modifies their optical and photoelectrochemical properties and increases the efficiency of the charge transfer both in the film bulk and through the semiconductor | electrolyte interface. Introducing lead into the bulk of Se films significantly promotes the process of Pb ad UPD onto Se surface. The underpotentially deposited Pb ad interact chemically with Se surface atoms, resulting in the formation of a PbSe monolayer. The PbSe formed can be identified by the anodic peak corresponding to its electrochemical oxidation.

  13. Thermomechanical Analysis on the Phase Stability of Nitrogen-Doped Amorphous Ge2Sb2Te5 Films

    Science.gov (United States)

    Park, Il-Mok; Cho, Ju-Young; Yang, Tae-Youl; Park, Eun Soo; Joo, Young-Chang

    2011-06-01

    The phase stability of amorphous Ge2Sb2Te5 (GST) films affects the performance and reliability of phase change memory (PRAM) devices. The viscosity and the glass forming ability of nitrogen (N)-doped amorphous GST films were investigated in terms of thermomechanical behavior using wafer curvature measurements. The viscosity which increased by two orders of magnitude was observed in the N-doped amorphous GST film by measuring the stress relaxation accompanied by bimolecular structural relaxation. The glass forming ability (ΔTx), difference between the glass transition temperature (Tg) and the crystallization temperature (Tc), of GST increased as the nitrogen contents increased. These increases in the viscosity and ΔTx indicate the retardation of atomic diffusion in amorphous GST and the stabilization of the amorphous phase.

  14. Nitrogen-doped amorphous oxide semiconductor thin film transistors with double-stacked channel layers

    Science.gov (United States)

    Xie, Haiting; Wu, Qi; Xu, Ling; Zhang, Lei; Liu, Guochao; Dong, Chengyuan

    2016-11-01

    The amorphous oxide semiconductor (AOS) thin film transistors (TFTs) with the double-stacked channel layers (DSCL) combing the amorphous InZnO (a-IZO) films and the nitrogen-doped amorphous InGaZnO (a-IGZO:N) films were proposed and fabricated, which showed the excellent performance with the field-effect mobility of 49.6 cm2 V-1 s-1 and the subthreshold swing of 0.5 V/dec. More interestingly, very stable properties were observed in the bias stress and light illumination tests for these a-IZO/a-IGZO:N TFTs, as seemed to be the evident improvements over the prior arts. The improved performance and stability might be mainly due to the hetero-junctions in the channel layers and less interface/bulk trap density from the in situ nitrogen doping process in the a-IGZO layers. In addition, the passivation effect of the a-IGZO:N films also made some contributions to the stable properties exhibited in these novel DSCL TFTs.

  15. The effect of empirical potential functions on modeling of amorphous carbon using molecular dynamics method

    Energy Technology Data Exchange (ETDEWEB)

    Li, Longqiu, E-mail: longqiuli@gmail.com [School of Mechatronics Engineering, Harbin Institute of Technology, Harbin, 150001 (China); Xu, Ming; Song, Wenping [School of Mechatronics Engineering, Harbin Institute of Technology, Harbin, 150001 (China); Ovcharenko, Andrey [Western Digital Corporation, San Jose, CA (United States); Zhang, Guangyu; Jia, Ding [School of Mechatronics Engineering, Harbin Institute of Technology, Harbin, 150001 (China)

    2013-12-01

    Empirical potentials have a strong effect on the hybridization and structure of amorphous carbon and are of great importance in molecular dynamics (MD) simulations. In this work, amorphous carbon at densities ranging from 2.0 to 3.2 g/cm{sup 3} was modeled by a liquid quenching method using Tersoff, 2nd REBO, and ReaxFF empirical potentials. The hybridization, structure and radial distribution function G(r) of carbon atoms were analyzed as a function of the three potentials mentioned above. The ReaxFF potential is capable to model the change of the structure of amorphous carbon and MD results are in a good agreement with experimental results and density function theory (DFT) at low density of 2.6 g/cm{sup 3} and below. The 2nd REBO potential can be used when amorphous carbon has a very low density of 2.4 g/cm{sup 3} and below. Considering the computational efficiency, the Tersoff potential is recommended to model amorphous carbon at a high density of 2.6 g/cm{sup 3} and above. In addition, the influence of the quenching time on the hybridization content obtained with the three potentials is discussed.

  16. Structural and Magnetic Anisotropy in Amorphous Terbium-Iron Thin Films

    Science.gov (United States)

    Hufnagel, Todd Clayton

    1995-01-01

    High density, removable media magnetooptic disk drives have recently begun to make significant gains in the information mass storage market. The media in these disks are amorphous rare-earth/transition-metal (RE-TM) alloys. One vital property of these materials is a large perpendicular magnetic anisotropy; that is, an easy axis of magnetization which is perpendicular to the plane of the film. A variety of theories, sometimes contradictory, have been proposed to account for this surprising presence of an anisotropic property in an amorphous material. Recent research indicates that there is an underlying atomic-scale structural anisotropy which is responsible for the observed magnetic anisotropy. Several different types of structural anisotropy have been proposed to account for the observed magnetic anisotropy, including pair-ordering anisotropy (anisotropic chemical short-range order) and bond orientation anisotropy (an anisotropy in coordination number or distances independent of chemical ordering). We have studied the structural origins of perpendicular magnetic anisotropy in amorphous Tb-Fe thin films by employing high-energy and anomalous dispersion x-ray scattering. The as-deposited films show a clear structural anisotropy, with a preference for Tb-Fe near neighbors to align in the out-of-plane direction. These films also have a large perpendicular magnetic anisotropy. Upon annealing, the magnetic anisotropy energy drops significantly, and we see a corresponding reduction in the structural anisotropy. The radial distribution functions indicate that the number of Tb-Fe near-neighbors increases in the in-plane direction, but does not change in the out-of-plane direction. Therefore, the distribution of Tb-Fe near-neighbors becomes more uniform upon annealing. We propose that the observed reduction in perpendicular magnetic anisotropy energy is a result of this change in structure. Our results support the pair -ordering anisotropy model of the structural anisotropy

  17. Infrared Insight into the Network of Hydrogenated Amorphous and Polycrystalline Silicon thin Films

    Directory of Open Access Journals (Sweden)

    Jarmila Mullerova

    2006-01-01

    Full Text Available IR measurements were carried out on both amorphous and polycrystalline silicon samples deposited by PECVDon glass substrate. The transition from amorphous to polycrystalline phase was achieved by increasing dilution of silaneplasma at the deposition process. The samples were found to be mixed phase materials. Commonly, infrared spectra ofhydrogenated silicon thin films yield information about microstructure, hydrogen content and hydrogen bonding to silicon. Inthis paper, additional understanding was retrieved from infrared response. Applying standard optical laws, effective mediatheory and Clausius-Mossoti approach concerning the Si-Si and Si-H bonds under IR irradiation as individual oscillators,refractive indices in the long wavelength limit, crystalline, amorphous and voids volume fractions and the mass density of thefilms were determined. The mass density was found to decrease with increasing crystalline volume fraction, which can beattributed to the void-dominated mechanism of network formation.

  18. The nanoindentation applied to predict the interface delamination for the C/amorphous Si composite film

    Science.gov (United States)

    Han, Chang-Fu; Huang, Chao-Yu; Wu, Bo-Hsiung; Lin, Jen-Fin

    2009-10-01

    In the present study, the indentation depth corresponding to the pop-in arising in the loading process is found to be quite close to the C/amorphous Si composite film thickness, regardless of the C-film thickness. This load-depth behavior gives a clue that the occurrence of pop-in is perhaps related to the buckling of the composite film, which had already delaminated from the silicon substrate. This indentation depth of buckling predicted by the present model is quite close to the pop-in depth obtained from experimental results, regardless of the change in the C-film thickness. This characteristic reveals that the present model is developed successfully to predict the pop-in depth of a specimen, and the pop-in is indeed created due to the buckling of the composite film under a compression stress.

  19. Electrical and switching properties of InSe amorphous thin films

    Energy Technology Data Exchange (ETDEWEB)

    Kenawy, M.A.; Zayed, H.A.; El-Zahid, H.A. (Univ. Coll. for Girls, Ain Shams Univ., Cairo (Egypt)); El-Shazly, A.F.; Afifi, M.A. (Faculty of Education, Ain Shams Univ., Cairo (Egypt))

    1991-05-15

    In this work electrical and switching properties of InSe thin films have been studied. The semiconductor compound InSe was obtained by direct synthesis from stoichiometric amounts of spectroscopically pure indium and selenium. By slow cooling of the synthesized InSe a polycrystalline material is obtained. The amorphous films were obtained by thermal evaporation under vacuum of the polycrystalline material on glass or pyrographite substrates. From electrical measurements, it was found that for all films the dark electrical resistivity decreases with an increase in film thickness and temperature. The InSe compound exhibits non-linear I-V characteristics and switching phenomena. The threshold voltage decreases with increasing annealing temperature and increases with increasing film thickness. (orig.).

  20. The Preparation and Characterization of Amorphous SiCN Thin Films

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    Radio Frequency plasma enhanced Chemical Vapor Deposition (RF CVD) using N2, SiH4 and C2H4 as the reaction sources was used to prepare amorphous ternary SixCyNz thin films. The chemical states of the C, Si and N atoms in the films were characterized by X-ray photoelectron spectroscopy (XPS) and Fourier Transform Infrared Spectroscopy (FTIR). The refractive index n, extinction coefficient k and optical band gap Eopt of the thin films were investigated by UV-visible spectrophotometer and spectroscopic ellipsometer.The results show that a complex chemical bonding network rather than a simple mixture of Si3N4,SiC,CNx and a-C etc. , may exist in the ternary thin films. The n's of the films are within the range of 1.90-2. 45, and Eopt's of all samples are within the range of 2.71 -2. 86 eV.

  1. Uniform dehydrogenation of amorphous silicon thin films using a wide thermal annealing system

    Science.gov (United States)

    Jung, Yong Chan; Seong, Sejong; Lee, Taehoon; Ahn, Jinho; Kim, Tae Hyun; Yeo, Won-Jae; Park, In-Sung

    2017-02-01

    To prevent ablation caused by sudden hydrogen eruption during crystallization of hydrogenated amorphous Si (a-Si:H) thin films, a wide dehydrogenation thermal annealing (wDTA) system was developed to reduce hydrogen content in a-Si:H film prior to its crystallization process. The annealed a-Si:H films were fully dehydrogenated and nanocrystallized by the wDTA system. Raman scattering measurement revealed that the dehydrogenation process lowers the hydrogen content through disappearance of the peak intensity at 2000 cm-1. The a-Si:H film was transformed into nanocrystallized Si with lower residual stress. The major advantage of this wDTA was the large area uniformity of the thermal and the resulting material properties for 8 generation display. The uniform material characteristics of the hydrogen content, thickness, energy bandgap, and transmittance of the annealed Si films in the overall area was confirmed by Raman spectroscopy, spectroscopic ellipsometry, and UV-vis spectrometer measurement.

  2. Structural stability of hydrogenated amorphous carbon overcoats used in heat-assisted magnetic recording investigated by rapid thermal annealing

    KAUST Repository

    Wang, N.

    2013-01-01

    Ultrathin amorphous carbon (a-C) films are extensively used as protective overcoats of magnetic recording media. Increasing demands for even higher storage densities have necessitated the development of new storage technologies, such as heat-assisted magnetic recording (HAMR), which uses laser-assisted heating to record data on high-stability media that can store single bits in extremely small areas (∼1 Tbit/in.2). Because HAMR relies on locally changing the coercivity of the magnetic medium by raising the temperature above the Curie temperature for data to be stored by the magnetic write field, it raises a concern about the structural stability of the ultrathin a-C film. In this study, rapid thermal annealing (RTA) experiments were performed to examine the thermal stability of ultrathin hydrogenated amorphous carbon (a-C:H) films deposited by plasma-enhanced chemical vapor deposition. Structural changes in the a-C:H films caused by RTA were investigated by x-ray photoelectron spectroscopy, Raman spectroscopy, x-ray reflectivity, and conductive atomic force microscopy. The results show that the films exhibit thermal stability up to a maximum temperature in the range of 400-450 °C. Heating above this critical temperature leads to hydrogen depletion and sp 2 clustering. The critical temperature determined by the results of this study represents an upper bound of the temperature rise due to laser heating in HAMR hard-disk drives and the Curie temperature of magnetic materials used in HAMR hard disks. © 2013 American Institute of Physics.

  3. Development of spin-on carbon hardmasks with comparable etch resistance to Amorphous Carbon Layer (ACL)

    Science.gov (United States)

    Cheon, Hwan-Sung; Yoon, Kyong-Ho; Kim, Min-Soo; Oh, Seung Bae; Song, Jee-Yun; Tokareva, Nataliya; Kim, Jong-Seob; Chang, Tuwon

    2008-11-01

    In recent microlithography of semiconductor fabrication, spin-on hardmask (SOH) process continue to gain popularity as it replaces the traditional SiON/ACL hardmask scheme which suffers from high CoO, low productivity, particle contamination, and layer alignment issues. In the SOH process, organic polymer with high carbon content is spin-cast to form a carbon hardmask film. In the previous papers, we reported the development of organic SOH materials and their application in sub-70 nm lithography. In this paper, we describe the synthesis of organic polymers with very high carbon contents (>92 wt.%) and the evaluation of the spin-coated films for the hardmask application. The high carbon content of the polymer ensures improved etch resistance which amounts to >90% of ACL's resistance. However, as the carbon content of the polymers increases, the solubility in common organic solvents becomes lower. Here we report the strategies to improve the solubility of the high carbon content resins and optimization of the film properties for the SOH application.

  4. Ultrathin diamond-like carbon films deposited by filtered carbon vacuum arcs

    Energy Technology Data Exchange (ETDEWEB)

    Anders, Andre; Fong, Walton; Kulkarni, Ashok; Ryan, Francis W.; Bhatia, C. Singh

    2001-07-13

    Ultrathin (< 5 nm) hard carbon films are of great interest to the magnetic storage industry as the areal density approaches 100 Gbit/in{sup 2}. These films are used as overcoats to protect the magnetic layers on disk media and the active elements of the read-write slider. Tetrahedral amorphous carbon films can be produced by filtered cathodic arc deposition, but the films will only be accepted by the storage industry only if the ''macroparticle'' issue has been solved. Better plasma filters have been developed over recent years. Emphasis is put on the promising twist filter system - a compact, open structure that operates with pulsed arcs and high magnetic field. Based on corrosion tests it is shown that the macroparticle reduction by the twist filter is satisfactory for this demanding application, while plasma throughput is very high. Ultrathin hard carbon films have been synthesized using S-filter and twist filter systems. Film properties such as hardness, elastic modulus, wear, and corrosion resistance have been tested.

  5. An APT investigation of an amorphous Cr–B–C thin film

    Energy Technology Data Exchange (ETDEWEB)

    Boll, T. [Department of Applied Physics, Chalmers University of Technology, SE-412 96 Göteborg (Sweden); Thuvander, M., E-mail: mattias.thuvander@chalmers.se [Department of Applied Physics, Chalmers University of Technology, SE-412 96 Göteborg (Sweden); Koch, S. [Department of Applied Physics, Chalmers University of Technology, SE-412 96 Göteborg (Sweden); Wagner, J.N. [KNMF, Karslruhe Institute of Technology, DE-76344 Eggenstein-Leopoldshafen (Germany); Nedfors, N.; Jansson, U. [Department of Chemistry, The Ångström Laboratory, Uppsala University, SE-751 21 Uppsala (Sweden); Stiller, K. [Department of Applied Physics, Chalmers University of Technology, SE-412 96 Göteborg (Sweden)

    2015-12-15

    A magnetron sputtered amorphous Cr–B–C thin film was investigated by means of atom probe tomography (APT). The film is constituted of two phases; a Cr-rich phase present as a few nanometer large regions embedded in a Cr-poor phase (tissue phase). The Cr-rich regions form columnar chains oriented parallel to the growth direction of the film. It was found that the Cr-rich regions have a higher B:C ratio than the Cr-poor regions. The composition of the phases was determined as approximately 35Cr–33B–30C and 15Cr–40B–42C (at%), respectively. The results suggest that this type of nanocomposite films has a more complex structure than previously anticipated, which may have an importance for the mechanical and electrical properties. - Highlights: • An amorphous Cr–B–C thin film has been analyzed using atom probe tomography. • The film was found to be nanostructured and to consist of two phases. • A Cr-rich phase was embedded in a Cr-poor tissue (matrix) phase. • The measurements suggest that the tissue phase contains as much as 15 at% Cr.

  6. Boron doping compensation of hydrogenated amorphous and polymorphous germanium thin films for infrared detection applications

    Energy Technology Data Exchange (ETDEWEB)

    Moreno, M., E-mail: mmoreno@inaoep.mx [National Institute of Astrophysics, Optics and Electronics, INAOE, P.O. Box 51 and 216, Puebla, Z. P. 72840 Puebla (Mexico); Delgadillo, N. [Universidad Autónoma de Tlaxcala, Av. Universidad No. 1, Z. P. 90006 Tlaxcala (Mexico); Torres, A. [National Institute of Astrophysics, Optics and Electronics, INAOE, P.O. Box 51 and 216, Puebla, Z. P. 72840 Puebla (Mexico); Ambrosio, R. [Technology and Engineering Institute, Ciudad Juarez University UACJ, Av. Del Charro 450N, Z. P. 32310 Chihuahua (Mexico); Rosales, P.; Kosarev, A.; Reyes-Betanzo, C.; Hidalga-Wade, J. de la; Zuniga, C.; Calleja, W. [National Institute of Astrophysics, Optics and Electronics, INAOE, P.O. Box 51 and 216, Puebla, Z. P. 72840 Puebla (Mexico)

    2013-12-02

    In this work we have studied boron doping of hydrogenated amorphous germanium a-Ge:H and polymorphous germanium (pm-Ge:H) in low regimes, in order to compensate the material from n-type (due to oxygen contamination that commonly occurs during plasma deposition) to intrinsic, and in this manner improve the properties that are important for infrared (IR) detection, as activation energy (E{sub a}) and temperature coefficient of resistance (TCR). Electrical, structural and optical characterization was performed on the films produced. Measurements of the temperature dependence of conductivity, room temperature conductivity (σ{sub RT}), E{sub a} and current–voltage characteristics under IR radiation were performed in the compensated a-Ge:H and pm-Ge:H films. Our results demonstrate that, effectively, the values of E{sub a}, TCR and IR detection are improved on the a-Ge:H/pm-Ge:H films, using boron doping in low regimes, which results of interest for infrared detectors. - Highlights: • We reported boron doping compensation of amorphous and polymorphous germanium. • The films were deposited by plasma enhanced chemical vapor deposition. • The aim is to use the films as thermo-sensing elements in un-cooled microbolometers. • Those films have advantages over boron doped a-Si:H used in commercial detectors.

  7. Fabrication of barium/strontium carbonate coated amorphous carbon nanotubes as an improved field emitter

    Science.gov (United States)

    Maity, S.; Jha, A.; Das, N. S.; Chattopadhyay, K. K.

    2013-02-01

    Amorphous carbon nanotubes (aCNTs) were synthesized by a chemical reaction between ferrocene and ammonium chloride at a temperature ˜250 ∘C in an air furnace. As-synthesized aCNTs were coated with the barium/strontium carbonate through a simple chemical process. The coating of barium/strontium carbonate was confirmed by a high resolution transmission electron microscopy, X-ray diffraction, and Fourier transformed infrared spectroscopy. Morphology of the as-prepared samples was studied by field emission scanning electron microscopy. Thermal gravimetric analysis showed that barium/strontium carbonate coated aCNTs are more stable than the pristine aCNTs. As-prepared barium/strontium carbonate coated aCNTs showed significantly improved field emission properties with a turn-on field as low as 2.5 V/μm. The variation of field emission characteristics of the barium/strontium carbonate coated aCNTs with interelectrode distances was also studied.

  8. Optical characterization of sputtered carbon films

    Energy Technology Data Exchange (ETDEWEB)

    Ager, J.W. III.

    1992-05-01

    Spattered carbon films are widely used as protective overcoats for thin film disk media. Raman spectroscopy is nondestructive and relatively rapid and is well suited for the characterization of carbon films. Specific features in the Raman spectra are empirically correlated with the rates of specific types of mechanical wear for both hydrogenated and unhydrogenated films. This observation is interpreted in terms of a random covalent network, in which the mechanical performance of the film is determined by the nature of the bonding that links sp{sup 2}-bonded domains.

  9. Controllable crystallization and enhanced amorphous stability of Sb-Te films modified by Ag-doping

    Science.gov (United States)

    Zhong, Juechen; Luo, Yang; Gu, Ting; Wang, Zhenglai; Jiang, Kefeng; Wang, Guoxiang; Lu, Yegang

    2016-10-01

    Ag-doped Sb-Te films were deposited by magnetron co-sputtering and the structure, electrical, optical and thermal properties were analyzed. The results show that Ag-doping restrains crystal grain size, and changes a preferred orientation of the crystalline phase. The crystallization temperature is increased due to the Ag addition. Both amorphous resistance and crystalline resistance are enhanced and the resistance ratio reaches ˜104. Compared with Ge2Sb2Te5, Ag26.82(Sb3Te)73.18 film exhibits a better amorphous thermal stability, a higher crystallization temperature (˜166 °C), a wider optical band gap (0.515 eV), a larger crystallization activation energy (3.17 eV) as well as a better 10 years data retention at 92 °C.

  10. Local structure and local conduction paths in amorphous (In,Ga,Hf)-ZnO semiconductor thin films

    Science.gov (United States)

    Yang, Dong-Seok; Cheol Lee, Jae; Chung, JaeGwan; Lee, Eunha; Anass, Benayad; Sung, Nark-Eon; Min Lee, Jay; Jae Kang, Hee

    2012-10-01

    The local structure and local conduction paths of Ga-In-Zn-O (GIZO) and Hf-In-Zn-O (HIZO) amorphous thin films were investigated by the extended X-ray absorption fine structure (EXAFS). We found that the local hindrance paths of In-Ga and In-Hf exist in the conduction paths of amorphous GIZO and HIZO semiconductor thin films, respectively.

  11. Photodeposition of amorphous polydiacetylene films from monomer solutions onto transparent substrates

    Science.gov (United States)

    Paley, M. S.; Frazier, D. O.; Abdeldeyem, H.; Armstrong, S.; McManus, S. P.

    1995-01-01

    Polydiacetylenes are a very promising class of polymers for both photonic and electronic applications because of their highly conjugated structures. For these applications, high-quality thin polydiacetylene films are required. We have discovered a novel technique for obtaining such films of a polydiacetylene derivative of 2-methyl-4-nitroaniline using photodeposition from monomer solutions onto UV transparent substrates. This heretofore unreported process yields amorphous polydiacetylene films with thicknesses on the order of I micron that have optical quality superior to that of films grown by standard crystal growth techniques. Furthermore, these films exhibit good third-order nonlinear optical susceptibilities; degenerate four-wave mixing experiments give x(3) values on the order of 10(exp -8) - 10(exp -7) esu. We have conducted masking experiments which demonstrate that photodeposition occurs only where the substrate is directly irradiated, clearly indicating that the reaction occurs at the surface. Additionally, we have also been able to carry out photodeposition using lasers to form thin polymer circuits. In this work, we discuss the photodeposition of polydiacetylene thin films from solution, perform chemical characterization of these films, investigate the role of the substrate, speculate on the mechanism of the reaction, and make a preliminary determination of the third-order optical nonlinearity of the films. This simple, straightforward technique may ultimately make feasible the production of polydiacetylene thin films for technological applications.

  12. Strong Metal-Support Interaction: Growth of Individual Carbon Nanofibers from Amorphous Carbon Interacting with an Electron Beam

    DEFF Research Database (Denmark)

    Zhang, Wei; Kuhn, Luise Theil

    2013-01-01

    The article discusses the growth behavior of carbon nanofibers (CNFs). It mentions that CNFs can be synthesized using methods such as arc-discharge, laser ablation and chemical vapor deposition. It further states that CNFs can be grown from a physical mixing of amorphous carbon and CGO...

  13. Optical and electrical properties of polycrystalline and amorphous Al-Ti thin films

    DEFF Research Database (Denmark)

    Canulescu, Stela; Borca, C. N.; Rechendorff, Kristian

    2016-01-01

    by electron scattering at the grain boundaries in the case of polycrystalline films and static defects, such as antisite effects and vacancies in the case of the amorphous alloys. The combination of Ti having a real refractive index (n) comparable with the extinction coefficient (k) and Al with n much smaller...... than k allows us to explore the parameter space for the free-electron behavior in transition metal-Al alloys. The free electron model, applied for the polycrystalline Al-Ti films with Ti content up to 20%, leads to an optical reflectance at near infrared wavelengths that scales linearly with the square...

  14. High stability of amorphous hafnium-indium-zinc-oxide thin film transistor

    Science.gov (United States)

    Chong, Eugene; Jo, Kyoung Chul; Lee, Sang Yeol

    2010-04-01

    Time dependence of the threshold voltage (Vth) shift in amorphous hafnium-indium-zinc oxide (a-HIZO) thin film transistor has been reported under on-current bias temperature stress measured at 60 °C. X-ray photoelectron spectroscopy results show the decrease in oxygen vacancies by Hf metal cations in a-HIZO systems after annealing process. High stability of a-HIZO systems has been observed due to low charge injection from the channel layer. Hf metal cations have been effectively incorporated into the IZO thin films as a suppressor against both the oxygen deficiencies and the carrier generation.

  15. Photochromism of amorphous molybdenum oxide films with different initial Mo{sup 5+} relative concentrations

    Energy Technology Data Exchange (ETDEWEB)

    Rouhani, Mehdi [Institute of Materials Research and Engineering, Agency for Science, Technology And Research, 3 Research Link, 117602 (Singapore); Foo, Yong L. [Singapore Institute of Technology, EFG Bank Building, 25 North Bridge Road 03-01 179104 (Singapore); Hobley, Jonathan; Pan, Jisheng; Subramanian, Gomathy Sandhya [Institute of Materials Research and Engineering, Agency for Science, Technology And Research, 3 Research Link, 117602 (Singapore); Yu, Xiaojiang [Singapore Synchrotron Light Source, National University of Singapore 5 Research Link, 117603 (Singapore); Rusydi, Andrivo [Singapore Synchrotron Light Source, National University of Singapore 5 Research Link, 117603 (Singapore); Department of Physics, National University of Singapore, 2 Science Drive 3, 117551 (Singapore); Gorelik, Sergey, E-mail: goreliks@imre.a-star.edu.sg [Institute of Materials Research and Engineering, Agency for Science, Technology And Research, 3 Research Link, 117602 (Singapore)

    2013-05-15

    We report the effect of deposition conditions on the intrinsic color and photochromic properties of amorphous MoO{sub 3} thin films (a-films) deposited by R.F. unbalanced magnetron sputtering. Optical transmission spectroscopy was used to measure optical properties of the films. The conversion between Mo{sup 6+} and Mo{sup 5+} for as-deposited and UV irradiated films was characterized using XPS. Raman spectroscopy was used to confirm that the results of XPS were consistent with the bulk of the films. It is shown that absorption coefficient of as-deposited films increases with Mo{sup 5+} content. The temporal evolution of absorption coefficients for all films under UV light irradiation is measured using optical transmission spectroscopy. The largest change in absorption was observed for the film with the highest initial Mo{sup 5+} content. The temporal evolution of absorption coefficients for all the films shows initial fast rise within first minute of irradiation. XPS and Raman results show that for all films Mo{sup 5+} content increases as a result of UV irradiation except for the film with the highest initial Mo{sup 5+} content, for which the Mo{sup 5+} content decreases relative to Mo{sup 6+} despite the fact that the absorption of the film continues to rise. Further understanding of this mechanism is important since it will lead to enhanced photochromism and extend the photo-colorability of the films beyond the point at which the conversion of Mo{sup 6+} to Mo{sup 5+} is saturated.

  16. Aluminium-induced crystallization of amorphous silicon films deposited by DC magnetron sputtering on glasses

    Energy Technology Data Exchange (ETDEWEB)

    Kezzoula, F., E-mail: kezzoula@usa.com [UDTS 2Bd Frantz Fanon 7 merveilles Algiers (Algeria); Laboratory of Materials, Mineral and Composite (LMMC), Boumerdes University (Algeria); Hammouda, A. [UPR CNRS 3079 CEMHTI - 1D Avenue de la Recherche Scientifique, 45071 Orleans Cedex 2 (France); Equipe Couches Minces, Laboratoire de Physique des Materiaux, Faculte de Physique, USTHB, Algiers (Algeria); Universite d' Orleans, 45067 Orleans Cedex 2 (France); Kechouane, M. [Equipe Couches Minces, Laboratoire de Physique des Materiaux, Faculte de Physique, USTHB, Algiers (Algeria); Simon, P. [UPR CNRS 3079 CEMHTI - 1D Avenue de la Recherche Scientifique, 45071 Orleans Cedex 2 (France); Universite d' Orleans, 45067 Orleans Cedex 2 (France); Abaidia, S.E.H. [Laboratory of Materials, Mineral and Composite (LMMC), Boumerdes University (Algeria); Keffous, A. [UDTS 2Bd Frantz Fanon 7 merveilles Algiers (Algeria); Cherfi, R. [Equipe Couches Minces, Laboratoire de Physique des Materiaux, Faculte de Physique, USTHB, Algiers (Algeria); Menari, H.; Manseri, A. [UDTS 2Bd Frantz Fanon 7 merveilles Algiers (Algeria)

    2011-09-15

    Amorphous silicon (a-Si) and hydrogenated amorphous silicon (a-Si:H) films were deposited by DC magnetron sputtering technique with argon and hydrogen plasma mixture on Al deposited by thermal evaporation on glass substrates. The a-Si/Al and a-Si:H/Al thin films were annealed at different temperatures ranging from 250 to 550 deg. C during 4 h in vacuum-sealed bulb. The effects of annealing temperature on optical, structural and morphological properties of as-grown as well as the vacuum-annealed a-Si/Al and a-Si:H/Al thin films are presented in this contribution. The averaged transmittance of a-Si:H/Al film increases upon increasing the annealing temperature. XRD measurements clearly evidence that crystallization is initiated at 450 deg. C. The number and intensity of diffraction peaks appearing in the diffraction patterns are more important in a-Si:H/Al than that in a-Si/Al layers. Results show that a-Si:H films deposited on Al/glass crystallize above 450 deg. C and present better crystallization than the a-Si layers. The presence of hydrogen induces an improvement of structural properties of poly-Si prepared by aluminium-induced crystallization (AIC).

  17. Optical properties of amorphous Sb2Se3:Sn films

    Science.gov (United States)

    Kumar, Praveen; Sathiaraj, T. S.; Thangaraj, R.

    2010-03-01

    The measurements and analysis of optical transmission and far-infrared (IR) reflectivity spectra of thermally evaporated Sb2Se3:Sn films are reported. The refractive index and film thickness have been determined from the upper and lower envelopes of the transmission spectra (Swanepoel's standard envelope method), measured at normal incidence, in the spectral range from 800 to 2500 nm. Values of the refractive index fit well to Cauchy's dispersion relation. The optical gap decreases with an increase in the Sn content, while a maximum in the tailing parameter and Urbach's energy occurs with only a small amount (∼1 at %) of this additive. Characteristic vibrational bands for SbSe3 structural units are revealed in the far-IR spectrum with no additional ones arising from the Sn additive. The Kramers-Kronig analysis has been used to calculate the dielectric constants and hence the longitudinal optic and transverse optic splitting for various compositions. The inclusion of Sn as a charged entity along with the Coulomb interactions which serve to polarize the glass medium is found to be responsible for these results.

  18. Field emission properties of amorphous GaN ultrathin films fabricated by pulsed laser deposition

    Institute of Scientific and Technical Information of China (English)

    WANG FengYing; WANG RuZhi; ZHAO Wei; SONG XueMei; WANG Bo; YAN Hui

    2009-01-01

    Amorphous gallium nitride (a-GaN) films with thicknesses of 5 and 300 nm are deposited on n-Si (100) substrates by pulsed laser deposition (PLD), and their field emission (FE) properties are studied. It shows that compared with thicker (300 nm) a-GaN film, better FE performance is obtained on ultrathin (5 nm) a-GaN film with a threshold field of 0.78 V/μm, which is the lowest value ever reported. Furthermore, the current density reaches 42 mA/cm~2 when the applied field is 3.72 V/μm. These experimental results unambiguously confirm Binh's theoretical analysis (Birth et al. Phys Rev Lett, 2000, 85(4): 864-867) that the FE performance would be prominently enhanced with the coating of an ultra-thin wide band-gap semiconductor film.

  19. Synthesis of novel amorphous calcium carbonate by sono atomization for reactive mixing.

    Science.gov (United States)

    Kojima, Yoshiyuki; Kanai, Makoto; Nishimiya, Nobuyuki

    2012-03-01

    Droplets of several micrometers in size can be formed in aqueous solution by atomization under ultrasonic irradiation at 2 MHz. This phenomenon, known as atomization, is capable of forming fine droplets for use as a reaction field. This synthetic method is called SARM (sono atomization for reactive mixing). This paper reports on the synthesis of a novel amorphous calcium carbonate formed by SARM. The amorphous calcium carbonate, obtained at a solution concentration of 0.8 mol/dm(3), had a specific surface area of 65 m(2)/g and a composition of CaCO(3)•0.5H(2)O as determined using thermogravimetric/differential thermal analysis (TG-DTA). Because the ACC had a lower hydrate composition than conventional amorphous calcium carbonate (ACC), the ACC synthesized in this paper was very stable at room temperature.

  20. Influence of bath composition on the electrodeposition of cobalt-molybdenum amorphous alloy thin films

    Institute of Scientific and Technical Information of China (English)

    Qiaoying Zhou; Hongliang Ge; Guoying Wei; Qiong Wu

    2008-01-01

    Cobalt-molybdenum (Co-Mo) amorphous alloy thin films were deposited on copper substrates by the electrochemical method at pH 4.0. Among the experimental electrodeposition parameters, only the concentration ratio of molybdate to cobalt ions ([ MoO2-4 ]/[CO2+]) was varied to analyze its influence on the mechanism of induced cobalt-molybdenum codeposition. Voltammetry was one of the main techniques, which was used to examine the voltammetric response, revealing that cobalt-molybdenum codeposi-tion depended on the nature of the species in solution. To correlate the type of the film to the electrochemical response, various co-bait-molybdenum alloy thin films obtained from different [ MoO2-4]/[Co2+] solutions were tested. Crack-free homogeneous films could be easily obtained from the low molybdate concentrations ([ MoO2-4]/[Co2+]≈0.05) applying low deposition potentials.Moreover, the content of molybdenum up to 30wt% could be obtained from high molybdate concentration; in this case, the films showed cracks. The formation of these cracked films could be predicted from the observed distortions in the curves of electric cur-rent-time (j-t) deposition transients. The films with amorphous stmeture were obtained. The hysteresis loops suggested that the easily film were obtained when the deposition potential was -1025 mV, and [ MoO2-4]/[Co2+] was 0.05 in solution, which exhibited a nicer soft-magnetic response.

  1. Ordered Growth of Topological Insulator Bi2Se3 Thin Films on Dielectric Amorphous SiO2 by MBE

    OpenAIRE

    2013-01-01

    Topological insulators (TIs) are exotic materials which have topologically protected states on the surface due to the strong spin-orbit coupling. However, a lack of ordered growth of TI thin films on amorphous dielectrics and/or insulators presents a challenge for applications of TI-junctions. We report the growth of topological insulator Bi2Se3 thin films on amorphous SiO2 by molecular beam epitaxy (MBE). To achieve the ordered growth of Bi2Se3 on amorphous surface, the formation of other ph...

  2. Nitrogen-doped amorphous carbon-silicon core-shell structures for high-power supercapacitor electrodes

    Science.gov (United States)

    Tali, S. A. Safiabadi; Soleimani-Amiri, S.; Sanaee, Z.; Mohajerzadeh, S.

    2017-02-01

    We report successful deposition of nitrogen-doped amorphous carbon films to realize high-power core-shell supercapacitor electrodes. A catalyst-free method is proposed to deposit large-area stable, highly conformal and highly conductive nitrogen-doped amorphous carbon (a-C:N) films by means of a direct-current plasma enhanced chemical vapor deposition technique (DC-PECVD). This approach exploits C2H2 and N2 gases as the sources of carbon and nitrogen constituents and can be applied to various micro and nanostructures. Although as-deposited a-C:N films have a porous surface, their porosity can be significantly improved through a modification process consisting of Ni-assisted annealing and etching steps. The electrochemical analyses demonstrated the superior performance of the modified a-C:N as a supercapacitor active material, where specific capacitance densities as high as 42 F/g and 8.5 mF/cm2 (45 F/cm3) on silicon microrod arrays were achieved. Furthermore, this supercapacitor electrode showed less than 6% degradation of capacitance over 5000 cycles of a galvanostatic charge-discharge test. It also exhibited a relatively high energy density of 2.3 × 103 Wh/m3 (8.3 × 106 J/m3) and ultra-high power density of 2.6 × 108 W/m3 which is among the highest reported values.

  3. Intrinsic stress analysis of sputtered carbon film

    Institute of Scientific and Technical Information of China (English)

    Liqin Liu; Zhanshan Wang; Jingtao Zhu; Zhong Zhang; Moyan Tan; Qiushi Huang; Rui Chen; Jing Xu; Lingyan Chen

    2008-01-01

    Intrinsic stresses of carbon films deposited by direct current (DC) magnetron sputtering were investigated.The bombardments of energetic particles during the growth of films were considered to be the main reason for compressive intrinsic stresses.The values of intrinsic stresses were determined by measuring the radius of curvature of substrates before and after film deposition.By varying argon pressure and target-substrate distance,energies of neutral carbon atoms impinging on the growing films were optimized to control the intrinsic stresses level.The stress evolution in carbon films as a function of film thickness was investigated and a void-related stress relief mechanism was proposed to interpret this evolution.

  4. Direct measurement of free-energy barrier to nucleation of crystallites in amorphous silicon thin films

    Science.gov (United States)

    Shi, Frank G.

    1994-01-01

    A method is introduced to measure the free-energy barrier W(sup *), the activation energy, and activation entropy to nucleation of crystallites in amorphous solids, independent of the energy barrier to growth. The method allows one to determine the temperature dependence of W(sup *), and the effect of the preparation conditions of the initial amorphous phase, the dopants, and the crystallization methds on W(sup *). The method is applied to determine the free-energy barrier to nucleation of crystallites in amorphous silicon (a-Si) thin films. For thermally induced nucleation in a-Si thin films with annealing temperatures in the range of from 824 to 983 K, the free-energy barrier W(sup *) to nucleation of silicon crystals is about 2.0 - 2.1 eV regardless of the preparation conditions of the films. The observation supports the idea that a-Si transforms into an intermediate amorphous state through the structural relaxation prior to the onset of nucleation of crystallites in a-Si. The observation also indicates that the activation entropy may be an insignificant part of the free-energy barrier for the nucleation of crystallites in a-Si. Compared with the free-energy barrier to nucleation of crystallites in undoped a-Si films, a significant reduction is observed in the free-energy barrier to nucleation in Cu-doped a-Si films. For a-Si under irradiation of Xe(2+) at 10(exp 5) eV, the free-energy barrier to ion-induced nucleation of crystallites is shown to be about half of the value associated with thermal-induced nucleation of crystallites in a-Si under the otherwise same conditions, which is much more significant than previously expected. The present method has a general kinetic basis; it thus should be equally applicable to nucleation of crystallites in any amorphous elemental semiconductors and semiconductor alloys, metallic and polymeric glasses, and to nucleation of crystallites in melts and solutions.

  5. Polycrystalline VO{sub 2} thin films via femtosecond laser processing of amorphous VO{sub x}

    Energy Technology Data Exchange (ETDEWEB)

    Charipar, N.A.; Kim, H.; Charipar, K.M.; Mathews, S.A.; Pique, A. [Naval Research Laboratory, Materials Science and Technology Division, Washington, DC (United States); Breckenfeld, E. [National Research Council Fellow at the Naval Research Laboratory, Washington, DC (United States)

    2016-05-15

    Femtosecond laser processing of pulsed laser-deposited amorphous vanadium oxide thin films was investigated. Polycrystalline VO{sub 2} thin films were achieved by femtosecond laser processing in air at room temperature. The electrical transport properties, crystal structure, surface morphology, and optical properties were characterized. The laser-processed films exhibited a metal-insulator phase transition characteristic of VO{sub 2}, thus presenting a pathway for the growth of crystalline vanadium dioxide films on low-temperature substrates. (orig.)

  6. CORROSION BEHAVIOR OF Cu-Nb AND Ni-Nb AMORPHOUS FILMS PREPARED BY ION BEAM ASSISTED DEPOSITION

    Institute of Scientific and Technical Information of China (English)

    B. Zhao; F. Zeng; D.M. Li; F. Pan

    2003-01-01

    The Cu25Nb75 and Ni45Nb55 amorphous films with about 500nm thickness were prepared by ion beam assisted deposition (IBAD). Potentiodynamic polarization measurement was adopted to investigate the corrosion resistance of samples and the tests were carried out respectively in 1mol/L H2SO4 and NaOH aquatic solution. The corrosion performance of the amorphous films was compared with that of multilayered and pure Nb films. Experimental results indicated that the corrosion resistance of amorphous films was better than that of the corresponding multilayers and pure Nb films for both Ni-Nb system with negative heat of formation and Cu-Nb system with positive heat of formation.

  7. Porous tablets of crystalline calcium carbonate via sintering of amorphous nanoparticles

    OpenAIRE

    Gebauer, Denis; Liu, Xing-Min; Aziz, Baroz; Hedin, Niklas; Zhao, Zhe

    2013-01-01

    Porous tablets of crystalline calcium carbonate were formed upon sintering of a precursor powder of amorphous calcium carbonate (ACC) under compressive stress (20 MPa) at relatively low temperatures (120–400 °C), induced by pulsed direct currents. Infrared spectroscopy ascertained the amorphous nature of the precursor powders. At temperatures of 120–350 °C and rates of temperature increase of 20–100 °C min−1, the nanoparticles of ACC transformed into crystallites of mainly aragonite, which is...

  8. Passive film growth on carbon steel and its nanoscale features at various passivating potentials

    Science.gov (United States)

    Li, Yuan; Cheng, Y. Frank

    2017-02-01

    In this work, the passivation and topographic sub-structure of passive films on a carbon steel in a carbonate/bicarbonate solution was characterized by electrochemical measurements, atomic force microscopy and X-ray photoelectron spectroscopy. When passivating at a potential near the active-passive transition, the film contains the mixture of Fe3O4, Fe2O3 and FeOOH, with numerous nanoscale features. As the film-forming potential shifts positively, the passive film becomes more compact and the nanoscale features disappear. When the film is formed at a passive potential where the oxygen evolution is enabled, the content of FeOOH in the film increases, resulting in an amorphous topography and reduced corrosion resistance.

  9. Piezoresistive effect in carbon nanotube films

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    The piezoresistive effect of the pristine carbon nanotube (CNT) films has been studied. Carbon nanotubes were synthesized by hot filament chemical vapor deposition. The piezoresistive effect in the pristine CNT films was studied by a three-point bending test. The gauge factor for the pristine CNT films under 500 microstrains was found to be at least 65 at room temperature, and increased with temperature, exceeding that of polycrystalline silicon (30) at 35℃. The origin of the piezoresistivity in CNT films may be ascribed to a pressure-induced change in the band gap and the defects.

  10. Carbon nanotube based transparent conductive thin films.

    Science.gov (United States)

    Yu, X; Rajamani, R; Stelson, K A; Cui, T

    2006-07-01

    Carbon nanotube (CNT) based optically transparent and electrically conductive thin films are fabricated on plastic substrates in this study. Single-walled carbon nanotubes (SWNTs) are chemically treated with a mixture of concentrated sulfuric acid and nitric acid before being dispersed in aqueous surfactant-contained solutions. SWNT thin films are prepared from the stable SWNT solutions using wet coating techniques. The 100 nm thick SWNT thin film exhibits a surface resistivity of 6 kohms/square nanometer with an average transmittance of 88% on the visible light range, which is three times better than the films prepared from the high purity as-received SWNTs.

  11. Ordered growth of topological insulator Bi2Se3 thin films on dielectric amorphous SiO2 by MBE.

    Science.gov (United States)

    Jerng, Sahng-Kyoon; Joo, Kisu; Kim, Youngwook; Yoon, Sang-Moon; Lee, Jae Hong; Kim, Miyoung; Kim, Jun Sung; Yoon, Euijoon; Chun, Seung-Hyun; Kim, Yong Seung

    2013-11-07

    Topological insulators (TIs) are exotic materials which have topologically protected states on the surface due to strong spin-orbit coupling. However, a lack of ordered growth of TI thin films on amorphous dielectrics and/or insulators presents a challenge for applications of TI-junctions. We report the growth of topological insulator Bi2Se3 thin films on amorphous SiO2 by molecular beam epitaxy (MBE). To achieve the ordered growth of Bi2Se3 on an amorphous surface, the formation of other phases at the interface is suppressed by Se passivation. Structural characterizations reveal that Bi2Se3 films are grown along the [001] direction with a good periodicity by the van der Waals epitaxy mechanism. A weak anti-localization effect of Bi2Se3 films grown on amorphous SiO2 shows a modulated electrical property by the gating response. Our approach for ordered growth of Bi2Se3 on an amorphous dielectric surface presents considerable advantages for TI-junctions with amorphous insulator or dielectric thin films.

  12. Optimizing amorphous indium zinc oxide film growth for low residual stress and high electrical conductivity

    Energy Technology Data Exchange (ETDEWEB)

    Kumar, Mukesh [Department of Metallurgical and Materials Engineering, Colorado School of Mines, Golden, CO 80401 (United States); Sigdel, A.K. [Department of Physics and Astronomy, University of Denver, Denver, CO 80208 (United States); National Center for Photovoltaics, National Renewal Energy Laboratory, 1617 Cole Boulevard, Golden, CO 80401 (United States); Gennett, T.; Berry, J.J.; Perkins, J.D.; Ginley, D.S. [National Center for Photovoltaics, National Renewal Energy Laboratory, 1617 Cole Boulevard, Golden, CO 80401 (United States); Packard, C.E., E-mail: cpackard@mines.edu [Department of Metallurgical and Materials Engineering, Colorado School of Mines, Golden, CO 80401 (United States); National Center for Photovoltaics, National Renewal Energy Laboratory, 1617 Cole Boulevard, Golden, CO 80401 (United States)

    2013-10-15

    With recent advances in flexible electronics, there is a growing need for transparent conductors with optimum conductivity tailored to the application and nearly zero residual stress to ensure mechanical reliability. Within amorphous transparent conducting oxide (TCO) systems, a variety of sputter growth parameters have been shown to separately impact film stress and optoelectronic properties due to the complex nature of the deposition process. We apply a statistical design of experiments (DOE) approach to identify growth parameter–material property relationships in amorphous indium zinc oxide (a-IZO) thin films and observed large, compressive residual stresses in films grown under conditions typically used for the deposition of highly conductive samples. Power, growth pressure, oxygen partial pressure, and RF power ratio (RF/(RF + DC)) were varied according to a full-factorial test matrix and each film was characterized. The resulting regression model and analysis of variance (ANOVA) revealed significant contributions to the residual stress from individual growth parameters as well as interactions of different growth parameters, but no conditions were found within the initial growth space that simultaneously produced low residual stress and high electrical conductivity. Extrapolation of the model results to lower oxygen partial pressures, combined with prior knowledge of conductivity–growth parameter relationships in the IZO system, allowed the selection of two promising growth conditions that were both empirically verified to achieve nearly zero residual stress and electrical conductivities >1480 S/cm. This work shows that a-IZO can be simultaneously optimized for high conductivity and low residual stress.

  13. Ceramics and amorphous thin films based on gallium sulphide doped by rare-earth sulphides

    Science.gov (United States)

    Popescu, M.; Sava, F.; Lőrinczi, A.; Velea, A.; Simandan, I. D.; Badica, P.; Burdusel, M.; Galca, A. C.; Matei, E.; Preda, N.; Secu, M.; Socol, G.; Jipa, F.; Zamfirescu, M.; Balan, A.

    2015-04-01

    Bulk ceramics of Ga2S3 and rare-earth sulfides (EuS, Gd2S3, Er2S3) as well as combinations thereof have been prepared by spark plasma sintering (SPS). The disk-shaped ceramics were used as targets for pulsed laser deposition (PLD) experiments to obtain amorphous thin films. The properties of these new bulks and amorphous thin films have been investigated by x-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive x-ray spectroscopy (EDX), optical transmission spectroscopy, and atomic force microscopy (AFM). In order to test the photoexpansion effect in Ga2S3 and the possibility to create planar arrays of microlenses, the film was irradiated with femtosecond laser pulses at different powers. For low laser power pulses (up to 100 mW power per pulse) a photoexpansion effect was observed, which leads to formation of hillocks with a height of 40-50 nm. EuS doped Ga2S3 thin film shows luminescence properties, which recommend them for optoelectronic applications.

  14. Novel Transrotational Solid State Order Discovered by TEM in Crystallizing Amorphous Films

    Science.gov (United States)

    Kolosov, Vladimir

    Exotic thin crystals with unexpected transrotational microstructures have been discovered by transmission electron microscopy (TEM) for crystal growth in thin (10-100 nm) amorphous films of different chemical nature (oxides, chalcogenides, metals and alloys) prepared by various methods. Primarily we use our TEM bend contour technique. The unusual phenomenon can be traced in situ in TEM column: dislocation independent regular internal bending of crystal lattice planes in a growing crystal. Such transrotation (unit cell trans lation is complicated by small rotationrealized round an axis lying in the film plane) can result in strong regular lattice orientation gradients (up to 300 degrees per micrometer) of different geometries: cylindrical, ellipsoidal, toroidal, saddle, etc. Transrotation is increasing as the film gets thinner. Transrotational crystal resembles ideal single crystal enclosed in a curved space. Transrotational micro crystals have been eventually recognized by other authors in some vital thin film materials, i.e. PCMs for memory, silicides, SrTiO3. Atomic model and possible mechanisms of the phenomenon are discussed. New transrotational nanocrystalline model of amorphous state is also proposed Support of RF Ministry of Education and Science is acknowledged.

  15. Optical bandgap of ultra-thin amorphous silicon films deposited on crystalline silicon by PECVD

    Energy Technology Data Exchange (ETDEWEB)

    Abdulraheem, Yaser, E-mail: yaser.abdulraheem@kuniv.edu.kw [Electrical Engineering Department, College of Engineering and Petroleum, Kuwait University. P.O. Box 5969, 13060 Safat (Kuwait); Gordon, Ivan; Bearda, Twan; Meddeb, Hosny; Poortmans, Jozef [IMEC, Kapeldreef 75, 3001, Leuven (Belgium)

    2014-05-15

    An optical study based on spectroscopic ellipsometry, performed on ultrathin hydrogenated amorphous silicon (a-Si:H) layers, is presented in this work. Ultrathin layers of intrinsic amorphous silicon have been deposited on n-type mono-crystalline silicon (c-Si) wafers by plasma enhanced chemical vapor deposition (PECVD). The layer thicknesses along with their optical properties –including their refractive index and optical loss- were characterized by spectroscopic ellipsometry (SE) in a wavelength range from 250 nm to 850 nm. The data was fitted to a Tauc-Lorentz optical model and the fitting parameters were extracted and used to compute the refractive index, extinction coefficient and optical bandgap. Furthermore, the a-Si:H film grown on silicon was etched at a controlled rate using a TMAH solution prepared at room temperature. The optical properties along with the Tauc-Lorentz fitting parameters were extracted from the model as the film thickness was reduced. The etch rate for ultrathin a-Si:H layers in TMAH at room temperature was found to slow down drastically as the c-Si interface is approached. From the Tauc-Lorentz parameters obtained from SE, it was found that the a-Si film exhibited properties that evolved with thickness suggesting that the deposited film is non-homogeneous across its depth. It was also found that the degree of crystallinity and optical (Tauc) bandgap increased as the layers were reduced in thickness and coming closer to the c-Si substrate interface, suggesting the presence of nano-structured clusters mixed into the amorphous phase for the region close to the crystalline silicon substrate. Further results from Atomic Force Microscopy and Transmission Electron Microscopy confirmed the presence of an interfacial transitional layer between the amorphous film and the underlying substrate showing silicon nano-crystalline enclosures that can lead to quantum confinement effects. Quantum confinement is suggested to be the cause of the observed

  16. Optical bandgap of ultra-thin amorphous silicon films deposited on crystalline silicon by PECVD

    Directory of Open Access Journals (Sweden)

    Yaser Abdulraheem

    2014-05-01

    Full Text Available An optical study based on spectroscopic ellipsometry, performed on ultrathin hydrogenated amorphous silicon (a-Si:H layers, is presented in this work. Ultrathin layers of intrinsic amorphous silicon have been deposited on n-type mono-crystalline silicon (c-Si wafers by plasma enhanced chemical vapor deposition (PECVD. The layer thicknesses along with their optical properties –including their refractive index and optical loss- were characterized by spectroscopic ellipsometry (SE in a wavelength range from 250 nm to 850 nm. The data was fitted to a Tauc-Lorentz optical model and the fitting parameters were extracted and used to compute the refractive index, extinction coefficient and optical bandgap. Furthermore, the a-Si:H film grown on silicon was etched at a controlled rate using a TMAH solution prepared at room temperature. The optical properties along with the Tauc-Lorentz fitting parameters were extracted from the model as the film thickness was reduced. The etch rate for ultrathin a-Si:H layers in TMAH at room temperature was found to slow down drastically as the c-Si interface is approached. From the Tauc-Lorentz parameters obtained from SE, it was found that the a-Si film exhibited properties that evolved with thickness suggesting that the deposited film is non-homogeneous across its depth. It was also found that the degree of crystallinity and optical (Tauc bandgap increased as the layers were reduced in thickness and coming closer to the c-Si substrate interface, suggesting the presence of nano-structured clusters mixed into the amorphous phase for the region close to the crystalline silicon substrate. Further results from Atomic Force Microscopy and Transmission Electron Microscopy confirmed the presence of an interfacial transitional layer between the amorphous film and the underlying substrate showing silicon nano-crystalline enclosures that can lead to quantum confinement effects. Quantum confinement is suggested to be the cause

  17. Stepwise morphological change of porous amorphous ice films observed through adsorption of methane

    Science.gov (United States)

    Horimoto, Noriko; Kato, Hiroyuki S.; Kawai, Maki

    2002-03-01

    Morphological change of amorphous ice films of D2O has been studied through adsorption of methane using thermal desorption spectroscopy (TDS) and infrared reflection absorption spectroscopy under ultrahigh vacuum. The investigated ice films were prepared under several different conditions; first, water (D2O) molecules are evaporated onto a Ru substrate at 25 K, and then subjected to an annealing process at various temperatures prior to methane deposition. On ice annealed at low temperatures, two desorption species of methane were observed in TDS: one was derived from methane adsorbed near the ice surface and the other was attributed to the desorption of methane encapsulated in ice during heating. Only the former species was observed when the annealing temperature exceeded 60 K. This indicates that reconstruction of ice occurs below 60 K, which inhibits the encapsulation of methane molecules from the amorphous ice. On the other hand, infrared spectra of ice covered with methane show that the micropores in ice start to collapse at ˜80 K, and ice becomes pore free at 120 K. We have found that the morphological change of amorphous ice induced by thermal relaxation takes place in a stepwise manner.

  18. Reduction of Photoluminescence Quenching by Deuteration of Ytterbium-Doped Amorphous Carbon-Based Photonic Materials

    Directory of Open Access Journals (Sweden)

    Hui-Lin Hsu

    2014-08-01

    Full Text Available In situ Yb-doped amorphous carbon thin films were grown on Si substrates at low temperatures (<200 °C by a simple one-step RF-PEMOCVD system as a potential photonic material for direct integration with Si CMOS back end-of-line processing. Room temperature photoluminescence around 1 µm was observed via direct incorporation of optically active Yb3+ ions from the selected Yb(fod3 metal-organic compound. The partially fluorinated Yb(fod3 compound assists the suppression of photoluminescence quenching by substitution of C–H with C–F bonds. A four-fold enhancement of Yb photoluminescence was demonstrated via deuteration of the a-C host. The substrate temperature greatly influences the relative deposition rate of the plasma dissociated metal-organic species, and hence the concentration of the various elements. Yb and F incorporation are promoted at lower substrate temperatures, and suppressed at higher substrate temperatures. O concentration is slightly elevated at higher substrate temperatures. Photoluminescence was limited by the concentration of Yb within the film, the concentration of Yb ions in the +3 state, and the relative amount of quenching due to the various de-excitation pathways associated with the vibrational modes of the host a-C network. The observed wide full-width-at-half-maximum photoluminescence signal is a result of the variety of local bonding environments due to the a-C matrix, and the bonding of the Yb3+ ions to O and/or F ions as observed in the X-ray photoelectron spectroscopy analyses.

  19. Nano-Impact (Fatigue Characterization of As-Deposited Amorphous Nitinol Thin Film

    Directory of Open Access Journals (Sweden)

    Rehan Ahmed

    2012-08-01

    Full Text Available This paper presents nano-impact (low cycle fatigue behavior of as-deposited amorphous nitinol (TiNi thin film deposited on Si wafer. The nitinol film was 3.5 µm thick and was deposited by the sputtering process. Nano-impact tests were conducted to comprehend the localized fatigue performance and failure modes of thin film using a calibrated nano-indenter NanoTest™, equipped with standard diamond Berkovich and conical indenter in the load range of 0.5 mN to 100 mN. Each nano-impact test was conducted for a total of 1000 fatigue cycles. Depth sensing approach was adapted to understand the mechanisms of film failure. Based on the depth-time data and surface observations of films using atomic force microscope, it is concluded that the shape of the indenter test probe is critical in inducing the localized indentation stress and film failure. The measurement technique proposed in this paper can be used to optimize the design of nitinol thin films.

  20. Phosphorus- and boron-doped hydrogenated amorphous silicon films prepared using vaporized liquid cyclopentasilane

    Energy Technology Data Exchange (ETDEWEB)

    Masuda, Takashi, E-mail: mtakashi@jaist.ac.jp [Japan Advanced Institute of Science and Technology, Nomi, Ishikawa, 923-1292 (Japan); Takagishi, Hideyuki; Shen, Zhongrong; Ohdaira, Keisuke; Shimoda, Tatsuya [Japan Advanced Institute of Science and Technology, Nomi, Ishikawa, 923-1292 (Japan); Japan Science and Technology Agency, ALCA, Nomi, Ishikawa, 923-1211 (Japan)

    2015-08-31

    A simple, inexpensive method for fabricating a hydrogenated amorphous silicon (a-Si:H) film using thermal chemical vapor deposition from cyclopentasilane (CPS) at atmospheric pressure with a substrate temperature of 370 °C is described. The reactant gas was generated from liquid CPS by vaporization in the deposition chamber. The vaporized CPS gas was transformed immediately into a-Si:H film on a heated substrate. The a-Si:H films could be doped either n- or p-type by dissolving appropriate amounts of white phosphorus or decaborane, respectively, in the liquid CPS before vaporization. This process allows deposition of doped a-Si:H films of photovoltaic device-quality without the need for handling, storage, or transportation of large amounts of gaseous reactants. - Highlights: • B and P doped a-Si:H films made from liquid materials is presented. • Decaborane and white phosphorus is dissolved in the liquid materials. • A simple, inexpensive method for fabricating a-Si:H films using non-vacuum process. • The doped a-Si:H films with usable quality for photovoltaic devices are deposited.

  1. Estimation of the composition parameter of electrochemically colored amorphous hydrogen tungsten oxide films

    Science.gov (United States)

    Kaneko, Hiroko; Miyake, Kiyoshi

    1989-07-01

    The electrical and optical steady state observed in electrochemical coloration has been studied using asymmetric cells consisting of evaporated amorphous tungsten oxide films with 350-6000 Å thickness. The counter electrode used is indium wire, steel wire, or antimony-tin oxide film, and the electrolyte is a 1-N H2SO4 aqueous solution containing 10 vol % glycerol. The current and optical transmittance of the cells decrease with increasing time during coloration, and simultaneously reach a steady state. The optical density (λ=0.5 μm) in the steady state is proportional to the thickness of the tungsten oxide film, and the absorption coefficient at λ=0.5 μm of the colored oxide film in the state is approximately 9.0×104 cm-1. The effective charges which contribute to the coloration of films calculated from the charge injected until the electro-optical steady state were found to be 1.03-1.20×103 C/cm3. Assuming that the evaporated tungsten oxide films used have a distorted ReO3 structure, and that a hydrogen tungsten bronze HxWO3 is formed by coloration, the composition parameter x calculated from the average value of the effective charge, is 0.36, which is comparable with that of hydrogen tungsten bronze H0.33WO3 obtained for the colored crystalline WO3 films.

  2. Tunable perpendicular magnetic anisotropy in GdFeCo amorphous films

    Energy Technology Data Exchange (ETDEWEB)

    Ding, Manli, E-mail: md3jx@virginia.edu [Department of Physics, University of Virginia, Charlottesville, VA 22904 (United States); Poon, S. Joseph, E-mail: sjp9x@virginia.edu [Department of Physics, University of Virginia, Charlottesville, VA 22904 (United States)

    2013-08-15

    We report the compositional and temperature dependence of magnetic compensation in amorphous ferrimagnetic Gd{sub x}Fe{sub 93−x}Co{sub 7} alloy films. Magnetic compensation is attributed to the competition between antiferromagnetic coupling of rare-earth (RE) with transition-metal (TM) ions and ferromagnetic interaction between the TM ions. The low-Gd region of x between 20 and 34 was found to exhibit compensation phenomena characterized by a low saturation magnetization and perpendicular magnetic anisotropy (PMA) near the compensation temperature. Compensation temperature was not observed in previously unreported high-Gd region of x=52–59, in qualitative agreement with results from recent model calculations. However, low magnetization was achieved at room temperature, accompanied by a large PMA with coercivity reaching ∼6.6 kOe. The observed perpendicular magnetic anisotropy of amorphous GdFeCo films probably has a structural origin consistent with certain aspects of the atomic-scale anisotropy. Our findings have broadened the composition range of transition metal-rare earth alloys for designing PMA films, making it attractive for tunable magnetic anisotropy in nanoscale devices. - Highlights: ► We measure the magnetic anisotropy of amorphous Gd{sub x}Fe{sub 93−x}Co{sub 7} films. ► The magnetization was controlled by varying the composition and temperature. ► At room temperature a large PMA with coercivity of 6.6 kOe was achieved. ► The PMA has a structural origin consistent with the atomic-scale anisotropy.

  3. Scaling of anomalous hall effect in amorphous CoFeB Films with accompanying quantum correction

    KAUST Repository

    Zhang, Yan

    2015-05-08

    Scaling of anomalous Hall effect in amorphous CoFeB films with thickness ranging from 2 to 160 nm have been investigated. We have found that the scaling relationship between longitudinal (ρxx) and anomalous Hall (ρAH) resistivity is distinctly different in the Bloch and localization regions. For ultrathin CoFeB films, the sheet resistance (Rxx) and anomalous Hall conductance (GAH) received quantum correction from electron localization showing two different scaling relationships at different temperature regions. In contrast, the thicker films show a metallic conductance, which have only one scaling relationship in the entire temperature range. Furthermore, in the dirty regime of localization regions, an unconventional scaling relationship View the MathML sourceσAH∝σxxα with α=1.99 is found, rather than α=1.60 predicted by the unified theory.

  4. Composition-Controlled Low Field Magnetostriction of TbFe Amorphous Films

    Institute of Scientific and Technical Information of China (English)

    JIANG Hong-Chuan; ZHANG Wan-Li; ZHANG Wen-Xu; PENG Bin

    2008-01-01

    @@ Amorphous TbFe films are fabricated by dc magnetron sputtering, and their magnetostrictions at low field are examined over a wide range of terbium content (from 32at.% to 70at.%). It is found that the terbium content plays an important role in the magnetic and magnetostrictive properties of TbFe films. TbFe film soft magnetic properties and low field magnetostriction can be efficiently improved by controlling the terbium at an optimum content. The magnetostriction at lower magnetic field is increased with the increase of terbium content up to 48.2at.%. After reaching the maximum value, further increase of terbium content would result in a great decrease of the low field magnetostriction. By contrast, at higher magnetic field, the magnetostriction is decreased monotonically with the increase of the terbium content.

  5. Investigation of the degradation of a thin-film hydrogenated amorphous silicon photovoltaic module

    Energy Technology Data Exchange (ETDEWEB)

    van Dyk, E.E.; Audouard, A.; Meyer, E.L. [Department of Physics, Nelson Mandela Metropolitan University, P.O. Box 77000, Port Elizabeth 6031 (South Africa); Woolard, C.D. [Department of Chemistry, Nelson Mandela Metropolitan University, P.O. Box 77000, Port Elizabeth 6031 (South Africa)

    2007-01-23

    The degradation of a thin-film hydrogenated single-junction amorphous silicon (a-Si:H) photovoltaic (PV) module has been studied. We investigated the different modes of electrical and physical degradation of a-Si:H PV modules by employing a degradation and failure assessment procedure used in conjunction with analytical techniques, including, scanning electron microscopy (SEM) and thermogravimetry. This paper reveals that due to their thickness, thin films are very sensitive to the type of degradation observed. Moreover, this paper deals with the problems associated with the module encapsulant, poly(ethylene-co-vinylacetate) (EVA). The main objective of this study was to establish the influence of outdoor environmental conditions on the performance of a thin-film PV module comprising a-Si:H single-junction cells. (author)

  6. Amorphous to nanocrystalline transition in HWCVD Si:H films by substrate temperature variation

    Energy Technology Data Exchange (ETDEWEB)

    Gogoi, Purabi; Jha, Himanshu S.; Agarwal, Pratima [Department of Physics, IIT Guwahati, Guwahati (India); Deva, Dinesh [Department of Chemical Engineering, IIT Kanpur, Kanpur (India)

    2010-04-15

    Thin films of hydrogenated silicon with band gap ranging from 2.0-2.34 eV are prepared at deposition rate 8-14A/sec in an indigenously fabricated HWCVD system keeping all parameters except substrate temperature fixed. The films grown at T{sub s}{<=}150 C are found to be pure amorphous, whereas the formation of nanocrystalline phase starts at T{sub s} {>=} 200 C. With increase in T{sub s}, crystalline fraction increases along with the increase in the band gap whereas the hydrogen content in the films and the deposition rate decreases. The variation of microstructure by varying substrate temperature without a significant decrease in deposition rate is useful for various device applications. (copyright 2010 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  7. Dehydration and crystallization of amorphous calcium carbonate in solution and in air.

    Science.gov (United States)

    Ihli, Johannes; Wong, Wai Ching; Noel, Elizabeth H; Kim, Yi-Yeoun; Kulak, Alexander N; Christenson, Hugo K; Duer, Melinda J; Meldrum, Fiona C

    2014-01-01

    The mechanisms by which amorphous intermediates transform into crystalline materials are poorly understood. Currently, attracting enormous interest is the crystallization of amorphous calcium carbonate, a key intermediary in synthetic, biological and environmental systems. Here we attempt to unify many contrasting and apparently contradictory studies by investigating this process in detail. We show that amorphous calcium carbonate can dehydrate before crystallizing, both in solution and in air, while thermal analyses and solid-state nuclear magnetic resonance measurements reveal that its water is present in distinct environments. Loss of the final water fraction--comprising less than 15% of the total--then triggers crystallization. The high activation energy of this step suggests that it occurs by partial dissolution/recrystallization, mediated by surface water, and the majority of the particle then crystallizes by a solid-state transformation. Such mechanisms are likely to be widespread in solid-state reactions and their characterization will facilitate greater control over these processes.

  8. Corrosion behavior of amorphous/nanocrystalline Al-Cr-Fe film deposited by double glow plasmas technique

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    In order to improve the corrosion resistance of AZ31 magnesium alloy,the amorphous/nanocrystal Al-Cr-Fe film has been successfully prepared on AZ31 magnesium alloy by double glow plasma tech-nology.The amorphous/nanocrystalline consists of two different regions,i.e.,an amorphous layer on outmost surface and an underlying lamellar nanocrystalline layer with a grain size of less than 10 nm.The corrosion behavior of amorphous/nanocrystalline Al-Cr-Fe film in 3.5% NaCl solution is investi-gated using an electrochemical polarization measurement.Compared with the AZ31 magnesium alloy,the amorphous/nanocrystalline Al-Cr-Fe film exhibits more positive corrosion potentials and lower corrosion current densities than that of AZ31 magnesium alloy.XPS measurement reveals that the passive film formed on the Al-Cr-Fe film after the anodic polarization tests is strongly enriched in Cr2O3,Fe2O3 and Al2O3 at outer surface of the film and in the inner layer consists of Cr2O3,FeO and Al2O3.

  9. Amorphization and recrystallization processes in monocrystalline beta silicon carbide thin films

    Energy Technology Data Exchange (ETDEWEB)

    Edmond, J.A.; Withrow, S.P.; Kong, H.S.; Davis, R.F.

    1985-01-01

    Individual, as well as multiple doses of /sup 27/Al/sup +/, /sup 31/P/sup +/, /sup 28/Si/sup +/, and /sup 28/Si/sup +/ and /sup 12/C/sup +/, were implanted into (100) oriented monocrystalline ..beta..-SiC films. The critical energy of approx. =16 eV/atom required for the amorphization of ..beta..-SiC via implantation of /sup 27/Al/sup +/ and /sup 31/P/sup +/ was determined using the TRIM84 computer program for calculation of the damage-energy profiles coupled with the results of RBS/ion channeling analyses. In order to recrystallize amorphized layers created by the individual implantation of all four ion species, thermal annealing at 1600, 1700, or 1800/sup 0/C was employed. Characterization of the recrystallized layers was performed using XTEM. Examples of SPE regrown layers containing precipitates and dislocation loops, highly faulted-microtwinned regions, and random crystallites were observed.

  10. Modeling the Crystallization of Amorphous Silicon Thin Films Using a High Repetition Rate Scanning Laser

    Directory of Open Access Journals (Sweden)

    R. Černý

    2000-01-01

    Full Text Available An optimum design of experimental setup for the preparation of polycrystalline silicon (pc-Si films from amorphous layers applicable in the solar cell production is analyzed in the paper. In the computational simulations, the influence of basic characteristic parameters of the experimental procedure on the mechanisms of pc-Si lateral growth is studied. Among these parameters, the energy density of the applied laser and the thickness of the amorphous silicon (a-Si layer are identified as the most significant. As an optimum solution, the mechanism of pc-Si growth consisting in repeated melting of a part of already crystallized pc-Si layer by the scanning laser is proposed.

  11. Highly efficient ultrathin-film amorphous silicon solar cells on top of imprinted periodic nanodot arrays

    Energy Technology Data Exchange (ETDEWEB)

    Yan, Wensheng, E-mail: yws118@gmail.com; Gu, Min, E-mail: mgu@swin.edu.au [Centre for Micro-Photonics, Faculty of Science, Engineering and Technology, Swinburne University of Technology, Hawthorn, Victoria 3122 (Australia); Tao, Zhikuo [College of Electronic Science and Engineering, Nanjing University of Posts and Telecommunications, Nanjing 210023 (China); Ong, Thiam Min Brian [Plasma Sources and Application Center, NIE, Nanyang Technological University, 1 Nanyang Walk, Singapore 637616 (Singapore); Institute of Materials Research and Engineering, A*STAR (Agency for Science, Technology and Research), 3 Research Link, Singapore 117602 (Singapore)

    2015-03-02

    The addressing of the light absorption and conversion efficiency is critical to the ultrathin-film hydrogenated amorphous silicon (a-Si:H) solar cells. We systematically investigate ultrathin a-Si:H solar cells with a 100 nm absorber on top of imprinted hexagonal nanodot arrays. Experimental evidences are demonstrated for not only notable silver nanodot arrays but also lower-cost ITO and Al:ZnO nanodot arrays. The measured external quantum efficiency is explained by the simulation results. The J{sub sc} values are 12.1, 13.0, and 14.3 mA/cm{sup 2} and efficiencies are 6.6%, 7.5%, and 8.3% for ITO, Al:ZnO, and silver nanodot arrays, respectively. Simulated optical absorption distribution shows high light trapping within amorphous silicon layer.

  12. Tuning the physical properties of amorphous In–Zn–Sn–O thin films using combinatorial sputtering

    Energy Technology Data Exchange (ETDEWEB)

    Ndione, P. F.; Zakutayev, A.; Kumar, M.; Packard, C. E.; Berry, J. J.; Perkins, J. D.; Ginley, D. S.

    2016-12-01

    Transparent conductive oxides and amorphous oxide semiconductors are important materials for many modern technologies. Here, we explore the ternary indium zinc tin oxide (IZTO) using combinatorial synthesis and spatially resolved characterization. The electrical conductivity, work function, absorption onset, mechanical hardness, and elastic modulus of the optically transparent (>85%) amorphous IZTO thin films were found to be in the range of 10–2415 S/cm, 4.6–5.3 eV, 3.20–3.34 eV, 9.0–10.8 GPa, and 111–132 GPa, respectively, depending on the cation composition and the deposition conditions. This study enables control of IZTO performance over a broad range of cation compositions.

  13. Amorphous thin films for solar cell application. Final technical report, March 15, 1979-February 29, 1980

    Energy Technology Data Exchange (ETDEWEB)

    Jonath, A D; Anderson, W W; Crowley, J L; MacMillan, H F; Junga, F A; Knudsen, J F; Monahan, K M; Thornton, J A

    1980-03-01

    Magnetron sputtering, a deposition method in which magnetic confinement of a plasma encourages high deposition rates at low working gas partial pressures, is under investigation in this program as a candidate production technology for large-scale manufacture of high-efficiency, thin-film amorphous silicon solar photovoltaic cells. The approach uses two dc magnetron geometries: (1) a low-cost planar magnetron (PM) system for exploratory and detailed examination of deposition parameter space; and (2) a cylindrical magnetron (CM) system, scalable to production sizes, for deposition of homogeneous films over large areas. Detailed descriptions of these two systems are included. During this first-year effort, amorphous silicon films and device structures were sputtered in both PM and CM systems under a wide range of deposition conditions (i.e., T/sub s/, P/sub Ar/, P/sub H/sub 2//) using both doped and undoped sputter targets. Measured electrical and optical film properties indicate that control over a wide range of conductivity, photoconductivity, conductivity activation energy, and optical and infrared absorption behavior is achievable. Multiple depositions to fabricate simple MIS device structures and simultaneously to deposit monitor samples of individual constituent layers have been successful. Other program highlights are: (1) deposition rates as great as 1500 A/min were achieved in high-power dc magnetron operation at practical substrate-target spacings; (2) p-type and n-type a-Si:H consistently deposited from p- and n-type targets, respectively; (3) demonstrated correlation of argon and hydrogen partial pressure variations with optical, electronic, and structural properties of magnetron-sputtered a-Si:H films; and (4) initial depositions have achieved properties comparable to those in films made by rf sputtering and glow-discharge methods.

  14. A novel nondestructive testing method for amorphous Si-Sn-O films

    Science.gov (United States)

    Liu, Xianzhe; Cai, Wei; Chen, Jianqiu; Fang, Zhiqiang; Ning, Honglong; Hu, Shiben; Tao, Ruiqiang; Zeng, Yong; Zheng, Zeke; Yao, Rihui; Xu, Miao; Wang, Lei; Lan, Linfeng; Peng, Junbiao

    2016-12-01

    Traditional methods to evaluate the quality of amorphous silicon-substituted tin oxide (a-STO) semiconductor film are destructive and time-consuming. Here, a novel non-destructive, quick, and facile method named microwave photoconductivity decay (μ-PCD) is utilized to evaluate the quality of a-STO film for back channel etch (BCE) thin-film transistors (TFTs) by simply measuring the D value and peak reflectivity signal. Through the μ-PCD method, both optimum deposition procedure and optimal annealing temperature are attained to prepare a-STO film with superior quality. The a-STO TFTs are fabricated by the obtained optimum procedure that exhibits a mobility of 8.14 cm2 V-1 s-1, a I on/I off ratio of 6.07  ×  109, a V on of -1.2 V, a steep subthreshold swing of 0.21 V/decade, a low trap density (D t) of 1.68  ×  1012 eV-1 cm-2, and good stability under the positive/negative gate-bias stress. Moreover, the validity of the μ-PCD measurement for a-STO films is verified by x-ray photoelectron spectroscopy, Hall effect measurement, and the performance of STO TFTs measured by traditional methods. The non-destructive μ-PCD method sheds light on the fast optimization of the deposition procedure for amorphous oxide semiconductor films with excellent quality.

  15. Structural and Physical Property Studies of Amorphous Zn-In-Sn-O Thin Films

    Energy Technology Data Exchange (ETDEWEB)

    Proffit, Diana E; Ma, Qing; Buchholz, Donald B; Chang, Robert P.H.; Bedzyk, Michael J; Mason, Thomas O [NWU

    2013-03-07

    The structures in amorphous (a-) Zn, Sn co-doped In2O3 (ZITO) thin films grown by pulsed laser deposition on glass under varying oxygen pressure or with varying Sn:Zn ratios were determined using X-ray absorption spectroscopy and anomalous X-ray scattering. Typical structures around cations in a-ZITO films are described and compared with crystalline (c-) ZITO films. The results show that the Zn cations are fourfold coordinated with Zn–O bond lengths of 1.98 ± 0.02 Å, which is close to that in bulk ZnO. As a consequence, the second coordination shells around Zn contract. At longer distances away from Zn, the structure is commensurate with the averaged structure. The unit volume around In also contracts slightly compared to bulk In2O3, whereas the Sn–O bond length is similar to the one in bulk SnO2. These unique structural characteristics may account for the films' superior thermal stability over amorphous Sn-doped In2O3, and suggest that Zn and Sn act as network-forming cations. Like in c-ZITO, coordination numbers (N) around Sn, In, and Zn follow the order NSn > NIn > NZn. Unlike in c-ZITO, where electrical properties change significantly with a slight variation in the Sn:Zn ratio, this variation does not markedly alter the electrical properties, or the local structures, of a-ZITO films. Dramatic changes in the electrical properties occur for films grown under various oxygen pressures, which point to oxygen “defects” as the source of charge carriers.

  16. Textured Sb2Te3 films and GeTe/Sb2Te3 superlattices grown on amorphous substrates by molecular beam epitaxy

    Science.gov (United States)

    Boschker, Jos E.; Tisbi, E.; Placidi, E.; Momand, Jamo; Redaelli, Andrea; Kooi, Bart J.; Arciprete, Fabrizio; Calarco, Raffaella

    2017-01-01

    The realization of textured films of 2-dimensionally (2D) bonded materials on amorphous substrates is important for the integration of this material class with silicon based technology. Here, we demonstrate the successful growth by molecular beam epitaxy of textured Sb2Te3 films and GeTe/Sb2Te3 superlattices on two types of amorphous substrates: carbon and SiO2. X-ray diffraction measurements reveal that the out-of-plane alignment of grains in the layers has a mosaic spread with a full width half maximum of 2.8°. We show that a good texture on SiO2 is only obtained for an appropriate surface preparation, which can be performed by ex situ exposure to Ar+ ions or by in situ exposure to an electron beam. X-ray photoelectron spectroscopy reveals that this surface preparation procedure results in reduced oxygen content. Finally, it is observed that film delamination can occur when a capping layer is deposited on top of a superlattice with a good texture. This is attributed to the stress in the capping layer and can be prevented by using optimized deposition conditions of the capping layer. The obtained results are also relevant to the growth of other 2D materials on amorphous substrates.

  17. Textured Sb2Te3 films and GeTe/Sb2Te3 superlattices grown on amorphous substrates by molecular beam epitaxy

    Directory of Open Access Journals (Sweden)

    Jos E. Boschker

    2017-01-01

    Full Text Available The realization of textured films of 2-dimensionally (2D bonded materials on amorphous substrates is important for the integration of this material class with silicon based technology. Here, we demonstrate the successful growth by molecular beam epitaxy of textured Sb2Te3 films and GeTe/Sb2Te3 superlattices on two types of amorphous substrates: carbon and SiO2. X-ray diffraction measurements reveal that the out-of-plane alignment of grains in the layers has a mosaic spread with a full width half maximum of 2.8°. We show that a good texture on SiO2 is only obtained for an appropriate surface preparation, which can be performed by ex situ exposure to Ar+ ions or by in situ exposure to an electron beam. X-ray photoelectron spectroscopy reveals that this surface preparation procedure results in reduced oxygen content. Finally, it is observed that film delamination can occur when a capping layer is deposited on top of a superlattice with a good texture. This is attributed to the stress in the capping layer and can be prevented by using optimized deposition conditions of the capping layer. The obtained results are also relevant to the growth of other 2D materials on amorphous substrates.

  18. Piezoresistive Sensors Based on Carbon Nanotube Films

    Institute of Scientific and Technical Information of China (English)

    L(U) Jian-wei; WANG Wan-lu; LIAO Ke-jun; WANG Yong-tian; LIU CHang-lin; Zeng Qing-gao

    2005-01-01

    Piezoresistive effect of carbon nanotube films was investigated by a three-point bending test.Carbon nanotubes were synthesized by hot filament chemical vapor deposition.The experimental results showed that the carbon nanotubes have a striking piezoresistive effect.The relative resistance was changed from 0 to 10.5×10-2 and 3.25×10-2 for doped and undoped films respectively at room temperature when the microstrain under stress from 0 to 500. The gauge factors for doped and undoped carbon nanotube films under 500 microstrain were about 220 and 67 at room temperature, respectively, exceeding that of polycrystalline silicon (30) at 35℃.The origin of the resistance changes in the films may be attributed to a strain-induced change in the band gap for the doped tubes and the defects for the undoped tubes.

  19. Preparation of composite electroheat carbon film

    Institute of Scientific and Technical Information of China (English)

    XIA Jin-tong; TU Chuan-jun; LI Yan; HU Li-min; DENG Jiu-hua

    2005-01-01

    A kind of conductive and heating unit, which can reach a high surface electroheat temperature at a low voltage, was developed in view of the traditional electroheat coating which has a low surface electroheat temperature and an insufficient heat resistance of its binder. The coating molded electroheat carbon film(CMECF) was prepared by carbonizing the coating which was prepared by adding modified resin into flake graphite and carbon fiber, coating molded onto the surface of the heat resisting matrix after dried, while the hot pressing molded electroheat thick carbon film(HPMETCF) was prepared by carbonizing the bodies whose powders were hot pressing molded directly.The surface and inner microstructure of the carbon film was characterized and analyzed by SEM and DSC/TG, while electroheat property was tested by voltage-current volume resistivity tester and electrical parameter tester. The results show that, close-packed carbon network configuration is formed within the composite electroheat carbon film film after anti-oxidizable treatment reaches a higher surface electroheat temperature than that of the existing electroheat coatings at a low voltage, and has excellent electroheat property, high thermal efficiency as well as stable physicochemical property. It is found that, at room temperature(19± 2 ℃) and 22 V for 5 min, the surface electroheat temperature of the self-produced CMECF (mfiller/mresin = 1. 8/1) reaches 112 ℃ while HPMETCF (mfiller/mresin = 3. 6/1) reaches 265 ℃.

  20. Hard graphitelike hydrogenated amorphous carbon grown at high rates by a remote plasma

    DEFF Research Database (Denmark)

    Singh, Shailendra Vikram; Zaharia, T.; Creatore, M.

    2010-01-01

    Hydrogenated amorphous carbon (a-C:H) deposited from an Ar-C 2H2 expanding thermal plasma chemical vapor deposition (ETP-CVD) is reported. The downstream plasma region of an ETP is characterized by a low electron temperature (∼0.3 eV), which leads to an ion driven chemistry and negligible physical...

  1. Understanding the catalyst-free transformation of amorphous carbon into graphene by current-induced annealing

    NARCIS (Netherlands)

    Barreiro, A.; Börrnert, F.; Avdoshenko, S.M.; Rellinghaus, B.; Cunibert, G.; Rümmeli, M.H.; Vandersypen, L.M.K.

    2013-01-01

    We shed light on the catalyst-free growth of graphene from amorphous carbon (a–C) by current induced annealing by witnessing the mechanism both with in-situ transmission electron microscopy and with molecular dynamics simulations. Both in experiment and in simulation, we observe that small a–C clust

  2. Citrate effects on amorphous calcium carbonate (ACC) structure, stability, and crystallization

    DEFF Research Database (Denmark)

    Tobler, Dominique Jeanette; Rodriguez Blanco, Juan Diego; Dideriksen, Knud;

    2015-01-01

    Understanding the role of citrate in the crystallization kinetics of amorphous calcium carbonate (ACC) is essential to explain the formation mechanisms, stabilities, surface properties, and morphologies of CaCO3 biominerals. It also contributes to deeper insight into fluid-mineral inte...

  3. Damage threshold of amorphous carbon mirror for 177 eV FEL radiation

    NARCIS (Netherlands)

    Farahani, S. D.; Chalupsky, J.; Burian, T.; Chapman, H.; Gleeson, A. J.; Hajkoya, V.; Juha, L.; Jurek, M.; Klinger, D.; Sinn, H.; Sobierajski, R.; Stormer, M.; Tiedtke, K.; Toleikis, S.; Tschentscher, T.; Wabnitz, H.; Gaudin, J.

    2011-01-01

    We present results of damage studies performed at the Free-Electron LASer in Hamburg (FLASH) on amorphous carbon (a-C). The experiment was performed in the total external reflection geometry representing the working configuration of X-ray mirrors. The 177 eV photon laser beam was focused on a 40 nm

  4. Electrical, electronic and optical properties of amorphous indium zinc tin oxide thin films

    Energy Technology Data Exchange (ETDEWEB)

    Denny, Yus Rama [Department of Physics, Chungbuk National University, Cheongju 361-763 (Korea, Republic of); Department of Electrical Engineering, University of Sultan Ageng Tirtayasa, Banten, Serang, 42435 (Indonesia); Lee, Kangil; Seo, Soonjoo; Oh, Suhk Kun [Department of Physics, Chungbuk National University, Cheongju 361-763 (Korea, Republic of); Kang, Hee Jae, E-mail: hjkang@cbu.ac.kr [Department of Physics, Chungbuk National University, Cheongju 361-763 (Korea, Republic of); Yang, Dong Seok [Department of Physics Education, Chungbuk National University, Cheongju 361-763 (Korea, Republic of); Heo, Sung; Chung, Jae Gwan; Lee, Jae Cheol [Analytical Engineering Center, Samsung Advanced Institute of Technology, Suwon 440-600 (Korea, Republic of)

    2014-10-01

    Highlights: • The electronic property of indium zinc tin oxide thin films was investigated by using XPS and REELS. • The band gap varied with different In/Zn/Sn compositions. • The EXAFS results showed that the smaller Zn–Zn separation distance led to higher electron mobility. • The Sn/Zn composition ratio played a crucial role in improving the electrical properties of a-IZTO thin films. - Abstract: The electrical and optical properties of amorphous indium zinc tin oxide (a-IZTO) thin films were examined as a function of chemical composition. Effects of Sn/Zn composition ratio and In content on the electrical and optical properties of a-IZTO thin films are discussed. The electron mobility of thin film transistors with higher Sn/Zn composition ratio was dramatically improved due to a shorter zinc–zinc separation distance. The thin film transistor with the composition of In:Zn:Sn = 20:48:32 exhibits a high mobility of 30.6 cm{sup 2} V{sup −1} s{sup −1} and a high on–off current ratio of 10{sup 9}.

  5. Biaxial CdTe/CaF{sub 2} films growth on amorphous surface

    Energy Technology Data Exchange (ETDEWEB)

    Yuan, W., E-mail: yuanw@rpi.ed [Department of Physics, Applied Physics and Astronomy, Rensselaer Polytechnic Institute, 110, 8th St., Troy, NY 12180 (United States); Tang, F.; Li, H.-F.; Parker, T. [Department of Physics, Applied Physics and Astronomy, Rensselaer Polytechnic Institute, 110, 8th St., Troy, NY 12180 (United States); LiCausi, N. [Department of Electrical, Computer and Systems Engineering, Rensselaer Polytechnic Institute, 110, 8th St., Troy, NY 12180 (United States); Lu, T.-M. [Department of Physics, Applied Physics and Astronomy, Rensselaer Polytechnic Institute, 110, 8th St., Troy, NY 12180 (United States); Bhat, I. [Department of Electrical, Computer and Systems Engineering, Rensselaer Polytechnic Institute, 110, 8th St., Troy, NY 12180 (United States); Wang, G.-C. [Department of Physics, Applied Physics and Astronomy, Rensselaer Polytechnic Institute, 110, 8th St., Troy, NY 12180 (United States); Lee, S. [US Army Armament Research, Development and Engineering Center, Benet Labs, Watervliet, NY 12189 (United States)

    2009-10-30

    A continuous and highly biaxially textured CdTe film was grown by metal organic chemical vapor deposition on an amorphous substrate using biaxial CaF{sub 2} nanorods as a buffer layer. The interface between the CdTe film and CaF{sub 2} nanorods and the morphology of the CdTe film were studied by transmission electron microscopy (TEM) and scanning electron microscopy. Both the TEM and X-ray pole figure analysis clearly reveal that the crystalline orientation of the continuous CdTe film followed the {l_brace}111{r_brace}<121> biaxial texture of the CaF{sub 2} nanorods. A high density of twin faults was observed in the CdTe film. Furthermore, the near surface texture of the CdTe thin film was investigated by reflection high-energy electron diffraction (RHEED) and RHEED surface pole figure analysis. Twinning was also observed from the RHEED surface pole figure analysis.

  6. Room Temperature Growth of Hydrogenated Amorphous Silicon Films by Dielectric Barrier Discharge Enhanced CVD

    Institute of Scientific and Technical Information of China (English)

    GUO Yu; ZHANG Xiwen; HAN Gaorong

    2007-01-01

    Hydrogenated amorphous silicon (a-Si:H) films were deposited on Si (100) and glass substrates by dielectric barrier discharge enhanced chemical vapour deposition (DBD-CVD)in (SiH4+H2) atmosphere at room temperature.Results of the thickness measurement,SEM (scanning electron microscope),Raman,and FTIR (Fourier transform infrared spectroscopy) show that with the increase in the applied peak voltage,the deposition rate and network order of the films increase,and the hydrogen bonding configurations mainly in di-hydrogen (Si-H2) and poly hydrogen (SiH2)n are introduced into the films.The UV-visible transmission spectra show that with the decrease in Sill4/ (SiH4+H2) the thin films'band gap shifts from 1.92 eV to 2.17 eV.These experimental results are in agreement with the theoretic analysis of the DBD discharge.The deposition of a-Si:H films by the DBD-CVD method as reported here for the first time is attractive because it allows fast deposition of a-Si:H films on large-area low-melting-point substrates and requires only a low cost of production without additional heating or pumping equipment.

  7. The microstructures and electrical properties of Y-doped amorphous vanadium oxide thin films

    Science.gov (United States)

    Gu, Deen; Zhou, Xin; Guo, Rui; Wang, Zhihui; Jiang, Yadong

    2017-03-01

    One of promising approaches for further improving the sensitivity of microbolometer arrays with greatly-reduced pixel size is using the thermal-sensitive materials with higher performance. In this paper, Y-doped vanadium oxide (VOx) thin films prepared by a reactively sputtering process exhibit enhanced performance for the microbolometer application compared with frequently-applied VOx thin films. Both undoped and Y-doped VOx thin films are amorphous due to the relatively low deposition temperature. Y-doped VOx thin films exhibit smoother surface morphology than VOx due to the restrained expansion of particles during depositions. Y-doping increases the temperature coefficient of resistivity by over 20% for the doping level of 1.30 at%. The change rate of resistivity, after aging for 72 h, of thin films was reduced from about 15% for undoped VOx to 2% due to the introduction of Y. Moreover, Y-doped VOx thin films have a low 1/f noise level as VOx ones. Y-doping provides an attractive approach for preparing VOx thermal-sensitive materials with enhanced performance for microbolometers.

  8. Quantum confinement in amorphous TiO(2) films studied via atomic layer deposition.

    Science.gov (United States)

    King, David M; Du, Xiaohua; Cavanagh, Andrew S; Weimer, Alan W

    2008-11-05

    Despite the significant recent increase in quantum-based optoelectronics device research, few deposition techniques can reliably create the required functional nanoscale systems. Atomic layer deposition (ALD) was used here to study the quantum effects attainable through the use of this ångström-level controlled growth process. Size-dependent quantum confinement has been demonstrated using TiO(2) layers of nanoscale thickness applied to the surfaces of silicon wafers. TiO(2) films were deposited at 100 °C using TiCl(4) and H(2)O(2) in a viscous flow ALD reactor, at a rate of 0.61 Å/cycle. The low-temperature process was utilized to guarantee the amorphous deposition of TiO(2) layers and post-deposition thermal annealing was employed to promote crystallite-size modification. Hydrogen peroxide significantly reduced the residual chlorine that remained from a typical TiCl(4)-H(2)O ALD process at this temperature, down to 1.6%. Spectroscopic ellipsometry was used to quantify the optical properties both below and above the bandgap energy. A central composite design was employed to map the surface response of the film thickness-dependent bandgap shift for the as-deposited case and up to a thermal annealing temperature of 550 °C. The Brus model was used to develop a correlation between the amorphous TiO(2) film thickness and the quantum length to promote equivalent bandgap shifts.

  9. 2.5 D Transrotational Microcrystals and Nanostructures Revealed by TEM in Crystallizing Amorphous Films

    Science.gov (United States)

    Kolosov, Vladimir

    2015-03-01

    Unexpected transrotational microcrystals can be grown in thin 10-100 nm amorphous films. Crystals of different morphology (from nanowhiskers to spherulites, complex textures) and chemical nature (oxides, chalcogenides, metals and alloys) grown in thin films prepared by various methods are studied by transmission electron microscopy (TEM). We use primarily our TEM bend-contour method and SAED (HREM, AFM are also performed). The phenomenon resides in strong (up to 300 degrees/ μm) regular internal bending of crystal lattice planes in a growing crystal. It can be traced inside TEM in situ. Usual translation is complicated by slight regular rotation of the crystal unit cell (transrotation) most prominent at the mesoscale. Different geometries of transrotation of positive and negative curvature are revealed. Transrotational crystal resembles ideal single crystal enclosed in a curved space. It can be also considered similar to hypothetical endless 2.5 D analogy of MW nanotube/nano-onion halves. Transrotation is strongly increasing as the film gets thinner in the range 100-15 nm. Transrotations supplement dislocations and disclinations. New transrotational nanocrystalline model of amorphous state is proposed. Support of Ministry of Higher Education and Science is acknowledged.

  10. Molecular dynamics simulation of benzene in graphite and amorphous carbon slit pores.

    Science.gov (United States)

    Fomin, Yu D

    2013-11-15

    It is well known that confining a liquid into a pore strongly alters the liquid behavior. Investigations of the effect of confinement are of great importance for many scientific and technological applications. Here, we present a study of the behavior of benzene confined in carbon slit pores. Two types of pores are considered-graphite and amorphous carbon ones. We show that the effect of different pore structure is of crucial importance for the benzene behavior.

  11. Amorphous calcium carbonate controls avian eggshell mineralization: A new paradigm for understanding rapid eggshell calcification.

    Science.gov (United States)

    Rodríguez-Navarro, Alejandro B; Marie, Pauline; Nys, Yves; Hincke, Maxwell T; Gautron, Joel

    2015-06-01

    Avian eggshell mineralization is the fastest biogenic calcification process known in nature. How this is achieved while producing a highly crystalline material composed of large calcite columnar single crystals remains largely unknown. Here we report that eggshell mineral originates from the accumulation of flat disk-shaped amorphous calcium carbonate (ACC) particles on specific organic sites on the eggshell membrane, which are rich in proteins and sulfated proteoglycans. These structures known as mammillary cores promote the nucleation and stabilization of a amorphous calcium carbonate with calcitic short range order which predetermine the calcite composition of the mature eggshell. The amorphous nature of the precursor phase was confirmed by the diffuse scattering of X-rays and electrons. The nascent calcitic short-range order of this transient mineral phase was revealed by infrared spectroscopy and HRTEM. The ACC mineral deposited around the mammillary core sites progressively transforms directly into calcite crystals without the occurrence of any intermediate phase. Ionic speciation data suggest that the uterine fluid is equilibrated with amorphous calcium carbonate, throughout the duration of eggshell mineralization process, supporting that this mineral phase is constantly forming at the shell mineralization front. On the other hand, the transient amorphous calcium carbonate mineral deposits, as well as the calcite crystals into which they are converted, form by the ordered aggregation of nanoparticles that support the rapid mineralization of the eggshell. The results of this study alter our current understanding of avian eggshell calcification and provide new insights into the genesis and formation of calcium carbonate biominerals in vertebrates.

  12. Effects of Atomic-Scale Structure on the Fracture Properties of Amorphous Carbon - Carbon Nanotube Composites

    Science.gov (United States)

    Jensen, Benjamin D.; Wise, Kristopher E.; Odegard, Gregory M.

    2015-01-01

    The fracture of carbon materials is a complex process, the understanding of which is critical to the development of next generation high performance materials. While quantum mechanical (QM) calculations are the most accurate way to model fracture, the fracture behavior of many carbon-based composite engineering materials, such as carbon nanotube (CNT) composites, is a multi-scale process that occurs on time and length scales beyond the practical limitations of QM methods. The Reax Force Field (ReaxFF) is capable of predicting mechanical properties involving strong deformation, bond breaking and bond formation in the classical molecular dynamics framework. This has been achieved by adding to the potential energy function a bond-order term that varies continuously with distance. The use of an empirical bond order potential, such as ReaxFF, enables the simulation of failure in molecular systems that are several orders of magnitude larger than would be possible in QM techniques. In this work, the fracture behavior of an amorphous carbon (AC) matrix reinforced with CNTs was modeled using molecular dynamics with the ReaxFF reactive forcefield. Care was taken to select the appropriate simulation parameters, which can be different from those required when using traditional fixed-bond force fields. The effect of CNT arrangement was investigated with three systems: a single-wall nanotube (SWNT) array, a multi-wall nanotube (MWNT) array, and a SWNT bundle system. For each arrangement, covalent bonds are added between the CNTs and AC, with crosslink fractions ranging from 0-25% of the interfacial CNT atoms. The SWNT and MWNT array systems represent ideal cases with evenly spaced CNTs; the SWNT bundle system represents a more realistic case because, in practice, van der Waals interactions lead to the agglomeration of CNTs into bundles. The simulation results will serve as guidance in setting experimental processing conditions to optimize the mechanical properties of CNT

  13. Microstructural analysis of carbon films obtained from C{sub 60} fullerene ion beams

    Energy Technology Data Exchange (ETDEWEB)

    Huck, H.; Halac, E.B.; Reinoso, M.; Dall' Asen, A.G.; Somoza, A.; Deng, W.; Brusa, R.S.; Karwasz, G.P.; Zecca, A

    2003-04-30

    Carbon films have been produced by accelerating C{sub 60}{sup +} ions on silicon substrates with energies between 100 and 800 eV. Furthermore some samples have been vacuum-annealed at 600 deg. C. The samples have been characterized by Raman and positron annihilation spectroscopies (RS-PAS). The measurements for the as-deposited material show that there is a coexistence of polymerized fullerenes and amorphous-carbon islands and that the structure depends on the energy of the incident ions. At low energies, fullerenes are deposited preserving the molecular identity and some intermolecular covalent bonds begin to insinuate; at higher energies, the amount of these covalent bonds increases and the amorphous islands predominate. After the annealing process, the amorphous phase organizes in graphitic clusters and the unbroken C{sub 60} cages are transformed back to pristine and slightly polymerized C{sub 60}.

  14. Nanostructured Diamond-Like Carbon Films Grown by Off-Axis Pulsed Laser Deposition

    Directory of Open Access Journals (Sweden)

    Seong Shan Yap

    2015-01-01

    Full Text Available Nanostructured diamond-like carbon (DLC films instead of the ultrasmooth film were obtained by pulsed laser ablation of pyrolytic graphite. Deposition was performed at room temperature in vacuum with substrates placed at off-axis position. The configuration utilized high density plasma plume arriving at low effective angle for the formation of nanostructured DLC. Nanostructures with maximum size of 50 nm were deposited as compared to the ultrasmooth DLC films obtained in a conventional deposition. The Raman spectra of the films confirmed that the films were diamond-like/amorphous in nature. Although grown at an angle, ion energy of >35 eV was obtained at the off-axis position. This was proposed to be responsible for subplantation growth of sp3 hybridized carbon. The condensation of energetic clusters and oblique angle deposition correspondingly gave rise to the formation of nanostructured DLC in this study.

  15. Maximum probing depth of low-energy photoelectrons in an amorphous organic semiconductor film

    Energy Technology Data Exchange (ETDEWEB)

    Ozawa, Yusuke [Graduate School of Advanced Integration Science, Chiba University, 1-33 Yayoi-cho, Inage-ku, Chiba 263-8522 (Japan); Nakayama, Yasuo, E-mail: nkym@restaff.chiba-u.jp [Graduate School of Advanced Integration Science, Chiba University, 1-33 Yayoi-cho, Inage-ku, Chiba 263-8522 (Japan); Machida, Shin’ichi; Kinjo, Hiroumi [Graduate School of Advanced Integration Science, Chiba University, 1-33 Yayoi-cho, Inage-ku, Chiba 263-8522 (Japan); Ishii, Hisao [Graduate School of Advanced Integration Science, Chiba University, 1-33 Yayoi-cho, Inage-ku, Chiba 263-8522 (Japan); Center for Frontier Science, Chiba University, 1-33 Yayoi-cho, Inage-ku, Chiba 263-8522 (Japan)

    2014-12-15

    Highlights: • Photoelectron attenuation lengths (AL) through amorphous organic films were examined. • In the energy range below 9 eV, AL fluctuates unlike a prediction by universal curve. • AL of photoelectron yield spectroscopy (PYS) measurements was found to be ∼3.6 nm. • PYS signals still survived through an 18 nm-thick film despite such a moderate AL. • This indicates buried interfaces in practical organic devices can be accessed by PYS. - Abstract: The attenuation length (AL) of low energy photoelectrons inside a thin film of a π-conjugated organic semiconductor material, 2,2′,2″-(1,3,5-benzinetriyl)-tris(1-phenyl-1-H-benzimidazole), was investigated using ultraviolet photoelectron spectroscopy (UPS) and photoelectron yield spectroscopy (PYS) to discuss their probing depth in amorphous organic thin films. The present UPS results indicated that the AL is 2–3 nm in the electron energy range of 6.3–8.3 eV with respect to the Fermi level, while the PYS measurements which collected the excited electrons in a range of 4.5–6 eV exhibited a longer AL of 3.6 nm. Despite this still short AL in comparison to a typical thickness range of electronic devices that are a few tens of nm-thick, the photoemission signal penetrating through further thicker (18 nm) organic film was successfully detected by PYS. This fact suggests that the electronic structures of “buried interfaces” inside practical organic devices are accessible using this rather simple measurement technique.

  16. Analytical drain current model for amorphous IGZO thin-film transistors in abovethreshold regime

    Institute of Scientific and Technical Information of China (English)

    He Hongyu; Zheng Xueren

    2011-01-01

    An analytical drain current model is presented for amorphous In-Ga-Zn-oxide thin-film transistors in the above-threshold regime,assuming an exponential trap states density within the bandgap.Using a charge sheet approximation,the trapped and free charge expressions are calculated,then the surface potential based drain current expression is developed.Moreover,threshold voltage based drain current expressions are presented using the Taylor expansion to the surface potential based drain current expression.The calculated results of the surface potential based and threshold voltage based drain current expressions are compared with experimental data and good agreements are achieved.

  17. High-energy ion treatments of amorphous As40Se60 thin films for optical applications

    OpenAIRE

    Rashmi Chauhan; Arvind Tripathi; Krishna Kant Srivastava

    2014-01-01

    The treatment of 100 MeV Ag swift-heavy ion (SHI) irradiation with five different fluences (3×1010, 1×1011, 3×1011, 1×1012, and 3×1012 ions/cm2) was used to design optical and structural properties of amorphous (a-) As40Se60 chalcogenide thin films. Swanepoel method was applied on transmission measurements to determine the changes in optical bandgap, Tauc parameter and linear optical parameters, i.e., linear optical absorption, extinction coefficient and linear refractive index. Dispersion of...

  18. Synthesis of Ag-doped hydrogenated carbon thin films by a hybrid PVD–PECVD deposition process

    Indian Academy of Sciences (India)

    Majji Venkatesh; Sukru Taktak; Efstathios I Meletis

    2014-12-01

    Silver-doped hydrogenated amorphous carbon (Ag-DLC) films were deposited on Si substrates using a hybrid plasma vapour deposition–plasma enhanced chemical vapour deposition (PVD–PECVD) process combining Ag target magnetron sputtering and PECVD in an Ar–CH4 plasma. Processing parameters (working pressure, CH4/Ar ratio and magnetron current) were varied to obtain good deposition rate and a wide variety of Ag films. Structure and bonding environment of the films were obtained from transmission electron microscopy (TEM), energy dispersive spectroscopy (EDS) and Fourier transform infrared (FTIR) spectroscopy studies. Variation of processing parameters was found to produce Ag-doped amorphous carbon or diamond-like carbon (DLC) films with a range of characteristics with CH4/Ar ratio exercising a dominant effect. It was pointed out that Ag concentration and deposition rate of the film increased with the increase in d.c. magnetron current. At higher Ar concentration in plasma, Ag content increased whereas deposition rate of the film decreased. FTIR study showed that the films contained a significant amount of hydrogen and, as a result of an increase in the Ag content in the hydrogenated DLC film, $sp^{2}$ bond content also increased. The TEM cross sectional studies revealed that crystalline Ag particles were formed with a size in the range of 2–4 nm throughout an amorphous DLC matrix.

  19. AMORPHOUS POLY(ETHYLENE TEREPHTHALATE) FILMS IN THE STATE OF HIGH GLOBAL CHAIN ORIENTATION BUT NEARLY RANDOM SEGMENTAL ORIENTATION

    Institute of Scientific and Technical Information of China (English)

    QIAN Renyuan; FAN Qingrong; GUAN Jiayu; Chung Long Choy; Shigeyoshi Osaki

    1997-01-01

    The isotropy or anisotropy in some physical properties of the amorphous poly(ethylene terephthalate) films uniaxially drawn at temperatures above its Tg and then quenched to room temperature have been studied. Experimental results here presented show that this amorphous state of high global chain orientation but nearly random segmental orientation,the GOLR state, is nearly isotropic in refractive indices and Young's modulus for small deformation, while it is very probably anisotropic in thermal conduction and microwave dielectric properties.

  20. Core-shell amorphous silicon-carbon nanoparticles for high performance anodes in lithium ion batteries

    Science.gov (United States)

    Sourice, Julien; Bordes, Arnaud; Boulineau, Adrien; Alper, John P.; Franger, Sylvain; Quinsac, Axelle; Habert, Aurélie; Leconte, Yann; De Vito, Eric; Porcher, Willy; Reynaud, Cécile; Herlin-Boime, Nathalie; Haon, Cédric

    2016-10-01

    Core-shell silicon-carbon nanoparticles are attractive candidates as active material to increase the capacity of Li-ion batteries while mitigating the detrimental effects of volume expansion upon lithiation. However crystalline silicon suffers from amorphization upon the first charge/discharge cycle and improved stability is expected in starting with amorphous silicon. Here we report the synthesis, in a single-step process, of amorphous silicon nanoparticles coated with a carbon shell (a-Si@C), via a two-stage laser pyrolysis where decomposition of silane and ethylene are conducted in two successive reaction zones. Control of experimental conditions mitigates silicon core crystallization as well as formation of silicon carbide. Auger electron spectroscopy and scanning transmission electron microscopy show a carbon shell about 1 nm in thickness, which prevents detrimental oxidation of the a-Si cores. Cyclic voltammetry demonstrates that the core-shell composite reaches its maximal lithiation during the first sweep, thanks to its amorphous core. After 500 charge/discharge cycles, it retains a capacity of 1250 mAh.g-1 at a C/5 rate and 800 mAh.g-1 at 2C, with an outstanding coulombic efficiency of 99.95%. Moreover, post-mortem observations show an electrode volume expansion of less than 20% and preservation of the nanostructuration.

  1. Room-temperature fabrication of transparent flexible thin-film transistors using amorphous oxide semiconductors

    Science.gov (United States)

    Nomura, Kenji; Ohta, Hiromichi; Takagi, Akihiro; Kamiya, Toshio; Hirano, Masahiro; Hosono, Hideo

    2004-11-01

    Transparent electronic devices formed on flexible substrates are expected to meet emerging technological demands where silicon-based electronics cannot provide a solution. Examples of active flexible applications include paper displays and wearable computers. So far, mainly flexible devices based on hydrogenated amorphous silicon (a-Si:H) and organic semiconductors have been investigated. However, the performance of these devices has been insufficient for use as transistors in practical computers and current-driven organic light-emitting diode displays. Fabricating high-performance devices is challenging, owing to a trade-off between processing temperature and device performance. Here, we propose to solve this problem by using a novel semiconducting material-namely, a transparent amorphous oxide semiconductor from the In-Ga-Zn-O system (a-IGZO)-for the active channel in transparent thin-film transistors (TTFTs). The a-IGZO is deposited on polyethylene terephthalate at room temperature and exhibits Hall effect mobilities exceeding 10cm2V-1s-1, which is an order of magnitude larger than for hydrogenated amorphous silicon. TTFTs fabricated on polyethylene terephthalate sheets exhibit saturation mobilities of 6-9cm2V-1s-1, and device characteristics are stable during repetitive bending of the TTFT sheet.

  2. Formulation and delivery of improved amorphous fenofibrate solid dispersions prepared by thin film freezing.

    Science.gov (United States)

    Zhang, Meimei; Li, Houli; Lang, Bo; O'Donnell, Kevin; Zhang, Haohao; Wang, Zhouhua; Dong, Yixuan; Wu, Chuanbin; Williams, Robert O

    2012-11-01

    The objective of this study was to prepare amorphous fenofibrate (FB) solid dispersions using thin film freezing (TFF) and to incorporate the solid dispersions into pharmaceutically acceptable dosage forms. FB solid dispersions prepared with optimized drug/polymer ratios were characterized by modulated differential scanning calorimetry (MDSC), powder X-ray diffraction (XRD), scanning electron microscopy (SEM), Brunauer-Emmett-Teller (BET) specific surface area measurements, Fourier-transform infrared spectroscopy-attenuated total reflectance (FTIR-ATR), and supersaturation dissolution testing. Furthermore, a dry granulation technique was used to encapsulate the TFF compositions for in vitro dissolution and in vivo animal pharmacokinetic studies. The results showed that the TFF process produced amorphous, porous, microstructured, and stable solid dispersions with high surface areas. Development of solid oral dosage forms revealed that the performance of the FB containing solid dispersions was not affected by the formulation process, which was confirmed by DSC and XRD. Moreover, an in vivo pharmacokinetic study in rats revealed a significant increase in FB absorption compared to bulk FB. We confirmed that amorphous solid dispersions with large surface areas produced by the TFF process displayed superior dissolution rates and corresponding enhanced bioavailability of the poorly water-soluble drug, FB.

  3. Crystallization study of amorphous sputtered NiTi bi-layer thin film

    Energy Technology Data Exchange (ETDEWEB)

    Mohri, Maryam, E-mail: mmohri@ut.ac.ir [School of Metallurgy and Materials Engineering, College of Engineering, University of Tehran, Tehran (Iran, Islamic Republic of); Karlsruhe Institute of Technology, Institute of Nanotechnology, 76021 Karlsruhe (Germany); Nili-Ahmadabadi, Mahmoud [School of Metallurgy and Materials Engineering, College of Engineering, University of Tehran, Tehran (Iran, Islamic Republic of); Center of Excellence for High Performance Materials, University of Tehran, Tehran (Iran, Islamic Republic of); Chakravadhanula, Venkata Sai Kiran [Karlsruhe Institute of Technology, Institute of Nanotechnology, 76021 Karlsruhe (Germany)

    2015-05-15

    The crystallization of Ni-rich/NiTiCu bi-layer thin film deposited by magnetron sputtering from two separate alloy targets was investigated. To achieve the shape memory effect, the NiTi thin films deposited at room temperature with amorphous structure were annealed at 773 K for 15, 30, and 60 min for crystallization. Characterization of the films was carried out by differential scanning calorimetry to indicate the crystallization temperature, grazing incidence X-ray diffraction to identify the phase structures, atomic force microscopy to evaluate surface morphology, scanning transmission electron microscopy to study the cross section of the thin films. The results show that the structure of the annealed thin films strongly depends on the temperature and time of the annealing. Crystalline grains nucleated first at the surface and then grew inward to form columnar grains. Furthermore, the crystallization behavior was markedly affected by composition variations. - Highlights: • A developed bi-layer Ni45TiCu5/Ni50.8Ti was deposited on Si substrate and crystallized. • During crystallization, The Ni{sub 45}TiCu{sub 5} layer is thermally less stable than the Ni-rich layer. • The activation energy is 302 and 464 kJ/mol for Cu-rich and Ni-rich layer in bi-layer, respectively.

  4. Electronic Power System Application of Diamond-Like Carbon Films

    Science.gov (United States)

    Wu, Richard L. C.; Kosai, H.; Fries-Carr, S.; Weimer, J.; Freeman, M.; Schwarze, G. E.

    2003-01-01

    A prototype manufacturing technology for producing high volume efficiency and high energy density diamond-like carbon (DLC) capacitors has been developed. Unique dual ion-beam deposition and web-handling systems have been designed and constructed to deposit high quality DLC films simultaneously on both sides of capacitor grade aluminum foil and aluminum-coated polymer films. An optimized process, using inductively coupled RF ion sources, has been used to synthesize electrically robust DLC films. DLC films are amorphous and highly flexible, making them suitable for the production of wound capacitors. DLC capacitors are reliable and stable over a wide range of AC frequencies from 20 Hz to 1 MHz, and over a temperature range from .500 C to 3000 C. The compact DLC capacitors offer at least a 50% decrease in weight and volume and a greater than 50% increase in temperature handling capability over equal value capacitors built with existing technologies. The DLC capacitors will be suitable for high temperature, high voltage, pulsed power and filter applications.

  5. Iron nanoparticles embedded in carbon films: structural and optical properties

    Science.gov (United States)

    Mashayekhi, Fatemeh; Shafiekhani, Azizollah; Sebt, Seyed Ali

    2016-06-01

    In the present work amorphous hydrogenated carbon films with sputtered iron nanoparticles (Fe NPs @ a-C:H) were deposited by co-deposition of RF-sputtering and RF-plasma enhanced chemical vapor deposition methods using acetylene gas and iron target on quartz and silicon substrates. Samples were prepared in different initial pressures and during constant deposition time. The crystalline structure of Fe NPs @ a-C:H was studied using X-ray diffraction and selected area electron diffraction patterns. The X-ray photoelectron spectroscopy analysis presents that increasing the initial pressure decreases the atomic ratio of Fe/C and the sp3-hybridized carbon content in prepared samples. The transmission electron microscope image shows the encapsulated Fe NPs in carbon films. The optical properties and localized surface plasmon resonance (LSPR) of samples were studied using UV-visible spectrophotometry, which is shown that increasing of Fe content decreases the intensity of LSPR peak and increases the optical band gap.

  6. Nanoporosity induced by ion implantation in deposited amorphous Ge thin films

    Energy Technology Data Exchange (ETDEWEB)

    Romano, L.; Impellizzeri, G.; Ruffino, F.; Miritello, M.; Grimaldi, M. G. [IMM-CNR MATIS and Dipartimento di Fisica e Astronomia, Universita di Catania, Via S. Sofia 64, I-95123 Catania (Italy); Bosco, L. [Scuola Superiore di Catania, Via Valdisavoia 9, I-95123 Catania (Italy)

    2012-06-01

    The formation of a nano-porous structure in amorphous Ge thin film (sputter-deposited on SiO{sub 2}) during ion irradiation at room temperature with 300 keV Ge{sup +} has been observed. The porous film showed a sponge-like structure substantially different from the columnar structure reported for ion implanted bulk Ge. The voids size and structure resulted to be strongly affected by the material preparation, while the volume expansion turned out to be determined only by the nuclear deposition energy. In SiGe alloys, the swelling occurs only if the Ge concentration is above 90%. These findings rely on peculiar characteristics related to the mechanism of voids nucleation and growth, but they are crucial for future applications of active nanostructured layers such as low cost chemical and biochemical sensing devices or electrodes in batteries.

  7. Domain wall energy landscapes in amorphous magnetic films with asymmetric arrays of holes

    Energy Technology Data Exchange (ETDEWEB)

    Alija, A; Perez-Junquera, A; RodrIguez-RodrIguez, G; Velez, M; Alameda, J M; MartIn, J I [Depto. Fisica, Fac. Ciencias, Universidad de Oviedo - CINN, Av. Calvo Sotelo s/n, 33007 Oviedo (Spain); Marconi, V I; Kolton, A B; Parrondo, J M R [Depto. Fisica Atomica, Molecular y Nuclear, and GISC, Universidad Complutense, 28040 Madrid (Spain); Anguita, J V [Instituto de Microelectronica de Madrid, CNM-CSIC, Isaac Newton 8, PTM, Tres Cantos, 28760 Madrid (Spain)

    2009-02-21

    Arrays of asymmetric holes have been defined in amorphous Co-Si films by e-beam lithography in order to study domain wall motion across the array subject to the asymmetric pinning potential created by the holes. Experimental results on Kerr effect magnetooptical measurements and hysteresis loops are compared with micromagnetic simulations in films with arrays of triangular holes. These show that the potential asymmetry favours forward wall propagation for flat walls but, if the wall contains a kink, net backward wall propagation is preferred at low fields, in agreement with minor loop experiments. The difference between the fields needed for forward and backward flat wall propagation increases as the size of the triangular holes is reduced, becoming maximum for 1 {mu}m triangles, which is the characteristic length scale set by domain wall width.

  8. Optical properties of amorphous and polycrystalline Sb2Se3 thin films prepared by thermal evaporation

    Science.gov (United States)

    Chen, Chao; Li, Weiqi; Zhou, Ying; Chen, Cheng; Luo, Miao; Liu, Xinsheng; Zeng, Kai; Yang, Bo; Zhang, Chuanwei; Han, Junbo; Tang, Jiang

    2015-07-01

    Sb2Se3 is a very promising photovoltaic material because of its attractive material, optical and electrical properties. Very recently, we reported a superstrate CdS/Sb2Se3 solar cell with 5.6% certified efficiency. In this letter, we focused on the optical properties of amorphous and polycrystalline Sb2Se3 thin films prepared by thermal evaporation. Using temperature dependent transmission spectrum and temperature dependent photoluminescence, the indirect optical transition nature and bandgap values as functions of temperature were acquired. Using ellipsometry measurements and Swanepoel's envelope method, the refractive indices as well as the dielectric constant in a wide wavelength range of 193-2615 nm were obtained. These works would lay the foundation for the further development of Sb2Se3 thin film solar cells.

  9. Photoelectronic properties of hydrogenated amorphous silicon films deposited by R. F sputtering and glow discharge methods

    Energy Technology Data Exchange (ETDEWEB)

    Abdel-Rahman, M.; Madkour, H. (Faculty of Science, Aswan (Egypt)); Hassan, H.H.; El-Desouki, S. (Cairo Univ., Giza (Egypt))

    1989-09-01

    Hydrogenated amorphous silicon films a-Si:H were deposited by both R.F. sputtering in a planar magnetron configuration and glow discharge methods on Corning glass substrates at different substrate temperatures. The dc and ac photoconductivities of the deposited films were extensively studied as a function of temperature, photon energy and photo-excitation intensity. The results showed that, the dark and photoconductivities have different dependency regions on temperature with different activation energies in the range of 0.08-0.20 eV. It has been also found that the photoconductivity is influenced by the method of deposition and the deposition parameters, indicating that the density of gap states is sensitive to the deposition conditions. The photoconductivity ({sigma}{sub ph}) has a power dependence on the illumination intensity (I) of the form {sigma}{sub ph} {alpha} I {sup {nu}}, where {nu} is a constant and was found also to be increase with temperature.

  10. Characteristics of Disorder and Defect in Hydrogenated Amorphous Silicon Nitride Thin Films Containing Silicon Nanograins

    Institute of Scientific and Technical Information of China (English)

    DING Wen-ge; YU Wei; ZHANG Jiang-yong; HAN Li; FU Guang-sheng

    2006-01-01

    The hydrogenated amorphous silicon nitride (SiNx) thin films embedded with nano-structural silicon were prepared and the microstructures at the interface of silicon nano-grains/SiNx were identified by the optical absorption and Raman scattering measurements. Characterized by the exponential tail of optical absorption and the band-width of the Raman scattering TO mode, the disorder in the interface region increases with the gas flow ratio increasing. Besides, as reflected by the sub-gap absorption coefficients, the density of interface defect states decreases, which can be attributed to the structural mismatch in the interface region and also the changes of hydrogen content in the deposited films. Additional annealing treatment results in a significant increase of defects and degree of disorder, for which the hydrogen out-diffusion in the annealing process would be responsible.

  11. Modelling the structure factors and pair distribution functions of amorphous germanium, silicon and carbon

    Energy Technology Data Exchange (ETDEWEB)

    Dalgic, Seyfettin; Gonzalez, Luis Enrique; Baer, Shalom; Silbert, Moises

    2002-12-01

    We present the results of calculations of the static structure factor S(k) and the pair distribution function g(r) of the tetrahedral amorphous semiconductors germanium, silicon and carbon using the structural diffusion model (SDM). The results obtained with the SDM for S(k) and g(r) are of comparable quality with those obtained by the unconstrained Reverse Monte Carlo simulations and existing ab initio molecular dynamics simulations for these systems. We have found that g(r) exhibits a small peak, or shoulder, a weak remnant of the prominent third neighbour peak present in the crystalline phase of these systems. This feature has been experimentally found to be present in recently reported high energy X-ray experiments of amorphous silicon (Phys. Rev. B 60 (1999) 13520), as well as in the previous X-ray diffraction of as-evaporated amorphous germanium (Phys. Rev. B 50 (1994) 539)

  12. Achieving an H-induced transparent state in 200 nm thick Mg-Ti film by amorphization

    Science.gov (United States)

    Fang, Fang; Zhao, Qiyang; Wu, Wangyang; Qiu, Jiameng; Song, Yun; Cui, Xiaoli; Sun, Dalin; Ouyang, Liuzhang; Zhu, Min

    2014-01-01

    Crystalline Mg-Ti films with a thickness of more than 50 nm are only switched to a highly absorbing state and cannot be further changed to the transparent state after hydrogen loading at room temperature. To solve this problem, 200 nm thick amorphous MgTix (x = 0.11-0.29) films were prepared and their switchable mirror properties upon hydrogen loading and unloading were investigated. The results show that amorphous MgTix films can be reversibly switched between mirror and transparent states without an absorbing state due to the significant acceleration of hydrogen diffusion by amorphization. Moreover, the switching time of amorphous MgTix films are dramatically shortened with increasing Ti content. Using quartz crystal microbalance method plus transmission spectrum, it is experimentally proved that Ti addition shows little influence on hydrogen diffusion but a strong catalytic effect on MgH2 formation and decomposition. Therefore, the quick formation of a blocking MgH2 layer due to the combined effect of slower hydrogen diffusion in crystalline films and rapid MgH2 formation under Ti catalysis is considered as the reason why the crystalline Mg-Ti films cannot be changed to transparent state after hydrogen loading.

  13. Solid solution or amorphous phase formation in TiZr-based ternary to quinternary multi-principal-element films

    Directory of Open Access Journals (Sweden)

    Mariana Braic

    2014-08-01

    The deposited films exhibited only solid solution (fcc, bcc or hcp or amorphous phases, no intermetallic components being detected. It was found that the hcp structure was stabilized by the presence of Hf or Y, bcc by Nb or Al and fcc by Cu. For the investigated films, the atomic size difference, mixing enthalpy, mixing entropy, Gibbs free energy of mixing and the electronegativity difference for solid solution and amorphous phases were calculated based on Miedema׳s approach of the regular solution model. It was shown that the atomic size difference and the ratio between the Gibbs free energies of mixing of the solid solution and amorphous phases were the most significant parameters controlling the film crystallinity.

  14. Albumin and fibrinogen adsorption on boron nitride and carbon-based thin films

    Energy Technology Data Exchange (ETDEWEB)

    Lousinian, S.; Kalfagiannis, N. [Laboratory for Thin Films - Nanosystems and Nanometrology (LTFN), Department of Physics, Aristotle University of Thessaloniki, GR-54124 Thessaloniki (Greece); Logothetidis, S. [Laboratory for Thin Films - Nanosystems and Nanometrology (LTFN), Department of Physics, Aristotle University of Thessaloniki, GR-54124 Thessaloniki (Greece)], E-mail: logot@auth.gr

    2008-08-25

    The haemocompatibility (in the sense of the least possibility of thrombus formation/thrombogenicity potential) of homogeneous and amorphous BN (a-BN) thin films through the adsorption of two basic blood plasma proteins, human serum albumin (HSA) and fibrinogen (Fib) is explored in this work. A comparative study of the thrombogenicity potential of BN, amorphous carbon (a-C) and amorphous hydrogenated carbon thin films (a-C:H) is also presented. a-BN and a-C thin films were produced by radio frequency (RF) magnetron sputtering onto c-Si (1 0 0) substrates under various values of substrate bias voltage. a-C:H thin films were developed by RF Reactive MS, with various values of substrate bias voltage and under different values of H{sub 2} partial pressure during deposition. For the consideration of the optical, compositional and structural properties of the films Spectroscopic Ellipsometry in the energy region of 1.5-6.5 eV was used, while for the study of surface topography and wetting properties Atomic Force Microscopy and Contact Angle measurements were additionally employed. The properties of the thin films were correlated with their thrombogenicity, through the estimation of the ratio of HSA/Fib surface concentration. a-BN films exhibit the smallest possibility of clot formation, with their wetting properties determining the thickness of the Fib layer formed on them as well as the ratio of HSA/Fib surface concentration. In the case of a-C thin films, the increase of % sp{sup 3} content is crucial, while the value of the fundamental gap seems to influence the possibility for clot formation on a-C:H thin films.

  15. Out-of-Plane Magnetic Anisotropy and Microwave Permeability of Magnetoelastic FeCoSiB Amorphous Thin Films

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    The amorphous magnetoelastic Fe66Co17Si1B6 thin films have been deposited by dc magnetron sputtering. A lot of "nano-trenches" have been observed on the film surfaces by AFM. The permeability of amorphous Fe66Co17Si1B6 thin films was measured within the frequency range of 0.6GHz-10.2 GHz. The ferromagnetic resonance frequency was found to be 1.2 GHz. MFM shows that the domain of thin film is a maze-type pattern, which indicates that an out-of-plane magnetic anisotropy exists. The out-of-plane anisotropy is believed due to the stress-induced magnetic anisotropy. It can be inferred that the internal stress is tensile stress and normal to the film plane.

  16. Reactive Infiltration of Silicon Melt Through Microporous Amorphous Carbon Preforms

    Science.gov (United States)

    Sangsuwan, P.; Tewari, S. N.; Gatica, J. E.; Singh, M.; Dickerson, R.

    1999-01-01

    The kinetics of unidirectional capillary infiltration of silicon melt into microporous carbon preforms have been investigated as a function of the pore morphology and melt temperature. The infiltrated specimens showed alternating bands of dark and bright regions, which corresponded to the unreacted free carbon and free silicon regions, respectively. The decrease in the infiltration front velocity for increasing infiltration distances, is in qualitative agreement with the closed-form solution of capillarity driven fluid flow through constant cross section cylindrical pores. However, drastic changes in the thermal response and infiltration front morphologies were observed for minute differences in the preforms microstructure. This suggests the need for a dynamic percolation model that would account for the exothermic nature of the silicon-carbon chemical reaction and the associated pore closing phenomenon.

  17. Microtribology of Nitrogen-doped Amorphous Carbon Coatings

    Institute of Scientific and Technical Information of China (English)

    Dong F. Wang

    2004-01-01

    The friction, wear and lubrication of carbon nitride coatings on silicon substrates are studied using a spherical diamond counter-face with nano-scale asperities. The first part of this paper clarifies the coating thickness effect on frictional behavior of carbon nitride coatings. The second part of this paper reports empirical data on wear properties in repeated sliding contacts through in situ examination and post-sliding observation. The third part will concentrate on wear mechanisms for the transition from "No observable wear particles" to "Wear particle generation." In light of the above tribological study, the application of carbon nitride coatings to MicroElectroMechanical system (MEMS) is therefore discussed from view points of both microtribology and micromachining.

  18. Charge transport in amorphous and tetragonal semiconducting YBaCuO films

    Science.gov (United States)

    Çelik-Butler, Z.; Shan, P. C.; Butler, D. P.; Jahanzeb, A.; Travers, C. M.; Kula, W.; Sobolewski, R.

    1997-06-01

    We have explored the charge transport mechanisms in six different YBaCuO semiconducting thin films in the temperature range of 70 K to room temperature. Two of the samples were deposited on LaAlO 3 substrate and were tetragonal with the composition of YBa 2Cu 3O 6.5 and YBa 2Cu 3O 6.3. The other four were amorphous as-deposited on Si substrate with and without a MgO buffer layer, and on an oxidized Si substrate with and without a MgO buffer layer. All tested films exhibited semiconductor-type resistance vs. temperature characteristics with increasing resistance as the temperature was decreased. Around room temperature all six samples had thermally activated transport characteristics that was interpreted as activation of hole-like carriers from localized states around the Fermi level to extended states. As the temperature was decreased, two tetragonal samples went through a transition to a variable range hopping-like conduction. The amorphous ones remained within the thermally-activated transport regime in the temperature range of 253 K to 318 K, with EA ≈ 0.2 eV.

  19. Carbon films produced from ionic liquid carbon precursors

    Science.gov (United States)

    Dai, Sheng; Luo, Huimin; Lee, Je Seung

    2013-11-05

    The invention is directed to a method for producing a film of porous carbon, the method comprising carbonizing a film of an ionic liquid, wherein the ionic liquid has the general formula (X.sup.+a).sub.x(Y.sup.-b).sub.y, wherein the variables a and b are, independently, non-zero integers, and the subscript variables x and y are, independently, non-zero integers, such that ax=by, and at least one of X.sup.+ and Y.sup.- possesses at least one carbon-nitrogen unsaturated bond. The invention is also directed to a composition comprising a porous carbon film possessing a nitrogen content of at least 10 atom %.

  20. Competing weak localization and weak antilocalization in amorphous indium-gallium-zinc-oxide thin-film transistors

    Science.gov (United States)

    Wang, Wei-Hsiang; Lyu, Syue-Ru; Heredia, Elica; Liu, Shu-Hao; Jiang, Pei-hsun; Liao, Po-Yung; Chang, Ting-Chang; Chen, Hua-Mao

    2017-01-01

    We have investigated the gate-voltage dependence and the temperature dependence of the magnetoconductivity of amorphous indium-gallium-zinc-oxide thin-film transistors. A weak-localization feature is observed at small magnetic fields on top of an overall negative magnetoconductivity at higher fields. An intriguing controllable competition between weak localization and weak antilocalization is observed by tuning the gate voltage or by varying the temperature. Our findings reflect controllable quantum interference competition in the electron systems in amorphous indium-gallium-zinc-oxide thin-film transistors.

  1. Use of successive ionic layer adsorption and reaction (SILAR) method for amorphous titanium dioxide thin films growth

    Science.gov (United States)

    Kale, S. S.; Mane, R. S.; Chung, Hoeil; Yoon, Moon-Young; Lokhande, C. D.; Han, Sung-Hwan

    2006-11-01

    Use of successive ionic layer adsorption and reaction (SILAR) method was preferred for the growth of amorphous titanium dioxide (TiO 2) thin films at ambient temperature. Further, these films were annealed at 673 K for 2 h in air for structural improvement and characterized for structural, surface morphological, optical and electrical properties. An amorphous structure of TiO 2 was retained even after annealing as confirmed from XRD studies. The spherical grains of relatively large size were compressed after annealing. A red shift in band gap energy and decrease in electrical resistivity were observed due to annealing treatment.

  2. The improvement of hole transport property and optical band gap for amorphous Cu{sub 2}O films

    Energy Technology Data Exchange (ETDEWEB)

    Huang, Qin; Li, Jin; Bi, Xiaofang

    2015-10-25

    This work presents an interesting observation that the suppression of crystallization for p-type Cu{sub 2}O facilitates the transition of transport behaviors from variable-range-hopping (VRH) to Arrhenius-like mechanism and further lead to a great reduction of thermal activation energy. Raman spectroscopy analysis shows a distortion of symmetrical O–Cu–O crosslink structure in the amorphous Cu{sub 2}O. The disruption of symmetry is revealed to increase dispersion of upper valence band and reduce Fermi as well, which results in possible intrusion of the Fermi level into a band tail state adjacent to the upper valence band level. Meanwhile, the amorphous Cu{sub 2}O film shows an optical band gap of 2.7 eV, much larger than 2.0 eV for the crystalline counterparts. The blue shift is consistent with the variation of energy band structure with the film changing from crystalline to amorphous state, suggesting that the O-mediated d–d interaction can be weakened with the nonsymmetrical structure in amorphous phase. - Graphical abstract: Suppression of crystallization for p-type Cu{sub 2}O is observed to facilitate the transition of transport behaviors from variable-range-hopping to the Arrhenius-like behavior based on the band tail transport mode. The amorphous Cu{sub 2}O film also shows a blue shift as compared to its crystalline counterpart. The effect of amorphous structure on the performances is discussed in combination with Raman spectroscopy and band structure calculation. - Highlights: • Amorphous Cu{sub 2}O films show Arrhenius-like p-type conductivity. • Raman spectroscopy is analyzed on the change of crystallization. • Physical origin of the transport behavior is clarified with electronic structure. • Optical band gap can be widened by suppressing crystallization of Cu{sub 2}O.

  3. Tuning the optoelectronic properties of amorphous MoOx films by reactive sputtering

    DEFF Research Database (Denmark)

    Fernandes Cauduro, André Luis; Fabrim, Zacarias Eduardo; Ahmadpour, Mehrad;

    2015-01-01

    In this letter, we report on the effect of oxygen partial pressure and sputtering power on amorphous DC-sputtered MoOx films. We observe abrupt changes in the optoelectronic properties of the reported films by increasing the oxygen partial pressure from 1.00 ? 10?3 mbar to 1.37 ? 10?3 mbar during...... the sputtering process. A strong impact on the electrical conductivity, varying from 1.6 ? 10?5 S/cm to 3.22 S/cm, and on the absorption coefficient in the range of 0.6–3.0 eV is observed for the nearly stoichiometric MoO3.00 and for the sub-stoichiometric MoO2.57 films, respectively, without modifying...... significantly the microstructure of the studied films. The presence of states within the band gap due to the lack of oxygen is the most probable mechanism for generat- ing a change in electrical conductivity as well as optical absorption in DC-sputtered MoOx. The large tuning range of the optoelectronic...

  4. Surface and bulk crystallization of amorphous solid water films: Confirmation of "top-down" crystallization

    Science.gov (United States)

    Yuan, Chunqing; Smith, R. Scott; Kay, Bruce D.

    2016-10-01

    The crystallization kinetics of nanoscale amorphous solid water (ASW) films are investigated using temperature-programmed desorption (TPD) and reflection absorption infrared spectroscopy (RAIRS). TPD measurements are used to probe surface crystallization and RAIRS measurements are used to probe bulk crystallization. Isothermal TPD results show that surface crystallization is independent of the film thickness (from 100 to 1000 ML). Conversely, the RAIRS measurements show that the bulk crystallization time increases linearly with increasing film thickness. These results suggest that nucleation and crystallization begin at the ASW/vacuum interface and then the crystallization growth front propagates linearly into the bulk. This mechanism was confirmed by selective placement of an isotopic layer (5% D2O in H2O) at various positions in an ASW (H2O) film. In this case, the closer the isotopic layer was to the vacuum interface, the earlier the isotopic layer crystallized. These experiments provide direct evidence to confirm that ASW crystallization in vacuum proceeds by a "top-down" crystallization mechanism.

  5. Surface and bulk crystallization of amorphous solid water films: Confirmation of “top-down” crystallization

    Energy Technology Data Exchange (ETDEWEB)

    Yuan, Chunqing; Smith, R. Scott; Kay, Bruce D.

    2016-10-01

    The crystallization kinetics of nanoscale amorphous solid water (ASW) films are investigated using temperature-programmed desorption (TPD) and reflection absorption infrared spectroscopy (RAIRS). TPD measurements are used to probe surface crystallization and RAIRS measurements are used to probe bulk crystallization. Isothermal TPD results show that surface crystallization is independent of the film thickness (from 100 to 1000 ML). Conversely, the RAIRS measurements show that the bulk crystallization time increases linearly with increasing film thickness. These results suggest that nucleation and crystallization begin at the ASW/vacuum interface and then the crystallization growth front propagates linearly into the bulk. This mechanism was confirmed by selective placement of an isotopic layer (5% D2O in H2O) at various positions in an ASW (H2O) film. In this case, the closer the isotopic layer was to the vacuum interface, the earlier the isotopic layer crystallized. These experiments provide direct evidence to confirm that ASW crystallization in vacuum proceeds by a “top-down” crystallization mechanism.

  6. Yttrium Iron Garnet Thin Films with Very Low Damping Obtained by Recrystallization of Amorphous Material.

    Science.gov (United States)

    Hauser, Christoph; Richter, Tim; Homonnay, Nico; Eisenschmidt, Christian; Qaid, Mohammad; Deniz, Hakan; Hesse, Dietrich; Sawicki, Maciej; Ebbinghaus, Stefan G; Schmidt, Georg

    2016-02-10

    We have investigated recrystallization of amorphous Yttrium Iron Garnet (YIG) by annealing in oxygen atmosphere. Our findings show that well below the melting temperature the material transforms into a fully epitaxial layer with exceptional quality, both structural and magnetic. In ferromagnetic resonance (FMR) ultra low damping and extremely narrow linewidth can be observed. For a 56 nm thick layer a damping constant of α = (6.15 ± 1.50) · 10(-5) is found and the linewidth at 9.6 GHz is as small as 1.30 ± 0.05 Oe which are the lowest values for PLD grown thin films reported so far. Even for a 20 nm thick layer a damping constant of α = (7.35 ± 1.40) · 10(-5) is found which is the lowest value for ultrathin films published so far. The FMR linewidth in this case is 3.49 ± 0.10 Oe at 9.6 GHz. Our results not only present a method of depositing thin film YIG of unprecedented quality but also open up new options for the fabrication of thin film complex oxides or even other crystalline materials.

  7. Films of Carbon Nanomaterials for Transparent Conductors

    Directory of Open Access Journals (Sweden)

    Jun Wei

    2013-05-01

    Full Text Available The demand for transparent conductors is expected to grow rapidly as electronic devices, such as touch screens, displays, solid state lighting and photovoltaics become ubiquitous in our lives. Doped metal oxides, especially indium tin oxide, are the commonly used materials for transparent conductors. As there are some drawbacks to this class of materials, exploration of alternative materials has been conducted. There is an interest in films of carbon nanomaterials such as, carbon nanotubes and graphene as they exhibit outstanding properties. This article reviews the synthesis and assembly of these films and their post-treatment. These processes determine the film performance and understanding of this platform will be useful for future work to improve the film performance.

  8. Measurement and Modeling of Short and Medium Range Order in Amorphous Ta2O5 Thin Films

    Science.gov (United States)

    Shyam, Badri; Stone, Kevin H.; Bassiri, Riccardo; Fejer, Martin M.; Toney, Michael F.; Mehta, Apurva

    2016-01-01

    Amorphous films and coatings are rapidly growing in importance. Yet, there is a dearth of high-quality structural data on sub-micron films. Not understanding how these materials assemble at atomic scale limits fundamental insights needed to improve their performance. Here, we use grazing-incidence x-ray total scattering measurements to examine the atomic structure of the top 50–100 nm of Ta2O5 films; mirror coatings that show high promise to significantly improve the sensitivity of the next generation of gravitational-wave detectors. Our measurements show noticeable changes well into medium range, not only between crystalline and amorphous, but also between as-deposited, annealed and doped amorphous films. It is a further challenge to quickly translate the structural information into insights into mechanisms of packing and disorder. Here, we illustrate a modeling approach that allows translation of observed structural features to a physically intuitive packing of a primary structural unit based on a kinked Ta-O-Ta backbone. Our modeling illustrates how Ta-O-Ta units link to form longer 1D chains and even 2D ribbons, and how doping and annealing influences formation of 2D order. We also find that all the amorphousTa2O5 films studied in here are not just poorly crystalline but appear to lack true 3D order. PMID:27562542

  9. Measurement and Modeling of Short and Medium Range Order in Amorphous Ta2O5 Thin Films

    Science.gov (United States)

    Shyam, Badri; Stone, Kevin H.; Bassiri, Riccardo; Fejer, Martin M.; Toney, Michael F.; Mehta, Apurva

    2016-08-01

    Amorphous films and coatings are rapidly growing in importance. Yet, there is a dearth of high-quality structural data on sub-micron films. Not understanding how these materials assemble at atomic scale limits fundamental insights needed to improve their performance. Here, we use grazing-incidence x-ray total scattering measurements to examine the atomic structure of the top 50-100 nm of Ta2O5 films; mirror coatings that show high promise to significantly improve the sensitivity of the next generation of gravitational-wave detectors. Our measurements show noticeable changes well into medium range, not only between crystalline and amorphous, but also between as-deposited, annealed and doped amorphous films. It is a further challenge to quickly translate the structural information into insights into mechanisms of packing and disorder. Here, we illustrate a modeling approach that allows translation of observed structural features to a physically intuitive packing of a primary structural unit based on a kinked Ta-O-Ta backbone. Our modeling illustrates how Ta-O-Ta units link to form longer 1D chains and even 2D ribbons, and how doping and annealing influences formation of 2D order. We also find that all the amorphousTa2O5 films studied in here are not just poorly crystalline but appear to lack true 3D order.

  10. Single-layer nano-carbon film, diamond film, and diamond/nano-carbon composite film field emission performance comparison

    Science.gov (United States)

    Wang, Xiaoping; Wang, Jinye; Wang, Lijun

    2016-05-01

    A series of single-layer nano-carbon (SNC) films, diamond films, and diamond/nano-carbon (D/NC) composite films have been prepared on the highly doped silicon substrate by using microwave plasma chemical vapor deposition techniques. The films were characterised by scanning electron microscopy, Raman spectroscopy, and field emission I-V measurements. The experimental results indicated that the field emission maximum current density of D/NC composite films is 11.8-17.8 times that of diamond films. And the field emission current density of D/NC composite films is 2.9-5 times that of SNC films at an electric field of 3.0 V/μm. At the same time, the D/NC composite film exhibits the advantage of improved reproducibility and long term stability (both of the nano-carbon film within the D/NC composite cathode and the SNC cathode were prepared under the same experimental conditions). And for the D/NC composite sample, a high current density of 10 mA/cm2 at an electric field of 3.0 V/μm was obtained. Diamond layer can effectively improve the field emission characteristics of nano-carbon film. The reason may be due to the diamond film acts as the electron acceleration layer.

  11. Characterization of boron doped diamond-like carbon film by HRTEM

    Energy Technology Data Exchange (ETDEWEB)

    Li, X.J., E-mail: lixj@alum.imr.ac.cn [College of Material Science and Engineering, Key Laboratory of Advanced Structural Materials, Ministry of Education, Changchun University of Technology, Changchun 130012 (China); He, L.L., E-mail: llhe@imr.ac.cn [Shenyang National Lab of Materials Science, Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016 (China); Li, Y.S. [Department of Mechanical Engineering, University of Saskatchewan, Saskatoon, SK S7N 5A9 (Canada); Plasma Physics Laboratory, University of Saskatchewan, Saskatoon, SK S7N 5E2 (Canada); Yang, Q. [Department of Mechanical Engineering, University of Saskatchewan, Saskatoon, SK S7N 5A9 (Canada); Hirose, A. [Plasma Physics Laboratory, University of Saskatchewan, Saskatoon, SK S7N 5E2 (Canada)

    2015-12-01

    Graphical abstract: - Highlights: • The microstructure of B-DLC film is studied by HRTEM in cross-sectional observation. • Many crystalline nanoparticles dispersed in the amorphous matrix film are observed. • Through composition and structure analysis, the nanoparticles are identified as B{sub 2}O. • The work implies the doped B element exists as oxide state in the B-DLC film. - Abstract: Boron doped diamond-like carbon (B-DLC) film was synthesized on silicon (1 0 0) wafer by biased target ion beam deposition. High-resolution transmission electron microscopy (HRTEM) is employed to investigate the microstructure of the B-DLC thin film in cross-sectional observation. Many crystalline nanoparticles randomly dispersed and embedded in the amorphous matrix film are observed. Through chemical compositional analysis of the B-DLC film, some amount of O element is confirmed to be contained. And also, some nanoparticles with near zone axes are indexed, which are accordance with B{sub 2}O phase. Therefore, the contained O element causing the B element oxidized is proposed, resulting in the formation of the nanoparticles. Our work indicates that in the B-DLC film a significant amount of the doped B element exists as boron suboxide nanoparticles.

  12. Hot-wire vapor deposition of amorphous MoS{sub 2} thin films

    Energy Technology Data Exchange (ETDEWEB)

    Papadimitropoulos, Georgios; Kontos, A.; Vasilopoulou, Maria; Kouvatsos, Dimitrios N.; Boukos, Nicolas; Davazoglou, Dimitrios [Institute of Nanoscience and Nanotechnology, NCSR ' ' Demokritos' ' , Attiki (Greece); Vourdas, Nikolaos [Technological Educational Institute of Chalkis (Greece); Gasparotto, Alberto [Department of Chemistry, Padova University (Italy); INSTM, Padova (Italy); Barreca, Davide [CNR-IENI, Padova (Italy); INSTM, Padova (Italy); Department of Chemistry, Padova University (Italy)

    2015-07-15

    Amorphous, as shown by X-ray diffraction measurements, MoS{sub 2} films (a-MoS{sub 2}) were deposited by heating a molybdenum wire at temperatures between 500 and 700 C in H{sub 2}S at 1 Torr. As shown by Scanning Electron Microscopy measurements, the morphology of samples depends significantly on the filament temperature; at low temperature samples are homogeneous and smooth, at intermediate temperatures they exhibit a granular microstructure and at high temperatures a columnar one. X-ray photoelectron spectroscopy measurements have shown S/Mo ratios in films varying between 2.5 and 1.5 dependent on filament temperature. Films also contain oxygen at atomic contents of 8 to 12%. As shown by XPS and Raman spectroscopy, at a filament temperature of 600 C films are mainly composed of MoS{sub 2} also containing oxygen at an atomic ratio of 8%. Spectroscopic ellipsometry measurements made on a-MoS{sub 2} films have shown that their band gap is of the order of 1.4 eV, slightly higher than that for the bulk crystalline material. Photoluminescence spectroscopy measurements have shown that samples exhibit a doublet of peaks at 2.8 and 3 eV blue shifted relatively to MoS{sub 2} samples composed of one or two mono-layers. The above indicate that the electronic structure of crystalline atomic-layer thick MoS{sub 2} is preserved in a-MoS{sub 2} films. (copyright 2015 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  13. Nanofrictional behavior of amorphous, polycrystalline and textured Y-Cr-O films

    Energy Technology Data Exchange (ETDEWEB)

    Gervacio-Arciniega, J.J. [Centro de Nanociencias y Nanotecnología (CNyN), Universidad Nacional Autónoma de México (UNAM), km. 107, Carretera Tijuana-Ensenada, 22860 Ensenada, B.C. (Mexico); Flores-Ruiz, F.J., E-mail: fcojfloresr@gmail.com [Centro de Nanociencias y Nanotecnología (CNyN), Universidad Nacional Autónoma de México (UNAM), km. 107, Carretera Tijuana-Ensenada, 22860 Ensenada, B.C. (Mexico); Diliegros-Godines, C.J. [Centro de Nanociencias y Nanotecnología (CNyN), Universidad Nacional Autónoma de México (UNAM), km. 107, Carretera Tijuana-Ensenada, 22860 Ensenada, B.C. (Mexico); Broitman, E. [Thin Film Physics Division, IFM, Linköping University, SE-58183 Linköping (Sweden); Enriquez-Flores, C.I.; Espinoza-Beltrán, F.J. [CINVESTAV Unidad Querétaro, Lib. Norponiente 2000, Real de Juriquilla, 76230 Querétaro, Qro. (Mexico); Siqueiros, J.; Cruz, M.P. [Centro de Nanociencias y Nanotecnología (CNyN), Universidad Nacional Autónoma de México (UNAM), km. 107, Carretera Tijuana-Ensenada, 22860 Ensenada, B.C. (Mexico)

    2016-08-15

    Highlights: • Friction coefficient (μ) of ferroelectric textured and polycrystalline YCrO{sub 3} films. • A simple method to evaluate μ from a single AFM image is presented. • The AFM-cantilever spring constant was determined from its dynamic response. • Polycrystalline and amorphous films have a lower μ than textured samples. - Abstract: Differences in friction coefficients (μ) of ferroelectric YCrO{sub 3}, textured and polycrystalline films, and non-ferroelectric Y-Cr-O films are analyzed. The friction coefficient was evaluated by atomic force microscopy using a simple quantitative procedure where the dependence of friction force with the applied load is obtained in only one topographical image. A simple code was developed with the MATLAB{sup ®} software to analyze the experimental data. The code includes a correction of the hysteresis in the forward and backward scanning directions. The quantification of load exerted on the sample surface was obtained by finite element analysis of the AFM cantilever starting from its experimental dynamic information. The results show that the ferroelectric YCrO{sub 3} film deposited on a Pt(150 nm)/TiO{sub 2}(30 nm)/SiO{sub 2}/Si (100) substrate is polycrystalline and has a lower friction coefficient than the deposited on SrTiO{sub 3} (110), which is highly textured. From a viewpoint of industrial application in ferroelectric memories, where the writing process is electrical or mechanically achieved by sliding AFM tips on the sample, polycrystalline YCrO{sub 3} films seem to be the best candidates due to their lower μ.

  14. Control and characterization of the structural, electrical, and optical properties of amorphous zinc-indium-tin oxide thin films.

    Science.gov (United States)

    Buchholz, D Bruce; Liu, Jun; Marks, Tobin J; Zhang, Ming; Chang, Robert P H

    2009-10-01

    Zinc-indium-tin oxide (ZITO) films are grown by pulsed-laser deposition in which 30% of the indium in the In(2)O(3) structure is replaced by substitution with zinc and tin in equal molar proportions: In(2-2x)Zn(x)Sn(x)O(3), where x = 0.3. Films grown at 25 and 100 degrees C exhibit electron diffraction patterns (EDPs) typical of amorphous materials. At a deposition temperature of 200 degrees C, evidence of crystallinity begins to appear in the EDP data and becomes more evident in films deposited at 400 degrees C. The advent of crystallinity affects the electrical properties of the ZITO film, and the effect is ascribed to the boundaries between phases in the films. The electrical and optical properties of the amorphous ZITO films grown at 25 degrees C are dependent on the oxygen partial pressure (P(O(2))) during film growth, transitioning from a high-mobility (36 cm(2)/V x s) conductor (sigma approximately 1700 S/cm) at P(O(2)) = 5 mTorr to a high-mobility semiconductor at P(O(2)) approximately 20 mTorr. Field-effect transistors (FETs) prepared with as-deposited amorphous ZITO channel layers on p(+)-Si/300 nm SiO(2) substrates yield FETs with on/off ratios of 10(6), off currents of 10(-8) A, and field-effect saturation mobilities of 10 cm(2)/V x s.

  15. Characterization of superconducting magnesium-diboride films on glassy carbon and sapphire substrates

    Energy Technology Data Exchange (ETDEWEB)

    Andrade, E.; Zavala, E. P. [Instituto de Fisica, UNAM, Apartado Postal 20-364, 01000 Mexico D. F. (Mexico); Rocha, M. F. [Escuela Superior de Ingenieria Mecanica y Electrica, IPN, Mexico D. F. (Mexico); Jergel, M.; Falcony, C. [Departamento de Fisica, CINVESTAV-IPN, Apartado postal 14-740, 07000 Mexico D. F. (Mexico)

    2008-02-15

    IBA methods were applied to measure elemental depth profiles of precursors and superconducting MgB{sub 2} thin films deposited on glassy carbon (Good Fellows) and sapphire (Al{sub 2}O{sub 3}) substrates. For each type of substrates we obtained a pair of samples i.e. one amorphous precursor and one superconducting film which were then characterized. A 3{sup H}e{sup +} beam was used to bombard both, precursors and superconducting films in order to obtain the samples elemental composition profiles. The zero resistance T{sub co} and the middle of transition T{sub cm} values were 26.0 K and 29.7 K for the MgB{sub 2} film deposited on glassy carbon substrate. In the case of sapphire substrate the T{sub co} and T{sub cm} values were 25.0 K and 27.9 K, respectively. (Author)

  16. In Situ Mechanical Property Measurements of Amorphous Carbon-Boron Nitride Nanotube Nanostructures

    Science.gov (United States)

    Kim, Jae-Woo; Lin, Yi; Nunez, Jennifer Carpena; Siochi, Emilie J.; Wise, Kristopher E.; Connell, John W.; Smith, Michael W.

    2011-01-01

    To understand the mechanical properties of amorphous carbon (a-C)/boron nitride nanotube (BNNT) nanostructures, in situ mechanical tests are conducted inside a transmission electron microscope equipped with an integrated atomic force microscope system. The nanotube structure is modified with amorphous carbon deposited by controlled electron beam irradiation. We demonstrate multiple in situ tensile, compressive, and lap shear tests with a-C/BNNT hybrid nanostructures. The tensile strength of the a-C/BNNT hybrid nanostructure is 5.29 GPa with about 90 vol% of a-C. The tensile strength and strain of the end-to-end joint structure with a-C welding is 0.8 GPa and 5.2% whereas the lap shear strength of the side-by-side joint structure with a-C is 0.25 GPa.

  17. Mapping residual organics and carbonate at grain boundaries and the amorphous interphase in mouse incisor enamel.

    Science.gov (United States)

    Gordon, Lyle M; Joester, Derk

    2015-01-01

    Dental enamel has evolved to resist the most grueling conditions of mechanical stress, fatigue, and wear. Adding insult to injury, it is exposed to the frequently corrosive environment of the oral cavity. While its hierarchical structure is unrivaled in its mechanical resilience, heterogeneity in the distribution of magnesium ions and the presence of Mg-substituted amorphous calcium phosphate (Mg-ACP) as an intergranular phase have recently been shown to increase the susceptibility of mouse enamel to acid attack. Herein we investigate the distribution of two important constituents of enamel, residual organic matter and inorganic carbonate. We find that organics, carbonate, and possibly water show distinct distribution patterns in the mouse enamel crystallites, at simple grain boundaries, and in the amorphous interphase at multiple grain boundaries. This has implications for the resistance to acid corrosion, mechanical properties, and the mechanism by which enamel crystals grow during amelogenesis.

  18. Optical Properties of Amorphous AlN Thin Films on Glass and Silicon Substrates Grown by Single Ion Beam Sputtering

    Science.gov (United States)

    Hajakbari, Fatemeh; Mojtahedzadeh Larijani, Majid; Ghoranneviss, Mahmood; Aslaninejad, Morteza; Hojabri, Alireza

    2010-09-01

    The structural and optical properties of aluminum nitride (AlN) films deposited on glass and silicon substrates by single ion beam sputtering technique have been investigated. The X-ray diffraction and Fourier transform infrared spectroscopy (FTIR) study revealed the formation of the amorphous phase of AlN. The optical characteristics of films, such as refractive index, extinction coefficient, and average thickness, were calculated by Swanepoel's method using transmittance measurements. The refractive index and average roughness values of the films increased with film thickness. Moreover, it was found that thickness augmentation leads to a decrease in optical band gap energy calculated using Tauc's relation.

  19. A study of the morphology of photochromic and thermochromic MoO 3 amorphous films using an atomic force microscope

    Science.gov (United States)

    Chudnovskii, F. A.; Schaefer, D. M.; Gavrilyuk, A. I.; Reifenberger, R.

    The surface morphology of amorphous MoO 3 films enhanced by a coating of N.N-dimethylformamide was studied with an atomic force microscope. Images of the as-grown films revealed a surface structure consisting of ˜25 nm diameter clusters which had coalesced to form irregular-shaped grains with dimensions ranging between 100 and 190 nm. Similar structure was found in the films after a photochromic or thermochromic transition had occured. The relative surface areas of the films have been calculated and little change is observed after the photochromic transition while a ˜29 increase in surface area is observed after the thermochromic transition has taken place.

  20. Electromagnetic characteristics of carbon nanotube film materials

    Directory of Open Access Journals (Sweden)

    Zhang Wei

    2015-08-01

    Full Text Available Carbon nanotube (CNT possesses remarkable electrical conductivity, which shows great potential for the application as electromagnetic shielding material. This paper aims to characterize the electromagnetic parameters of a high CNT loading film by using waveguide method. The effects of layer number of CNT laminate, CNT alignment and resin impregnation on the electromagnetic characteristics were analyzed. It is shown that CNT film exhibits anisotropic electromagnetic characteristic. Pristine CNT film shows higher real part of complex permittivity, conductivity and shielding effectiveness when the polarized direction of incident wave is perpendicular to the winding direction of CNT film. For the CNT film laminates, complex permittivity increases with increasing layer number, and correspondingly, shielding effectiveness decreases. The five-layer CNT film shows extraordinary shielding performance with shielding effectiveness ranging from 67 dB to 78 dB in X-band. Stretching process induces the alignment of CNTs. When aligned direction of CNTs is parallel to the electric field, CNT film shows negative permittivity and higher conductivity. Moreover, resin impregnation into CNT film leads to the decrease of conductivity and shielding effectiveness. This research will contribute to the structural design for the application of CNT film as electromagnetic shielding materials.

  1. Capillarity creates single-crystal calcite nanowires from amorphous calcium carbonate.

    Science.gov (United States)

    Kim, Yi-Yeoun; Hetherington, Nicola B J; Noel, Elizabeth H; Kröger, Roland; Charnock, John M; Christenson, Hugo K; Meldrum, Fiona C

    2011-12-23

    Single-crystal calcite nanowires are formed by crystallization of morphologically equivalent amorphous calcium carbonate (ACC) particles within the pores of track etch membranes. The polyaspartic acid stabilized ACC is drawn into the membrane pores by capillary action, and the single-crystal nature of the nanowires is attributed to the limited contact of the intramembrane ACC particle with the bulk solution. The reaction environment then supports transformation to a single-crystal product.

  2. Vacuum ultraviolet of hydrogenated amorphous carbons. II. Small hydrocarbons production in Photon Dominated Regions

    Science.gov (United States)

    Alata, I.; Jallat, A.; Gavilan, L.; Chabot, M.; Cruz-Diaz, G. A.; Munoz Caro, G. M.; Béroff, K.; Dartois, E.

    2015-12-01

    Context. Hydrogenated amorphous carbons (a-C:H) are a major component of the carbonaceous solids present in the interstellar medium. The production and existence of these grains is connected in particular with the balance between their photolysis, radiolysis, and hydrogenation. During grain processing, H2 and other small organic molecules, radicals, and fragments are released into the gas phase. Aims: We perform photolytic experiments on laboratory produced interstellar a-C:H analogues to monitor and quantify the release of species and compare to relevant observations in the interstellar medium. Methods: Hydrogenated amorphous carbon analogues at low temperature are exposed to ultraviolet (UV) photons, under ultra-high vacuum conditions. The species produced are monitored using mass spectrometry and post irradiation temperature-programmed desorption. Additional experiments are performed using deuterated analogues and the species produced are unambiguously separated from background contributions. We implement the laboratory measured yields for the released species in a time dependent model to investigate the effect of the UV photon irradiation of hydrogenated amorphous carbons in a photon dominated region, and estimate the associated time scale. Results: The UV photolysis of hydrogenated amorphous carbons leads to the production of H2 molecules and small hydrocarbons. The model shows that the photolytic evolution of a-C:Hs in photon dominated regions, such as the Horsehead Nebula, can raise the abundance of carbonaceous molecules by several orders of magnitude at intermediate visual extinctions, i.e., after the C+ maximum and before the dense cloud conditions prevail where models generally show a minimum abundance for such carbonaceous species. The injection time peak ranges from a thousand to ten thousand years in the models, considering only the destruction of such grains and no re-hydrogenation. This time scale is consistent with the estimated advection front of

  3. Influence of thermal heating on diamond-like carbon film properties prepared by filtered cathodic arc

    Energy Technology Data Exchange (ETDEWEB)

    Khamnualthong, N., E-mail: nattapornkh@gmail.com [Department of Physics, Faculty of Science, King Mongkut' s University of Technology Thonburi, Bangkok, 10140 (Thailand); Western Digital Thailand Co. Ltd, Ayutthaya, 13160 (Thailand); Siangchaew, K. [Western Digital Thailand Co. Ltd, Ayutthaya, 13160 (Thailand); Limsuwan, P. [Department of Physics, Faculty of Science, King Mongkut' s University of Technology Thonburi, Bangkok, 10140 (Thailand); Thailand Center of Excellence in Physics, CHE, Ministry of Education, Bangkok 10400 (Thailand)

    2013-10-01

    Tetrahedral amorphous diamond-like carbon (ta-DLC) films were deposited on magnetic recording heads using the filtered cathodic arc method. The deposited film thickness was on the order of several nanometers. The DLC films were then annealed to 100 °C–300 °C for 30 and 60 min, and the structure of the ta-DLC films was investigated using Raman spectroscopy, where the gross changes were observed in the Raman D and G peaks. Detailed interpretation concluded that there was sp{sup 2} clustering as a function of temperature, and there was no sp{sup 3}-to-sp{sup 2} conversion after heating up to 300 °C. Furthermore, X-ray photoelectron spectroscopy suggested that oxidation of both the ta-DLC film and the adhesion layer occurs at 300 °C. Additionally, more film wear was observed with heating as measured by a nanoindenter. - Highlights: • Tetrahedral-amorphous diamond-like carbon (ta-DLC) by filtered cathodic arc • ta-DLC used in magnetic recording head as head overcoat • ta-DLC thickness range of less than 2 nm • ta-DLC property dependence on heating • Temperature effect range of up to 300 °C.

  4. Anode properties of silicon-rich amorphous silicon suboxide films in all-solid-state lithium batteries

    Science.gov (United States)

    Miyazaki, Reona; Ohta, Narumi; Ohnishi, Tsuyoshi; Takada, Kazunori

    2016-10-01

    This paper reports the effects of introducing oxygen into amorphous silicon films on their anode properties in all-solid-state lithium batteries. Although poor cycling performance is a critical issue in silicon anodes, it has been effectively improved by introducing even a small amount of oxygen, that is, even in Si-rich amorphous silicon suboxide (a-SiOx) films. Because of the small amount of oxygen in the films, high cycling performance has been achieved without lowering the capacity and power density: an a-Si film delivers discharge capacity of 2500 mAh g-1 under high discharge current density of 10 mA cm-2 (35 C). These results demonstrate that a-SiOx is a promising candidate for high-capacity anode materials in solid-state batteries.

  5. Steady-state photoconductivity of amorphous (As4S3Se3)1-x:Snx films

    Science.gov (United States)

    Iaseniuc, O. V.; Iovu, M. S.; Cojocaru, I. A.; Prisacar, A. M.

    2015-02-01

    Amorphous arsenic trisulfide (As2S3) and arsenic triselenide (As2Se3) are among widely investigated amorphous materials due to its interesting electrical, optical and photoelectrical properties. In order to improve the physical properties and recording characteristics, and to extend the spectral range of photosensibility, a special interest represents the mixed amorphous materials, like (As2S3):(As2Se3). Chalcogenide vitreous semiconductors (ChVS) of the As-S-Se system exhibit photostructural transformations with reversible and irreversible properties, and are promising materials as registration media for holography and optical information, for fabrication of diffractive elements, and other optoelectronic applications. Because many optoelectronic devices on amorphous semiconductors are based on the photoconductivity effect, special interests represent investigation of the stationary and non-stationary characteristics of photoconductivity. In this paper the experimental results of steady-state photoconductivity and holographic characteristics of amorphous (As4S3Se3)1-x:Snx thin films are presented. It was shown that the photoconductivity spectra depend on the polarity on the top illuminated electrode and on the Sn concentration in the host glass. The photosensitivity of amorphous ((As4S3Se3)1-x:Snx thin films is almost constant for all Sn-containing glasses. The Moss rule was used for determination of the optical forbidden gap Eg from the photoconductivity spectra. It was demonstrated that the investigated amorphous films are sensitive to the light irradiation and can be used as effective registration media for holographic information. The relaxation of photodarkening in amorphous (As4S3Se3)1-x:Snx thin films was investigated and was shown that the relaxation curves of transmittance T/T0 = f(t) can be described the stretch exponential function T(t)/T(0) = A0+Aexp[-(t-t0)/τ] (1-β) . The kinetics of diffraction efficiency growth η(t) was measured by registration of

  6. Solar cells and thin film LED using amorphous SiC. Amorphous SiC wo mochiita taiyou denchi oyobi usumaku LED

    Energy Technology Data Exchange (ETDEWEB)

    Hamakawa, Y. (Osaka Univ., Osaka (Japan). Faculty of Engineering Science)

    1990-03-25

    This paper introduced the photoelectric properties of amorphous SiC (a-SiC), application to highly efficient solar cells, application to wide area emitting elements such as LED (light emitting diode) and application to OEIC (optoelectronic integrated circuit) which is expected in near future. The light sensitizing effect in which photoconductivity of a-SiC:H film increases 2-3 figures by B dopping, was found. Flexible and wide area thin film LED has been able to manufacture by this discovery. In addition, highly efficient conversion rate has been able to get by the technical development such as solar cells made of a-SiC/ a-Si hetrojunction. Further, wide area sollar cells has been able to manufacture on any substrate by the development of TFLED (thin film light emitting diode). The application of TFLED made of SiC to OEIC is also investigated. 18 refs., 15 figs., 2 tabs.

  7. Effect of applied dc bias voltage on composition, chemical bonding and mechanical properties of carbon nitride films prepared by PECVD

    Institute of Scientific and Technical Information of China (English)

    LI Hong-xuan; XU Tao; HAO Jun-ying; CHEN Jian-min; ZHOU Hui-di; XUE Qun-ji; LIU Hui-wen

    2004-01-01

    Carbon nitride films were deposited on Si (100) substrates using plasma-enhanced chemical vapor deposition (PECVD) technique from CH4 and N2 at different applied dc bias voltage. The microstructure, composition and chemical bonding of the resulting films were characterized by Raman spectroscopy, Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD). The mechanical properties such as hardness and elastic modulus of the films were evaluated using nano-indentation. As the results, the Raman spectra, showing the G and D bands, indicate the amorphous structure of the films. XPS and FTIR measurements demonstrate the existence of various carbon-nitride bonds in the films and the hydrogenation of carbon nitride phase. The composition ratio of N to C, the nano-hardness and the elastic modulus of the carbon nitride films increase with increasing dc bias voltage and reach the maximums at a dc bias voltage of 300 V, then they decrease with further increase of the dc bias voltage. Moreover, the XRD analyses indicate that the carbon nitride film contains some polycrystalline C3N4 phase embedded in the amorphous matrix at optimized deposition condition of dc bias voltage of 300 V.

  8. Experimental Investigation of Multipacting Suppression by amorphous Carbon Coatings

    CERN Document Server

    Holz, Michael

    The presence of electron cloud is considered as the most important limitation concerning the quality of the particle beam in the accelerators, especially with respect to the forthcoming LHC luminosity upgrade. The electron cloud can be mitigated by coating the vacuum beam chambers with thin films of low secondary electron yield (SEY). This technique is applied to two stand-alone main bending dipoles of the SPS, where the RF power is fed through a tungsten wire, stretched inside the vacuum chamber. A dipole with a bare stainless steel chamber shows a clear power threshold initiating an abrupt rise in reflected power and pressure. The effect is enhanced at RF frequencies corresponding to electron cyclotron resonances for given magnetic fields. The first results of a fully coated beam chamber do not exhibit any pressure rise or reflected RF power up to the maximum available input power. Here, reflected power has been observed only once and could not be reproduced. The results of a partially coated beam chamber s...

  9. Effect of crystallisation on the magnetic properties of FeCuNbBSi amorphous thin films produced by sputtering

    Energy Technology Data Exchange (ETDEWEB)

    Celegato, Federica; Coisson, Marco; Tiberto, Paola; Vinai, Franco [INRIM, Electromagnetism Division, Torino (Italy); Baricco, Marcello [Dipartimento di Chimica IFM and NIS, Universita di Torino (Italy)

    2011-11-15

    Soft magnetic thin films of FeCuNbSiB alloy having different thickness were deposited on a Si{sub 3}N{sub 4} substrate by rf sputtering. The target was made of amorphous ribbons having nominal composition Fe{sub 73.5}Cu{sub 1}Nb{sub 3}Si{sub 13.5}B{sub 9}. The amorphicity of as-deposited films has been checked by X-ray diffraction technique. Selected samples have been submitted to controlled annealing to induce the amorphous-to-crystalline transformation. The influence of thermal treatments on the hysteresis properties has been studied as a function of thickness and microstructure on as prepared and annealed samples. (copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  10. Surface properties of diamond-like carbon films prepared by CVD and PVD methods

    Institute of Scientific and Technical Information of China (English)

    Liu Dong-Ping; Liu Yan-Hong; Chen Bao-Xiang

    2006-01-01

    Diamond-like carbon (DLC) films have been deposited using three different techniques: (a) electron cyclotron resonance-plasma source ion implantation, (b) low-pressure dielectric barrier discharge, (c) filtered-pulsed cathodic arc discharge. The surface and mechanical properties of these films are compared using atomic force microscopebased tests. The experimental results show that hydrogenated DLC films are covered with soft surface layers enriched with hydrogen and sp3 hybridized carbon while the soft surface layers of tetrahedral amorphous carbon (ta-C) films have graphite-like structure. The formation of soft surface layers can be associated with the surface diffusion and growth induced by the low-energy deposition process. For typical CVD methods, the atomic hydrogen in the plasmas can contribute to the formation of hydrogen and sp3 hybridized carbon enriched surface layers. The high-energy ion implantation causes the rearrangement of atoms beneath the surface layer and leads to an increase in film density. The ta-C films can be deposited using the medium energy carbon ions in the highly-ionized plasma.

  11. Effect of ion irradiation on the stability of amorphous Ge{sub 2}Sb{sub 2}Te{sub 5} thin films

    Energy Technology Data Exchange (ETDEWEB)

    De Bastiani, R. [Dipartimento di Fisica e Astronomia, Universita di Catania and MATIS CNR-INFM, Via S. Sofia 64, I-95123 Catania (Italy)], E-mail: riccardo.debastiani@ct.infn.it; Piro, A.M.; Crupi, I.; Grimaldi, M.G. [Dipartimento di Fisica e Astronomia, Universita di Catania and MATIS CNR-INFM, Via S. Sofia 64, I-95123 Catania (Italy); Rimini, E. [Dipartimento di Fisica e Astronomia, Universita di Catania, Via S. Sofia 64, I-95123 Catania (Italy); Consiglio Nazionale delle Ricerche - Istituto per la Microelettronica e Microsistemi (CNR-IMM), Stradale Primosole 50, I-95121 Catania (Italy)

    2008-05-15

    The archival life of phase-change memories (PCM) is determined by the thermal stability of amorphous phase in a crystalline matrix. In this paper, we report the effect of ion beam irradiation on the crystallization kinetics of amorphous Ge{sub 2}Sb{sub 2}Te{sub 5} alloy (GST). The transition rate of amorphous GST films was measured by in situ time resolved reflectivity (TRR). The amorphous to crystal transformation time decreases considerably in irradiated amorphous GST samples when ion fluence increases. The stability of amorphous Ge{sub 2}Sb{sub 2}Te{sub 5} thin films subjected to ion irradiation is discussed in terms of the free energy variation of the amorphous state because of damage accumulation.

  12. Microcellular Foaming of Amorphous High-Tg Polymers Using Carbon Dioxyde

    NARCIS (Netherlands)

    Krause, B.; Mettinkhof, R.; Vegt, van der N.F.A.; Wessling, M.

    2001-01-01

    The foaming of thin (~100 m) polysulfone (PSU), poly(ether sulfone) (PES), and cyclic olefin copolymer (COC) films using carbon dioxide as a physical blowing agent has been studied. Microcellular foam morphologies were obtained by saturating the polymer with carbon dioxide and heating the sample abo

  13. Deposition and characterization of amorphous silicon with embedded nanocrystals and microcrystalline silicon for thin film solar cells

    Energy Technology Data Exchange (ETDEWEB)

    Ambrosio, R., E-mail: rambrosi@uacj.mx [Instituto Nacional de Astrofísica, Óptica y Electrónica, INAOE, Puebla (Mexico); Instituto de Ingeniería y Tecnología, Universidad Autónoma de Ciudad Juárez, UACJ, C.J., Chihuahua (Mexico); Moreno, M.; Torres, A. [Instituto Nacional de Astrofísica, Óptica y Electrónica, INAOE, Puebla (Mexico); Carrillo, A. [Instituto de Ingeniería y Tecnología, Universidad Autónoma de Ciudad Juárez, UACJ, C.J., Chihuahua (Mexico); Vivaldo, I.; Cosme, I. [Instituto Nacional de Astrofísica, Óptica y Electrónica, INAOE, Puebla (Mexico); Heredia, A. [Universidad Popular Autónoma del Estado de Puebla, Puebla (Mexico)

    2015-09-15

    Highlights: • Nanostructured silicon thin films were deposited by PECVD. • Polymorphous and microcrystalline were obtained varying the pressure and power. • Structural and optoelectronics properties were studied. • The σ{sub dark} changed by 5 order of magnitude under illumination, V{sub d} was at 2.5 A/s. • The evidence of embedded nanocrystals into the amorphous matrix was investigated. - Abstract: Amorphous silicon thin films with embedded nanocrystals and microcrystalline silicon were deposited by the standard Radio Frequency (RF) Plasma Enhanced Chemical Vapor Deposition (PECVD) technique, from SiH{sub 4}, H{sub 2}, Ar gas mixture at substrate temperature of 200 °C. Two series of films were produced varying deposition parameters as chamber pressure and RF power density. The chemical bonding in the films was characterized by Fourier transform infrared spectroscopy, where it was observed a correlation between the hydrogen content and the morphological and electrical properties in the films. Electrical and optical parameters were extracted in both series of films, as room temperature conductivity (σ{sub RT}), activation energy (E{sub a}), and optical band gap (E{sub g}). As well, structural analysis in the films was performed by Raman spectroscopy and Atomic Force Microscopy (AFM), which gives an indication of the films crystallinity. The photoconductivity changed in a range of 2 and 6 orders of magnitude from dark to AM 1.5 illumination conditions, which is of interest for thin film solar cells applications.

  14. Raman spectra of nitrogen-doped tetrahedral amorphous carbon from first principles

    Institute of Scientific and Technical Information of China (English)

    NIU Li; ZHU JiaQi; GAO Wei; HAN Xiao; DU ShanYi

    2009-01-01

    The non-resonant vibrational Raman spectra of nitrogen-doped tetrahedral amorphous carbon have been calculated from first principles, including the generation of s structural model, and the calculation of vibrational frequencies, vibrational eigenmodes and Raman coupling tensors. The calculated Raman spectra are in good agreement with the experimental results. The broad band at around 500 cm~(-1) arises from mixed bonds. The T peak originates from the vibrations of sp~3 carbon and the G peak comes from the stretching vibrations of sp~2-type bonding of C=C and C=N. The simulation results indicate the direct contribution of N vibrations to Raman spectra.

  15. Low-temperature formation of source–drain contacts in self-aligned amorphous oxide thin-film transistors

    NARCIS (Netherlands)

    Nag, M.; Muller, R.; Steudel, S.; Smout, S.; Bhoolokam, A.; Myny, K.; Schols, S.; Genoe, J.; Cobb, B.; Kumar, A.; Gelinck, G.; Fukui, Y.; Groeseneken, G.; Heremans, P.

    2015-01-01

    We demonstrated self-aligned amorphous-Indium-Gallium-Zinc-Oxide (a-IGZO) thin-film transistors (TFTs) where the source–drain (S/D) regions were made conductive via chemical reduction of the a-IGZO via metallic calcium (Ca). Due to the higher chemical reactivity of Ca, the process can be operated at

  16. Effect of amorphous C films deposited by RF magnetron sputtering on smoothing K9 glass substrate

    Science.gov (United States)

    Deng, Songwen; Qi, Hongji; Wei, Chaoyang; Yi, Kui; Fan, Zhengxiu; Shao, Jianda

    2009-12-01

    Soft X-ray multilayer reflectors must be deposited on super-smooth surface such as super-polished silicon wafers or glasses, which are complicate, time-consuming and expensive to produce. To overcome this shortage, C films deposited by RF magnetron sputtering were considered to smooth the K9 glass substrates' surface in the present paper. The structure of C films was systematically studied by XRD and Raman spectrum. The surface morphology and rms-roughness were obtained by AFM. Then, we calculated the impact of the C layers on the reflectivity curve of Mo/Si soft X-ray multilayer reflector around 13.5 nm. The C films exhibit typical amorphous state. With the increasing of power and thickness, the content of sp3 hybrid bonding decreases while the amount or size of well-organized graphite clusters increases. The surface rms-roughness decreases from 2.4 nm to 0.62 nm after smoothed by an 80 nm thick C layer deposited in 500 W, which is the smoothest C layer surface we have obtained. The calculation results show that the theoretical normal incidence reflectivity of Mo/Si multilayer at 13.5 nm increases from 7% to 63%.

  17. Effect of interface layers on electron field emission properties of amorphous diamond films

    Institute of Scientific and Technical Information of China (English)

    茅东升[1; 赵俊[2; 李炜[3; 王曦[4; 柳襄怀[5; 诸玉坤[6; 范忠[7; 周江云[8; 李琼[9; 徐静芳[10

    1999-01-01

    Hydrogen-free high sp~3 content amorphous diamond (AD) films are deposited on three different substrates——Au-coated Si (Au/Si), Ti-coated Si (Ti/Si) and Si wafers. Electron field emission properties and fluorescent displays of the above AD films are studied by using a sample diode structure. The compositional profile of the interfaces of AD/Ti/Si and AD/Si is examined by using secondary ions mass spectroscopy (SIMS). Because of the reaction and interdiffusion between Ti and C, the formation of a thin TiC intermediate layer is possible between AD film and Ti/Si substrate. The field emission properties of AD/Ti/Si are sufficiently improved, especially its uniformity. A field emission density of 0.352 mA/cm~2 is obtained under an electric field of 19.7 V/μm. The value is much more than that of AD/Au/Si and AD/Si under the same electric field.

  18. Anisotropic imprint of amorphization and phase separation in manganite thin films via laser interference irradiation

    KAUST Repository

    Ding, Junfeng

    2014-09-16

    Materials with mesoscopic structural and electronic phase separation, either inherent from synthesis or created via external means, are known to exhibit functionalities absent in the homogeneous counterparts. One of the most notable examples is the colossal magnetoresistance discovered in mixed-valence manganites, where the coexistence of nano-to micrometer-sized phase-separated domains dictates the magnetotransport. However, it remains challenging to pattern and process such materials into predesigned structures and devices. In this work, a direct laser interference irradiation (LII) method is employed to produce periodic stripes in thin films of a prototypical phase-separated manganite Pr0.65(Ca0.75Sr0.25)0.35MnO3 (PCSMO). LII induces selective structural amorphization within the crystalline PCSMO matrix, forming arrays with dimensions commensurate with the laser wavelength. Furthermore, because the length scale of LII modification is compatible to that of phase separation in PCSMO, three orders of magnitude of increase in magnetoresistance and significant in-plane transport anisotropy are observed in treated PCSMO thin films. Our results show that LII is a rapid, cost-effective and contamination-free technique to tailor and improve the physical properties of manganite thin films, and it is promising to be generalized to other functional materials.

  19. Effect of high magnetic field on structure and magnetic properties of evaporated crystalline and amorphous Fe-Sm thin films

    Science.gov (United States)

    Li, Guojian; Li, Mengmeng; Wang, Jianhao; Du, Jiaojiao; Wang, Kai; Wang, Qiang

    2017-02-01

    Crystalline and amorphous Fe-Sm thin films have been fabricated by using molecular beam vapor deposition method. Then, the effects of both variation of Sm content and application of high magnetic field during film growth on the structure and magnetic properties of the Fe-Sm films have been explored. The results show that bcc structure of the Fe-Sm films with 5.8% Sm transforms to amorphization with 33.0% Sm. Meanwhile, nanocrystallite is formed in the amorphous Fe-Sm films. However, no Fe-Sm compound exists with the change of Sm content and with the application of high magnetic field. Nevertheless, high magnetic field decreases interplanar spacing. The structural evolution has a significant effect on magnetic properties. Saturation magnetization decreases 290% from 1456 emu/cm3 to 373 emu/cm3 with the increase of Sm content from 5.8% to 33.0%. The coercivity increases 1225% from 20 Oe to 265 Oe. Meanwhile, both the saturation magnetization and coercivity of the films decrease with the application of high magnetic field. The reason has been discussed.

  20. Nanocrystallization of amorphous M-Si thin film composites (M=Cr, Mn) and their thermoelectric properties

    Science.gov (United States)

    Burkov, A. T.; Novikov, S. V.; Schumann, J.

    2012-06-01

    We report on electrical resistivity and thermoelectric power of Cr-Si and Mn-Si composite films at temperatures from 300 K to 1000 K. The films were deposited on unheated Si/SiO2 substrates by magnetron sputtering from composite targets. The as-deposited films have amorphous structure. We use annealing with in-situ transport properties measurements to transform the films into nanocrystalline state with continuous monitoring their state. Nanocrystallization is considered as a promising way to improve thermoelectric efficiency, primarily due to reduction of lattice thermal conductivity κ. Among variety of methods for fabrication of NC materials, crystallization from amorphous state has features which are crucially important with respect to their electronic transport properties: since the crystallites and their interfaces are formed in this method via solid state reaction, the NC samples are dense and the interfaces are clean. This removes additional factors affecting properties of a nanocrystalline composite, such as contamination of nanocrystal interfaces by elements from environment or nanocrystal lattice distortion during nanocrystallization. Depending on the initial film composition, the films are transformed during annealing into single phase or multi-phase nanocrystalline composites with average grain size of 10 nm to 20 nm. We study the crystallization kinetics, stability of amorphous and nanocrystalline state and relation between electronic transport properties and structural state of the composites.

  1. Physical and optical properties of binary amorphous selenium-antimony thin films

    Science.gov (United States)

    Sharma, Pankaj; Sharma, Ishu; Katyal, S. C.

    2009-03-01

    Amorphous thin films with compositions Se1-xSbx (x =0, 0.025, 0.05, 0.075, and 0.10 at. %) have been deposited by thermal evaporation (at ˜10-4 Pa) from bulk samples. The compositional dependence of their optical properties, refractive index, extinction coefficient, absorption coefficient, and optical band gap with increasing Sb content is investigated using transmission spectra in the range of 400-1200 nm. The refractive-index dispersion has been analyzed on the basis of the Wemple-DiDomenico single-oscillator approach. It has been found that the refractive index increases with increasing Sb content. The behavior of the optical band gap, when the composition of the material is varied, shows, as expected, just the opposite trends. The optical band gap decreases from 2.025 to 1.753 eV with ±0.001 eV uncertainty. Band gap calculated theoretically also shows a decrease with the increase in Sb content. The optical behavior is supported by physical properties, i.e., decrease in optical band gap is supported by the decrease in cohesive energy of the system. Some other physical properties, viz., coordination number, lone-pair electrons, and glass transition temperature, are also investigated theoretically. The optical results may lead to yield more sensitive detectors based on amorphous selenium, and physical properties may be useful in achieving more stable alloys which are favorable in x-ray imaging applications.

  2. Direct observation of small cluster mobility and ripening. [during annealing of metal films on amorphous substrates

    Science.gov (United States)

    Heinemann, K.; Poppa, H.

    1975-01-01

    Direct evidence is reported for the simultaneous occurrence of Ostwald ripening and short-distance cluster mobility during annealing of discontinuous metal films on clean amorphous substrates. The annealing characteristics of very thin particulate deposits of silver on amorphized clean surfaces of single crystalline thin graphite substrates were studied by in-situ transmission electron microscopy (TEM) under controlled environmental conditions (residual gas pressure of 10 to the minus 9th power torr) in the temperature range from 25 to 450 C. Sputter cleaning of the substrate surface, metal deposition, and annealing were monitored by TEM observation. Pseudostereographic presentation of micrographs in different annealing stages, the observation of the annealing behavior at cast shadow edges, and measurements with an electronic image analyzing system were employed to aid the visual perception and the analysis of changes in deposit structure recorded during annealing. Slow Ostwald ripening was found to occur in the entire temperature range, but the overriding surface transport mechanism was short-distance cluster mobility.

  3. Absorption enhancement in amorphous silicon thin films via plasmonic resonances in nickel silicide nanoparticles

    Science.gov (United States)

    Hachtel, Jordan; Shen, Xiao; Pantelides, Sokrates; Sachan, Ritesh; Gonzalez, Carlos; Dyck, Ondrej; Fu, Shaofang; Kalnayaraman, Ramki; Rack, Phillip; Duscher, Gerd

    2013-03-01

    Silicon is a near ideal material for photovoltaics due to its low cost, abundance, and well documented optical properties. The sole detriment of Si in photovoltaics is poor absorption in the infrared. Nanoparticle surface plasmon resonances are predicted to increase absorption by scattering to angles greater than the critical angle for total internal reflection (16° for a Si/air interface), trapping the light in the film. Experiments confirm that nickel silicide nanoparticles embedded in amorphous silicon increases absorption significantly in the infrared. However, it remains to be seen if electron-hole pair generation is increased in the solar cell, or whether the light is absorbed by the nanoparticles themselves. The nature of the absorption is explored by a study of the surface plasmon resonances through electron energy loss spectrometry and scanning transmission electron microscopy experiments, as well as first principles density functional theory calculations. Initial experimental results do not show strong plasmon resonances on the nanoparticle surfaces. Calculations of the optical properties of the nickel silicide particles in amorphous silicon are performed to understand why this resonance is suppressed. Work supported by NSF EPS 1004083 (TN-SCORE).

  4. N-type crystalline silicon films free of amorphous silicon deposited on glass by HCl addition using hot wire chemical vapour deposition.

    Science.gov (United States)

    Chung, Yung-Bin; Park, Hyung-Ki; Lee, Sang-Hoon; Song, Jean-Ho; Hwang, Nong-Moon

    2011-09-01

    Since n-type crystalline silicon films have the electric property much better than those of hydrogenated amorphous and microcrystalline silicon films, they can enhance the performance of advanced electronic devices such as solar cells and thin film transistors (TFTs). Since the formation of amorphous silicon is unavoidable in the low temperature deposition of microcrystalline silicon on a glass substrate at temperatures less than 550 degrees C in the plasma-enhanced chemical vapour deposition and hot wire chemical vapour deposition (HWCVD), crystalline silicon films have not been deposited directly on a glass substrate but fabricated by the post treatment of amorphous silicon films. In this work, by adding the HCl gas, amorphous silicon-free n-type crystalline silicon films could be deposited directly on a glass substrate by HWCVD. The resistivity of the n-type crystalline silicon film for the flow rate ratio of [HCl]/[SiH4] = 7.5 and [PH3]/[SiH4] = 0.042 was 5.31 x 10(-4) ohms cm, which is comparable to the resistivity 1.23 x 10(-3) ohms cm of films prepared by thermal annealing of amorphous silicon films. The absence of amorphous silicon in the film could be confirmed by high resolution transmission electron microscopy.

  5. Atomic scale structure of amorphous aluminum oxyhydroxide, oxide and oxycarbide films probed by very high field (27)Al nuclear magnetic resonance.

    Science.gov (United States)

    Baggetto, L; Sarou-Kanian, V; Florian, P; Gleizes, A N; Massiot, D; Vahlas, C

    2017-03-15

    The atomic scale structure of aluminum in amorphous alumina films processed by direct liquid injection chemical vapor deposition from aluminum tri-isopropoxide (ATI) and dimethyl isopropoxide (DMAI) is investigated by solid-state (27)Al nuclear magnetic resonance (SSNMR) using a very high magnetic field of 20.0 T. This study is performed as a function of the deposition temperature in the range 300-560 °C, 150-450 °C, and 500-700 °C, for the films processed from ATI, DMAI (+H2O), and DMAI (+O2), respectively. While the majority of the films are composed of stoichiometric aluminum oxide, other samples are partially or fully hydroxylated at low temperature, or contain carbidic carbon when processed from DMAI above 500 °C. The quantitative analysis of the SSNMR experiments reveals that the local structure of these films is built from AlO4, AlO5, AlO6 and Al(O,C)4 units with minor proportions of the 6-fold aluminum coordination and significant amounts of oxycarbides in the films processed from DMAI (+O2). The aluminum coordination distribution as well as the chemical shift distribution indicate that the films processed from DMAI present a higher degree of structural disorder compared to the films processed from ATI. Hydroxylation leads to an increase of the 6-fold coordination resulting from the trend of OH groups to integrate into AlO6 units. The evidence of an additional environment in films processed from DMAI (+O2) by (27)Al SSNMR and first-principle NMR calculations on Al4C3 and Al4O4C crystal structures supports that carbon is located in Al(O,C)4 units. The concentration of this coordination environment strongly increases with increasing process temperature from 600 to 700 °C favoring a highly disordered structure and preventing from crystallizing into γ-alumina. The obtained results are a valuable guide to the selection of process conditions for the CVD of amorphous alumina films with regard to targeted applications.

  6. Numerical simulation of offset-drain amorphous oxide-based thin-film transistors

    Science.gov (United States)

    Jeong, Jaewook

    2016-11-01

    In this study, we analyzed the electrical characteristics of amorphous indium-gallium-zinc-oxide (a-IGZO) thin-film transistors (TFTs) with an offset-drain structure by technology computer aided design (TCAD) simulation. When operating in a linear region, an enhancement-type TFT shows poor field-effect mobility because most conduction electrons are trapped in acceptor-like defects in an offset region when the offset length (L off) exceeds 0.5 µm, whereas a depletion-type TFT shows superior field-effect mobility owing to the high free electron density in the offset region compared with the trapped electron density. When operating in the saturation region, both types of TFTs show good field-effect mobility comparable to that of a reference TFT with a large gate overlap. The underlying physics of the depletion and enhancement types of offset-drain TFTs are systematically analyzed.

  7. Self-aligned coplanar amorphous indium zinc oxide thin-film transistors with high performance

    Science.gov (United States)

    Park, Jae Chul; Lee, Ho-Nyeon

    2015-01-01

    Self-aligned coplanar amorphous indium zinc oxide thin-film transistors (a-IZO TFTs) were fabricated. The a-IZO TFTs had a field-effect mobility of μFE = 24.4 cm2 V-1 s-1, a subthreshold slope of 180 mV/dec, and an on/off ratio of 109. As the channel length decreased, the threshold voltage VTH shifted to more negative voltages, and μFE increased due to the diffused carriers from the contact regions. The intrinsic field-effect mobility was estimated to be 15.05 cm2 V-1 s-1 in the linear mode and 13.28 cm2 V-1 s-1 in saturation mode. Under positive/negative bias-temperature-illumination stress, the shift in VTH was less than ±0.7 V after 11,000 s.

  8. Process and properties of electroless Ni-W-B amorphous electrical resistance film

    Institute of Scientific and Technical Information of China (English)

    ZHU Xiao-yun; GUO Zhong-cheng; XU Rui-dong

    2004-01-01

    The process and properties of electroless plating Ni-W-B alloy have been studied. The results show that the deposits containing W and B are obtained, and the deposition rate of the bath is increased with increase of W content when a certain amount of sodium tungstate solution is added in the Ni-B bath. The Ni-W-B alloy is amorphous as deposition and its resistivity increases directly with the increase of W content in the coating, but decreases gradually with increasing the deposit thickness. XRD and SEM show that the distributions of W and B in the Ni-W-B alloy film are very uniform and dispersed without any segregation.

  9. Spin orientation driven static and dynamic magnetic process in amorphous FeCoBSi thin films

    Energy Technology Data Exchange (ETDEWEB)

    Zhou, Peiheng; Luo, Xiaojia; Zhang, Li; Lu, Haipeng; Xie, Jianliang; Deng, Longjiang [State Key Laboratory of Electronic Thin Film and Integrated Devices, National Engineering Research Center of Electromagnetic Radiation Control Materials, University of Electronic Science and Technology of China, Chengdu 610054 (China)

    2015-06-07

    The spin orientation dependence of magnetic hysteresis and microwave ferromagnetic resonance data are investigated in FeCoBSi amorphous thin films. Demagnetization effect allows the weak interface-rooted out-of-plane anisotropy to build up local spin orientation domains under the dominant in-plane anisotropy. As a result, two phase magnetization reversal and double-peak ferromagnetic resonance traces with varying damping behavior are observed. Due to the distribution of in-plane and out-of-plane spin orientations, the ferromagnetic resonance bandwidth has been extensively expanded with the full width at half maximum increased from 1.2 GHz to 3.5 GHz.

  10. Ambient effect on thermal stability of amorphous InGaZnO thin film transistors

    Science.gov (United States)

    Xu, Jianeng; Wu, Qi; Xu, Ling; Xie, Haiting; Liu, Guochao; Zhang, Lei; Dong, Chengyuan

    2016-12-01

    The thermal stability of amorphous InGaZnO thin film transistors (a-IGZO TFTs) with various ambient gases was investigated. The a-IGZO TFTs in air were more thermally stable than the devices in the ambient argon. Oxygen, rather than nitrogen and moisture, was responsible for this improvement. Furthermore, the thermal stability of the a-IGZO TFTs improved with the increasing oxygen content in the surrounding atmosphere. The related physical mechanism was examined, indicating that the higher ambient oxygen content induced more combinations of the oxygen vacancies and adsorbed oxygen ions in the a-IGZO, which resulted in the larger defect formation energy. This larger defect formation energy led to the smaller variation in the threshold voltage for the corresponding TFT devices.

  11. Hard Carbon Films Deposited under Various Atmospheres

    Science.gov (United States)

    Wei, M.-K.; Chen, S.-C.; Wu, T. C.; Lee, Sanboh

    1998-03-01

    Using a carbon target ablated with an XeCl-excimer laser under various gas atmospheres at different pressures, hard carbon was deposited on silicon, iron and tungsten carbide substrates. The hardness, friction coefficient, and wear rate of the film against steel are better than pure substrate material, respectively, so that it has potential to be used as a protective coating for micromechanical elements. The influences of gas pressure, gas atmosphere, and power density of laser irradiation on the thermal stability of film were analyzed by means of Raman-spectroscope, time-of-flight method, and optical emission spectrum. It was found that the film deposited under higher pressure has less diamond-like character. The film deposited under rest gas or argon atmosphere was very unstable and looked like a little graphite-like character. The film deposited at high vacuum (10-5 mbar rest gas) was the most stable and looked like the most diamond-like character. The film deposited at higher power density was more diamond-like than that at lower power density.

  12. Carbon Nanotube Thin-Film Antennas.

    Science.gov (United States)

    Puchades, Ivan; Rossi, Jamie E; Cress, Cory D; Naglich, Eric; Landi, Brian J

    2016-08-17

    Multiwalled carbon nanotube (MWCNT) and single-walled carbon nanotube (SWCNT) dipole antennas have been successfully designed, fabricated, and tested. Antennas of varying lengths were fabricated using flexible bulk MWCNT sheet material and evaluated to confirm the validity of a full-wave antenna design equation. The ∼20× improvement in electrical conductivity provided by chemically doped SWCNT thin films over MWCNT sheets presents an opportunity for the fabrication of thin-film antennas, leading to potentially simplified system integration and optical transparency. The resonance characteristics of a fabricated chlorosulfonic acid-doped SWCNT thin-film antenna demonstrate the feasibility of the technology and indicate that when the sheet resistance of the thin film is >40 ohm/sq no power is absorbed by the antenna and that a sheet resistance of antenna. The dependence of the return loss performance on the SWCNT sheet resistance is consistent with unbalanced metal, metal oxide, and other CNT-based thin-film antennas, and it provides a framework for which other thin-film antennas can be designed.

  13. Determination of the optical band gap for amorphous and nanocrystalline copper oxide thin films prepared by SILAR technique

    Science.gov (United States)

    Abdel Rafea, M.; Roushdy, N.

    2009-01-01

    Amorphous copper oxide films were deposited using the SILAR technique. Both Cu2O and CuO crystallographic phases exist in deposited and annealed films. Crystallization and growth processes by annealing at temperatures up to 823 K form grains with nano- and micro-spherical shapes. The calculated crystallite size from the XRD measurement was found to be in the range 14-21 nm while nano-spheres in the diameter range 50-100 nm were observed by SEM micrographs. The band gap for amorphous film was found to be 2.3 eV which increased slowly to 2.4 eV by annealing the film at 373 K. This was explained by defect redistribution in amorphous films. Annealing in the temperature range 373-673 K decreased the band gap gradually to 1.85 eV. The decrease of the band gap with annealing temperature in the range 373-673 K agrees well with the Brus model of the energy gap confinement effect in nanostructured semiconducting materials. Annealing in the temperature range 673-823 K decreases the band gap slowly to 1.7 eV due to the smaller contribution of the confinement effect. Below 573 K, Cu2O is the most probable crystalline phase in the film, while Cu2O and CuO crystalline phases may coexist at annealing temperatures above 573 K due to further oxidation of Cu2O. A wider transmittance spectral window in the visible region was obtained by controlling the annealing conditions of the amorphous copper oxide film and its applicability to the window layer of solar cell was suggested.

  14. Determination of the optical band gap for amorphous and nanocrystalline copper oxide thin films prepared by SILAR technique

    Energy Technology Data Exchange (ETDEWEB)

    Abdel Rafea, M; Roushdy, N [Electronic Materials Department, Advanced Technologies and New Materials Institute, Mubarak City for Scientific Research and Technology Applications, PO Box 21934, New Borg El-Arab City, Alexandria (Egypt)], E-mail: m.abdelrafea@mucsat.sci.eg

    2009-01-07

    Amorphous copper oxide films were deposited using the SILAR technique. Both Cu{sub 2}O and CuO crystallographic phases exist in deposited and annealed films. Crystallization and growth processes by annealing at temperatures up to 823 K form grains with nano- and micro-spherical shapes. The calculated crystallite size from the XRD measurement was found to be in the range 14-21 nm while nano-spheres in the diameter range 50-100 nm were observed by SEM micrographs. The band gap for amorphous film was found to be 2.3 eV which increased slowly to 2.4 eV by annealing the film at 373 K. This was explained by defect redistribution in amorphous films. Annealing in the temperature range 373-673 K decreased the band gap gradually to 1.85 eV. The decrease of the band gap with annealing temperature in the range 373-673 K agrees well with the Brus model of the energy gap confinement effect in nanostructured semiconducting materials. Annealing in the temperature range 673-823 K decreases the band gap slowly to 1.7 eV due to the smaller contribution of the confinement effect. Below 573 K, Cu{sub 2}O is the most probable crystalline phase in the film, while Cu{sub 2}O and CuO crystalline phases may coexist at annealing temperatures above 573 K due to further oxidation of Cu{sub 2}O. A wider transmittance spectral window in the visible region was obtained by controlling the annealing conditions of the amorphous copper oxide film and its applicability to the window layer of solar cell was suggested.

  15. Novel Low Temperature Processing for Enhanced Properties of Ion Implanted Thin Films and Amorphous Mixed Oxide Thin Film Transistors

    Science.gov (United States)

    Vemuri, Rajitha

    This research emphasizes the use of low energy and low temperature post processing to improve the performance and lifetime of thin films and thin film transistors, by applying the fundamentals of interaction of materials with conductive heating and electromagnetic radiation. Single frequency microwave anneal is used to rapidly recrystallize the damage induced during ion implantation in Si substrates. Volumetric heating of the sample in the presence of the microwave field facilitates quick absorption of radiation to promote recrystallization at the amorphous-crystalline interface, apart from electrical activation of the dopants due to relocation to the substitutional sites. Structural and electrical characterization confirm recrystallization of heavily implanted Si within 40 seconds anneal time with minimum dopant diffusion compared to rapid thermal annealed samples. The use of microwave anneal to improve performance of multilayer thin film devices, e.g. thin film transistors (TFTs) requires extensive study of interaction of individual layers with electromagnetic radiation. This issue has been addressed by developing detail understanding of thin films and interfaces in TFTs by studying reliability and failure mechanisms upon extensive stress test. Electrical and ambient stresses such as illumination, thermal, and mechanical stresses are inflicted on the mixed oxide based thin film transistors, which are explored due to high mobilities of the mixed oxide (indium zinc oxide, indium gallium zinc oxide) channel layer material. Semiconductor parameter analyzer is employed to extract transfer characteristics, useful to derive mobility, subthreshold, and threshold voltage parameters of the transistors. Low temperature post processing anneals compatible with polymer substrates are performed in several ambients (oxygen, forming gas and vacuum) at 150 °C as a preliminary step. The analysis of the results pre and post low temperature anneals using device physics fundamentals

  16. Microstructural study of oxidation of carbon-rich amorphous boron carbide coating

    Institute of Scientific and Technical Information of China (English)

    Bin ZENG; Zu-de FENG; Si-wei LI; Yong-sheng LIU

    2008-01-01

    Carbon-rich amorphous boron carbide (BxC) coatings were annealed at 400℃, 700℃, 1000℃ and 1200℃ for 2 h in air atmosphere. The microstructure and composition of the as-deposited and annealed coat-ings were investigated by scanning electron microscopy (SEM), X-ray diffraction (XRD), micro-Raman spectro-scopy and energy dispersive X-ray spectroscopy (EDS). All of the post-anneal characterizations demonstrated the ability of carbon-rich BxC coatings to protect the graphite substrate against oxidation. Different oxidation modes of the coatings were found at low temperature (400℃), moderate temperature (700℃) and high temper-ature (1000℃ and 1200℃). Finally, the feasibility of the application of carbon-rich BxC instead of pyrolytic car-bon (PyC) as a fiber/matrix interlayer in ceramics-matrix composites (CMCs) is discussed here.

  17. Effective Route to Graphitic carbon Nitride from Ball-Milled Amorphous carbon in NH3 Atmosphere Under Annealing

    Institute of Scientific and Technical Information of China (English)

    费振义; 刘玉先

    2003-01-01

    Graphitic carbon nitride (g-C3N4) powders were successfully synthesized from ball-milled amorphous carbon under NHs atmosphere at high temperature, for the first time to the best of our knowledge. The combined characteristic data obtained by x-ray diffraction, high-resolution transmission-electron microscopy, electron energy loss spectroscopy, Raman spectroscopy, energy dispersive spectroscopic analysis, and Fourier transformation infrared spectroscopy provide substantial evidence for the graphite-like sp2-bonded structure with C3N4 stoichiometry.

  18. Nano-Crystallization of High-Entropy Amorphous NbTiAlSiWxNy Films Prepared by Magnetron Sputtering

    Directory of Open Access Journals (Sweden)

    Wenjie Sheng

    2016-06-01

    Full Text Available High-entropy amorphous NbTiAlSiWxNy films (x = 0 or 1, i.e., NbTiAlSiNy and NbTiAlSiWNy were prepared by magnetron sputtering method in the atmosphere of a mixture of N2 + Ar (N2 + Ar = 24 standard cubic centimeter per minute (sccm, where N2 = 0, 4, and 8 sccm. All the as-deposited films present amorphous structures, which remain stable at 700 °C for over 24 h. After heat treatment at 1000 °C the films began to crystalize, and while the NbTiAlSiNy films (N2 = 4, 8 sccm exhibit a face-centered cubic (FCC structure, the NbTiAlSiW metallic films show a body-centered cubic (BCC structure and then transit into a FCC structure composed of nanoscaled particles with increasing nitrogen flow rate. The hardness and modulus of the as-deposited NbTiAlSiNy films reach maximum values of 20.5 GPa and 206.8 GPa, respectively. For the as-deposited NbTiAlSiWNy films, both modulus and hardness increased to maximum values of 13.6 GPa and 154.4 GPa, respectively, and then decrease as the N2 flow rate is increased. Both films could be potential candidates for protective coatings at high temperature.

  19. A study on the properties of C-doped Ge8Sb2Te11 thin films during an amorphous-to-crystalline phase transition

    Science.gov (United States)

    Park, Cheol-Jin; Kong, Heon; Lee, Hyun-Yong; Yeo, Jong-Bin

    2016-04-01

    In this work, we evaluated the structural, electrical and optical properties of carbon-doped Ge8Sb2Te11 thin films. In a previous work, GeSbTe alloys were doped with different materials in an attempt to improve the thermal stability. Ge8Sb2Te11 and carbon-doped Ge8Sb2Te11 films of 250 nm in thickness were deposited on p-type Si (100) and glass substrates by using a RF magnetron reactive co-sputtering system at room temperature. The fabricated films were annealed in a furnance in the 0 ~ 400°C temperature range. The structural properties were analyzed by using X-ray diffraction (XRD), and the result showed that the carbon-doped Ge8Sb2Te11 had a face-centeredcubic (fcc) crystalline structure and an increased crystallization temperature ( T c ). An increase in the T c leads to thermal stability in the amorphous state. The optical properties were analyzed by using an UV-Vis-IR spectrophotometer, and the result showed an increase in the optical-energy band gap ( E op ) in the crystalline materials and an increase in the E op difference (Δ E op ), which is a good effect for reducing the noise in the memory device. The electrical properties were analyzed by using a 4-point probe, which showed an increase in the sheet resistance ( R s ) in the amorphous state and the crystalline state, which means a reduced programming current in the memory device.

  20. High-performance solution-processed amorphous zinc-indium-tin oxide thin-film transistors.

    Science.gov (United States)

    Kim, Myung-Gil; Kim, Hyun Sung; Ha, Young-Geun; He, Jiaqing; Kanatzidis, Mercouri G; Facchetti, Antonio; Marks, Tobin J

    2010-08-04

    Films of the high-performance solution-processed amorphous oxide semiconductor a-ZnIn(4)Sn(4)O(15), grown from 2-methoxyethanol/ethanolamine solutions, were used to fabricate thin-film transistors (TFTs) in combination with an organic self-assembled nanodielectric as the gate insulator. This structurally dense-packed semiconductor composition with minimal Zn(2+) incorporation strongly suppresses transistor off-currents without significant mobility degradation, and affords field-effect electron mobilities of approximately 90 cm(2) V(-1) s(-1) (104 cm(2) V(-1) s(-1) maximum obtained for patterned ZITO films), with I(on)/I(off) ratio approximately 10(5), a subthreshhold swing of approximately 0.2 V/dec, and operating voltage <2 V for patterned devices with W/L = 50. The microstructural and electronic properties of ZITO semiconductor film compositions in the range Zn(9-2x)In(x)Sn(x)O(9+1.5x) (x = 1-4) and ZnIn(8-x)Sn(x)O(13+0.5x) (x = 1-7) were systematically investigated to elucidate those factors which yield optimum mobility, I(on)/I(off), and threshold voltage parameters. It is shown that structural relaxation and densification by In(3+) and Sn(4+) mixing is effective in reducing carrier trap sites and in creating carrier-generating oxygen vacancies. In contrast to the above results for TFTs fabricated with the organic self-assembled nanodielectric, ZnIn(4)Sn(4)O(15) TFTs fabricated with SiO(2) gate insulators exhibit electron mobilities of only approximately 11 cm(2) V(-1) s(-1) with I(on)/I(off) ratios approximately 10(5), and a subthreshhold swing of approximately 9.5 V/dec.

  1. Solid solution or amorphous phase formation in TiZr-based ternary to quinternary multi-principal-element films

    Institute of Scientific and Technical Information of China (English)

    Mariana Braic; Viorel Braic; Alina Vladescu; Catalin N. Zoita; Mihai Balaceanu

    2014-01-01

    TiZr-based multicomponent metallic films composed of 3-5 constituents with almost equal atomic concentrations were prepared by co-sputtering of pure metallic targets in an Ar atmosphere. X-ray diffraction was employed to determine phase composition, crystalline structure, lattice parameters, texture and crystallite size of the deposited films. The deposited films exhibited only solid solution (fcc, bcc or hcp) or amorphous phases, no intermetallic components being detected. It was found that the hcp structure was stabilized by the presence of Hf or Y, bcc by Nb or Al and fcc by Cu. For the investigated films, the atomic size difference, mixing enthalpy, mixing entropy, Gibbs free energy of mixing and the electronegativity difference for solid solution and amorphous phases were calculated based on Miedema's approach of the regular solution model. It was shown that the atomic size difference and the ratio between the Gibbs free energies of mixing of the solid solution and amorphous phases were the most significant parameters controlling the film crystallinity.

  2. A Novel Carbon Nanotube-Supported NiP Amorphous Alloy Catalyst and Its Hydrogenation Activity

    Institute of Scientific and Technical Information of China (English)

    Yan Ju; Fengyi Li

    2006-01-01

    A carbon nanotube-supported NiP amorphous catalyst (NiP/CNT) was prepared by induced reduction. Benzene hydrogenation was used as a probe reaction for the study of catalytic activity. The effects of the support on the activity and thermal stability of the supported catalyst were discussed based on various characterizations, including XRD, TEM, ICP, XPS, H2-TPD, and DTA. In comparison with the NiP amorphous alloy, the benzene conversion on NiP/CNT catalyst was lower, but the specific activity of NiP/CNT was higher, which is attributed to the dispersion produced by the support, an electron-donating effect, and the hydrogen-storage ability of CNT. The NiP/CNT thermal stability was improved because of the dispersion and electronic effects and the good heat-conduction ability of the CNT support.

  3. Enhanced photocurrent in thin-film amorphous silicon solar cells via shape controlled three-dimensional nanostructures.

    Science.gov (United States)

    Hilali, Mohamed M; Yang, Shuqiang; Miller, Mike; Xu, Frank; Banerjee, Sanjay; Sreenivasan, S V

    2012-10-12

    In this paper, we have explored manufacturable approaches to sub-wavelength controlled three-dimensional (3D) nano-patterns with the goal of significantly enhancing the photocurrent in amorphous silicon solar cells. Here we demonstrate efficiency enhancement of about 50% over typical flat a-Si thin-film solar cells, and report an enhancement of 20% in optical absorption over Asahi textured glass by fabricating sub-wavelength nano-patterned a-Si on glass substrates. External quantum efficiency showed superior results for the 3D nano-patterned thin-film solar cells due to enhancement of broadband optical absorption. The results further indicate that this enhanced light trapping is achieved with minimal parasitic absorption losses in the deposited transparent conductive oxide for the nano-patterned substrate thin-film amorphous silicon solar cell configuration. Optical simulations are in good agreement with experimental results, and also show a significant enhancement in optical absorption, quantum efficiency and photocurrent.

  4. Unconventional magnetization of Fe3O4 thin film grown on amorphous SiO2 substrate

    Directory of Open Access Journals (Sweden)

    Jia-Xin Yin

    2016-06-01

    Full Text Available High quality single crystal Fe3O4 thin films with (111 orientation had been prepared on amorphous SiO2 substrate by pulsed laser deposition. The magnetization properties of the films are found to be unconventional. The Verwey transition temperature derived from the magnetization jump is around 140K, which is higher than the bulk value and it can be slightly suppressed by out-plane magnetic field; the out-of-plane magnetization, which is unexpectedly higher than the in-plane value, is also significantly increased as compared with the bulk value. Our findings highlight the unusual magnetization of Fe3O4 thin film grown on the amorphous SiO2 substrate.

  5. Crystalline and Amorphous Phosphorus – Carbon Nanotube Composites as Promising Anodes for Lithium-Ion Batteries

    KAUST Repository

    Smajic, Jasmin

    2016-05-04

    Battery research has been going full steam and with that the search for alternative anodes. Among many proposed electrode materials, little attention has been given to phosphorus. Phosphorus boasts the third highest gravimetric charge capacity and the highest volumetric charge capacity of all elements. Because of that, it would be an attractive battery anode material were it not for its poor cyclability with significant capacity loss immediately after the first cycle. This is known to be the consequence of considerable volume changes of phosphorus during charge/discharge cycles. In this work, we propose circumventing this issue by mixing amorphous red phosphorus with carbon nanotubes. By employing a non-destructive sublimation-deposition method, we have synthesized composites where the synergetic effect between phosphorus and carbon nanotubes allow for an improvement in the electrochemical performance of battery anodes. In fact, it has been shown that carbon nanotubes can act as an effective buffer to phosphorus volumetric expansions and contractions during charging and discharging of the half-cells [1]. By modifying the synthesis parameters, we have also been able to change the degree of crystallinity of the phosphorus matrix in the composites. In fact, the less common phase of red phosphorus, named fibrous phosphorus, was obtained, and that explains some of the varying electrochemical performances observed in the composites. Overall, it is found that a higher surface area of amorphous phosphorus allows for a better anode material when using single-walled carbon nanotubes as fillers.

  6. Amorphous calcium carbonate precipitation by cellular biomineralization in mantle cell cultures of Pinctada fucata.

    Directory of Open Access Journals (Sweden)

    Liang Xiang

    Full Text Available The growth of molluscan shell crystals is generally thought to be initiated from the extrapallial fluid by matrix proteins, however, the cellular mechanisms of shell formation pathway remain unknown. Here, we first report amorphous calcium carbonate (ACC precipitation by cellular biomineralization in primary mantle cell cultures of Pinctada fucata. Through real-time PCR and western blot analyses, we demonstrate that mantle cells retain the ability to synthesize and secrete ACCBP, Pif80 and nacrein in vitro. In addition, the cells also maintained high levels of alkaline phosphatase and carbonic anhydrase activity, enzymes responsible for shell formation. On the basis of polarized light microscopy and scanning electron microscopy, we observed intracellular crystals production by mantle cells in vitro. Fourier transform infrared spectroscopy and X-ray diffraction analyses revealed the crystals to be ACC, and de novo biomineralization was confirmed by following the incorporation of Sr into calcium carbonate. Our results demonstrate the ability of mantle cells to perform fundamental biomineralization processes via amorphous calcium carbonate, and these cells may be directly involved in pearl oyster shell formation.

  7. Amorphous and crystalline calcium carbonate distribution in the tergite cuticle of moulting Porcellio scaber (Isopoda, Crustacea).

    Science.gov (United States)

    Neues, Frank; Hild, Sabine; Epple, Matthias; Marti, Othmar; Ziegler, Andreas

    2011-07-01

    The main mineral components of the isopod cuticle consists of crystalline magnesium calcite and amorphous calcium carbonate. During moulting isopods moult first the posterior and then the anterior half of the body. In terrestrial species calcium carbonate is subject to resorption, storage and recycling in order to retain significant fractions of the mineral during the moulting cycle. We used synchrotron X-ray powder diffraction, elemental analysis and Raman spectroscopy to quantify the ACC/calcite ratio, the mineral phase distribution and the composition within the anterior and posterior tergite cuticle during eight different stages of the moulting cycle of Porcellio scaber. The results show that most of the amorphous calcium carbonate (ACC) is resorbed from the cuticle, whereas calcite remains in the old cuticle and is shed during moulting. During premoult resorption of ACC from the posterior cuticle is accompanied by an increase within the anterior tergites, and mineralization of the new posterior cuticle by resorption of mineral from the anterior cuticle. This suggests that one reason for using ACC in cuticle mineralization is to facilitate resorption and recycling of cuticular calcium carbonate. Furthermore we show that ACC precedes the formation of calcite in distal layers of the tergite cuticle.

  8. Effect of Si additions on thermal stability and the phase transition sequence of sputtered amorphous alumina thin films

    Energy Technology Data Exchange (ETDEWEB)

    Bolvardi, H.; Baben, M. to; Nahif, F.; Music, D., E-mail: music@mch.rwth-aachen.de; Schnabel, V.; Shaha, K. P.; Mráz, S.; Schneider, J. M. [Materials Chemistry, RWTH Aachen University, Kopernikusstr. 10, D-52074 Aachen (Germany); Bednarcik, J.; Michalikova, J. [Deutsches Elektronen Synchrotron DESY, FS-PE group, Notkestrasse 85, D-22607 Hamburg (Germany)

    2015-01-14

    Si-alloyed amorphous alumina coatings having a silicon concentration of 0 to 2.7 at. % were deposited by combinatorial reactive pulsed DC magnetron sputtering of Al and Al-Si (90-10 at. %) split segments in Ar/O{sub 2} atmosphere. The effect of Si alloying on thermal stability of the as-deposited amorphous alumina thin films and the phase formation sequence was evaluated by using differential scanning calorimetry and X-ray diffraction. The thermal stability window of the amorphous phase containing 2.7 at. % of Si was increased by more than 100 °C compared to that of the unalloyed phase. A similar retarding effect of Si alloying was also observed for the α-Al{sub 2}O{sub 3} formation temperature, which increased by more than 120 °C. While for the latter retardation, the evidence for the presence of SiO{sub 2} at the grain boundaries was presented previously, this obviously cannot explain the stability enhancement reported here for the amorphous phase. Based on density functional theory molecular dynamics simulations and synchrotron X-ray diffraction experiments for amorphous Al{sub 2}O{sub 3} with and without Si incorporation, we suggest that the experimentally identified enhanced thermal stability of amorphous alumina with addition of Si is due to the formation of shorter and stronger Si–O bonds as compared to Al–O bonds.

  9. Polycrystalline Si films with unique microstructures formed from amorphous Si films by non-thermal equilibrium flash lamp annealing

    Energy Technology Data Exchange (ETDEWEB)

    Ohdaira, Keisuke; Nishikawa, Takuya; Shiba, Kazuhiro; Takemoto, Hiroyuki; Matsumura, Hideki [School of Materials Science, Japan Advanced Institute of Science and Technology (JAIST), Ishikawa (Japan)

    2010-04-15

    Flash lamp annealing (FLA), with millisecond-order duration, can crystallize amorphous silicon (a-Si) films a few {mu}m thick on glass substrates, resulting in formation of polycrystalline Si (poly-Si) films with unprecedented periodic microstructures. The characteristic microstructure, formed spontaneously during crystallization, consists of large-grain regions, containing relatively large grains more than 100 nm in size, and fine-grain regions, including only 10-nm-sized fine grains. The microstructures results from explosive crystallization (EC), driven by heat generation corresponding to the difference of the enthalpies of meta-stable a-Si and stable crystalline Si(c-Si) states, which realizes lateral crystallization velocity on the order of m/s. The lateral crystallization may stop when the temperature of a-Si in the vicinity of c-Si, which is decided by both homogeneous heating from flash irradiation and thermal diffusion from c-Si, falls below a crystallization temperature. This idea is supported by the experimental fact that a lateral crystallization length decreases with decreasing pulse duration. (copyright 2010 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  10. Structure and Bonding in Amorphous Cr1-xCx Nanocomposite Thin Films: X-ray Absorption Spectra and First-Principles Calculation

    CERN Document Server

    Olovsson, Weine; Magnuson, Martin

    2016-01-01

    The local structure and chemical bonding in two-phase amorphous Cr$_{1-x}$C$_{x}$ nanocomposite thin films are investigated by Cr $K$-edge ($1s$) X-ray absorption near-edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) spectroscopies in comparison to theory. By utilizing the computationally efficient \\textit{stochastic quenching} (SQ) technique, we reveal the complexity of different Cr-sites in the transition metal carbides, highlighting the need for large scale averaging to obtain theoretical XANES and EXAFS spectra for comparison with measurements. As shown in this work, it is advantageous to use \\textit{ab initio} theory as an assessment to correctly model and fit experimental spectra and investigate the trends of bond lengths and coordination numbers in complex amorphous materials. With sufficient total carbon content ($\\geq$ 30 at\\%), we find that the short-range coordination in the amorphous carbide phase exhibit similarities to that of a Cr$_{7}$C$_{3\\pm{}y}$ structure, while e...

  11. Surface morphology stabilization by chemical sputtering in carbon nitride film growth

    Energy Technology Data Exchange (ETDEWEB)

    Buijnsters, J G [Institute for Molecules and Materials (IMM), Radboud University Nijmegen, Toernooiveld 1, 6525 ED Nijmegen (Netherlands); Vazquez, L [Instituto de Ciencia de Materiales de Madrid (CSIC), C/Sor Juana Ines de la Cruz 3, 28049 Madrid (Spain)

    2008-01-07

    We have studied the influence of chemical sputtering effects on the morphology of carbon nitride films grown on silicon substrates by electron cyclotron resonance chemical vapour deposition. This study has been performed by comparing the evolution of their morphology with that of hydrogenated amorphous carbon films grown under similar conditions, where these effects are not present. When chemical sputtering effects operate we observe a film surface stabilization for length scales in the 60-750 nm range after a threshold roughness of about 3-4 nm has been developed. This stabilization is explained on the basis of the re-emission of nitrogen etching species, which is confirmed by growth experiments on microstructured substrates. (fast track communication)

  12. Structural and mechanical properties of nanocrystalline Zr co-sputtered a-C(:H) amorphous films

    Energy Technology Data Exchange (ETDEWEB)

    Escudeiro, A., E-mail: ana.escudeiro@dem.uc.pt [SEG-CEMUC DEM University of Coimbra, Coimbra (Portugal); Figueiredo, N.M. [SEG-CEMUC DEM University of Coimbra, Coimbra (Portugal); Polcar, T. [Engineering Materials, Faculty of Engineering and the Environment, University of Southampton, SO17 1BJ (United Kingdom); Department of Control Engineering, Czech Technical University in Prague, Technicka 2, Prague 6 (Czech Republic); Cavaleiro, A. [SEG-CEMUC DEM University of Coimbra, Coimbra (Portugal)

    2015-01-15

    Highlights: • The incorporation of Zr led to formation of nanocrystalline ZrC embedded into C-matrix. • The incorporation of Zr and H decreased the typical columnar microstructure of a-C films. • The hardness was independent on Zr content but increased with the introduction of H. - Abstract: The aim of this study was to investigate the effect of Zr as alloying element to carbon films, particularly in respect to film structure and mechanical properties. The films were deposited by magnetron sputtering in reactive (Ar + CH{sub 4}) and non-reactive (Ar) atmosphere with different Zr contents (from 0 to 14 at.%) in order to achieve a nanocomposite based films. With an increase of Zr content a broad peak was observed in X-ray diffraction spectra suggesting the presence of nanocrystalline (nc) ZrC phase for the coatings with Zr content higher than 4 at.%. The application of Scherrer formula yielded a grain sizes with a dimension of 1.0–2.2 nm. These results were supported by X-ray photoelectron spectroscopy showing typical charge transfer at Zr-C nanograins and carbon matrix interface. The nc-ZrC phase was also observed by transmission electron microscopy. The hardness of the coatings was approximately independent of Zr content. However, the Young modulus increased linearly. The residual stress of the coatings was strongly improved by the presence of nc-ZrC phase embedded in the a-C matrix. Finally, the incorporation of H into the matrix led to denser and harder films.

  13. Dual-ion-beam deposition of carbon films with diamond-like properties

    Science.gov (United States)

    Mirtich, M. J.; Swec, D. M.; Angus, J. C.

    1985-01-01

    A single and dual ion beam system was used to generate amorphous carbon films with diamond like properties. A methane/argon mixture at a molar ratio of 0.28 was ionized in the low pressure discharge chamber of a 30-cm-diameter ion source. A second ion source, 8 cm in diameter was used to direct a beam of 600 eV Argon ions on the substrates (fused silica or silicon) while the deposition from the 30-cm ion source was taking place. Nuclear reaction and combustion analysis indicate H/C ratios for the films to be 1.00. This high value of H/C, it is felt, allowed the films to have good transmittance. The films were impervious to reagents which dissolve graphitic and polymeric carbon structures. Although the measured density of the films was approximately 1.8 gm/cu cm, a value lower than diamond, the films exhibited other properties that were relatively close to diamond. These films were compared with diamond like films generated by sputtering a graphite target.

  14. Amorphous carbon nitride as an alternative electrode material in electroanalysis: Simultaneous determination of dopamine and ascorbic acid

    Energy Technology Data Exchange (ETDEWEB)

    Medeiros, Roberta A., E-mail: roantigo@hotmail.com [Departamento de Química, Universidade Federal de São Carlos, C.P. 676, 13560-970 São Carlos, SP (Brazil); Matos, Roberto [Departamento de Química, Universidade Federal de São Carlos, C.P. 676, 13560-970 São Carlos, SP (Brazil); Benchikh, Abdelkader [LECVE, Faculté de la Technologie, Département de Génie des Procédés, Université Abderrahmane MIRA, Béjaïa (Algeria); LISE UPR 15 du CNRS, Université Pierre et Marie Curie, 4, Place Jussieu, 75005 Paris (France); Saidani, Boualem [LECVE, Faculté de la Technologie, Département de Génie des Procédés, Université Abderrahmane MIRA, Béjaïa (Algeria); Debiemme-Chouvy, Catherine [LISE UPR 15 du CNRS, Université Pierre et Marie Curie, 4, Place Jussieu, 75005 Paris (France); Deslouis, Claude, E-mail: claude.deslouis@upmc.fr [LISE UPR 15 du CNRS, Université Pierre et Marie Curie, 4, Place Jussieu, 75005 Paris (France); Rocha-Filho, Romeu C.; Fatibello-Filho, Orlando [Departamento de Química, Universidade Federal de São Carlos, C.P. 676, 13560-970 São Carlos, SP (Brazil)

    2013-10-03

    Graphical abstract: -- Highlights: •a-CN{sub x} films are a new class of electrodic carbon materials that present several properties similar to those of BDD films. •a-CN{sub x} and BDD were used as working electrodes for simultaneous determination of DA and AA. •Electrochemical pretreatments on a-CN{sub x} or BDD modified the nature of the surface terminations. •An anodic pretreatment in 0.1 mol L{sup −1} KOH was necessary to attain an adequate separation of the DA and AA oxidation potential peaks. •For the first time in the literature, the use of an a-CN{sub x} electrode in a complete electroanalytical procedure is reported. -- Abstract: Boron-doped diamond (BDD) films are excellent electrode materials, whose electrochemical activity for some analytes can be tuned by controlling their surface termination, most commonly either to predominantly hydrogen or oxygen. This tuning can be accomplished by e.g. suitable cathodic or anodic electrochemical pretreatments. Recently, it has been shown that amorphous carbon nitride (a-CN{sub x}) films may present electrochemical characteristics similar to those of BDD, including the influence of surface termination on their electrochemical activity toward some analytes. In this work, we report for the first time a complete electroanalytical method using an a-CN{sub x} electrode. Thus, an a-CN{sub x} film deposited on a stainless steel foil by DC magnetron sputtering is proposed as an alternative electrode for the simultaneous determination of dopamine (DA) and ascorbic acid (AA) in synthetic biological samples by square-wave voltammetry. The obtained results are compared with those attained using a BDD electrode. For both electrodes, a same anodic pretreatment in 0.1 mol L{sup −1} KOH was necessary to attain an adequate and equivalent separation of the DA and AA oxidation potential peaks of about 330 mV. The detection limits obtained for the simultaneous determination of these analytes using the a-CN{sub x

  15. An ab initio study of the nickel-catalyzed transformation of amorphous carbon into graphene in rapid thermal processing

    Science.gov (United States)

    Chen, Shuang; Xiong, Wei; Zhou, Yun Shen; Lu, Yong Feng; Zeng, Xiao Cheng

    2016-05-01

    Ab initio molecular dynamics (AIMD) simulations are employed to investigate the chemical mechanism underlying the Ni-catalyzed transformation of amorphous carbon (a-C) into graphene in the rapid thermal processing (RTP) experiment to directly grow graphene on various dielectric surfaces via the evaporation of surplus Ni and C at 1100 °C (below the melting point of bulk Ni). It is found that the a-C-to-graphene transformation entails the metal-induced crystallization and layer exchange mechanism, rather than the conventional dissolution/precipitation mechanism typically involved in Ni-catalyzed chemical vapor deposition (CVD) growth of graphene. The multi-layer graphene can be tuned by changing the relative thicknesses of deposited a-C and Ni thin films. Our AIMD simulations suggest that the easy evaporation of surplus Ni with excess C is likely attributed to the formation of a viscous-liquid-like Ni-C solution within the temperature range of 900-1800 K and to the faster diffusion of C atoms than that of Ni atoms above 600 K. Even at room temperature, sp3-C atoms in a-C are quickly converted to sp2-C atoms in the course of the simulation, and the graphitic C formation can occur at low temperature. When the temperature is as high as 1200 K, the grown graphitic structures reversely dissolve into Ni. Because the rate of temperature increase is considerably faster in the AIMD simulations than in realistic experiments, defects in the grown graphitic structures are kinetically trapped. In this kinetic growth stage, the carbon structures grown from sp3-carbon or from sp2-carbon exhibit marked differences.Ab initio molecular dynamics (AIMD) simulations are employed to investigate the chemical mechanism underlying the Ni-catalyzed transformation of amorphous carbon (a-C) into graphene in the rapid thermal processing (RTP) experiment to directly grow graphene on various dielectric surfaces via the evaporation of surplus Ni and C at 1100 °C (below the melting point of bulk

  16. Structural, nanomechanical and variable range hopping conduction behavior of nanocrystalline carbon thin films deposited by the ambient environment assisted filtered cathodic jet carbon arc technique

    Energy Technology Data Exchange (ETDEWEB)

    Panwar, O.S., E-mail: ospanwar@mail.nplindia.ernet.in [Polymorphic Carbon Thin Films Group, Physics of Energy Harvesting Division, CSIR-National Physical Laboratory, Dr. K. S. Krishnan Road, New Delhi - 110 012 (India); Rawal, Ishpal; Tripathi, R.K. [Polymorphic Carbon Thin Films Group, Physics of Energy Harvesting Division, CSIR-National Physical Laboratory, Dr. K. S. Krishnan Road, New Delhi - 110 012 (India); Srivastava, A.K. [Electron and Ion Microscopy, Sophisticated and Analytical Instruments, CSIR-National Physical Laboratory, Dr. K. S. Krishnan Road, New Delhi - 110 012 (India); Kumar, Mahesh [Ultrafast Opto-Electronics and Tetrahertz Photonics Group, CSIR-National Physical Laboratory, Dr. K. S. Krishnan Road, New Delhi - 110 012 (India)

    2015-04-15

    Highlights: • Nanocrystalline carbon thin films are grown by filtered cathodic jet carbon arc process. • Effect of gaseous environment on the properties of carbon films has been studied. • The structural and nanomechanical properties of carbon thin films have been studied. • The VRH conduction behavior in nanocrystalline carbon thin films has been studied. - Abstract: This paper reports the deposition and characterization of nanocrystalline carbon thin films by filtered cathodic jet carbon arc technique assisted with three different gaseous environments of helium, nitrogen and hydrogen. All the films are nanocrystalline in nature as observed from the high resolution transmission electron microscopic (HRTEM) measurements, which suggests that the nanocrystallites of size ∼10–50 nm are embedded though out the amorphous matrix. X-ray photoelectron spectroscopic studies suggest that the film deposited under the nitrogen gaseous environment has the highest sp{sup 3}/sp{sup 2} ratio accompanied with the highest hardness of ∼18.34 GPa observed from the nanoindentation technique. The film deposited under the helium gaseous environment has the highest ratio of the area under the Raman D peak to G peak (A{sub D}/A{sub G}) and the highest conductivity (∼2.23 S/cm) at room temperature, whereas, the film deposited under the hydrogen environment has the lowest conductivity value (2.27 × 10{sup −7} S/cm). The temperature dependent dc conduction behavior of all the nanocrystalline carbon thin films has been analyzed in the light of Mott’s variable range hopping (VRH) conduction mechanism and observed that all the films obey three dimension VRH conduction mechanism for the charge transport.

  17. High-energy ion treatments of amorphous As40Se60 thin films for optical applications

    Directory of Open Access Journals (Sweden)

    Rashmi Chauhan

    2014-06-01

    Full Text Available The treatment of 100 MeV Ag swift-heavy ion (SHI irradiation with five different fluences (3×1010, 1×1011, 3×1011, 1×1012, and 3×1012 ions/cm2 was used to design optical and structural properties of amorphous (a- As40Se60 chalcogenide thin films. Swanepoel method was applied on transmission measurements to determine the changes in optical bandgap, Tauc parameter and linear optical parameters, i.e., linear optical absorption, extinction coefficient and linear refractive index. Dispersion of the material was determined by Wemple–DiDomenico relation. Changes in nonlinear optical parameters of third-order optical susceptibility and nonlinear refractive index were determined using semi-empirical relations. Changes in surface morphology of the films were investigated using SEM observation, which indicated that fluence 3×1012 ions/cm2 was upper threshold limit for these films for ion treatment. It is observed that optical bandgap reduces from 1.76 eV to 1.64 eV, and nonlinear refractive index increases from 1.31×10−10 [esu] to 1.74×10−10 [esu]. Linear refractive index initially increases from 2.80 to 3.52 (for fluence 3×1010 ions/cm2 and then keeps decreasing. The observed changes in optical properties upon irradiation were explained in terms of structural rearrangements by Raman measurement. The study was compiled with the previous literature to propose SHI as an effective optical engineering technique to achieve desired changes according to the need of optical/photonic applications.

  18. High-energy ion treatments of amorphous As40Se60 thin films for optical applications

    Institute of Scientific and Technical Information of China (English)

    Rashmi Chauhan; Arvind Tripathi; Krishna Kant Srivastava

    2014-01-01

    The treatment of 100 MeV Ag swift-heavy ion (SHI) irradiation with five different fluences (3 ? 1010, 1 ? 1011, 3 ? 1011, 1 ? 1012, and 3 ? 1012 ions/cm2) was used to design optical and structural properties of amorphous (a-) As40Se60 chalcogenide thin films. Swanepoel method was applied on transmission measurements to determine the changes in optical bandgap, Tauc parameter and linear optical parameters, i.e., linear optical absorption, extinction coefficient and linear refractive index. Dispersion of the material was determined by Wemple-DiDomenico relation. Changes in nonlinear optical parameters of third-order optical susceptibility and nonlinear refractive index were determined using semi-empirical relations. Changes in surface morphology of the films were investigated using SEM observation, which indicated that fluence 3 ? 1012 ions/cm2 was upper threshold limit for these films for ion treatment. It is observed that optical bandgap reduces from 1.76 eV to 1.64 eV, and nonlinear refractive index increases from 1.31 ? 10 ? 10 [esu] to 1.74 ? 10 ? 10 [esu]. Linear refractive index initially increases from 2.80 to 3.52 (for fluence 3 ? 1010 ions/cm2) and then keeps decreasing. The observed changes in optical properties upon irradiation were explained in terms of structural rearrangements by Raman measurement. The study was compiled with the previous literature to propose SHI as an effective optical engineering technique to achieve desired changes according to the need of optical/photonic applications.

  19. Resonant tunnelling assisted electrical switching in amorphous-carbon multilayer-superlattice structures

    Science.gov (United States)

    Bhattacharyya, Somnath; Silva, S. R. P.

    2007-03-01

    Negative differential resistance (NDR) in an amorphous carbon (a-C) double barrier resonant tunnel diode (DB-RTD) with an estimated cut-off frequency well into the gigahertz regime is reported [1]. Presently we extend this work in carbon multi-layer superlattice structures by showing room temperature resonant tunnelling and establish a high value of the phase coherence length of ˜10 nm for low-dimensional amorphous materials. By applying a high bias, these structures are modified with reversible current switching of up to four orders of magnitude with a NDR signature and multiple peaks representative of resonant tunnelling in the ON state. In addition to the formation of filamentary channels by applying high bias, all these features are also explained using concepts based on tunnelling through the interface of the carbon layers, quantum-dot heterostructures and the presence of a confined two dimensional electron gas. This switching behavior and its tunability have been tested by applying a microwave signal up to 100 GHz which suggest the potential for novel high-speed memory devices. [1] S. Bhattacharyya, S.J. Henley, E. Mendoza, L.G-Rojas, J. Allam and S.R.P. Silva, Nature Mater. 5, 19 (2006).

  20. Nanocomposite tantalum-carbon-based films deposited by femtosecond pulsed laser ablation

    Energy Technology Data Exchange (ETDEWEB)

    Benchikh, N. [Laboratoire Traitement du Signal et Instrumentation, UMR 5516, Universite J. Monnet, 10 rue Barrouin, 42000 Saint-Etienne (France); Garrelie, F. [Laboratoire Traitement du Signal et Instrumentation, UMR 5516, Universite J. Monnet, 10 rue Barrouin, 42000 Saint-Etienne (France); Wolski, K. [Ecole Nationale Superieure des Mines de Saint-Etienne, Centre SMS - URA CNRS 5146, 158 cours Fauriel, 42023 Saint-Etienne, Cedex 02 (France); Donnet, C. [Laboratoire Traitement du Signal et Instrumentation, UMR 5516, Universite J. Monnet, 10 rue Barrouin, 42000 Saint-Etienne (France)]. E-mail: Christophe.Donnet@univ-st-etienne.fr; Fillit, R.Y. [Ecole Nationale Superieure des Mines de Saint-Etienne, Centre SMS - URA CNRS 5146, 158 cours Fauriel, 42023 Saint-Etienne, Cedex 02 (France); Rogemond, F. [Laboratoire Traitement du Signal et Instrumentation, UMR 5516, Universite J. Monnet, 10 rue Barrouin, 42000 Saint-Etienne (France); Subtil, J.L. [Laboratoire Traitement du Signal et Instrumentation, UMR 5516, Universite J. Monnet, 10 rue Barrouin, 42000 Saint-Etienne (France); Rouzaud, J.N. [Laboratoire de Geologie de l' Ecole Normale Superieure de Paris 24, rue Lhomond 75231-Paris Cedex 5 (France); Laval, J.Y. [Laboratoire de Physique du Solide, UPR5 CNRS-ESPCI, 10 rue Vauquelin 75231-Paris Cedex 05 (France)

    2006-01-03

    Nanostructured coatings of metal (tantalum) containing diamond-like carbon (a-C:Ta) have been prepared by femtosecond pulsed laser deposition (PLD). The films, containing 15 at.% tantalum, have been deposited by ablating sequentially graphite and metallic tantalum in vacuum conditions with an amplified Ti:sapphire laser. The coatings have been investigated by X-ray photoelectron spectroscopy, grazing angle X-ray diffraction, energy filtered transmission electron microscopy, scanning and high resolution transmission electron microscopies. Evidence of metallic {alpha}-Ta and {beta}-Ta particles (diameter in the 100 nm range) and smaller quasi-amorphous tantalum clusters embedded in the carbonaceous matrix have been shown. A thin tantalum carbide interface between the carbon matrix and the top surface of the tantalum nodules has also been identified. The ability of femtosecond pulsed laser deposition to synthetize nanocomposite carbon-based films and to control their nanostructure is discussed.

  1. Self Exchange Bias and Bi-stable Magneto-Resistance States in Amorphous TbFeCo and TbSmFeCo Thin Films

    Science.gov (United States)

    Ma, Chung; Li, Xiaopu; Lu, Jiwei; Poon, Joseph; Comes, Ryan; Devaraj, Arun; Spurgeon, Steven

    Amorphous ferrimagetic TbFeCo and TbSmFeCo thin films are found to exhibit strong perpendicular magnetic anisotropy. Self exchange bias effect and bi-stable magneto-resistance states are observed near compensation temperature by magnetic hysteresis loop, anomalous Hall effect and transverse magneto-resistance measurements. Atom probe tomography, scanning transmission electron microscopy, and energy dispersive spectroscopy mapping have revealed two nanoscale amorphous phases with different Tb concentration distributed within the amorphous films. The observed exchange anisotropy originates from the exchange interaction between the two nanoscale amorphous phases. Exchange bias effect is used for increasing stability in spin valves and magnetic tunneling junctions. This study opens up a new platform for using amorphous ferrimagnetic thin films that require no epitaxial growth in nanodevices.. The work was supported by the Defense Threat Reduction Agency Grant and the U.S. Department of Energy.

  2. Study on the Crystallization of Amorphous Cr-Si-Ni Thin Films Using in situ X-ray Diffraction

    Institute of Scientific and Technical Information of China (English)

    Xianping DONG; Jiansheng WU

    2001-01-01

    Crystallization behavior of amorphous Cr-Si-Ni thin films was investigated by means of high temperature in situ X-ray diffraction measurements. The diffraction spectra were recorded isothermally at temperature between 250 and 750℃. The in situ testing of crystallization enables the direct observation of structure evolution which is dependent on heat treatment.Based on the testing results, the grain sizes of the crystalline phases were compared and phase transition tendency was understood. In the mean time, electrical properties of the films as functions of annealing temperature and time have been studied. The increase of volume fraction of CrSi2 crystallinc phases in the Cr-Si-Ni films leads to the decrease in conductivity of the films.The annealing behavior of temperature coefficient of resistance (TCR) is a result of competition between a negative contribution caused by the weak localization effects in amorphous region and a positive contribution caused by CrSi2 grains. Thus the proper mixture of amorphous and crystalline constituents could result in a final zero TCR.

  3. Dark conductivity and photoconductivity of amorphous Hg0.78Cd0.22Te thin films

    Institute of Scientific and Technical Information of China (English)

    Qiu Feng; Ji Rongbin; Xiang Jinzhong; Kong Jincheng; Yu Lianjie; Kong Lingde; Wang Guanghua; Li Xiongjun; Yang Lili; Li Cong

    2011-01-01

    This paper reports the dark conductivity and photoconductivity of amorphous Hg0.78Cd0.22 Te thin films deposited on an Al2O3 substrate by RF magnetron sputtering.It is determined that dark conduction activation energy is 0.417 eV for the as-grown sample.Thermal quenching is absent for the as-grown sample during the testing temperature zone,but the reverse is true for the polycrystalline sample.Photosensitivity shows the maximum at 240 K for amorphous thin films,while it is higher for the as-grown sample than for polycrystalline thin films in the range from 170 to 300 K.The recombination mechanism is the monomolecular recombination process at room temperature,which is different from the low temperature range.Theμτ-product is low in the range of 10-11-10-9 cm2/V,which indicates that some defect states exist in the amorphous thin films.

  4. Application of photo-doping phenomenon in amorphous chalcogenide GeS2 film to optical device

    Science.gov (United States)

    Murakami, Yoshihisa; Arai, Katsuya; Wakaki, Moriaki; Shibuya, Takehisa; Shintaku, Toshihiro

    2015-03-01

    Photodoping phenomenon is observed when a double-layer consisting of an amorphous chalcogenide film (As2S3, GeS2, GeSe2 etc.) and a metal (Ag, Cu etc.) film is illuminated by light. The metal diffuses abnormally into the amorphous chalcogenide layer. Amorphous chalcogenide films of GeS2 with an Ag over layer exhibited large increase of refractive index through the abnormal doping of Ag by irradiating the light around the absorption edge of the GeS2 chalcogenide. In this study, we aimed the application of this effect for the fabrication of optical devices and fabricated various micro doped patterns by using a laser beam. Mask less pattering with refractive index modified films are possible by manipulating the scanning of the laser beam. Micro gratings were fabricated using a confocal laser microscope to work as both fabrication and observation system. Waveguides were also fabricated by scanning the laser beam for photodoping. Holographic gratings were fabricated by utilizing the photodoping of the two beam interference pattern, which showed the possibility to produce large scale optical devices or mass production.

  5. Element specific spin and orbital moments of nanoscale CoFeB amorphous thin films on GaAs(100

    Directory of Open Access Journals (Sweden)

    Yu Yan

    2016-09-01

    Full Text Available CoFeB amorphous films have been synthesized on GaAs(100 and studied with X-ray magnetic circular dichroism (XMCD and transmission electron microscopy (TEM. We have found that the ratios of the orbital to spin magnetic moments of both the Co and Fe in the ultrathin amorphous film have been enhanced by more than 300% compared with those of the bulk crystalline Co and Fe, and specifically a large orbital moment of 0.56 μB from the Co atoms has been observed and at the same time the spin moment of the Co atoms remains comparable to that of the bulk hcp Co. The results indicate that the large uniaxial magnetic anisotropy (UMA observed in the ultrathin CoFeB film on GaAs(100 is related to the enhanced spin-orbital coupling of the Co atoms in the CoFeB. This work offers experimental evidences of the correlation between the UMA and the element specific spin and orbital moments in the CoFeB amorphous film on the GaAs(100 substrate, which is of significance for spintronics applications.

  6. Present status of amorphous In–Ga–Zn–O thin-film transistors

    Directory of Open Access Journals (Sweden)

    Toshio Kamiya, Kenji Nomura and Hideo Hosono

    2010-01-01

    Full Text Available The present status and recent research results on amorphous oxide semiconductors (AOSs and their thin-film transistors (TFTs are reviewed. AOSs represented by amorphous In–Ga–Zn–O (a-IGZO are expected to be the channel material of TFTs in next-generation flat-panel displays because a-IGZO TFTs satisfy almost all the requirements for organic light-emitting-diode displays, large and fast liquid crystal and three-dimensional (3D displays, which cannot be satisfied using conventional silicon and organic TFTs. The major insights of this review are summarized as follows. (i Most device issues, such as uniformity, long-term stability against bias stress and TFT performance, are solved for a-IGZO TFTs. (ii A sixth-generation (6G process is demonstrated for 32'' and 37'' displays. (iii An 8G sputtering apparatus and a sputtering target have been developed. (iv The important effect of deep subgap states on illumination instability is revealed. (v Illumination instability under negative bias has been intensively studied, and some mechanisms are proposed. (vi Degradation mechanisms are classified into back-channel effects, the creation of traps at an interface and in the gate insulator, and the creation of donor states in annealed a-IGZO TFTs by the Joule heating; the creation of bulk defects should also be considered in the case of unannealed a-IGZO TFTs. (vii Dense passivation layers improve the stability and photoresponse and are necessary for practical applications. (viii Sufficient knowledge of electronic structures and electron transport in a-IGZO has been accumulated to construct device simulation models.

  7. Thermally induced formation of metastable nanocomposites in amorphous Cr-Zr-O thin films deposited using reactive ion beam sputtering

    Energy Technology Data Exchange (ETDEWEB)

    Rafaja, David, E-mail: rafaja@ww.tu-freiberg.de [Institute of Materials Science, Freiberg University of Technology, D-09599 Freiberg (Germany); Wüstefeld, Christina [Institute of Materials Science, Freiberg University of Technology, D-09599 Freiberg (Germany); Abrasonis, Gintautas [Helmholtz-Zentrum Dresden-Rossendorf, P.O. Box 510119, D-01314 Dresden (Germany); Braeunig, Stefan [Institute of Materials Science, Freiberg University of Technology, D-09599 Freiberg (Germany); Baehtz, Carsten [Helmholtz-Zentrum Dresden-Rossendorf, P.O. Box 510119, D-01314 Dresden (Germany); Hanzig, Florian; Dopita, Milan [Institute of Materials Science, Freiberg University of Technology, D-09599 Freiberg (Germany); Krause, Matthias [Helmholtz-Zentrum Dresden-Rossendorf, P.O. Box 510119, D-01314 Dresden (Germany); Gemming, Sibylle [Helmholtz-Zentrum Dresden-Rossendorf, P.O. Box 510119, D-01314 Dresden (Germany); Institute of Physics, Technische Universität Chemnitz, D-09126 Chemnitz (Germany)

    2016-08-01

    Successive crystallization of amorphous Cr-Zr-O thin films, formation of the (Cr,Zr){sub 2}O{sub 3}/(Zr,Cr)O{sub 2} nanocomposites and the thermally induced changes in the hexagonal crystal structure of metastable (Cr,Zr){sub 2}O{sub 3} were investigated by means of in situ high-temperature synchrotron diffraction experiments up to 1100 °C. The thin films were deposited at room temperature by using reactive ion beam sputtering, and contained 3–15 at.% Zr. At low Zr concentrations, chromium-rich (Cr,Zr){sub 2}O{sub 3} crystallized first, while the crystallization of zirconium-rich (Zr,Cr)O{sub 2} was retarded. Increasing amount of zirconium shifted the onset of crystallization in both phases to higher temperatures. For 3 at.% of zirconium in amorphous Cr-Zr-O, (Cr,Zr){sub 2}O{sub 3} crystallized at 600 °C. At 8 at.% Zr in the films, the crystallization of (Cr,Zr){sub 2}O{sub 3} started at 700 °C. At 15 at.% Zr, the Cr-Zr-O films remained amorphous up to the annealing temperature of 1000 °C. Metastable hexagonal (Cr,Zr){sub 2}O{sub 3} accommodated up to ~ 3 at.% Zr. Excess of zirconium formed tetragonal zirconia, which was stabilized by chromium. - Highlights: • Amorphous Cr-Zr-O thin films were deposited using reactive ion beam sputtering. • After annealing in vacuum, metastable (Cr,Zr){sub 2}O{sub 3}/(Zr,Cr)O{sub 2} nanocomposites form. • The crystallization temperature depends strongly on the Zr concentration. • Metastable hexagonal (Cr,Zr){sub 2}O{sub 3} accommodates up to 3.2 at.% of zirconium. • Zirconium oxide crystallizes in tetragonal form, as it is stabilized by chromium.

  8. Ultrafast sub-threshold photo-induced response in crystalline and amorphous GeSbTe thin films

    Science.gov (United States)

    Shu, M. J.; Chatzakis, I.; Kuo, Y.; Zalden, P.; Lindenberg, A. M.

    2013-05-01

    Pump-probe optical reflectivity and terahertz transmission measurements have been used to investigate time resolved sub-threshold photo-induced effects in crystalline and amorphous GeSbTe films at MHz repetition rates. The reflectivity in both phases exhibits long-lived modulations consistent with the sign of the changes that occur upon switching but of smaller magnitude. These can be understood by the generation of acoustic strains with the crystalline phase response dominated by thermal effects and the amorphous phase response associated with electronically induced changes. Evidence for a photo-induced distortion is observed in the amorphous phase which develops homogeneously within the excited region on few-picosecond time scales.

  9. Bipolar resistive switching behavior of an amorphous Ge₂Sb₂Te₅ thin films with a Te layer.

    Science.gov (United States)

    Yoo, Sijung; Eom, Taeyong; Gwon, Taehong; Hwang, Cheol Seong

    2015-04-14

    The mechanism of bipolar resistive switching (BRS) of amorphous Ge2Sb2Te5 (GST) thin films sandwiched between inert electrodes (Ti and Pt) was examined. Typical bipolar resistive switching behavior with a high resistance ratio (∼10(3)) and reliable switching characteristics was achieved. High-resolution transmission electron microscopy revealed the presence of a conductive Te-filament bridging between the top and bottom electrodes through an amorphous GST matrix. The conduction mechanism analysis showed that the low-resistance state was semiconducting and dominated by band transport, whereas Poole-Frenkel conduction governed the carrier transport in the high-resistance state. Thus, the BRS behavior can be attributed to the formation and rupture of the semiconducting conductive Te bridge through the migration of the Te ions in the amorphous GST matrix under a high electric field. The Te ions are provided by the thin (∼5 nm) Te-rich layer formed at the bottom electrode interface.

  10. Bipolar resistive switching behavior of an amorphous Ge2Sb2Te5 thin films with a Te layer

    Science.gov (United States)

    Yoo, Sijung; Eom, Taeyong; Gwon, Taehong; Hwang, Cheol Seong

    2015-03-01

    The mechanism of bipolar resistive switching (BRS) of amorphous Ge2Sb2Te5 (GST) thin films sandwiched between inert electrodes (Ti and Pt) was examined. Typical bipolar resistive switching behavior with a high resistance ratio (~103) and reliable switching characteristics was achieved. High-resolution transmission electron microscopy revealed the presence of a conductive Te-filament bridging between the top and bottom electrodes through an amorphous GST matrix. The conduction mechanism analysis showed that the low-resistance state was semiconducting and dominated by band transport, whereas Poole-Frenkel conduction governed the carrier transport in the high-resistance state. Thus, the BRS behavior can be attributed to the formation and rupture of the semiconducting conductive Te bridge through the migration of the Te ions in the amorphous GST matrix under a high electric field. The Te ions are provided by the thin (~5 nm) Te-rich layer formed at the bottom electrode interface.

  11. THE EFFECT OF DIAMETER ON THE MECHANICAL-PROPERTIES OF AMORPHOUS-CARBON FIBERS FROM LINEAR LOW-DENSITY POLYETHYLENE

    NARCIS (Netherlands)

    PENNING, JP; LAGCHER, R; PENNINGS, AJ

    1991-01-01

    The mechanical properties of amorphous carbon fibers, derived from linear low density polyethylene strongly depend on the fibre diameter, which may be attributed to the presence of a skin/core structure in these fibres. High strength carbon fibres could thus be prepared by using thin precursor filam

  12. Characterization of optical constants and dispersion parameters of highly transparent Ge20Se76Sn4 amorphous thin film

    Science.gov (United States)

    Abd-Elrahman, M. I.; Hafiz, M. M.; Abdelraheem, A. M.; Abu-Sehly, A. A.

    2015-12-01

    Amorphous chalcogenide Ge20Se76Sn4 thin films of six different thicknesses (50-350 nm) are prepared by the thermal evaporation technique. Optical transmission and reflection spectra, in the wavelength range of the incident photons from 250 to 2500 nm, are used to study the effect of the film thickness on some optical properties. It is found that the effect of film thickness leads to increase in the absorption coefficient, refractive index, extinction coefficient and the width of the tails of localized states in the gap region. The decrease in optical band gap energy with increasing the film thickness is attributed to the formation of a band tail which narrows down the band gap. Dispersion analyses of refractive index reveal a decrease in the single-oscillator energy and an increase in the dispersion energy with increase in film thickness.

  13. Surface effect on ion track formation in amorphous Si{sub 3}N{sub 4} films

    Energy Technology Data Exchange (ETDEWEB)

    Morita, Y.; Nakajima, K.; Suzuki, M. [Department of Micro Engineering, Kyoto University, Kyoto 615-8540 (Japan); Narumi, K.; Saitoh, Y. [Takasaki Advanced Radiation Research Institute, Japan Atomic Energy Agency, 1233 Watanuki-machi, Takasaki, Gumma 370-1292 (Japan); Ishikawa, N. [Nuclear Science and Engineering Directorate, Japan Atomic Energy Agency, Tokai, Naka, Ibaraki 319-1195 (Japan); Hojou, K. [Advanced Science Research Center, Japan Atomic Energy Agency, Tokai, Naka, Ibaraki 319-1195 (Japan); Tsujimoto, M.; Isoda, S. [Institute for Integrated Cell-Material Sciences, Kyoto University, Kyoto 615-8540 (Japan); Kimura, K., E-mail: kimura@kues.kyoto-u.ac.jp [Department of Micro Engineering, Kyoto University, Kyoto 615-8540 (Japan)

    2013-11-15

    Thin films of amorphous Si{sub 3}N{sub 4} (thickness 5–30 nm) were irradiated with 360–720 keV C{sub 60}{sup 2+} ions. Ion tracks were observed using transmission electron microscopy (TEM) and high-angle annular dark field scanning transmission electron microscopy (HAADF-STEM). The track length and the radial density profile of the track were measured for various combinations of the film thickness and the energy of C{sub 60}{sup 2+}. The length of the ion track produced in a 30-nm film was found shorter than that in a 20-nm film indicating that there is surface effect on track formation. This can be qualitatively understood in terms of the energy dissipation process. The observed radial density profile also depends on the film thickness. The result can be explained by surface cratering.

  14. Amorphous Ultrathin SnO2 Films by Atomic Layer Deposition on Graphene Network as Highly Stable Anodes for Lithium-Ion Batteries.

    Science.gov (United States)

    Xie, Ming; Sun, Xiang; George, Steven M; Zhou, Changgong; Lian, Jie; Zhou, Yun

    2015-12-23

    Amorphous SnO2 (a-SnO2) thin films were conformally coated onto the surface of reduced graphene oxide (G) using atomic layer deposition (ALD). The electrochemical characteristics of the a-SnO2/G nanocomposites were then determined using cyclic voltammetry and galvanostatic charge/discharge curves. Because the SnO2 ALD films were ultrathin and amorphous, the impact of the large volume expansion of SnO2 upon cycling was greatly reduced. With as few as five formation cycles best reported in the literature, a-SnO2/G nanocomposites reached stable capacities of 800 mAh g(-1) at 100 mA g(-1) and 450 mAh g(-1) at 1000 mA g(-1). The capacity from a-SnO2 is higher than the bulk theoretical values. The extra capacity is attributed to additional interfacial charge storage resulting from the high surface area of the a-SnO2/G nanocomposites. These results demonstrate that metal oxide ALD on high surface area conducting carbon substrates can be used to fabricate high power and high capacity electrode materials for lithium-ion batteries.

  15. Distinct Short-Range Order Is Inherent to Small Amorphous Calcium Carbonate Clusters (<2 nm)

    Energy Technology Data Exchange (ETDEWEB)

    Sun, Shengtong [Physical Chemistry, University of Konstanz, Universitätsstrasse 10 78457 Konstanz Germany; School of Chemical Engineering, State Key Laboratory of Chemical Engineering, Shanghai Key Laboratory of Multiphase Materials Chemical Engineering, East China University of Science and Technology, 130 Meilong Road Shanghai 200237 P.R. China; Chevrier, Daniel M. [Department of Chemistry and Institute for Research in Materials, Dalhousie University, Halifax Nova Scotia B3H 4R2 Canada; Zhang, Peng [Department of Chemistry and Institute for Research in Materials, Dalhousie University, Halifax Nova Scotia B3H 4R2 Canada; Gebauer, Denis [Physical Chemistry, University of Konstanz, Universitätsstrasse 10 78457 Konstanz Germany; Cölfen, Helmut [Physical Chemistry, University of Konstanz, Universitätsstrasse 10 78457 Konstanz Germany

    2016-09-09

    Amorphous intermediate phases are vital precursors in the crystallization of many biogenic minerals. While inherent short-range orders have been found in amorphous calcium carbonates (ACCs) relating to different crystalline forms, it has never been clarified experimentally whether such orders already exist in very small clusters less than 2 nm in size. Here, we studied the stability and structure of 10,12-pentacosadiynoic acid (PCDA) protected ACC clusters with a core size of ca. 1.4 nm consisting of only seven CaCO3 units. Ligand concentration and structure are shown to be key factors in stabilizing the ACC clusters. More importantly, even in such small CaCO3 entities, a proto-calcite short-range order can be identified but with a relatively high degree of disorder that arises from the very small size of the CaCO3 core. Our findings support the notion of a structural link between prenucleation clusters, amorphous intermediates, and final crystalline polymorphs, which appears central to the understanding of polymorph selection.

  16. An ab initio study of the nickel-catalyzed transformation of amorphous carbon into graphene in rapid thermal processing.

    Science.gov (United States)

    Chen, Shuang; Xiong, Wei; Zhou, Yun Shen; Lu, Yong Feng; Zeng, Xiao Cheng

    2016-05-14

    Ab initio molecular dynamics (AIMD) simulations are employed to investigate the chemical mechanism underlying the Ni-catalyzed transformation of amorphous carbon (a-C) into graphene in the rapid thermal processing (RTP) experiment to directly grow graphene on various dielectric surfaces via the evaporation of surplus Ni and C at 1100 °C (below the melting point of bulk Ni). It is found that the a-C-to-graphene transformation entails the metal-induced crystallization and layer exchange mechanism, rather than the conventional dissolution/precipitation mechanism typically involved in Ni-catalyzed chemical vapor deposition (CVD) growth of graphene. The multi-layer graphene can be tuned by changing the relative thicknesses of deposited a-C and Ni thin films. Our AIMD simulations suggest that the easy evaporation of surplus Ni with excess C is likely attributed to the formation of a viscous-liquid-like Ni-C solution within the temperature range of 900-1800 K and to the faster diffusion of C atoms than that of Ni atoms above 600 K. Even at room temperature, sp(3)-C atoms in a-C are quickly converted to sp(2)-C atoms in the course of the simulation, and the graphitic C formation can occur at low temperature. When the temperature is as high as 1200 K, the grown graphitic structures reversely dissolve into Ni. Because the rate of temperature increase is considerably faster in the AIMD simulations than in realistic experiments, defects in the grown graphitic structures are kinetically trapped. In this kinetic growth stage, the carbon structures grown from sp(3)-carbon or from sp(2)-carbon exhibit marked differences.

  17. Dissociation of carbon dioxide and creation of carbon particles and films at room temperature

    Energy Technology Data Exchange (ETDEWEB)

    Fukuda, Takahiro [Bio-Nano Electronics Research Centre, Toyo University, 2100 Kujirai, Kawagoe Saitama 350-8585 (Japan); Maekawa, Toru [Bio-Nano Electronics Research Centre, Toyo University, 2100 Kujirai, Kawagoe Saitama 350-8585 (Japan); Hasumura, Takashi [Bio-Nano Electronics Research Centre, Toyo University, 2100 Kujirai, Kawagoe Saitama 350-8585 (Japan); Rantonen, Nyrki [Bio-Nano Electronics Research Centre, Toyo University, 2100 Kujirai, Kawagoe Saitama 350-8585 (Japan); Ishii, Koji [Bio-Nano Electronics Research Centre, Toyo University, 2100 Kujirai, Kawagoe Saitama 350-8585 (Japan); Nakajima, Yoshikata [Bio-Nano Electronics Research Centre, Toyo University, 2100 Kujirai, Kawagoe Saitama 350-8585 (Japan); Hanajiri, Tatsuro [Bio-Nano Electronics Research Centre, Toyo University, 2100 Kujirai, Kawagoe Saitama 350-8585 (Japan); Yoshida, Yoshikazu [Bio-Nano Electronics Research Centre, Toyo University, 2100 Kujirai, Kawagoe Saitama 350-8585 (Japan); Whitby, Raymond [School of Pharmacy and Biomolecular Sciences, University of Brighton, Cockroft Building, Lewes Road, Brighton BN2 4GJ (United Kingdom); Mikhalovsky, Sergey [School of Pharmacy and Biomolecular Sciences, University of Brighton, Cockroft Building, Lewes Road, Brighton BN2 4GJ (United Kingdom)

    2007-09-15

    As fluids approach their gas-liquid critical points, the physical properties such as the specific heat and compressibility diverge due to the formation of large molecular clusters. Incident light cannot penetrate near-critical fluids because of the large clusters, a phenomenon known as critical opalescence. In this paper, we irradiate near-critical carbon dioxide (ncCO{sub 2}), the critical temperature and pressure of which are 31.0{sup 0}C and 7.38 MPa, with a laser beam of 213, 266, 355 and 532 nm wavelength and show that CO{sub 2} is dissociated and particles are produced when the system is set so close to the critical point that critical opalescence occurs in the case of 213 and 266 nm wavelength, whereas no particles are produced when the temperature is made to deviate from the critical value. We also apply a dc electric field to ncCO{sub 2} during irradiation with a laser beam of 213 and 266 nm wavelength and find that particles are formed on both anode and cathode. As the intensity of the electric field increases, films are formed on the electrodes. Electron diffraction patterns and energy-dispersive x-ray, Auger electron, x-ray photoelectron and Raman spectroscopic analyses show that the particles and films are composed of amorphous carbon.

  18. Dissociation of carbon dioxide and creation of carbon particles and films at room temperature

    Science.gov (United States)

    Fukuda, Takahiro; Maekawa, Toru; Hasumura, Takashi; Rantonen, Nyrki; Ishii, Koji; Nakajima, Yoshikata; Hanajiri, Tatsuro; Yoshida, Yoshikazu; Whitby, Raymond; Mikhalovsky, Sergey

    2007-09-01

    As fluids approach their gas-liquid critical points, the physical properties such as the specific heat and compressibility diverge due to the formation of large molecular clusters. Incident light cannot penetrate near-critical fluids because of the large clusters, a phenomenon known as critical opalescence. In this paper, we irradiate near-critical carbon dioxide (ncCO2), the critical temperature and pressure of which are 31.0°C and 7.38 MPa, with a laser beam of 213, 266, 355 and 532 nm wavelength and show that CO2 is dissociated and particles are produced when the system is set so close to the critical point that critical opalescence occurs in the case of 213 and 266 nm wavelength, whereas no particles are produced when the temperature is made to deviate from the critical value. We also apply a dc electric field to ncCO2 during irradiation with a laser beam of 213 and 266 nm wavelength and find that particles are formed on both anode and cathode. As the intensity of the electric field increases, films are formed on the electrodes. Electron diffraction patterns and energy-dispersive x-ray, Auger electron, x-ray photoelectron and Raman spectroscopic analyses show that the particles and films are composed of amorphous carbon.

  19. Amorphous carbon nitride as an alternative electrode material in electroanalysis: simultaneous determination of dopamine and ascorbic acid.

    Science.gov (United States)

    Medeiros, Roberta A; Matos, Roberto; Benchikh, Abdelkader; Saidani, Boualem; Debiemme-Chouvy, Catherine; Deslouis, Claude; Rocha-Filho, Romeu C; Fatibello-Filho, Orlando

    2013-10-03

    Boron-doped diamond (BDD) films are excellent electrode materials, whose electrochemical activity for some analytes can be tuned by controlling their surface termination, most commonly either to predominantly hydrogen or oxygen. This tuning can be accomplished by e.g. suitable cathodic or anodic electrochemical pretreatments. Recently, it has been shown that amorphous carbon nitride (a-CNx) films may present electrochemical characteristics similar to those of BDD, including the influence of surface termination on their electrochemical activity toward some analytes. In this work, we report for the first time a complete electroanalytical method using an a-CNx electrode. Thus, an a-CNx film deposited on a stainless steel foil by DC magnetron sputtering is proposed as an alternative electrode for the simultaneous determination of dopamine (DA) and ascorbic acid (AA) in synthetic biological samples by square-wave voltammetry. The obtained results are compared with those attained using a BDD electrode. For both electrodes, a same anodic pretreatment in 0.1 mol L(-1) KOH was necessary to attain an adequate and equivalent separation of the DA and AA oxidation potential peaks of about 330 mV. The detection limits obtained for the simultaneous determination of these analytes using the a-CNx electrode were 0.0656 μmol L(-1) for DA and 1.05 μmol L(-1) for AA, whereas with the BDD electrode these values were 0.283 μmol L(-1) and 0.968 μmol L(-1), respectively. Furthermore, the results obtained in the analysis of the analytes in synthetic biological samples were satisfactory, attesting the potential application of the a-CNx electrode in electroanalysis.

  20. Precipitation of Co(2+) carbonates from aqueous solution: insights on the amorphous to crystalline transformation.

    Science.gov (United States)

    González-López, Jorge; Fernández-González, Ángeles; Jiménez, Amalia

    2016-04-01

    Cobalt is toxic metal that is present only as a trace in the Earth crust. However, Co might concentrate on specific areas due to both natural and anthropogenic factors and thus, soils and groundwater can be contaminated. It is from this perspective that we are interested in the precipitation of cobalt carbonates, since co-precipitation with minerals phases is a well-known method for metal immobilization in the environment. In particular, the carbonates are widely used due to its reactivity and natural abundance. In order to evaluate the cobalt carbonate precipitation at room temperature, a simple experimental work was carried out in this work. The precipitation occurred via reaction of two common salts: 0.05M of CoCl2 and 0.05M of Na2CO3 in aqueous solution. After reaction, the precipitated solid was kept in the remaining water at 25 oC and under constant stirring for different aging times of 5 min, 1 and 5 hours, 1, 2, 4, 7, 30 and 60 days. In addition to the aging and precipitation experiments, we carried out experiments to determine the solubility of the solids. In these experiments each precipitate was dissolved in Milli-Q water until equilibrium was reached and then the aqueous solution was analyzed regarding Co2+ and total alkalinity. Furthermore, acid solution calorimetry of the products were attained. Finally, we modeled the results using the PHREEQC code. Solid and aqueous phase identification and characterization have been extensively reported in a previous work (González-López et al., 2015). The main results of our investigation were the initial precipitation of an amorphous cobalt carbonate that evolve towards a poorly crystalline cobalt hydroxide carbonate with aging treatment. Solubility of both phases have been calculated under two different approaches: precipitation and dissolution. Values of solubility from each approach were obtained with a general error due to differences in experiment conditions, for instance, ionic strength, temperature and

  1. Thin film solar cells with Si nanocrystallites embedded in amorphous intrinsic layers by hot-wire chemical vapor deposition.

    Science.gov (United States)

    Park, Seungil; Parida, Bhaskar; Kim, Keunjoo

    2013-05-01

    We investigated the thin film growths of hydrogenated silicon by hot-wire chemical vapor deposition with different flow rates of SiH4 and H2 mixture ambient and fabricated thin film solar cells by implementing the intrinsic layers to SiC/Si heterojunction p-i-n structures. The film samples showed the different infrared absorption spectra of 2,000 and 2,100 cm(-1), which are corresponding to the chemical bonds of SiH and SiH2, respectively. The a-Si:H sample with the relatively high silane concentration provides the absorption peak of SiH bond, but the microc-Si:H sample with the relatively low silane concentration provides the absorption peak of SiH2 bond as well as SiH bond. Furthermore, the microc-Si:H sample showed the Raman spectral shift of 520 cm(-1) for crystalline phase Si bonds as well as the 480 cm(-1) for the amorphous phase Si bonds. These bonding structures are very consistent with the further analysis of the long-wavelength photoconduction tail and the formation of nanocrystalline Si structures. The microc-Si:H thin film solar cell has the photovoltaic behavior of open circuit voltage similar to crystalline silicon thin film solar cell, indicating that microc-Si:H thin film with the mixed phase of amorphous and nanocrystalline structures show the carrier transportation through the channel of nanocrystallites.

  2. Study of barrier properties and chemical resistance of recycled PET coated with amorphous carbon through a plasma enhanced chemical vapour deposition (PECVD) process.

    Science.gov (United States)

    Cruz, S A; Zanin, M; Nerin, C; De Moraes, M A B

    2006-01-01

    Many studies have been carried out in order to make bottle-to-bottle recycling feasible. The problem is that residual contaminants in recycled plastic intended for food packaging could be a risk to public health. One option is to use a layer of virgin material, named functional barrier, which prevents the contaminants migration process. This paper shows the feasibility of using polyethylene terephthalate (PET) recycled for food packaging employing a functional barrier made from hydrogen amorphous carbon film deposited by Plasma Enhanced Chemical Vapour Deposition (PECVD) process. PET samples were deliberately contaminated with a series of surrogates using a FDA protocol. After that, PET samples were coated with approximately 600 and 1200 Angstrons thickness of amorphous carbon film. Then, the migration tests using as food simulants: water, 10% ethanol, 3% acetic acid, and isooctane were applied to the sample in order to check the chemical resistance of the new coated material. After the tests, the liquid extracts were analysed using a solid-phase microextraction device (SPME) coupled to GC-MS.

  3. Fabrication and optical properties of InGaN/GaN multiple quantum well light emitting diodes with amorphous BaTiO3 ferroelectric film

    Science.gov (United States)

    Peng, Jing; Wu, Chuan-Ju; Sun, Tang-You; Zhao, Wen-Ning; Wu, Xiao-Feng; Liu, Wen; Wang, Shuang-Bao; Jie, Quan-Lin; Xu, Zhi-Mou

    2012-06-01

    BaTiO3 (BTO) ferroelectric thin films are prepared by the sol-gel method. The fabrication and the optical properties of an InGaN/GaN multiple quantum well light emitting diode (LED) with amorphous BTO ferroelectric thin film are studied. The photoluminescence (PL) of the BTO ferroelectric film is attributed to the structure. The ferroelectric film which annealed at 673 K for 8 h has the better PL property. The peak width is about 30 nm from 580 nm to 610 nm, towards the yellow region. The mixed electroluminescence (EL) spectrum of InGaN/GaN multiple quantum well LED with 150-nm thick amorphous BTO ferroelectric thin film displays the blue-white light. The Commission Internationale De L'Eclairage (CIE) coordinate of EL is (0.2139, 0.1627). EL wavelength and intensity depends on the composition, microstructure and thickness of the ferroelectric thin film. The transmittance of amorphous BTO thin film is about 93% at a wavelength of 450 nm-470 nm. This means the amorphous ferroelectric thin films can output more blue-ray and emission lights. In addition, the amorphous ferroelectric thin films can be directly fabricated without a binder and used at higher temperatures (200 °C-400 °C). It is very favourable to simplify the preparation process and reduce the heat dissipation requirements of an LED. This provides a new way to study LEDs.

  4. Fabrication and optical properties of InGaN/GaN multiple quantum well light emitting diodes with amorphous BaTiO3 ferroelectric film

    Institute of Scientific and Technical Information of China (English)

    Peng Jing; Wu Chuan-Ju; Sun Tang-You; Zhao Wen-Ning; Wu Xiao-Feng; Liu Wen; Wang Shuang-Bao; Jie Quan-Lin; Xu Zhi-Mou

    2012-01-01

    BaTiO3 (BTO) ferroelectric thin films are prepared by the sol-gel method.The fabrication and the optical properties of an InGaN/GaN multiple quantum well light emitting diode (LED) with amorphous BTO ferroelectric thin film are studied.The photoluminescence (PL) of the BTO ferroelectric film is attributed to the structure.The ferroelectric film which annealed at 673 K for 8 h has the better PL property.The peak width is about 30 nm from 580 nm to 610 nm,towards the yellow region.The mixed electroluminescence (EL) spectrum of InGaN/GaN multiple quantum well LED with 150-nm thick amorphous BTO ferroelectric thin film displays the blue-white light.The Commission Internationale De L'Eclairage (CIE) coordinate of EL is (0.2139,0.1627).EL wavelength and intensity depends on the composition,microstructure and thickness of the ferroelectric thin film.The transmittance of amorphous BTO thin film is about 93% at a wavelength of 450 nm-470 nm.This means the amorphous ferroelectric thin films can output more blue-ray and emission lights.In addition,the amorphous ferroelectric thin films can be directly fabricated without a binder and used at higher temperatures (200 ℃-400 ℃).It is very favourable to simplify the preparation process and reduce the heat dissipation requirements of an LED.This provides a new way to study LEDs.

  5. Vertical electric field stimulated neural cell functionality on porous amorphous carbon electrodes.

    Science.gov (United States)

    Jain, Shilpee; Sharma, Ashutosh; Basu, Bikramjit

    2013-12-01

    We demonstrate the efficacy of amorphous macroporous carbon substrates as electrodes to support neuronal cell proliferation and differentiation in electric field mediated culture conditions. The electric field was applied perpendicular to carbon substrate electrode, while growing mouse neuroblastoma (N2a) cells in vitro. The placement of the second electrode outside of the cell culture medium allows the investigation of cell response to electric field without the concurrent complexities of submerged electrodes such as potentially toxic electrode reactions, electro-kinetic flows and charge transfer (electrical current) in the cell medium. The macroporous carbon electrodes are uniquely characterized by a higher specific charge storage capacity (0.2 mC/cm(2)) and low impedance (3.3 kΩ at 1 kHz). The optimal window of electric field stimulation for better cell viability and neurite outgrowth is established. When a uniform or a gradient electric field was applied perpendicular to the amorphous carbon substrate, it was found that the N2a cell viability and neurite length were higher at low electric field strengths (≤ 2.5 V/cm) compared to that measured without an applied field (0 V/cm). While the cell viability was assessed by two complementary biochemical assays (MTT and LDH), the differentiation was studied by indirect immunostaining. Overall, the results of the present study unambiguously establish the uniform/gradient vertical electric field based culture protocol to either enhance or to restrict neurite outgrowth respectively at lower or higher field strengths, when neuroblastoma cells are cultured on porous glassy carbon electrodes having a desired combination of electrochemical properties.

  6. Delafossite-CuAlO{sub 2} films prepared by annealing of amorphous Cu-Al-O films at high temperature under controlled atmosphere

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Hong-Ying, E-mail: hychen@cc.kuas.edu.tw; Tsai, Ming-Wei

    2011-07-01

    In this study, amorphous Cu-Al-O films were deposited onto a (100) p-type silicon substrate by a magnetron sputtering system. The films were then annealed at 700 deg. C and 800 deg. C for 2 h in N{sub 2}, air and O{sub 2}. X-ray diffraction patterns showed that the as-deposited films were amorphous. When the films were annealed at 700 deg. C, the monoclinic-CuO and spinel-CuAl{sub 2}O{sub 4} phases were detected in all atmospheres. As the annealing temperature increased to 800 deg. C, delafossite-CuAlO{sub 2} (R3-bar m and P6{sub 3}/mmc phases) appeared in N{sub 2} whereas monoclinic-CuO and spinel-CuAl{sub 2}O{sub 4} phases were detected in air and O{sub 2}. Thermodynamic calculations can explain the formation of delafossite-CuAlO{sub 2} films. The optical bandgap and conductivity of delafossite-CuAlO{sub 2} films were 3.30 eV and 6.8 x 10{sup -3} S/cm, respectively, which are compatible with other data in the literature. The p-type characteristic in delafossite-CuAlO{sub 2} films was verified by a hot-probe method.

  7. Charge storage characteristics and tunneling mechanism of amorphous Ge-doped HfO{sub x} films

    Energy Technology Data Exchange (ETDEWEB)

    Qiu, X.Y.; Zhang, S.Y.; Zhang, T.; Wang, R.X.; Li, L.T.; Zhang, Y. [Southwest University, School of Physical Science and Technology, Chongqing (China); Dai, J.Y. [The Hong Kong Polytechnic University, Department of Applied Physics, Hong Kong (China)

    2016-09-15

    Amorphous Ge-doped HfO{sub x} films have been deposited on p-Si(100) substrates by means of RF magnetron sputtering. Microstructural investigations reveal the partial oxidation of doped Ge atoms in the amorphous HfO{sub x} matrix and the existence of HfSiO{sub x} interfacial layer. Capacitance-voltage hysteresis of the Ag-/Ge-doped HfO{sub x}/Si/Ag memory capacitor exhibits a memory window of 3.15 V which can maintain for >5 x 10{sup 4} cycles. Current-voltage characteristics reveal that Poole-Frenkel tunneling is responsible for electron transport in the Ge-doped HfO{sub x} film. (orig.)

  8. Effect of acetylene flow rate on morphology and structure of carbon nanotube thick films grown by thermal chemical vapor deposition

    Institute of Scientific and Technical Information of China (English)

    CAO Zhangyi; SUN Zhuo; GUO Pingsheng; CHEN Yiwei

    2007-01-01

    Carbon nanotube (CNT) films were grown on nickel foil substrates by thermal chemical vapor deposition (CVD) with acetylene and hydrogen as the precursors. The morphology and structure of CNTs depending on the acetylene flow rate were characterized by a scanning electron microscope (SEM),a transmission electron microscope (TEM) and a Raman spectrometer,respectively.The effect of acetylene flow rate on the morphology and structure of CNT films was investigated.By increasing the acetylene flow rate from 10 to 90 sccm (standard cubic centimeter perminute),the yield and the diameter of CNTs increase.Also, the defects and amorphous phase in CNT films increase with increasing acetylene flow rate.

  9. Improved adhesion of photoresist to III-V substrates using PECVD carbon films

    Science.gov (United States)

    Mancini, David P.; Smith, Steven M.; Hooper, Andrew F.; Talin, A.; Chang, Daniel; Resnick, Douglas J.; Voight, Steven A.

    2002-07-01

    Amorphous PECVD carbon films have been investigated as a means to prepare III-V compound semiconductor substrates for improved photoresist adhesion. Results show that significant improvements in adhesive durability of patterned photoresist occurred for carbon primed GaAs and InGaAs wafers used in conjunction with both i-line and DUV lithography processes. These carbon layers, were 50-100 Angstrom in thickness, and varied in composition and morphology from a nitrogen-doped, diamond-like material (DLC), to a more hydrogen rich, polymer-like material (PLC). Adhesion durability tests performed in baths of ammonium hydroxide (NH4OH) and hydrochloric acid (HCl) in general showed superior performance compared to non-primed substrates. The sole exception was a failure of PLC priming on GaAs wafers used with a DUV anti-reflective coating. This same system, however, was shown to work extremely well when a DLC coating was substituted. Characterization of PLC and DLC films included use of AES, XPS, FTIR, AFM, and contact angle analysis. Results indicate that carbon films passivate III-V oxides, creating a stable, hydrophobic surface. This factor is proposed as a key reason for the improved resistance to aggressive aqueous environments. AFM results show that carbon films are extremely smooth and actually decrease surface roughness, indicating that mechanical adhesion is unlikely.

  10. Comparison of the electrical and optical properties of direct current and radio frequency sputtered amorphous indium gallium zinc oxide films

    Energy Technology Data Exchange (ETDEWEB)

    Yao, Jianke, E-mail: yaojk@pkusz.edu.cn [School of Computer and Information Engineering, Shenzhen Graduate School of Peking University, Shenzhen 518055 (China); Gong, Li [Instrumental Analysis and Research Center, Sun Yat-Sen University, Guangzhou 10275 (China); Xie, Lei [School of Computer and Information Engineering, Shenzhen Graduate School of Peking University, Shenzhen 518055 (China); Zhang, Shengdong, E-mail: zhangsd@pku.edu.cn [School of Computer and Information Engineering, Shenzhen Graduate School of Peking University, Shenzhen 518055 (China); Institute of Microelectronics, Peking University, Beijing 100871 (China)

    2013-01-01

    The electrical and optical properties of direct current and radio frequency (RF) sputtered amorphous indium gallium zinc oxide (a-IGZO) films are compared. It is found that the RF sputtered a-IGZO films have better stoichiometry (In:Ga:Zn:O = 1:1:1:2.5–3.0), lower electrical conductivity (σ < 8 S/cm), higher refractive index (n = 1.9–2.0) and larger band gap (E{sub g} = 3.02–3.29 eV), and show less shift of Fermi level (△ E{sub F} ∼ 0.26 eV) and increased concentration of electrons (△ N{sub e} ∼ 10{sup 4}) in the conduction band with the reduction concentration of oxygen vacancy (V{sub O}). Although a-IGZO has intensively been studied for a semiconductor channel material of thin film transistors in next-generation flat panel displays, its fundamental material parameters have not been thoroughly reported. In this work, the work function (φ) of a-IGZO films is tested with the ultraviolet photoelectron spectroscopy. It is found that the φ of a-IGZO films is in the range of 4.0–5.0 eV depending on the V{sub O}. - Highlights: ► Amorphous InGaZnO{sub 4} (a-IGZO) films were prepared with different sputtering modes. ► Electrical and optical properties of the different films were compared. ► Fermi level (△E{sub F}) shift in a-IGZO films were tested by X-ray photoelectron spectroscopy. ► The relation of △E{sub F} with the properties of a-IGZO films were discussed. ► Work function was tested by ultraviolet photoelectron spectroscopy.

  11. Amorphous Si layers co-doped with B and Mn: Thin film growth and steering of magnetic properties

    Energy Technology Data Exchange (ETDEWEB)

    Drera, G. [I-LAMP, Dipartimento di Matematica e Fisica, Università Cattolica del Sacro Cuore, Via dei Musei 41, 25121 Brescia (Italy); Mozzati, M.C. [CNISM, Dipartimento di Fisica, Università di Pavia, Via Bassi 6, 27100 Pavia (Italy); Colombi, P. [CSMT Gestione s.c.a.r.l, Via Branze 45, 25123 Brescia (Italy); Salvinelli, G.; Pagliara, S.; Visentin, D. [I-LAMP, Dipartimento di Matematica e Fisica, Università Cattolica del Sacro Cuore, Via dei Musei 41, 25121 Brescia (Italy); Sangaletti, L., E-mail: sangalet@dmf.unicatt.it [I-LAMP, Dipartimento di Matematica e Fisica, Università Cattolica del Sacro Cuore, Via dei Musei 41, 25121 Brescia (Italy)

    2015-09-01

    Amorphous silicon thin films co-doped with manganese (5% at.) and boron (1.8% at.) have been prepared by RF sputtering on Al{sub 2}O{sub 3} substrates held at room temperature (RT). The films, with an average thickness of about 0.9 μm, were carefully characterized by micro-Raman and X-ray photoemission spectroscopies. A ferromagnetic (FM) behavior up to RT was observed. In order to discuss and possibly rule out extrinsic effects usually related to segregations of ferromagnetic impurities in the samples, magnetization measurements were carried out on the Al{sub 2}O{sub 3} substrates, as well as on Si:B and Si:Mn films grown with the same RF sputtering system. Only the Si:B:Mn films displayed a FM behavior up to RT. Since amorphous films doped with Mn alone did not display any signature of FM ordering, boron co-doping results to be crucial for the onset of the FM behavior. The conductivity of the samples is not affected by boron doping that, therefore, does not appear to significantly contribute to a possible carrier-mediated FM interaction between Mn ions by supplying extra charges to the system. On this basis, the capability of B to hinder the quenching of the Mn 3d magnetic moments has also to be regarded as a possible role of this co-dopant in the observed magnetization. - Highlights: • We successfully deposited amorphous silicon thin films co-doped with Mn and B. • Structural, electronic, and magnetic properties have been carefully characterized. • A ferromagnetic behavior up to room temperature was detected. • The extrinsic origin of magnetism is excluded. • Boron can play a relevant role to avoid quenching of magnetic moment in Mn ions.

  12. Effect of metal doping on structural characteristics of amorphous carbon system: A first-principles study

    Energy Technology Data Exchange (ETDEWEB)

    Li, Xiaowei; Zhang, Dong [Key Laboratory of Marine Materials and Related Technologies, Key Laboratory of Marine Materials and Protective Technologies of Zhejiang Province, Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences, Ningbo 315201 (China); Lee, Kwang-Ryeol, E-mail: krlee@kist.re.kr [Computational Science Center, Korea Institute of Science and Technology, Seoul 136-791 (Korea, Republic of); Wang, Aiying, E-mail: aywang@nimte.ac.cn [Key Laboratory of Marine Materials and Related Technologies, Key Laboratory of Marine Materials and Protective Technologies of Zhejiang Province, Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences, Ningbo 315201 (China)

    2016-05-31

    First-principles calculation was performed to investigate the effect of metal doping on the structural characteristics of amorphous carbon system, and the 3d transition metals (TM) were particularly selected as representative case. Results showed that the total energy in TM–C systems caused by distorting the bond angles was reduced distinctly for comparison with that in C–C system. Further electronic structure revealed that as the 3d electrons of doped TM increased, the bond characteristic of highest occupied molecular orbital changed from bonding (Sc, Ti) to nonbonding (V, Cr, Mn, Fe) and finally to antibonding (Co, Ni, Cu) between the TM and C atoms. Meanwhile, the TM–C bond presented a mixture of the covalent and ionic characters. The decrease of strength and directionality of TM–C bonds resulted in the total energy change upon bond angle distortion, which demonstrated that the bond characteristics played an important role in reducing residual stress of TM-doped amorphous carbon systems. - Highlights: • The bond characteristics as 3d electrons changed from bonding, nonbonding to antibonding. • The TM–C bond was a mixture of covalent and ionic characters. • Reduced strength and directionality of TM–C bond led to small distortion energy change. • The weak TM–C bond accounted for the reduced compressive stress caused by TM.

  13. Superconducting transitions in amorphous molybdenum-germanium ultrathin films and multilayers

    Energy Technology Data Exchange (ETDEWEB)

    Missert, N.

    1989-01-01

    The primary goal of this work was to clarify the role of enhanced Coulomb interactions in the destruction of superconductivity in disordered systems of reduced dimensions. Through a systematic study of the critical temperatures in single film sandwich and multilayer structures, the author has examined the role of dimensionality in the reduction of {Tc} in disordered superconductors. The author has observed a continuous crossover from two to three dimensional behavior as electron diffusion between individual superconducting layers in the multilayer becomes possible. This demonstrates unambiguously that the reduction in {Tc} is an artistic 2D effect and is not simply due to interface or proximity effects, as has often been assumed in the past. Multilayers were fabricated by sequential cosputtering of alternate layers of superconducting and nonsuperconducting amorphous Mo-Ge alloys. The effects of screening at short length scales in these films are probed via a systematic variation of both the distance between superconducting layers and the conductivity of the nonsuperconducting layers in a multilayer structure. As the conductivity of the nonsuperconducting layer increases, electron diffusion becomes more three dimensional. However this increased conductivity also introduces a reduction in {Tc} due to the proximity effect. This has been accounted for by comparing the T, of the multilayers with a corresponding NISIN single layer sandwich structure, designed to have an identical proximity effect reduction of {Tc}, in addition to compensating for any effect of the SIN interface itself. X-ray diffraction measurements and cross-sectional TEM micrographs confirm that the layers are structurally well defined, uniform, and continuous.

  14. Microstructural and conductivity comparison of Ag films grown on amorphous TiO2 and polycrystalline ZnO

    Energy Technology Data Exchange (ETDEWEB)

    Dannenberg, Rand; Stach, Eric; Glenn, Darin; Sieck, Peter; Hukari, Kyle

    2001-03-26

    8 nm thick Ag films were sputter deposited onto amorphous TiO{sub 2} underlayers 25 nm thick, and also amorphous TiO{sub 2} (25 nm)/ZnO (5 nm) multiunderlayers. The substrates were back-etched Si with a 50 nm thick LPCVD Si{sub 3}N{sub 4} electron transparent membrane. The ZnO, sputtered onto amorphous TiO{sub 2}, formed a continuous layer with a grain size of 5 nm in diameter, on the order of the film thickness. There are several microstructural differences in the Ag dependent on the underlayers, revealed by TEM. First a strong {l_brace}0001{r_brace} ZnO to {l_brace}111{r_brace} Ag fibre-texture relationship exists. On TiO{sub 2} the Ag microstructure shows many abnormal grains whose average diameter is about 60-80 nm, whereas the films on ZnO show few abnormal grains. The background matrix of normal grains on the TiO{sub 2} is roughly 15 nm, while the normal grain size on the ZnO is about 25 nm. Electron diffraction patterns show that the film on ZnO has a strong {l_brace}111{r_brace} orientation, and dark field images with this diffraction condition have a grain size of about 30 nm. In a region near the center of the TEM grid where there is the greatest local heating during deposition, Ag films grown on amorphous TiO{sub 2} are discontinuous, whereas on ZnO, the film is continuous. When films 8 nm films are grown on solid glass substrates, those with ZnO underlayers have sheet resistances of 5.68 {Omega}/, whereas those on TiO{sub 2} are 7.56 {Omega}/, and when 16 nm thick, the corresponding sheet resistances are 2.7 {Omega}/ and 3.3 {Omega}/. The conductivity difference is very repeatable. The improved conductivity is thought to be a combined effect of reduced grain boundary area per unit volume, the predominance of low grain boundary resistivity Coincidence Site Lattice boundaries from the Ag {l_brace}111{r_brace} orientation, and Ag planarization on ZnO resulting in less groove formation on deposition, concluded from atomic force microscopy.

  15. Thermoelectric and electrical properties of micro-quantity Sn-doped amorphous indium-zinc oxide thin films

    Science.gov (United States)

    Byeon, Jayoung; Kim, Seohan; Lim, Jae-Hong; Song, Jae Yong; Park, Sun Hwa; Song, Pungkeun

    2017-01-01

    To realize high thermoelectric performance, it was tried to control both high electrical conductivity (σ) and low thermal conductivity (K) for the Sn-doped indium-zinc oxide films prepared by DC magnetron sputtering. The highest power factor was obtained post-annealed at 200 °C due to the highest σ. However, the highest figure of merit was obtained annealed at 500 °C. It could be attributed to both amorphous structure with low K by phonon and the highest Hall mobility. Thermoelectric and electrical properties of the film could be controlled by both heat treatment and Sn doping with high bond enthalpy.

  16. Amorphous Silicon Film Deposition from SiH4 by Chemical Vapor Deposition with Argon Excimer Lamp

    Science.gov (United States)

    Toshikawa, Kiyohiko; Yokotani, Atsushi; Kurosawa, Kou

    2005-11-01

    We have deposited amorphous silicon thin films from monosilane (SiH4) gas by photochemical vapor deposition using a vacuum ultraviolet excimer lamp (VUV-CVD). We used an argon excimer lamp (λ=126 nm, hν=9.8 eV) whose photons are strongly absorbed by SiH4 gas. The substrate temperatures were changed from 25 to 300°C. When the temperature was lower than 150°C, the films included H--Si--H units and H2 molecules in its structure. When it was higher than 150°C, the main structural unit was Si--H.

  17. Micrometer-Scale Photochromic Recording on Amorphous Diarylethene Film and Nondestructive Readout Using Near-Field IR Light

    Science.gov (United States)

    Takata, Atsushi; Saito, Masaaki; Yokojima, Satoshi; Murakami, Akinori; Nakamura, Shinichiro; Irie, Masahiro; Uchida, Kingo

    2006-09-01

    An amorphous photochromic recording film was prepared by spin coating a solution of a diarylethene derivative having bulky m-terphenyl groups. Near-field IR detection was carried out to read out the photochromic recording spots recorded by green laser irradiation on the film, and a spot with a diameter of approximately 5 μm was nondestructively read out by the technique. The spot size was smaller than the wavelengths used for the read out, indicating the advantage of using the near-field technique.

  18. Effect of hydrogen on dynamic charge transport in amorphous oxide thin film transistors

    Science.gov (United States)

    Kim, Taeho; Nam, Yunyong; Hur, Ji-Hyun; Park, Sang-Hee Ko; Jeon, Sanghun

    2016-08-01

    Hydrogen in zinc oxide based semiconductors functions as a donor or a defect de-activator depending on its concentration, greatly affecting the device characteristics of oxide thin-film transistors (TFTs). Thus, controlling the hydrogen concentration in oxide semiconductors is very important for achieving high mobility and minimizing device instability. In this study, we investigated the charge transport dynamics of the amorphous semiconductor InGaZnO at various hydrogen concentrations as a function of the deposition temperature of the gate insulator. To examine the nature of dynamic charge trapping, we employed short-pulse current-voltage and transient current-time measurements. Among various examined oxide devices, that with a high hydrogen concentration exhibits the best performance characteristics, such as high saturation mobility (10.9 cm2 v-1 s-1), low subthreshold slope (0.12 V/dec), and negligible hysteresis, which stem from low defect densities and negligible transient charge trapping. Our finding indicates that hydrogen atoms effectively passivate the defects in subgap states of the bulk semiconductor, minimizing the mobility degradation and threshold voltage instability. This study indicates that hydrogen plays a useful role in TFTs by improving the device performance and stability.

  19. High performance thin film transistors with cosputtered amorphous indium gallium zinc oxide channel

    Science.gov (United States)

    Jeong, Jae Kyeong; Jeong, Jong Han; Yang, Hui Won; Park, Jin-Seong; Mo, Yeon-Gon; Kim, Hye Dong

    2007-09-01

    The authors report the fabrication of high performance thin film transistors (TFTs) with an amorphous indium gallium zinc oxide (a-IGZO) channel, which was deposited by cosputtering using a dual IGZO and indium zinc oxide (IZO) target. The effect of the indium content on the device performance of the a-IGZO TFTs was investigated. At a relatively low IZO power of 400W, the field-effect mobility (μFE) and subthreshold gate swing (S) of the a-IGZO TFTs were dramatically improved to 19.3cm2/Vs and 0.35V/decade, respectively, compared to those (11.2cm2/Vs and 1.11V/decade) for the TFTs with the a-IGZO channel (reference sample) prepared using only the IGZO target. The enhancement in the subthreshold IDS-VGS characteristics at an IZO power of 400W compared to those of the reference sample was attributed to the reduction of the interface trap density rath