Epitaxial growth of fcc-CoxNi100-x thin films on MgO(110) single-crystal substrates

International Nuclear Information System (INIS)

Ohtake, Mitsuru; Nukaga, Yuri; Sato, Yoichi; Futamoto, Masaaki; Kirino, Fumiyoshi

2009-01-01

Co x Ni 100-x (x=100, 80, 20, 0 at. %) epitaxial thin films were prepared on MgO(110) single-crystal substrates heated at 300 deg. C by ultrahigh vacuum molecular beam epitaxy. The growth mechanism is discussed based on lattice strain and crystallographic defects. CoNi(110) single-crystal films with a fcc structure are obtained for all compositions. Co x Ni 100-x film growth follows the Volmer-Weber mode. X-ray diffraction analysis indicates that the out-of-plane and the in-plane lattice spacings of the Co x Ni 100-x films are in agreement within ±0.5% with the values of the respective bulk Co x Ni 100-x crystals, suggesting that the strain in the film is very small. High-resolution cross-sectional transmission microscopy shows that an atomically sharp boundary is formed between a Co(110) fcc film and a MgO(110) substrate, where periodical misfit dislocations are preferentially introduced in the film at the Co/MgO interface. The presence of such periodical misfit dislocations relieves the strain caused by the lattice mismatch between the film and the substrate.

Positron reemission: measurement of thin single crystal W(100) films to be used as transmission moderator or re-moderators

International Nuclear Information System (INIS)

Chen, D.M.; Lynn, K.G.; Pareja, R.; Nielsen, B.

1984-11-01

It has been shown that one can produce thin single crystal W films capable of reemitting positrons at a sufficiently high fraction to be used either as a moderator or as a re-moderator. Both the impurities and the defects could be removed by the appropriate cleaning and annealing procedures, and narrow beam emission could be attained when the films were cleaned. This technique would also be a good method for characterizing defect concentration at interfaces or in thin films

Effect of annealing ambient on anisotropic retraction of film edges during solid-state dewetting of thin single crystal films

Energy Technology Data Exchange (ETDEWEB)

Kim, Gye Hyun; Thompson, Carl V., E-mail: cthomp@mit.edu [Department of Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 01239 (United States); Ma, Wen [Department of Nuclear Science and Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 01239 (United States); Yildiz, Bilge [Department of Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 01239 (United States); Department of Nuclear Science and Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 01239 (United States)

2016-08-21

During solid-state dewetting of thin single crystal films, film edges retract at a rate that is strongly dependent on their crystallographic orientations. Edges with kinetically stable in-plane orientations remain straight as they retract, while those with other in-plane orientations develop in-plane facets as they retract. Kinetically stable edges have retraction rates that are lower than edges with other orientations and thus determine the shape of the natural holes that form during solid-state dewetting. In this paper, measurements of the retraction rates of kinetically stable edges for single crystal (110) and (100) Ni films on MgO are presented. Relative retraction rates of kinetically stable edges with different crystallographic orientations are observed to change under different annealing conditions, and this accordingly changes the initial shapes of growing holes. The surfaces of (110) and (100) films were also characterized using low energy electron diffraction, and different surface reconstructions were observed under different ambient conditions. The observed surface structures were found to correlate with the observed changes in the relative retraction rates of the kinetically stable edges.

Structural characterization of metastable hcp-Ni thin films epitaxially grown on Au(100) single-crystal underlayers

International Nuclear Information System (INIS)

Ohtake, Mitsuru; Tanaka, Takahiro; Futamoto, Masaaki; Kirino, Fumiyoshi

2010-01-01

Ni(1120) epitaxial thin films with hcp structure were prepared on Au(100) single-crystal underlayers at 100 deg. C by ultra high vacuum molecular beam epitaxy. The detailed film structure is studied by in situ reflection high energy electron diffraction, x-ray diffraction, and transmission electron microscopy. The hcp-Ni film consists of two types of variants whose c-axes are rotated around the film normal by 90 deg. each other. An atomically sharp boundary is recognized between the film and the underlayer, where misfit dislocations are introduced. Presence of such dislocations seems to relieve the strain caused by the lattice mismatch between the film and the underlayer.

Properties of laser-crystallized polycrystalline SiGe thin films

Energy Technology Data Exchange (ETDEWEB)

Weizman, Moshe

2008-06-06

In this thesis, structural, electrical, and optical properties of laser-crystallized polycrystalline Si{sub 1-x}Ge{sub x} thin films with 0crystallization of amorphous Si{sub 1-x}Ge{sub x} thin films with 0.3film, which is directly coupled to a periodic compositional variation. - Amorphous SiGe samples that are exposed to a single laser pulse exhibit a ripple structure that evolves into a hillock structure when the samples are irradiated with additional laser pulses. - It is maintained that the main mechanism behind the structure formation is an instability of the propagating solid-liquid interface during solidification. - The study of defects with electron spin resonance showed that laser-crystallized poly-Si{sub 1-x}Ge{sub x} thin films with 0crystallization method and Ge content. The defect density for solid-phase crystallized SiGe films was lower and amounted to N{sub s}=7 x 10{sup 17} cm{sup -3}. - Germanium-rich laser-crystallized poly-SiGe thin films exhibited mostly a broad atypical electric dipole spin resonance (EDSR) signal that was accompanied by a nearly temperature-independent electrical conductivity in the range 20-100 K. - Most likely, the origin of the grain boundary conductance is due to dangling-bond defects and not impurities. Metallic-like conductance occurs when the dangling-bond defect density is above a critical value of about N{sub C} {approx} 10{sup 18} cm{sup -3}. - Laser crystallized poly-Si{sub 1-x}Ge{sub x} thin films with x{>=}0.5 exhibit optical absorption behavior that is characteristic for disordered SiGe, implying that the absorption occurs primarily at the grain boundaries. A sub-band-gap absorption peak was found for

Manufacture of Bi-cuprate thin films on MgO single crystal substrates by chemical solution deposition

DEFF Research Database (Denmark)

Grivel, Jean-Claude; Bertelsen, Christian Vinther; Andersen, Niels Hessel

2014-01-01

Bi2Sr2CaCu2O8 thin films have been deposited on MgO single crystal substrates by spin-coating a solution based on 2-ethylhexanoate precursors dissolved in xylene. Pyrolysis takes place between 200°C and 450°C and is accompanied by the release of 2-ethylhexanoic acid, CO2 and H2O vapour. Highly c...

Liquid crystals for organic thin-film transistors

Science.gov (United States)

Iino, Hiroaki; Usui, Takayuki; Hanna, Jun-Ichi

2015-04-01

Crystalline thin films of organic semiconductors are a good candidate for field effect transistor (FET) materials in printed electronics. However, there are currently two main problems, which are associated with inhomogeneity and poor thermal durability of these films. Here we report that liquid crystalline materials exhibiting a highly ordered liquid crystal phase of smectic E (SmE) can solve both these problems. We design a SmE liquid crystalline material, 2-decyl-7-phenyl-[1]benzothieno[3,2-b][1]benzothiophene (Ph-BTBT-10), for FETs and synthesize it. This material provides uniform and molecularly flat polycrystalline thin films reproducibly when SmE precursor thin films are crystallized, and also exhibits high durability of films up to 200 °C. In addition, the mobility of FETs is dramatically enhanced by about one order of magnitude (over 10 cm2 V-1 s-1) after thermal annealing at 120 °C in bottom-gate-bottom-contact FETs. We anticipate the use of SmE liquid crystals in solution-processed FETs may help overcome upcoming difficulties with novel technologies for printed electronics.

High-Performance Flexible Thin-Film Transistors Based on Single-Crystal-like Silicon Epitaxially Grown on Metal Tape by Roll-to-Roll Continuous Deposition Process.

Science.gov (United States)

Gao, Ying; Asadirad, Mojtaba; Yao, Yao; Dutta, Pavel; Galstyan, Eduard; Shervin, Shahab; Lee, Keon-Hwa; Pouladi, Sara; Sun, Sicong; Li, Yongkuan; Rathi, Monika; Ryou, Jae-Hyun; Selvamanickam, Venkat

2016-11-02

Single-crystal-like silicon (Si) thin films on bendable and scalable substrates via direct deposition are a promising material platform for high-performance and cost-effective devices of flexible electronics. However, due to the thick and unintentionally highly doped semiconductor layer, the operation of transistors has been hampered. We report the first demonstration of high-performance flexible thin-film transistors (TFTs) using single-crystal-like Si thin films with a field-effect mobility of ∼200 cm 2 /V·s and saturation current, I/l W > 50 μA/μm, which are orders-of-magnitude higher than the device characteristics of conventional flexible TFTs. The Si thin films with a (001) plane grown on a metal tape by a "seed and epitaxy" technique show nearly single-crystalline properties characterized by X-ray diffraction, Raman spectroscopy, reflection high-energy electron diffraction, and transmission electron microscopy. The realization of flexible and high-performance Si TFTs can establish a new pathway for extended applications of flexible electronics such as amplification and digital circuits, more than currently dominant display switches.

Domains in Ferroic Crystals and Thin Films

CERN Document Server

Tagantsev, Alexander K; Fousek, Jan

2010-01-01

Domains in Ferroic Crystals and Thin Films presents experimental findings and theoretical understanding of ferroic (non-magnetic) domains developed during the past 60 years. It addresses the situation by looking specifically at bulk crystals and thin films, with a particular focus on recently-developed microelectronic applications and methods for observation of domains with techniques such as scanning force microscopy, polarized light microscopy, scanning optical microscopy, electron microscopy, and surface decorating techniques. Domains in Ferroic Crystals and Thin Films covers a large area of material properties and effects connected with static and dynamic properties of domains, which are extremely relevant to materials referred to as ferroics. In most solid state physics books, one large group of ferroics is customarily covered: those in which magnetic properties play a dominant role. Numerous books are specifically devoted to magnetic ferroics and cover a wide spectrum of magnetic domain phenomena. In co...

Crystallization kinetics of a-Se, part 4: thin films

Science.gov (United States)

Svoboda, Roman; Gutwirth, Jan; Málek, Jiří

2014-09-01

Differential scanning calorimetry was used to study the crystallization behaviour of selenium thin films in dependence on film thickness and deposition rate. In the current work, which is the fourth in a sequence of articles dealing with crystallization kinetics of a-Se, the non-isothermal crystallization kinetics was described in terms of the Johnson-Mehl-Avrami nucleation-growth model. Two-dimensional crystallite growth, consistent with the idea of sterically restricted crystallization in a thin layer, was confirmed for all data. It was found that neither the film thickness (tested within the 100-2350 nm range) nor the deposition rate appears to have any significant influence on the crystallization kinetics. However, the higher amount of intrinsic defects possibly produced by a higher deposition rate seems to accelerate the crystallization, shifting it towards lower temperatures. Very good correlation between the results obtained for thin films and those for fine powders was found. Based on the obtained results, interpretations of relevant literature data were made.

Solution coating of large-area organic semiconductor thin films with aligned single-crystalline domains

KAUST Repository

Diao, Ying

2013-06-02

Solution coating of organic semiconductors offers great potential for achieving low-cost manufacturing of large-area and flexible electronics. However, the rapid coating speed needed for industrial-scale production poses challenges to the control of thin-film morphology. Here, we report an approach - termed fluid-enhanced crystal engineering (FLUENCE) - that allows for a high degree of morphological control of solution-printed thin films. We designed a micropillar-patterned printing blade to induce recirculation in the ink for enhancing crystal growth, and engineered the curvature of the ink meniscus to control crystal nucleation. Using FLUENCE, we demonstrate the fast coating and patterning of millimetre-wide, centimetre-long, highly aligned single-crystalline organic semiconductor thin films. In particular, we fabricated thin films of 6,13-bis(triisopropylsilylethynyl) pentacene having non-equilibrium single-crystalline domains and an unprecedented average and maximum mobilities of 8.1±1.2 cm2 V-1 s -1 and 11 cm2 V-1 s-1. FLUENCE of organic semiconductors with non-equilibrium single-crystalline domains may find use in the fabrication of high-performance, large-area printed electronics. © 2013 Macmillan Publishers Limited. All rights reserved.

Single-crystal-like GdNdOx thin films on silicon substrates by magnetron sputtering and high-temperature annealing for crystal seed layer application

Directory of Open Access Journals (Sweden)

Ziwei Wang

2016-06-01

Full Text Available Single-crystal-like rare earth oxide thin films on silicon (Si substrates were fabricated by magnetron sputtering and high-temperature annealing processes. A 30-nm-thick high-quality GdNdOx (GNO film was deposited using a high-temperature sputtering process at 500°C. A Gd2O3 and Nd2O3 mixture was used as the sputtering target, in which the proportions of Gd2O3 and Nd2O3 were controlled to make the GNO’s lattice parameter match that of the Si substrate. To further improve the quality of the GNO film, a post-deposition annealing process was performed at a temperature of 1000°C. The GNO films exhibited a strong preferred orientation on the Si substrate. In addition, an Al/GNO/Si capacitor was fabricated to evaluate the dielectric constant and leakage current of the GNO films. It was determined that the single-crystal-like GNO films on the Si substrates have potential for use as an insulator layer for semiconductor-on-insulator and semiconductor/insulator multilayer applications.

Applications of thin-film sandwich crystallization platforms

Energy Technology Data Exchange (ETDEWEB)

Axford, Danny, E-mail: danny.axford@diamond.ac.uk; Aller, Pierre; Sanchez-Weatherby, Juan; Sandy, James [Diamond Light Source, Harwell Oxford, Didcot OX11 0DE (United Kingdom)

2016-03-24

Crystallization via sandwiches of thin polymer films is presented and discussed. Examples are shown of protein crystallization in, and data collection from, solutions sandwiched between thin polymer films using vapour-diffusion and batch methods. The crystallization platform is optimal for both visualization and in situ data collection, with the need for traditional harvesting being eliminated. In wells constructed from the thinnest plastic and with a minimum of aqueous liquid, flash-cooling to 100 K is possible without significant ice formation and without any degradation in crystal quality. The approach is simple; it utilizes low-cost consumables but yields high-quality data with minimal sample intervention and, with the very low levels of background X-ray scatter that are observed, is optimal for microcrystals.

Raman analysis of gold on WSe2 single crystal film

International Nuclear Information System (INIS)

Mukherjee, Bablu; Sun Leong, Wei; Li, Yida; Thong, John T L; Gong, Hao; Sun, Linfeng; Xiang Shen, Ze; Simsek, Ergun

2015-01-01

Synthesis and characterization of high-quality single-crystal tungsten diselenide (WSe 2 ) films on a highly insulating substrate is presented. We demonstrate for the first time that the presence of gold (Au) nanoparticles in the basal plane of a WSe 2 film can enhance its Raman scattering intensity. The experimentally observed enhancement ratio in the Raman signal correlates well with the simulated electric field intensity using both three-dimensional electromagnetic software and theoretical calculation considering layered medium coupled-dipole approximation (LM-CDA). This work serves as a guideline for the use of Au nanoparticles on WSe 2 single-crystal thin films for surface enhanced Raman scattering (SERS) applications in the future. (paper)

Surface structure determinations of crystalline ionic thin films grown on transition metal single crystal surfaces by low energy electron diffraction

Energy Technology Data Exchange (ETDEWEB)

Roberts, Joel Glenn [Univ. of California, Berkeley, CA (United States)

2000-05-01

The surface structures of NaCl(100), LiF(100) and alpha-MgCl2(0001) adsorbed on various metal single crystals have been determined by low energy electron diffraction (LEED). Thin films of these salts were grown on metal substrates by exposing the heated metal surface to a molecular flux of salt emitted from a Knudsen cell. This method of investigating thin films of insulators (ionic salts) on a conducting substrate (metal) circumvents surface charging problems that plagued bulk studies, thereby allowing the use of electron-based techniques to characterize the surface.

Microstructure of Co(112-bar 0) epitaxial thin films, grown on MgO(100) single-crystal substrates

Energy Technology Data Exchange (ETDEWEB)

Nukaga, Yuri; Ohtake, Mitsuru; Futamoto, Masaaki [Faculty of Science and Engineering, Chuo University, 1-13-27 Kasuga, Bunkyo-ku, Tokyo 112-8551 (Japan); Kirino, Fumiyoshi, E-mail: nukaga@futamoto.elect.chuo-u.ac.j [Graduate School of Fine Arts, Tokyo National University of Fine Arts and Music, 12-8 Ueno-koen, Taito-ku, Tokyo 110-8714 (Japan)

2010-01-01

Co(112-bar 0) epitaxial thin films with hcp structure were prepared on MgO(100) single-crystal substrates heated at 300 {sup 0}C by ultra high vacuum molecular beam epitaxy. The microstructure is investigated by employing X-ray diffraction and high-resolution transmission electron microscopy. The film consists of two types of domains whose c-axes are rotated around the film normal by 90{sup 0} each other. Stacking faults are observed for the film along the Co[0001] direction. An atomically sharp boundary is recognized between the film and the substrate, where some misfit dislocations are introduced in the film at the Co/MgO interface. Dislocations are also observed in the film up to 15 nm thickness from the interface. Presence of such stacking faults and misfit dislocations seem to relieve the strain caused by the lattice mismatch between the film and the substrate. X-ray diffraction analysis indicates that the out-of-plane and the in-plane lattice spacings of the film are in agreement within 0.5% and 0.1%, respectively, with those of the bulk hcp-Co crystal, suggesting the strain in the film is very small.

Microstructure of Co(112-bar 0) epitaxial thin films, grown on MgO(100) single-crystal substrates

International Nuclear Information System (INIS)

Nukaga, Yuri; Ohtake, Mitsuru; Futamoto, Masaaki; Kirino, Fumiyoshi

2010-01-01

Co(112-bar 0) epitaxial thin films with hcp structure were prepared on MgO(100) single-crystal substrates heated at 300 0 C by ultra high vacuum molecular beam epitaxy. The microstructure is investigated by employing X-ray diffraction and high-resolution transmission electron microscopy. The film consists of two types of domains whose c-axes are rotated around the film normal by 90 0 each other. Stacking faults are observed for the film along the Co[0001] direction. An atomically sharp boundary is recognized between the film and the substrate, where some misfit dislocations are introduced in the film at the Co/MgO interface. Dislocations are also observed in the film up to 15 nm thickness from the interface. Presence of such stacking faults and misfit dislocations seem to relieve the strain caused by the lattice mismatch between the film and the substrate. X-ray diffraction analysis indicates that the out-of-plane and the in-plane lattice spacings of the film are in agreement within 0.5% and 0.1%, respectively, with those of the bulk hcp-Co crystal, suggesting the strain in the film is very small.

Comparative study of broadband electrodynamic properties of single-crystal and thin-film strontium titanate

International Nuclear Information System (INIS)

Findikoglu, A. T.; Jia, Q. X.; Kwon, C.; Reagor, D. W.; Kaduchak, G.; Rasmussen, K. Oe.; Bishop, A. R.

1999-01-01

We have used a coplanar waveguide structure to study broadband electrodynamic properties of single-crystal and thin-film strontium titanate. We have incorporated both time- and frequency-domain measurements to determine small-signal effective refractive index and loss tangent as functions of frequency (up to 4 GHz), dc bias (up to 10 6 V/m), and cryogenic temperature (17 and 60 K). The large-signal impulse response of the devices and the associated phenomenological nonlinear wave equation illustrate how dissipation and nonlinearity combine to produce the overall response in the large-signal regime. (c) 1999 American Institute of Physics

Stepwise crystallization and the layered distribution in crystallization kinetics of ultra-thin poly(ethylene terephthalate) film

Energy Technology Data Exchange (ETDEWEB)

Zuo, Biao, E-mail: chemizuo@zstu.edu.cn, E-mail: wxinping@yahoo.com; Xu, Jianquan; Sun, Shuzheng; Liu, Yue; Yang, Juping; Zhang, Li; Wang, Xinping, E-mail: chemizuo@zstu.edu.cn, E-mail: wxinping@yahoo.com [Department of Chemistry, Key Laboratory of Advanced Textile Materials and Manufacturing Technology of the Education Ministry, Zhejiang Sci-Tech University, Hangzhou 310018 (China)

2016-06-21

Crystallization is an important property of polymeric materials. In conventional viewpoint, the transformation of disordered chains into crystals is usually a spatially homogeneous process (i.e., it occurs simultaneously throughout the sample), that is, the crystallization rate at each local position within the sample is almost the same. Here, we show that crystallization of ultra-thin poly(ethylene terephthalate) (PET) films can occur in the heterogeneous way, exhibiting a stepwise crystallization process. We found that the layered distribution of glass transition dynamics of thin film modifies the corresponding crystallization behavior, giving rise to the layered distribution of the crystallization kinetics of PET films, with an 11-nm-thick surface layer having faster crystallization rate and the underlying layer showing bulk-like behavior. The layered distribution in crystallization kinetics results in a particular stepwise crystallization behavior during heating the sample, with the two cold-crystallization temperatures separated by up to 20 K. Meanwhile, interfacial interaction is crucial for the occurrence of the heterogeneous crystallization, as the thin film crystallizes simultaneously if the interfacial interaction is relatively strong. We anticipate that this mechanism of stepwise crystallization of thin polymeric films will allow new insight into the chain organization in confined environments and permit independent manipulation of localized properties of nanomaterials.

Crystallization kinetics of amorphous aluminum-tungsten thin films

Energy Technology Data Exchange (ETDEWEB)

Car, T.; Radic, N. [Rugjer Boskovic Inst., Zagreb (Croatia). Div. of Mater. Sci.; Ivkov, J. [Institute of Physics, Bijenicka 46, P.O.B. 304, HR-10000 Zagreb (Croatia); Babic, E.; Tonejc, A. [Faculty of Sciences, Physics Department, Bijenicka 32, P.O.B. 162, HR-10000 Zagreb (Croatia)

1999-01-01

Crystallization kinetics of the amorphous Al-W thin films under non-isothermal conditions was examined by continuous in situ electrical resistance measurements in vacuum. The estimated crystallization temperature of amorphous films in the composition series of the Al{sub 82}W{sub 18} to Al{sub 62}W{sub 38} compounds ranged from 800 K to 920 K. The activation energy for the crystallization and the Avrami exponent were determined. The results indicated that the crystallization mechanism in films with higher tungsten content was a diffusion-controlled process, whereas in films with the composition similar to the stoichiometric compound (Al{sub 4}W), the interface-controlled crystallization probably occurred. (orig.) With 4 figs., 1 tab., 26 refs.

Progress in thin-film silicon solar cells based on photonic-crystal structures

Science.gov (United States)

Ishizaki, Kenji; De Zoysa, Menaka; Tanaka, Yoshinori; Jeon, Seung-Woo; Noda, Susumu

2018-06-01

We review the recent progress in thin-film silicon solar cells with photonic crystals, where absorption enhancement is achieved by using large-area resonant effects in photonic crystals. First, a definitive guideline for enhancing light absorption in a wide wavelength range (600–1100 nm) is introduced, showing that the formation of multiple band edges utilizing higher-order modes confined in the thickness direction and the introduction of photonic superlattice structures enable significant absorption enhancement, exceeding that observed for conventional random scatterers. Subsequently, experimental evidence of this enhancement is demonstrated for a variety of thin-film Si solar cells: ∼500-nm-thick ultrathin microcrystalline silicon cells, few-µm-thick microcrystalline silicon cells, and ∼20-µm-thick thin single-crystalline silicon cells. The high short-circuit current densities and/or efficiencies observed for each cell structure confirm the effectiveness of using multiple band-edge resonant modes of photonic crystals for enhancing broadband absorption in actual solar cells.

Picosecond laser pulse-driven crystallization behavior of SiSb phase change memory thin films

International Nuclear Information System (INIS)

Huang Huan; Li Simian; Zhai Fengxiao; Wang Yang; Lai Tianshu; Wu Yiqun; Gan Fuxi

2011-01-01

Highlights: → We reported crystallization dynamics of a novel SiSb phase change material. → We measured optical constants of as-deposited and irradiated SiSb areas. → Optical properties of as-deposited and irradiated SiSb thin film were compared. → Crystallization of irradiated SiSb was confirmed by using AFM and micro-Raman spectra. → The heat conduction effect of lower metal layer of multi-layer films was studied. - Abstract: Transient phase change crystallization process of SiSb phase change thin films under the irradiation of picosecond (ps) laser pulse was studied using time-resolved reflectivity measurements. The ps laser pulse-crystallized domains were characterized by atomic force microscope, Raman spectra and ellipsometrical spectra measurements. A reflectivity contrast of about 15% can be achieved by ps laser pulse-induced crystallization. A minimum crystallization time of 11 ns was achieved by a low-fluence single ps laser pulse after pre-irradiation. SiSb was shown to be very promising for fast phase change memory applications.

Thin Single Crystal Silicon Solar Cells on Ceramic Substrates: November 2009 - November 2010

Energy Technology Data Exchange (ETDEWEB)

Kumar, A.; Ravi, K. V.

2011-06-01

In this program we have been developing a technology for fabricating thin (< 50 micrometres) single crystal silicon wafers on foreign substrates. We reverse the conventional approach of depositing or forming silicon on foreign substrates by depositing or forming thick (200 to 400 micrometres) ceramic materials on high quality single crystal silicon films ~ 50 micrometres thick. Our key innovation is the fabrication of thin, refractory, and self-adhering 'handling layers or substrates' on thin epitaxial silicon films in-situ, from powder precursors obtained from low cost raw materials. This 'handling layer' has sufficient strength for device and module processing and fabrication. Successful production of full sized (125 mm X 125 mm) silicon on ceramic wafers with 50 micrometre thick single crystal silicon has been achieved and device process flow developed for solar cell fabrication. Impurity transfer from the ceramic to the silicon during the elevated temperature consolidation process has resulted in very low minority carrier lifetimes and resulting low cell efficiencies. Detailed analysis of minority carrier lifetime, metals analysis and device characterization have been done. A full sized solar cell efficiency of 8% has been demonstrated.

Mechanical design of thin-film diamond crystal mounting apparatus with optimized thermal contact and crystal strain for coherence preservation x-ray optics

Science.gov (United States)

Shu, Deming; Shvydko, Yury; Stoupin, Stanislav; Kim, Kwang-Je

2018-05-08

A method and mechanical design for a thin-film diamond crystal mounting apparatus for coherence preservation x-ray optics with optimized thermal contact and minimized crystal strain are provided. The novel thin-film diamond crystal mounting apparatus mounts a thin-film diamond crystal supported by a thick chemical vapor deposition (CVD) diamond film spacer with a thickness slightly thicker than the thin-film diamond crystal, and two groups of thin film thermal conductors, such as thin CVD diamond film thermal conductor groups separated by the thick CVD diamond spacer. The two groups of thin CVD film thermal conductors provide thermal conducting interface media with the thin-film diamond crystal. A piezoelectric actuator is integrated into a flexural clamping mechanism generating clamping force from zero to an optimal level.

Atomic Structure Control of Silica Thin Films on Pt(111)

KAUST Repository

Crampton, Andrew S; Ridge, Claron J.; Rö tzer, Marian David; Zwaschka, Gregor; Braun, Thomas; D'Elia, Valerio; Basset, Jean-Marie; Schweinberger, Florian Frank; Gü nther, Sebastian; Heiz, Ueli

2015-01-01

Metal oxide thin films grown on metal single crystals are commonly used to model heterogeneous catalyst supports. The structure and properties of thin silicon dioxide films grown on metal single crystals have only recently been thoroughly

Single-crystal-like GdNdO{sub x} thin films on silicon substrates by magnetron sputtering and high-temperature annealing for crystal seed layer application

Energy Technology Data Exchange (ETDEWEB)

Wang, Ziwei; Xiao, Lei; Liang, Renrong, E-mail: wang-j@tsinghua.edu.cn, E-mail: liangrr@tsinghua.edu.cn; Shen, Shanshan; Xu, Jun; Wang, Jing, E-mail: wang-j@tsinghua.edu.cn, E-mail: liangrr@tsinghua.edu.cn [Tsinghua National Laboratory for Information Science and Technology, Institute of Microelectronics, Tsinghua University, Beijing 100084 (China)

2016-06-15

Single-crystal-like rare earth oxide thin films on silicon (Si) substrates were fabricated by magnetron sputtering and high-temperature annealing processes. A 30-nm-thick high-quality GdNdO{sub x} (GNO) film was deposited using a high-temperature sputtering process at 500°C. A Gd{sub 2}O{sub 3} and Nd{sub 2}O{sub 3} mixture was used as the sputtering target, in which the proportions of Gd{sub 2}O{sub 3} and Nd{sub 2}O{sub 3} were controlled to make the GNO’s lattice parameter match that of the Si substrate. To further improve the quality of the GNO film, a post-deposition annealing process was performed at a temperature of 1000°C. The GNO films exhibited a strong preferred orientation on the Si substrate. In addition, an Al/GNO/Si capacitor was fabricated to evaluate the dielectric constant and leakage current of the GNO films. It was determined that the single-crystal-like GNO films on the Si substrates have potential for use as an insulator layer for semiconductor-on-insulator and semiconductor/insulator multilayer applications.

Grain Boundaries Act as Solid Walls for Charge Carrier Diffusion in Large Crystal MAPI Thin Films.

Science.gov (United States)

Ciesielski, Richard; Schäfer, Frank; Hartmann, Nicolai F; Giesbrecht, Nadja; Bein, Thomas; Docampo, Pablo; Hartschuh, Achim

2018-03-07

Micro- and nanocrystalline methylammonium lead iodide (MAPI)-based thin-film solar cells today reach power conversion efficiencies of over 20%. We investigate the impact of grain boundaries on charge carrier transport in large crystal MAPI thin films using time-resolved photoluminescence (PL) microscopy and numerical model calculations. Crystal sizes in the range of several tens of micrometers allow for the spatially and time resolved study of boundary effects. Whereas long-ranged diffusive charge carrier transport is observed within single crystals, no detectable diffusive transport occurs across grain boundaries. The observed PL transients are found to crucially depend on the microscopic geometry of the crystal and the point of observation. In particular, spatially restricted diffusion of charge carriers leads to slower PL decay near crystal edges as compared to the crystal center. In contrast to many reports in the literature, our experimental results show no quenching or additional loss channels due to grain boundaries for the studied material, which thus do not negatively affect the performance of the derived thin-film devices.

Solid thin film materials for use in thin film charge-coupled devices

International Nuclear Information System (INIS)

Lynch, S.J.

1983-01-01

Solid thin films deposited by vacuum deposition were evaluated to ascertain their effectiveness for use in the manufacturing of charge-coupled devices (CCDs). Optical and electrical characteristics of tellurium and Bi 2 Te 3 solid thin films were obtained in order to design and to simulate successfully the operation of thin film (TF) CCDs. In this article some of the material differences between single-crystal material and the island-structured thin film used in TFCCDs are discussed. The electrical parameters were obtained and tabulated, e.g. the mobility, conductivity, dielectric constants, permittivity, lifetime of holes and electrons in the thin films and drift diffusion constants. The optical parameters were also measured and analyzed. After the design was complete, experimental TFCCDs were manufactured and were successfully operated utilizing the aforementioned solid thin films. (Auth.)

Photoinduced Optical Spectroscopy of La2CuO4+x Single Crystals and C60 Thin Films

International Nuclear Information System (INIS)

Bazhenov, A.V.; Gorbunov, A.V.; Timofeev, V.B.

1995-01-01

The evolution of both vibration and electronic spectra of insulating La 2 CuO 4+x single crystals upon charge-transfer gap photoexcitation has been studied by means of photoinduced reflection spectroscopy. Interaction of self-localized hole with some of the A g , B 2g (B 3g ), B 3u optical phonons has been observed. Formation of self-localized hole state and its multiparticle complexes is supposed. Photoinduced absorption in C 60 thin films has been found to differ essentially from that in cuprates

Preparation of metastable bcc permalloy epitaxial thin films on GaAs(011)B3 single-crystal substrates

International Nuclear Information System (INIS)

Ohtake, Mitsuru; Higuchi, Jumpei; Yabuhara, Osamu; Kirino, Fumiyoshi; Futamoto, Masaaki

2011-01-01

Permalloy (Py) single-crystal films with bcc structure were obtained on GaAs(011) B3 single-crystal substrates by ultra high vacuum rf magnetron sputtering. The film growth and the detailed film structures were investigated by refection high energy electron diffraction and pole figure X-ray diffraction. bcc-Py films epitaxially grow on the substrates in the orientation relationship of Py(011)[011-bar] bcc || GaAs(011)[011-bar] B3 . The lattice constant of bcc-Py film is determined to be a = 0.291 nm. With increasing the film thickness, parts of the bcc crystal transform into more stable fcc structure by atomic displacement parallel to the bcc{011} close-packed planes. The resulting film thus consists of a mixture of bcc and fcc crystals. The phase transformation mechanism is discussed based on the experimental results. The in-plane magnetization properties reflecting the magnetocrystalline anisotropy of bcc-Py crystal are observed for the Py films grown on GaAs(011) B3 substrates.

Crystal structures of sol-gel deposited zirconia thin films

International Nuclear Information System (INIS)

Bell, J.M.; Cheary, R.W.; Rice, M.; Ben-Nissan, B.; Cocking, J.L.; Johnstone, G.R.

1992-01-01

The authors reports on the crystal structure of zirconia thin films by high temperature x-ray diffraction. The films were deposited by sol-gel processing onto polished stainless steel substrates, and dried at 200 deg C. X-ray diffraction at temperatures between 400 deg C and 800 deg C was carried out using an APEX diffractometer with a position sensitive detector. Previous results indicated that there was a transformation between the tetragonal phase and the monoclinic phase at approximately 770 deg C. Two experiments have been carried out: temperature runs, where the structure evolution is studied as a function of temperature; and time evolution of the structure at fixed temperatures. The results for both experiments, including structural analysis of the different phases found in the thin zirconia films and an analysis of the kinetics of the phase transformation(s) from the time evolution work are presented. This will include a comparison with theories of nucleation and crystallisation in single element films. Impurity phases introduced by interaction of the zirconia with the substrate have been observed, and the effect of increasing annealing time on the substrate-film interaction will also be discussed. 17 refs., 1 tab., 3 figs

Thin films of metal oxides on metal single crystals: Structure and growth by scanning tunneling microscopy

International Nuclear Information System (INIS)

Galloway, H.C.

1995-12-01

Detailed studies of the growth and structure of thin films of metal oxides grown on metal single crystal surfaces using Scanning Tunneling Microscopy (STM) are presented. The oxide overlayer systems studied are iron oxide and titanium oxide on the Pt(III) surface. The complexity of the metal oxides and large lattice mismatches often lead to surface structures with large unit cells. These are particularly suited to a local real space technique such as scanning tunneling microscopy. In particular, the symmetry that is directly observed with the STM elucidates the relationship of the oxide overlayers to the substrate as well as distinguishing, the structures of different oxides

Thin film polarizer and color filter based on photo-polymerizable nematic liquid crystal

Science.gov (United States)

Mohammadimasoudi, Mohammad; Neyts, Kristiaan; Beeckman, Jeroen

2015-03-01

We present a method to fabricate a thin film color filter based on a mixture of photo-polymerizable liquid crystal and chiral dopant. A chiral nematic liquid crystal layer reflects light for a certain wavelength interval Δλ (= Δn.P) with the period and Δn the birefringence of the liquid crystal. The reflection band is determined by the chiral dopant concentration. The bandwidth is limited to 80nm and the reflectance is at most 50% for unpolarized incident light. The thin color filter is interesting for innovative applications like polarizer-free reflective displays, polarization-independent devices, stealth technologies, or smart switchable reflective windows to control solar light and heat. The reflected light has strong color saturation without absorption because of the sharp band edges. A thin film polarizer is developed by using a mixture of photo-polymerizable liquid crystal and color-neutral dye. The fabricated thin film absorbs light that is polarized parallel to the c axis of the LC. The obtained polarization ratio is 80% for a film of only 12 μm. The thin film polarizer and the color filter feature excellent film characteristics without domains and can be detached from the substrate which is useful for e.g. flexible substrates.

Preparation and structural characterization of FeCo epitaxial thin films on insulating single-crystal substrates

International Nuclear Information System (INIS)

Nishiyama, Tsutomu; Ohtake, Mitsuru; Futamoto, Masaaki; Kirino, Fumiyoshi

2010-01-01

FeCo epitaxial films were prepared on MgO(111), SrTiO 3 (111), and Al 2 O 3 (0001) single-crystal substrates by ultrahigh vacuum molecular beam epitaxy. The effects of insulating substrate material on the film growth process and the structures were investigated. FeCo(110) bcc films grow on MgO substrates with two type domains, Nishiyama-Wassermann (NW) and Kurdjumov-Sachs (KS) relationships. On the contrary, FeCo films grown on SrTiO 3 and Al 2 O 3 substrates include FeCo(111) bcc crystal in addition to the FeCo(110) bcc crystals with NW and KS relationships. The FeCo(111) bcc crystal consists of two type domains whose orientations are rotated around the film normal by 180 deg. each other. The out-of-plane and the in-plane lattice spacings of FeCo(110) bcc and FeCo(111) bcc crystals formed on the insulating substrates are in agreement with those of the bulk Fe 50 Co 50 (at. %) crystal with small errors ranging between +0.2% and +0.4%, showing that the strains in the epitaxial films are very small.

Epitaxial growth of bcc-FexCo100-x thin films on MgO(1 1 0) single-crystal substrates

International Nuclear Information System (INIS)

Ohtake, Mitsuru; Nishiyama, Tsutomu; Shikada, Kouhei; Kirino, Fumiyoshi; Futamoto, Masaaki

2010-01-01

Fe x Co 100-x (x=100, 65, 50 at%) epitaxial thin films were prepared on MgO(1 1 0) single-crystal substrates heated at 300 deg. C by ultra-high vacuum molecular beam epitaxy. The film structure and the growth mechanism are discussed. FeCo(2 1 1) films with bcc structure grow epitaxially on MgO(1 1 0) substrates with two types of variants whose orientations are rotated around the film normal by 180 deg. each other for all compositions. Fe x Co 100-x film growth follows the Volmer Weber mode. X-ray diffraction analysis indicates the out-of-plane and the in-plane lattice spacings are in agreement with the values of respective bulk Fe x Co 100-x crystals with very small errors less than ±0.4%, suggesting the strains in the films are very small. High-resolution cross-sectional transmission electron microscopy shows that periodical misfit dislocations are preferentially introduced in the film at the Fe 50 Co 50 /MgO interface along the MgO[1 1-bar 0] direction. The presence of such periodical dislocations decreases the large lattice mismatch of about -17% existing at the FeCo/MgO interface along the MgO[1 1-bar 0] direction.

Preparation of metastable bcc permalloy epitaxial thin films on GaAs(011){sub B3} single-crystal substrates

Energy Technology Data Exchange (ETDEWEB)

Ohtake, Mitsuru, E-mail: ohtake@futamoto.elect.chuo-u.ac.jp [Faculty of Science and Engineering, Chuo University, 1-13-27 Kasuga, Bunkyo-ku, Tokyo 112-8551 (Japan); Higuchi, Jumpei; Yabuhara, Osamu [Faculty of Science and Engineering, Chuo University, 1-13-27 Kasuga, Bunkyo-ku, Tokyo 112-8551 (Japan); Kirino, Fumiyoshi [Graduate School of Fine Arts, Tokyo National University of Fine Arts and Music, 12-8 Ueno-koen, Taito-ku, Tokyo 110-8714 (Japan); Futamoto, Masaaki [Faculty of Science and Engineering, Chuo University, 1-13-27 Kasuga, Bunkyo-ku, Tokyo 112-8551 (Japan)

2011-09-30

Permalloy (Py) single-crystal films with bcc structure were obtained on GaAs(011){sub B3} single-crystal substrates by ultra high vacuum rf magnetron sputtering. The film growth and the detailed film structures were investigated by refection high energy electron diffraction and pole figure X-ray diffraction. bcc-Py films epitaxially grow on the substrates in the orientation relationship of Py(011)[011-bar]{sub bcc} || GaAs(011)[011-bar]{sub B3}. The lattice constant of bcc-Py film is determined to be a = 0.291 nm. With increasing the film thickness, parts of the bcc crystal transform into more stable fcc structure by atomic displacement parallel to the bcc{l_brace}011{r_brace} close-packed planes. The resulting film thus consists of a mixture of bcc and fcc crystals. The phase transformation mechanism is discussed based on the experimental results. The in-plane magnetization properties reflecting the magnetocrystalline anisotropy of bcc-Py crystal are observed for the Py films grown on GaAs(011){sub B3} substrates.

Thin-film photovoltaic technology

Energy Technology Data Exchange (ETDEWEB)

Bhattacharya, R.N. [National Renewable Energy Laboratory, Golden, CO (United States)

2010-07-01

The high material and processing costs associated with single-crystal and polycrystalline silicon wafers that are commonly used in photovoltaic cells render these modules expensive. This presentation described thin-film solar cell technology as a promising alternative to silicon solar cell technology. Cadmium telluride (CdTe) thin films along with copper, indium, gallium, and selenium (CIGS) thin films have become the leaders in this field. Their large optical absorption coefficient can be attributed to a direct energy gap that allows the use of thin layers (1-2 {mu}m) of active material. The efficiency of thin-film solar cell devices based on CIGS is 20 per cent, compared to 16.7 per cent for thin-film solar cell devices based on CdTe. IBM recently reported an efficiency of 9.7 per cent for a new type of inorganic thin-film solar cell based on a Cu{sub 2}ZnSn(S, Se){sub 4} compound. The efficiency of an organic thin-film solar cell is 7.9 per cent. This presentation included a graph of PV device efficiencies and discussed technological advances in non-vacuum deposited, CIGS-based thin-film solar cells. 1 fig.

Solution Coating of Superior Large-Area Flexible Perovskite Thin Films with Controlled Crystal Packing

KAUST Repository

Li, Jianbo

2017-05-08

Solution coating of organohalide lead perovskites offers great potential for achieving low-cost manufacturing of large-area flexible optoelectronics. However, the rapid coating speed needed for industrial-scale production poses challenges to the control of crystal packing. Herein, this study reports using solution shearing to confine crystal nucleation and growth in large-area printed MAPbI3 thin films. Near single-crystalline perovskite microarrays are demonstrated with a high degree of controlled macroscopic alignment and crystal orientation, which exhibit significant improvements in optical and optoelectronic properties comparing with their random counterparts, spherulitic, and nanograined films. In particular, photodetectors based on the confined films showing intense anisotropy in charge transport are fabricated, and the device exhibits significantly improved performance in all aspects by one more orders of magnitude relative to their random counterparts. It is anticipated that perovskite films with controlled crystal packing may find applications in high-performance, large-area printed optoelectronics, and solar cells.

Solution Coating of Superior Large-Area Flexible Perovskite Thin Films with Controlled Crystal Packing

KAUST Repository

Li, Jianbo; Liu, Yucheng; Ren, Xiaodong; Yang, Zhou; Li, Ruipeng; Su, Hang; Yang, Xiaoming; Xu, Junzhuo; Xu, Hua; Hu, Jian-Yong; Amassian, Aram; Zhao, Kui; Liu, Shengzhong Frank

2017-01-01

Solution coating of organohalide lead perovskites offers great potential for achieving low-cost manufacturing of large-area flexible optoelectronics. However, the rapid coating speed needed for industrial-scale production poses challenges to the control of crystal packing. Herein, this study reports using solution shearing to confine crystal nucleation and growth in large-area printed MAPbI3 thin films. Near single-crystalline perovskite microarrays are demonstrated with a high degree of controlled macroscopic alignment and crystal orientation, which exhibit significant improvements in optical and optoelectronic properties comparing with their random counterparts, spherulitic, and nanograined films. In particular, photodetectors based on the confined films showing intense anisotropy in charge transport are fabricated, and the device exhibits significantly improved performance in all aspects by one more orders of magnitude relative to their random counterparts. It is anticipated that perovskite films with controlled crystal packing may find applications in high-performance, large-area printed optoelectronics, and solar cells.

Preparation of hcp-Ni(112-bar 0) epitaxial thin films on Au(100) single-crystal underlayers

International Nuclear Information System (INIS)

Ohtake, Mitsuru; Tanaka, Takahiro; Futamoto, Masaaki; Kirino, Fumiyoshi

2010-01-01

Ni epitaxial films with an hcp structure are successfully obtained on Au(100) single-crystal underlayers formed on MgO(100) substrates at temperatures lower than 300 0 C by molecular beam epitaxy. With increasing the substrate temperature, the volume ratio of more stable fcc phase inc r eases in the film. The Ni film prepared at 100 0 C consists primarily of hcp crystal with the (112-bar 0) plane parallel to the substrate surface coexisting with a small amount of fcc-Ni(100) crystal. The lattice constant of hcp-Ni crystal is determined as a = 0.249 nm, c = 0.398 nm, and c/a = 1.60.

van der Waals epitaxy of SnS film on single crystal graphene buffer layer on amorphous SiO2/Si

Science.gov (United States)

Xiang, Yu; Yang, Yunbo; Guo, Fawen; Sun, Xin; Lu, Zonghuan; Mohanty, Dibyajyoti; Bhat, Ishwara; Washington, Morris; Lu, Toh-Ming; Wang, Gwo-Ching

2018-03-01

Conventional hetero-epitaxial films are typically grown on lattice and symmetry matched single crystal substrates. We demonstrated the epitaxial growth of orthorhombic SnS film (∼500 nm thick) on single crystal, monolayer graphene that was transferred on the amorphous SiO2/Si substrate. Using X-ray pole figure analysis we examined the structure, quality and epitaxy relationship of the SnS film grown on the single crystal graphene and compared it with the SnS film grown on commercial polycrystalline graphene. We showed that the SnS films grown on both single crystal and polycrystalline graphene have two sets of orientation domains. However, the crystallinity and grain size of the SnS film improve when grown on the single crystal graphene. Reflection high-energy electron diffraction measurements show that the near surface texture has more phases as compared with that of the entire film. The surface texture of a film will influence the growth and quality of film grown on top of it as well as the interface formed. Our result offers an alternative approach to grow a hetero-epitaxial film on an amorphous substrate through a single crystal graphene buffer layer. This strategy of growing high quality epitaxial thin film has potential applications in optoelectronics.

Stress-Induced Crystallization of Ge-Doped Sb Phase-Change Thin Films

NARCIS (Netherlands)

Eising, Gert; Pauza, Andrew; Kooi, Bart J.

The large effects of moderate stresses on the crystal growth rate in Ge-doped Sb phase-change thin films are demonstrated using direct optical imaging. For Ge6Sb94 and Ge7Sb93 phase-change films, a large increase in crystallization temperature is found when using a polycarbonate substrate instead of

Preparation of hcp-Ni(112-bar 0) epitaxial thin films on Au(100) single-crystal underlayers

Energy Technology Data Exchange (ETDEWEB)

Ohtake, Mitsuru; Tanaka, Takahiro; Futamoto, Masaaki [Faculty of Science and Engineering, Chuo University, 1-13-27 Kasuga, Bunkyo-ku, Tokyo 112-8551 (Japan); Kirino, Fumiyoshi, E-mail: ohtake@futamoto.elect.chuo-u.ac.j [Graduate School of Fine Arts, Tokyo National University of Fine Arts and Music, 12-8 Ueno-koen, Taito-ku, Tokyo 110-8714 (Japan)

2010-01-01

Ni epitaxial films with an hcp structure are successfully obtained on Au(100) single-crystal underlayers formed on MgO(100) substrates at temperatures lower than 300 {sup 0}C by molecular beam epitaxy. With increasing the substrate temperature, the volume ratio of more stable fcc phase inc{sub r}eases in the film. The Ni film prepared at 100 {sup 0}C consists primarily of hcp crystal with the (112-bar 0) plane parallel to the substrate surface coexisting with a small amount of fcc-Ni(100) crystal. The lattice constant of hcp-Ni crystal is determined as a = 0.249 nm, c = 0.398 nm, and c/a = 1.60.

Characterization of single crystal uranium-oxide thin films grown via reactive-gas magnetron sputtering on yttria-stabilized zirconia and sapphire

Energy Technology Data Exchange (ETDEWEB)

Strehle, Melissa M.; Heuser, Brent J., E-mail: bheuser@illinois.edu; Elbakhshwan, Mohamed S.; Han Xiaochun; Gennardo, David J.; Pappas, Harrison K.; Ju, Hyunsu

2012-06-30

The microstructure and valence states of three single crystal thin film systems, UO{sub 2} on (11{sup Macron }02) r-plane sapphire, UO{sub 2} on (001) yttria-stabilized zirconia, and U{sub 3}O{sub 8} on (11{sup Macron }02) r-plane sapphire, grown via reactive-gas magnetron sputtering are analyzed primarily with X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and ultraviolet photoelectron spectroscopy (UPS). XRD analysis indicates the growth of single crystal domains with varying degrees of mosaicity. XPS and UPS analyses yield U-4f, U-5f, O-1s, and O-2p electron binding energies consistent with reported bulk values. A change from p-type to n-type semiconductor behavior induced by preferential sputtering of oxygen during depth profile analysis was observed with both XPS and UPS. Trivalent cation impurities (Nd and Al) in UO{sub 2} lower the Fermi level, shifting the XPS spectral weight. This observation is consistent with hole-doping of a Mott-Hubbard insulator. The uranium oxide-(11{sup Macron }02) sapphire system is unstable with respect to Al interdiffusion across the film-substrate interface at elevated temperature. - Highlights: Black-Right-Pointing-Pointer Single crystal uranium-oxides grown on sapphire and yttria-stabilized zirconia. Black-Right-Pointing-Pointer Anion and cation valence states studied by photoelectron emission spectroscopy. Black-Right-Pointing-Pointer Trivalent Nd and Al impurities lower the Fermi level. Black-Right-Pointing-Pointer Uranium-oxide films on sapphire found to be unstable with respect to Al interdiffusion.

Crystallization characteristic and scaling behavior of germanium antimony thin films for phase change memory.

Science.gov (United States)

Wu, Weihua; Zhao, Zihan; Shen, Bo; Zhai, Jiwei; Song, Sannian; Song, Zhitang

2018-04-19

Amorphous Ge8Sb92 thin films with various thicknesses were deposited by magnetron sputtering. The crystallization kinetics and optical properties of the Ge8Sb92 thin films and related scaling effects were investigated by an in situ thermally induced method and an optical technique. With a decrease in film thickness, the crystallization temperature, crystallization activation energy and data retention ability increased significantly. The changed crystallization behavior may be ascribed to the smaller grain size and larger surface-to-volume ratio as the film thickness decreased. Regardless of whether the state was amorphous or crystalline, the film resistance increased remarkably as the film thickness decreased to 3 nm. The optical band gap calculated from the reflection spectra increases distinctly with a reduction in film thickness. X-ray diffraction patterns confirm that the scaling of the Ge8Sb92 thin film can inhibit the crystallization process and reduce the grain size. The values of exponent indices that were obtained indicate that the crystallization mechanism experiences a series of changes with scaling of the film thickness. The crystallization time was estimated to determine the scaling effect on the phase change speed. The scaling effect on the electrical switching performance of a phase change memory cell was also determined. The current-voltage and resistance-voltage characteristics indicate that phase change memory cells based on a thinner Ge8Sb92 film will exhibit a higher threshold voltage, lower RESET operational voltage and greater pulse width, which implies higher thermal stability, lower power consumption and relatively lower switching velocity.

Crystallization and growth of Ni-Si alloy thin films on inert and on silicon substrates

Science.gov (United States)

Grimberg, I.; Weiss, B. Z.

1995-04-01

The crystallization kinetics and thermal stability of NiSi2±0.2 alloy thin films coevaporated on two different substrates were studied. The substrates were: silicon single crystal [Si(100)] and thermally oxidized silicon single crystal. In situ resistance measurements, transmission electron microscopy, x-ray diffraction, Auger electron spectroscopy, and Rutherford backscattering spectroscopy were used. The postdeposition microstructure consisted of a mixture of amorphous and crystalline phases. The amorphous phase, independent of the composition, crystallizes homogeneously to NiSi2 at temperatures lower than 200 °C. The activation energy, determined in the range of 1.4-2.54 eV, depends on the type of the substrate and on the composition of the alloyed films. The activation energy for the alloys deposited on the inert substrate was found to be lower than for the alloys deposited on silicon single crystal. The lowest activation energy was obtained for nonstoichiometric NiSi2.2, the highest for NiSi2—on both substrates. The crystallization mode depends on the structure of the as-deposited films, especially the density of the existing crystalline nuclei. Substantial differences were observed in the thermal stability of the NiSi2 compound on both substrates. With the alloy films deposited on the Si substrate, only the NiSi2 phase was identified after annealing to temperatures up to 800 °C. In the films deposited on the inert substrate, NiSi and NiSi2 phases were identified when the Ni content in the alloy exceeded 33 at. %. The effects of composition and the type of substrate on the crystallization kinetics and thermal stability are discussed.

Effect of the Ultrasonic Substrate Vibration on Nucleation and Crystallization of PbI2 Crystals and Thin Films

Directory of Open Access Journals (Sweden)

Fatemeh Zabihi

2018-01-01

Full Text Available Preparation of defect-free and well-controlled solution-processed crystalline thin films is highly desirable for emerging technologies, such as perovskite solar cells. In this work, using PbI2 as a model solution with a vast variety of applications, we demonstrate that the excitation of a liquid thin film by imposed ultrasonic vibration on the film substrate significantly affects the nucleation and crystallization kinetics of PbI2 and the morphology of the resulting solid thin film. It is found that by applying ultrasonic vibration to PbI2 solution spun onto an ITO substrate with a moderate power and excitation duration (5 W and 1 min for the 40 kHz transducer used in this study, the nucleation rate increases and the crystals transform from 2D or planar to epitaxial 3D columnar structures, resulting in the suppression of crystallization dewetting. The effects of various induced physical phenomena as a result of the excitation by ultrasonic vibration are discussed, including microstreaming and micromixing, increased heat transfer and local temperature, a change in the thermodynamic state of the solution, and a decrease in the supersaturation point. It is shown that the ultrasonic-assisted solution deposition of the PbI2 thin films is controllable and reproducible, a process which is low-cost and in line with the large-scale fabrication of such solution-processed thin films.

Crystallization of Electrodeposited Germanium Thin Film on Silicon (100).

Science.gov (United States)

Abidin, Mastura Shafinaz Zainal; Matsumura, Ryo; Anisuzzaman, Mohammad; Park, Jong-Hyeok; Muta, Shunpei; Mahmood, Mohamad Rusop; Sadoh, Taizoh; Hashim, Abdul Manaf

2013-11-06

We report the crystallization of electrodeposited germanium (Ge) thin films on n-silicon (Si) (100) by rapid melting process. The electrodeposition was carried out in germanium (IV) chloride: propylene glycol (GeCl₄:C₃H₈O₂) electrolyte with constant current of 50 mA for 30 min. The measured Raman spectra and electron backscattering diffraction (EBSD) images show that the as-deposited Ge thin film was amorphous. The crystallization of deposited Ge was achieved by rapid thermal annealing (RTA) at 980 °C for 1 s. The EBSD images confirm that the orientations of the annealed Ge are similar to that of the Si substrate. The highly intense peak of Raman spectra at 300 cm -1 corresponding to Ge-Ge vibration mode was observed, indicating good crystal quality of Ge. An additional sub peak near to 390 cm -1 corresponding to the Si-Ge vibration mode was also observed, indicating the Ge-Si mixing at Ge/Si interface. Auger electron spectroscopy (AES) reveals that the intermixing depth was around 60 nm. The calculated Si fraction from Raman spectra was found to be in good agreement with the value estimated from Ge-Si equilibrium phase diagram. The proposed technique is expected to be an effective way to crystallize Ge films for various device applications as well as to create strain at the Ge-Si interface for enhancement of mobility.

Carrier mobility and crystal perfection of tetracene thin film FET

International Nuclear Information System (INIS)

Moriguchi, N.; Nishikawa, T.; Anezaki, T.; Unno, A.; Tachibana, M.; Kojima, K.

2006-01-01

It is well-known that the carrier mobility of an organic field effect semiconductor (FET) depended on the crystal quality and/or the crystal perfection of the organic thin films [T.W. Kelly, D.V. Muyres, P.F. Baude, T.P. Smith, T.D. Jones, Mater. Res. Soc. Symp. Proc. 771 (2003) L6.5.1; D.J. Gundlach, J.A. Nichols, L. Zhou, T.N. Jackson, Appl. Phys. Lett. 80 (2002) 2925; H.K. Lauk, M. Halik, U. Zschieschang, G. Schmid, W. Radlik, J. Appl. Phys. 92 (2002) 5259; M. Shtein, J. Mapel, J.B. Benziger, S.R. Forrest, Appl. Phys. Lett. 81 (2002) 268; D. Knipp, R.A. Street, A.R. Volkel, Appl. Phys. Lett. 82 (2003) 3907; R. Ruiz, A.C. Mayer, G.G. Malliaras, Appl. Phys. Lett. 85 (2004) 4926; R.W.I. de Boer, M.E. Gershenson, A.F. Morpurgo, V. Podzorov, Phys. Stat. Sol. A 201 (2004) 1031]. To improve the crystal quality of the thin film many efforts were made. One of the important improvements was the surface treatment of the substrate. The tetracene thin film FET (top contact structure) was fabricated using the substrate, which was coated by a spin-coating method with a 0.1% poly α-methylstyrene (AMS) solution. The crystal quality was improved by this treatment so that the carrier mobility was higher than that of non-treatment. The maximum mobility of the AMS-treated sample was obtained to be 0.12 cm 2 /V s

Experiment-scale molecular simulation study of liquid crystal thin films

Science.gov (United States)

Nguyen, Trung Dac; Carrillo, Jan-Michael Y.; Matheson, Michael A.; Brown, W. Michael

2014-03-01

Supercomputers have now reached a performance level adequate for studying thin films with molecular detail at the relevant scales. By exploiting the power of GPU accelerators on Titan, we have been able to perform simulations of characteristic liquid crystal films that provide remarkable qualitative agreement with experimental images. We have demonstrated that key features of spinodal instability can only be observed with sufficiently large system sizes, which were not accessible with previous simulation studies. Our study emphasizes the capability and significance of petascale simulations in providing molecular-level insights in thin film systems as well as other interfacial phenomena.

Mechanism of Crystallization and Implications for Charge Transport in Poly(3-ethylhexylthiophene) Thin Films

KAUST Repository

Duong, Duc T.

2014-04-09

In this work, crystallization kinetics and aggregate growth of poly(3-ethylhexylthiophene) (P3EHT) thin films are studied as a function of film thickness. X-ray diffraction and optical absorption show that individual aggregates and crystallites grow anisotropically and mostly along only two packing directions: the alkyl stacking and the polymer chain backbone direction. Further, it is also determined that crystallization kinetics is limited by the reorganization of polymer chains and depends strongly on the film thickness and average molecular weight. Time-dependent, field-effect hole mobilities in thin films reveal a percolation threshold for both low and high molecular weight P3EHT. Structural analysis reveals that charge percolation requires bridged aggregates separated by a distance of ≈2-3 nm, which is on the order of the polymer persistence length. These results thus highlight the importance of tie molecules and inter-aggregate distance in supporting charge percolation in semiconducting polymer thin films. The study as a whole also demonstrates that P3EHT is an ideal model system for polythiophenes and should prove to be useful for future investigations into crystallization kinetics. Recrystallization kinetics and its relationship to charge transport in poly(3-ethylhexylthiophene) (P3EHT) thin films are investigated using a combination of grazing incidence X-ray diffraction, optical absorption, and field-effect transistor measurements. These results show that thin film crystallization kinetics is limited by polymer chain reorganization and that charge percolation depends strongly on the edge-to-edge distance between aggregates. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Fast neutron induced flux pinning in Tl-based high-Tc single crystals and thin films, highly textured tapes and melt-textured bulk 123-superconductors

International Nuclear Information System (INIS)

Brandstaetter, G.; Samadi Hosseinalli, G.; Kern, C.; Sauerzopf, F.M.; Schulz, G.W.; Straif, W.; Yang, X.; Weber, H.W.; Hu, Q.Y.

1999-01-01

Various compounds (TI-2223, TI-1223, TI-2212) as well as material forms (single crystals, thin films, ceramics, tapes) of TI-based high temperature superconductors were investigated by magnetic and transport techniques. TI-2223 has a very 'low lying' irreversibility line (H parallel e) and negligible critical current densities J c at 77 K. However, the irreversibility line shifts to higher fields and temperatures and J c is strongly enhanced, even at 77 K, after fast neutron irradiation. In contrast, the related TI-1223 compound has a much steeper irreversibility line (H parallel c) similar to that of Y-123. J c is significant up to 77 K, even in the unirradiated state, and can be largely improved by neutron irradiation. Transport measurements made on TI-1223 tapes still show much lower critical current densities. TI-2212 and Tl-2223 thin films have J c 's at 77 K, which are comparable to those of TI-1223 single crystals. Transport measurements on highly textured Bi-2223 tapes as well as flux profile measurements on Nd-123 bulk superconductors confirm the beneficial effects of neutron induced defects (collision cascades) for flux pinning. (author)

Defect free single crystal thin layer

KAUST Repository

Elafandy, Rami Tarek Mahmoud

2016-01-28

A gallium nitride film can be a dislocation free single crystal, which can be prepared by irradiating a surface of a substrate and contacting the surface with an etching solution that can selectively etch at dislocations.

Defect free single crystal thin layer

KAUST Repository

Elafandy, Rami Tarek Mahmoud; Ooi, Boon S.

2016-01-01

A gallium nitride film can be a dislocation free single crystal, which can be prepared by irradiating a surface of a substrate and contacting the surface with an etching solution that can selectively etch at dislocations.

Plastic response of thin films due to thermal cycling

NARCIS (Netherlands)

Nicola, L.; van der Giessen, E.; Needleman, A.; Ahzi, S; Cherkaoui, M; Khaleel, MA; Zbib, HM; Zikry, MA; Lamatina, B

2004-01-01

Discrete dislocation simulations of thin films on semi-infinite substrates under cyclic thermal loading are presented. The thin film is modelled as a two-dimensional single crystal under plane strain conditions. Dislocations of edge character can be generated from initially present sources and glide

Two-dimensional photonic crystal bandedge laser with hybrid perovskite thin film for optical gain

Energy Technology Data Exchange (ETDEWEB)

Cha, Hyungrae [Department of Biophysics and Chemical Biology, Seoul National University, Seoul 08826 (Korea, Republic of); Inter-University Semiconductor Research Center, Seoul National University, Seoul 08826 (Korea, Republic of); Bae, Seunghwan [Department of Materials Science and Engineering, Seoul National University, Seoul 08826 (Korea, Republic of); Lee, Myungjae [Inter-University Semiconductor Research Center, Seoul National University, Seoul 08826 (Korea, Republic of); Department of Physics and Astronomy, Seoul National University, Seoul 08826 (Korea, Republic of); Jeon, Heonsu, E-mail: hsjeon@snu.ac.kr [Department of Biophysics and Chemical Biology, Seoul National University, Seoul 08826 (Korea, Republic of); Inter-University Semiconductor Research Center, Seoul National University, Seoul 08826 (Korea, Republic of); Department of Physics and Astronomy, Seoul National University, Seoul 08826 (Korea, Republic of)

2016-05-02

We report optically pumped room temperature single mode laser that contains a thin film of hybrid perovskite, an emerging photonic material, as gain medium. Two-dimensional square lattice photonic crystal (PhC) backbone structure enables single mode laser operation via a photonic bandedge mode, while a thin film of methyl-ammonium lead iodide (CH{sub 3}NH{sub 3}PbI{sub 3}) spin-coated atop provides optical gain for lasing. Two kinds of bandedge modes, Γ and M, are employed, and both devices laser in single mode at similar laser thresholds of ∼200 μJ/cm{sup 2} in pulse energy density. Polarization dependence measurements reveal a clear difference between the two kinds of bandedge lasers: isotropic for the Γ-point laser and highly anisotropic for the M-point laser. These observations are consistent with expected modal properties, confirming that the lasing actions indeed originate from the corresponding PhC bandedge modes.

Lasing in liquid crystal thin films

Energy Technology Data Exchange (ETDEWEB)

Palto, S. P. [Russian Academy of Sciences, Shubnikov Institute of Crystallography (Russian Federation)], E-mail: palto@online.ru

2006-09-15

A lasing condition is formulated in matrix form for optically anisotropic thin films. Lasing behavior of liquid-crystal slabs is analyzed. In particular, it is shown that if the spatial extent of a liquid crystal slab is much larger than its thickness, then laser emission is feasible not only along the normal to the slab, but also in the entire angular sector. The generated laser light can be observed experimentally as a spot or as concentric rings on a screen. The lowest lasing threshold corresponds to in-plane sliding modes leaking into the substrate. The feedback required for lasing is provided by reflection from the interfaces, rather than edges, of the liquid-crystal slab operating as a planar Fabry-Perot cavity. For cholesteric liquid crystals, it is shown that energy loss to the sliding modes leaking into the substrates and escaping through their edges is a key factor that limits the efficiency of band-edge emission along the normal to the slab.

Crystal orientation dependent thermoelectric properties of highly oriented aluminum-doped zinc oxide thin films

KAUST Repository

Abutaha, Anas I.; Sarath Kumar, S. R.; Alshareef, Husam N.

2013-01-01

We demonstrate that the thermoelectric properties of highly oriented Al-doped zinc oxide (AZO) thin films can be improved by controlling their crystal orientation. The crystal orientation of the AZO films was changed by changing the temperature

Growth of HfO{sub x} thin films by reactive molecular beam epitaxy

Energy Technology Data Exchange (ETDEWEB)

Hildebrandt, Erwin; Kurian, Jose; Alff, Lambert [Institut fuer Materialwissenschaft, TU Darmstadt (Germany)

2008-07-01

Thin films of hafnium oxide were grown on single crystal r-cut and c-cut sapphire by reactive molecular beam epitaxy. The conditions for the growth of single oriented hafnium oxide thin films have been established. Hafnium oxide thin films were characterized by X-ray diffraction and optical absorption measurements. It was found that hafnium oxide thin films grown on r-cut sapphire were (00l) oriented whereas, on c-cut sapphire, hafnium oxide films showed different orientations depending on the growth temperature and oxidation conditions. The hafnium oxide films grown at higher temperature and under strong oxidation conditions yielded (001) oriented films on c-cut sapphire whereas slightly weaker oxidation condition leads to (111) oriented hafnium oxide films. The bandgap deducted from optical absorption measurement carried out on hafnium oxide films grown under optimized conditions agreed well with the values reported in literature. A range of oxygen deficient thin films of hafnium oxide were also grown on single crystal sapphire substrates in order to investigate the effect of oxygen vacancies on dielectric properties of hafnium oxide. The oxygen deficient thin films of hafnium oxide show a decrease in bandgap with increase in oxygen deficiency.

Crystallization of Electrodeposited Germanium Thin Film on Silicon (100

Directory of Open Access Journals (Sweden)

Abdul Manaf Hashim

2013-11-01

Full Text Available We report the crystallization of electrodeposited germanium (Ge thin films on n-silicon (Si (100 by rapid melting process. The electrodeposition was carried out in germanium (IV chloride: propylene glycol (GeCl4:C3H8O2 electrolyte with constant current of 50 mA for 30 min. The measured Raman spectra and electron backscattering diffraction (EBSD images show that the as-deposited Ge thin film was amorphous. The crystallization of deposited Ge was achieved by rapid thermal annealing (RTA at 980 °C for 1 s. The EBSD images confirm that the orientations of the annealed Ge are similar to that of the Si substrate. The highly intense peak of Raman spectra at 300 cm−1 corresponding to Ge-Ge vibration mode was observed, indicating good crystal quality of Ge. An additional sub peak near to 390 cm−1 corresponding to the Si-Ge vibration mode was also observed, indicating the Ge-Si mixing at Ge/Si interface. Auger electron spectroscopy (AES reveals that the intermixing depth was around 60 nm. The calculated Si fraction from Raman spectra was found to be in good agreement with the value estimated from Ge-Si equilibrium phase diagram. The proposed technique is expected to be an effective way to crystallize Ge films for various device applications as well as to create strain at the Ge-Si interface for enhancement of mobility.

A coupled atomistics and discrete dislocation plasticity simulation of nanoindentation into single crystal thin films

International Nuclear Information System (INIS)

Miller, Ronald E.; Shilkrot, L.E.; Curtin, William A.

2004-01-01

The phenomenon of 2D nanoindentation of circular 'Brinell' indenter into a single crystal metal thin film bonded to a rigid substrate is investigated. The simulation method is the coupled atomistics and discrete dislocation (CADD) model recently developed by the authors. The CADD model couples a continuum region containing any number of discrete dislocations to an atomistic region, and permits accurate, automatic detection and passing of dislocations between the atomistic and continuum regions. The CADD model allows for a detailed study of nanoindentation to large penetration depths (up to 60 A here) using only a small region of atoms just underneath the indenter where dislocation nucleation, cross-slip, and annihilation occur. Indentation of a model hexagonal aluminum crystal shows: (i) the onset of homogeneous dislocation nucleation at points away from the points of maximum resolved shear stress; (ii) size-dependence of the material hardness, (iii) the role of dislocation dissociation on deformation; (iv) reverse plasticity, including nucleation of dislocations on unloading and annihilation; (v) permanent deformation, including surface uplift, after full unloading; (vi) the effects of film thickness on the load-displacement response; and (vii) the differences between displacement and force controlled loading. This application demonstrates the power of the CADD method in capturing both long-range dislocation plasticity and short-range atomistic phenomena. The use of CADD permits for a clear study of the physical and mechanical influence of both complex plastic flow and non-continuum atomistic-level processes on the macroscopic response of material under indentation loading

Gallium arsenide single crystal solar cell structure and method of making

Science.gov (United States)

Stirn, Richard J. (Inventor)

1983-01-01

A production method and structure for a thin-film GaAs crystal for a solar cell on a single-crystal silicon substrate (10) comprising the steps of growing a single-crystal interlayer (12) of material having a closer match in lattice and thermal expansion with single-crystal GaAs than the single-crystal silicon of the substrate, and epitaxially growing a single-crystal film (14) on the interlayer. The material of the interlayer may be germanium or graded germanium-silicon alloy, with low germanium content at the silicon substrate interface, and high germanium content at the upper surface. The surface of the interface layer (12) is annealed for recrystallization by a pulsed beam of energy (laser or electron) prior to growing the interlayer. The solar cell structure may be grown as a single-crystal n.sup.+ /p shallow homojunction film or as a p/n or n/p junction film. A Ga(Al)AS heteroface film may be grown over the GaAs film.

Spectroelectrochemical study of the adsorption of acetate anions at gold single crystal and thin-film electrodes

International Nuclear Information System (INIS)

Berna, Antonio; Delgado, Jose Manuel; Orts, Jose Manuel; Rodes, Antonio; Feliu, Juan Miguel

2008-01-01

Acetate adsorption at gold electrodes is studied in perchloric acid solutions by cyclic voltammetry and in-situ infrared spectroscopy. External reflection measurements, performed with gold single crystal electrodes, are combined with Surface Enhanced Infrared Reflection Absorption Spectroscopy experiments under attenuated total reflection conditions (ATR-SEIRAS) carried out with sputtered gold thin-film electrodes. Theoretical harmonic IR frequencies of acetate species adsorbed with different geometries on Au clusters with (1 1 1), (1 0 0) and (1 1 0) orientations have been obtained from B3LYP/LANL2DZ, 6-31 + G* calculations. The theoretical and experimental results confirm that, irrespective of the surface crystallographic orientation, bonding of acetate to the surface involves the two oxygen atoms of the carboxylate group, with the OCO plane perpendicular to the metal surface. DFT calculations reveal also that the total charge of the metal cluster-acetate supermolecule has small effect on the vibrational frequencies of adsorbed acetate species. Both the external and the internal reflection measurements show the co-adsorption of acetate and perchlorate anions. Step-scan measurements carried out with the gold thin-film electrodes have allowed the monitoring of the time-dependent behaviour of perchlorate, acetate and water bands in potential step experiments. Acetate adsorption under those conditions is shown to involve perchlorate desorption and to follow a Langmuir-type kinetics. The step-scan spectra also show the rise and decay of transient water structures with parallel time-dependent shifts of the background intensity in the infrared spectra

Periodic domain inversion in x-cut single-crystal lithium niobate thin film

Energy Technology Data Exchange (ETDEWEB)

Mackwitz, P., E-mail: peterm@mail.upb.de; Rüsing, M.; Berth, G.; Zrenner, A. [Department Physik, Universität Paderborn, 33095 Paderborn (Germany); Center for Optoelectronics and Photonics Paderborn, 33095 Paderborn (Germany); Widhalm, A.; Müller, K. [Department Physik, Universität Paderborn, 33095 Paderborn (Germany)

2016-04-11

We report the fabrication of periodically poled domain patterns in x-cut lithium niobate thin-film. Here, thin films on insulator have drawn particular attention due to their intrinsic waveguiding properties offering high mode confinement and smaller devices compared to in-diffused waveguides in bulk material. In contrast to z-cut thin film lithium niobate, the x-cut geometry does not require back electrodes for poling. Further, the x-cut geometry grants direct access to the largest nonlinear and electro-optical tensor element, which overall promises smaller devices. The domain inversion was realized via electric field poling utilizing deposited aluminum top electrodes on a stack of LN thin film/SiO{sub 2} layer/Bulk LN, which were patterned by optical lithography. The periodic domain inversion was verified by non-invasive confocal second harmonic microscopy. Our results show domain patterns in accordance to the electrode mask layout. The second harmonic signatures can be interpreted in terms of spatially, overlapping domain filaments which start their growth on the +z side.

Crystal structure and phase composition of aluminium thin films with holmium additions

International Nuclear Information System (INIS)

Koleshko, V.M.; Belitskij, V.F.; Obukhov, V.E.; Rumak, N.V.; Urban, T.P.

1984-01-01

The effect of holmium additions on the crystal structure and phase composition of thin aluminium films has been studied. A regularity in grain size changes in aluminium thin films versus the holmium content in them is established. The holmium introduction is shown to result in the appearance of axial texture in the aluminium films, the texture axis being determined by the quantity of the addition. During heat treatment of the aluminium films, containing holmium additions, in the range of low ( approximately 100-200 deg C) annealing temperatures holmium monohydroxide is formed, and at annealing temperatures 300 deg C 0 3 is formed

Epitaxial growth of bcc-Fe{sub x}Co{sub 100-x} thin films on MgO(1 1 0) single-crystal substrates

Energy Technology Data Exchange (ETDEWEB)

Ohtake, Mitsuru, E-mail: ohtake@futamoto.elect.chuo-u.ac.j [Faculty of Science and Engineering, Chuo University, 1-13-27 Kasuga, Bunkyo-ku, Tokyo 112-8551 (Japan); Nishiyama, Tsutomu; Shikada, Kouhei [Faculty of Science and Engineering, Chuo University, 1-13-27 Kasuga, Bunkyo-ku, Tokyo 112-8551 (Japan); Kirino, Fumiyoshi [Graduate School of Fine Arts, Tokyo National University of Fine Arts and Music, 12-8 Ueno-koen, Taito-ku, Tokyo 110-8714 (Japan); Futamoto, Masaaki [Faculty of Science and Engineering, Chuo University, 1-13-27 Kasuga, Bunkyo-ku, Tokyo 112-8551 (Japan)

2010-07-15

Fe{sub x}Co{sub 100-x} (x=100, 65, 50 at%) epitaxial thin films were prepared on MgO(1 1 0) single-crystal substrates heated at 300 deg. C by ultra-high vacuum molecular beam epitaxy. The film structure and the growth mechanism are discussed. FeCo(2 1 1) films with bcc structure grow epitaxially on MgO(1 1 0) substrates with two types of variants whose orientations are rotated around the film normal by 180 deg. each other for all compositions. Fe{sub x}Co{sub 100-x} film growth follows the Volmer Weber mode. X-ray diffraction analysis indicates the out-of-plane and the in-plane lattice spacings are in agreement with the values of respective bulk Fe{sub x}Co{sub 100-x} crystals with very small errors less than +-0.4%, suggesting the strains in the films are very small. High-resolution cross-sectional transmission electron microscopy shows that periodical misfit dislocations are preferentially introduced in the film at the Fe{sub 50}Co{sub 50}/MgO interface along the MgO[1 1-bar 0] direction. The presence of such periodical dislocations decreases the large lattice mismatch of about -17% existing at the FeCo/MgO interface along the MgO[1 1-bar 0] direction.

Epitaxial single-crystal thin films of MnxTi1-xO2-δ grown on (rutile)TiO2 substrates with pulsed laser deposition: Experiment and theory

Energy Technology Data Exchange (ETDEWEB)

Ilton, Eugene S.; Droubay, Timothy C.; Chaka, Anne M.; Kovarik, Libor; Varga, Tamas; Arey, Bruce W.; Kerisit, Sebastien N.

2015-02-01

Epitaxial rutile-structured single-crystal MnxTi1-xO2-δ films were synthesized on rutile- (110) and -(001) substrates using pulsed laser deposition. The films were characterized by reflection high-energy electron diffraction (RHEED), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and aberration-corrected transmission electron microscopy (ACTEM). Under the present conditions, 400oC and PO2 = 20 mTorr, single crystal epitaxial thin films were grown for x = 0.13, where x is the nominal average mole fraction of Mn. In fact, arbitrarily thick films could be grown with near invariant Mn/Ti concentration profiles from the substrate/film interface to the film surface. In contrast, at x = 0.25, Mn became enriched towards the surface and a secondary nano-scale phase formed which appeared to maintain the basic rutile structure but with enhanced z-contrast in the tunnels, or tetrahedral interstitial sites. Ab initio thermodynamic calculations provided quantitative estimates for the destabilizing effect of expanding the β-MnO2 lattice parameters to those of TiO2-rutile, the stabilizing effect of diluting Mn with increasing Ti concentration, and competing reaction pathways.

The single-phase multiferroic oxides: from bulk to thin film

International Nuclear Information System (INIS)

Prellier, W; Singh, M P; Murugavel, P

2005-01-01

Complex perovskite oxides exhibit a rich spectrum of properties, including magnetism, ferroelectricity, strongly correlated electron behaviour, superconductivity and magnetoresistance, which have been research areas of great interest among the scientific and technological community for decades. There exist very few materials which exhibit multiple functional properties; one such class of materials is called the multiferroics. Multiferroics are interesting because they exhibit simultaneously ferromagnetic and ferroelectric polarizations and a coupling between them. Due to the nontrivial lattice coupling between the magnetic and electronic domains (the magnetoelectric effect), the magnetic polarization can be switched by applying an electric field; likewise the ferroelectric polarization can be switched by applying a magnetic field. As a consequence, multiferroics offer rich physics and novel devices concepts, which have recently become of great interest to researchers. In this review article the recent experimental status, for both the bulk single phase and the thin film form, has been presented. Current studies on the ceramic compounds in the bulk form including Bi(Fe,Mn)O 3 , REMnO 3 and the series of REMn 2 O 5 single crystals (RE = rare earth) are discussed in the first section and a detailed overview on multiferroic thin films grown artificially (multilayers and nanocomposites) is presented in the second section. (topical review)

Atomic Structure Control of Silica Thin Films on Pt(111)

KAUST Repository

Crampton, Andrew S

2015-05-27

Metal oxide thin films grown on metal single crystals are commonly used to model heterogeneous catalyst supports. The structure and properties of thin silicon dioxide films grown on metal single crystals have only recently been thoroughly characterized and their spectral properties well established. We report the successful growth of a three- dimensional, vitreous silicon dioxide thin film on the Pt(111) surface and reproduce the closed bilayer structure previously reported. The confirmation of the three dimensional nature of the film is unequivocally shown by the infrared absorption band at 1252 cm−1. Temperature programmed desorption was used to show that this three-dimensional thin film covers the Pt(111) surface to such an extent that its application as a catalyst support for clusters/nanoparticles is possible. The growth of a three-dimensional film was seen to be directly correlated with the amount of oxygen present on the surface after the silicon evaporation process. This excess of oxygen is tentatively attributed to atomic oxygen being generated in the evaporator. The identification of atomic oxygen as a necessary building block for the formation of a three-dimensional thin film opens up new possibilities for thin film growth on metal supports, whereby simply changing the type of oxygen enables thin films with different atomic structures to be synthesized. This is a novel approach to tune the synthesis parameters of thin films to grow a specific structure and expands the options for modeling common amorphous silica supports under ultra high vacuum conditions.

Preparation and characterization of Bi2Sr2CaCu2O8+δ thin films on MgO single crystal substrates by chemical solution deposition

DEFF Research Database (Denmark)

Grivel, Jean-Claude; Kepa, Katarzyna; Hlásek, T.

2013-01-01

Bi2Sr2CaCu2O8 thin films have been deposited on MgO single crystal substrates by spin-coating a solution based on 2-ethylhexanoate precursors. Pyrolysis takes place between 200°C and 450°C and is accompanied by the release of 2-ethylhexanoic acid, CO2 and H2O vapour. Highly c-axis oriented Bi2Sr2Ca...

Hydrogen absorption in thin ZnO films prepared by pulsed laser deposition

International Nuclear Information System (INIS)

Melikhova, O.; Čížek, J.; Lukáč, F.; Vlček, M.; Novotný, M.; Bulíř, J.; Lančok, J.; Anwand, W.; Brauer, G.; Connolly, J.; McCarthy, E.; Krishnamurthy, S.; Mosnier, J.-P.

2013-01-01

Highlights: ► Thin ZnO films and high quality ZnO crystal were electrochemically doped with hydrogen. ► Hydrogen absorbed in ZnO causes plastic deformation both in ZnO crystal and thin films. ► In ZnO crystal a sub-surface region with very high density of defects was formed. ► Moreover, plastic deformation causes specific surface modification of ZnO crystal. ► In ZnO films hydrogen-induced plastic deformation introduced defects in the whole film. -- Abstract: ZnO films with thickness of ∼80 nm were grown by pulsed laser deposition (PLD) on MgO (1 0 0) single crystal and amorphous fused silica (FS) substrates. Structural studies of ZnO films and a high quality reference ZnO single crystal were performed by slow positron implantation spectroscopy (SPIS). It was found that ZnO films exhibit significantly higher density of defects than the reference ZnO crystal. Moreover, the ZnO film deposited on MgO substrate exhibits higher concentration of defects than the film deposited on amorphous FS substrate most probably due to a dense network of misfit dislocations. The ZnO films and the reference ZnO crystal were subsequently loaded with hydrogen by electrochemical cathodic charging. SPIS characterizations revealed that absorbed hydrogen introduces new defects into ZnO

Hydrogen absorption in thin ZnO films prepared by pulsed laser deposition

Energy Technology Data Exchange (ETDEWEB)

Melikhova, O., E-mail: oksivmel@yahoo.com [Charles University in Prague, Faculty of Mathematics and Physics, V Holesovickach 2, CZ-180 00 Praha 8 (Czech Republic); Čížek, J.; Lukáč, F.; Vlček, M. [Charles University in Prague, Faculty of Mathematics and Physics, V Holesovickach 2, CZ-180 00 Praha 8 (Czech Republic); Novotný, M.; Bulíř, J.; Lančok, J. [Institute of Physics, Academy of Sciences of the Czech Republic, Na Slovance 2, 182 21 Prague (Czech Republic); Anwand, W.; Brauer, G. [Institut für Strahlenphysik, Helmholtz-Zentrum Dresden-Rossendorf, PO Box 510 119, D-01314 Dresden (Germany); Connolly, J.; McCarthy, E.; Krishnamurthy, S.; Mosnier, J.-P. [National Centre for Plasma Science and Technology, School of Physical Sciences, Glasnevin, Dublin 9 (Ireland)

2013-12-15

Highlights: ► Thin ZnO films and high quality ZnO crystal were electrochemically doped with hydrogen. ► Hydrogen absorbed in ZnO causes plastic deformation both in ZnO crystal and thin films. ► In ZnO crystal a sub-surface region with very high density of defects was formed. ► Moreover, plastic deformation causes specific surface modification of ZnO crystal. ► In ZnO films hydrogen-induced plastic deformation introduced defects in the whole film. -- Abstract: ZnO films with thickness of ∼80 nm were grown by pulsed laser deposition (PLD) on MgO (1 0 0) single crystal and amorphous fused silica (FS) substrates. Structural studies of ZnO films and a high quality reference ZnO single crystal were performed by slow positron implantation spectroscopy (SPIS). It was found that ZnO films exhibit significantly higher density of defects than the reference ZnO crystal. Moreover, the ZnO film deposited on MgO substrate exhibits higher concentration of defects than the film deposited on amorphous FS substrate most probably due to a dense network of misfit dislocations. The ZnO films and the reference ZnO crystal were subsequently loaded with hydrogen by electrochemical cathodic charging. SPIS characterizations revealed that absorbed hydrogen introduces new defects into ZnO.

Unique Crystal Orientation of Poly(ethylene oxide) Thin Films by Crystallization Using a Thermal Gradient

DEFF Research Database (Denmark)

Gbabode, Gabin; Delvaux, Maxime; Schweicher, Guillaume

2017-01-01

Poly(ethylene oxide), (PEO), thin films of different thicknesses (220, 450, and 1500 nm) and molecular masses (4000, 8000, and 20000 g/mol) have been fabricated by spin-coating of methanol solutions onto glass substrates. All these samples have been recrystallized from the melt using a directional......, to significantly decrease the distribution of crystal orientation obtained after crystallization using the thermal gradient technique....

Biocorrosion investigation of two shape memory nickel based alloys: Ni-Mn-Ga and thin film NiTi.

Science.gov (United States)

Stepan, L L; Levi, D S; Gans, E; Mohanchandra, K P; Ujihara, M; Carman, G P

2007-09-01

Thin film nitinol and single crystal Ni-Mn-Ga represent two new shape memory materials with potential to be used as percutaneously placed implant devices. However, the biocompatibility of these materials has not been adequately assessed. Immersion tests were conducted on both thin film nitinol and single crystal Ni-Mn-Ga in Hank's balanced salt solution at 37 degrees C and pH 7.4. After 12 h, large pits were found on the Ni-Mn-Ga samples while thin film nitinol displayed no signs of corrosion. Further electrochemical tests on thin film nitinol samples revealed breakdown potentials superior to a mechanically polished nitinol disc. These results suggest that passivation or electropolishing of thin film nitinol maybe unnecessary to promote corrosion resistance.

Effect of crystal structure on optical properties of sol–gel derived zirconia thin films

Energy Technology Data Exchange (ETDEWEB)

Wang, Xiaodong, E-mail: xiaodong_wang@tongji.edu.cn [Pohl Institute of Solid State Physics, Shanghai Key Laboratory of Special Artificial Microstructure Materials and Technology, Tongji University, Shanghai 200092 (China); Wu, Guangming; Zhou, Bin [Pohl Institute of Solid State Physics, Shanghai Key Laboratory of Special Artificial Microstructure Materials and Technology, Tongji University, Shanghai 200092 (China); Shen, Jun, E-mail: shenjun67@tongji.edu.cn [Pohl Institute of Solid State Physics, Shanghai Key Laboratory of Special Artificial Microstructure Materials and Technology, Tongji University, Shanghai 200092 (China)

2013-04-15

Highlights: ► ZrO{sub 2} films were deposited by sol–gel method. ► Crystal structures of the films were tuned by different thermal annealing methods. ► The refractive indices vary with the crystal structures of the films. ► Lattice-mismatch was found to reduce the refractive index of ZrO{sub 2} films. -- Abstract: The optical properties of sol–gel derived zirconia thin films and their relation to the crystal structure are studied in this paper. ZrO{sub 2} films were deposited on quartz glass and silicon wafer substrates by sol–gel method with conventional furnace annealing (CFA) and rapid thermal annealing (RTA). Crystal structures of the films were analyzed by X-ray diffraction (XRD) and Raman spectroscopy, while refractive indices of the films were determined from the reflectance and transmittance spectra. The refractive indices vary with the function of crystal structure and density of the films, which depends on annealing temperature and annealing technique. Lattice-mismatch between monoclinic phase and tetragonal phase was found to reduce the refractive index of ZrO{sub 2} films.

Magnetic surfaces, thin films, and multilayers

International Nuclear Information System (INIS)

Parkin, S.S.P.; Renard, J.P.; Shinjo, T.; Zinn, W.

1992-01-01

This paper details recent developments in the magnetism of surfaces, thin films and multilayers. More than 20 invited contributions and more than 60 contributed papers attest to the great interest and vitality of this subject. In recent years the study of magnetic surfaces, thin films and multilayers has undergone a renaissance, partly motivated by the development of new growth and characterization techniques, but perhaps more so by the discovery of many exciting new properties, some quite unanticipated. These include, most recently, the discovery of enormous values of magnetoresistance in magnetic multilayers far exceeding those found in magnetic single layer films and the discovery of oscillatory interlayer coupling in transition metal multilayers. These experimental studies have motivated much theoretical work. However these developments are to a large extent powered by materials engineering and our ability to control and understand the growth of thin layers just a few atoms thick. The preparation of single crystal thin film layers and multilayers remains important for many studies, in particular, for properties dependent. These studies obviously require engineering not just a layer thicknesses but of lateral dimensions as well. The properties of such structures are already proving to be a great interest

Crystallization kinetics of GeTe phase-change thin films grown by pulsed laser deposition

Science.gov (United States)

Sun, Xinxing; Thelander, Erik; Gerlach, Jürgen W.; Decker, Ulrich; Rauschenbach, Bernd

2015-07-01

Pulsed laser deposition was employed to the growth of GeTe thin films on Silicon substrates. X-ray diffraction measurements reveal that the critical crystallization temperature lies between 220 and 240 °C. Differential scanning calorimetry was used to investigate the crystallization kinetics of the as-deposited films, determining the activation energy to be 3.14 eV. Optical reflectivity and in situ resistance measurements exhibited a high reflectivity contrast of ~21% and 3-4 orders of magnitude drop in resistivity of the films upon crystallization. The results show that pulsed laser deposited GeTe films can be a promising candidate for phase-change applications.

Crystallization kinetics of GeTe phase-change thin films grown by pulsed laser deposition

International Nuclear Information System (INIS)

Sun, Xinxing; Thelander, Erik; Gerlach, Jürgen W; Decker, Ulrich; Rauschenbach, Bernd

2015-01-01

Pulsed laser deposition was employed to the growth of GeTe thin films on Silicon substrates. X-ray diffraction measurements reveal that the critical crystallization temperature lies between 220 and 240 °C. Differential scanning calorimetry was used to investigate the crystallization kinetics of the as-deposited films, determining the activation energy to be 3.14 eV. Optical reflectivity and in situ resistance measurements exhibited a high reflectivity contrast of ∼21% and 3–4 orders of magnitude drop in resistivity of the films upon crystallization. The results show that pulsed laser deposited GeTe films can be a promising candidate for phase-change applications. (paper)

Wrinkle-Free Single-Crystal Graphene Wafer Grown on Strain-Engineered Substrates.

Science.gov (United States)

Deng, Bing; Pang, Zhenqian; Chen, Shulin; Li, Xin; Meng, Caixia; Li, Jiayu; Liu, Mengxi; Wu, Juanxia; Qi, Yue; Dang, Wenhui; Yang, Hao; Zhang, Yanfeng; Zhang, Jin; Kang, Ning; Xu, Hongqi; Fu, Qiang; Qiu, Xiaohui; Gao, Peng; Wei, Yujie; Liu, Zhongfan; Peng, Hailin

2017-12-26

Wrinkles are ubiquitous for graphene films grown on various substrates by chemical vapor deposition at high temperature due to the strain induced by thermal mismatch between the graphene and substrates, which greatly degrades the extraordinary properties of graphene. Here we show that the wrinkle formation of graphene grown on Cu substrates is strongly dependent on the crystallographic orientations. Wrinkle-free single-crystal graphene was grown on a wafer-scale twin-boundary-free single-crystal Cu(111) thin film fabricated on sapphire substrate through strain engineering. The wrinkle-free feature of graphene originated from the relatively small thermal expansion of the Cu(111) thin film substrate and the relatively strong interfacial coupling between Cu(111) and graphene, based on the strain analyses as well as molecular dynamics simulations. Moreover, we demonstrated the transfer of an ultraflat graphene film onto target substrates from the reusable single-crystal Cu(111)/sapphire growth substrate. The wrinkle-free graphene shows enhanced electrical mobility compared to graphene with wrinkles.

Preparation and structure characterization of SmCo5(0001) epitaxial thin films grown on Cu(111) underlayers

International Nuclear Information System (INIS)

Ohtake, Mitsuru; Nukaga, Yuri; Futamoto, Masaaki; Kirino, Fumiyoshi

2009-01-01

SmCo 5 (0001) epitaxial films were prepared on Cu(111) single-crystal underlayers formed on Al 2 O 3 (0001) substrates at 500 deg. C. The nucleation and growth mechanism of (0001)-oriented SmCo 5 crystal on Cu(111) underlayer is investigated and a method to control the nucleation is proposed. The SmCo 5 epitaxial thin film formed directly on Cu underlayer consists of two types of domains whose orientations are rotated around the film normal by 30 deg. each other. By introducing a thin Co seed layer on the Cu underlayer, a SmCo 5 (0001) single-crystal thin film is successfully obtained. Nucleation of SmCo 5 crystal on Cu underlayer seems controllable by varying the interaction between the Cu underlayer and the SmCo 5 layer

Self-assembled single-phase perovskite nanocomposite thin films.

Science.gov (United States)

Kim, Hyun-Suk; Bi, Lei; Paik, Hanjong; Yang, Dae-Jin; Park, Yun Chang; Dionne, Gerald F; Ross, Caroline A

2010-02-10

Thin films of perovskite-structured oxides with general formula ABO(3) have great potential in electronic devices because of their unique properties, which include the high dielectric constant of titanates, (1) high-T(C) superconductivity in cuprates, (2) and colossal magnetoresistance in manganites. (3) These properties are intimately dependent on, and can therefore be tailored by, the microstructure, orientation, and strain state of the film. Here, we demonstrate the growth of cubic Sr(Ti,Fe)O(3) (STF) films with an unusual self-assembled nanocomposite microstructure consisting of (100) and (110)-oriented crystals, both of which grow epitaxially with respect to the Si substrate and which are therefore homoepitaxial with each other. These structures differ from previously reported self-assembled oxide nanocomposites, which consist either of two different materials (4-7) or of single-phase distorted-cubic materials that exhibit two or more variants. (8-12) Moreover, an epitaxial nanocomposite SrTiO(3) overlayer can be grown on the STF, extending the range of compositions over which this microstructure can be formed. This offers the potential for the implementation of self-organized optical/ferromagnetic or ferromagnetic/ferroelectric hybrid nanostructures integrated on technologically important Si substrates with applications in magnetooptical or spintronic devices.

Investigating the crystal growth behavior of biodegradable polymer blend thin films using in situ atomic force microscopy

CSIR Research Space (South Africa)

Malwela, T

2014-01-01

Full Text Available This article reports the crystal growth behavior of biodegradable polylactide (PLA)/poly[(butylene succinate)-co-adipate] (PBSA) blend thin films using atomic force microscopy (AFM). Currently, polymer thin films have received increased research...

Stress and stability of sputter deposited A-15 and bcc crystal structure tungsten thin films

Energy Technology Data Exchange (ETDEWEB)

O' Keefe, M.J.; Stutz, C.E.

1997-07-01

Magnetron sputter deposition was used to fabricate body centered cubic (bcc) and A-15 crystal structure W thin films. Previous work demonstrated that the as-deposited crystal structure of the films was dependent on the deposition parameters and that the formation of a metastable A-15 structure was favored over the thermodynamically stable bcc phase when the films contained a few atomic percent oxygen. However, the A-15 phase was shown to irreversibly transform into the bcc phase between 500 C and 650 C and that a significant decrease in the resistivity of the metallic films was measured after the transformation. The current investigation of 150 nm thick, sputter deposited A-15 and bcc tungsten thin films on silicon wafers consisted of a series of experiments in which the stress, resistivity and crystal structure of the films was measured as a function of temperatures cycles in a Flexus 2900 thin film stress measurement system. The as-deposited film stress was found to be a function of the sputtering pressure and presputter time; under conditions in which the as-deposited stress of the film was {approximately}1.5 GPa compressive delamination of the W film from the substrate was observed. Data from the thermal studies indicated that bcc film stress was not affected by annealing but transformation of the A-15 structure resulted in a large tensile increase in the stress of the film, regardless of the as-deposited stress of the film. In several instances, complete transformation of the A-15 structure into the bcc phase resulted in {ge}1 GPa tensile increase in film stress.

Stress and stability of sputter deposited A-15 and bcc crystal structure tungsten thin films

International Nuclear Information System (INIS)

O'Keefe, M.J.; Stutz, C.E.

1997-01-01

Magnetron sputter deposition was used to fabricate body centered cubic (bcc) and A-15 crystal structure W thin films. Previous work demonstrated that the as-deposited crystal structure of the films was dependent on the deposition parameters and that the formation of a metastable A-15 structure was favored over the thermodynamically stable bcc phase when the films contained a few atomic percent oxygen. However, the A-15 phase was shown to irreversibly transform into the bcc phase between 500 C and 650 C and that a significant decrease in the resistivity of the metallic films was measured after the transformation. The current investigation of 150 nm thick, sputter deposited A-15 and bcc tungsten thin films on silicon wafers consisted of a series of experiments in which the stress, resistivity and crystal structure of the films was measured as a function of temperatures cycles in a Flexus 2900 thin film stress measurement system. The as-deposited film stress was found to be a function of the sputtering pressure and presputter time; under conditions in which the as-deposited stress of the film was approximately1.5 GPa compressive delamination of the W film from the substrate was observed. Data from the thermal studies indicated that bcc film stress was not affected by annealing but transformation of the A-15 structure resulted in a large tensile increase in the stress of the film, regardless of the as-deposited stress of the film. In several instances, complete transformation of the A-15 structure into the bcc phase resulted in ge1 GPa tensile increase in film stress

Solid-phase crystallization of amorphous silicon on ZnO:Al for thin-film solar cells

Energy Technology Data Exchange (ETDEWEB)

Becker, C.; Conrad, E.; Dogan, P.; Fenske, F.; Gorka, B.; Haenel, T.; Lee, K.Y.; Rau, B.; Ruske, F.; Weber, T.; Gall, S.; Rech, B. [Helmholtz-Zentrum Berlin fuer Materialien und Energie (formerly Hahn-Meitner-Institut Berlin), Kekulestr. 5, D-12489 Berlin (Germany); Berginski, M.; Huepkes, J. [Institute of Photovoltaics, Forschungszentrum Juelich GmbH, D-52425 Juelich (Germany)

2009-06-15

The suitability of ZnO:Al thin films for polycrystalline silicon (poly-Si) thin-film solar cell fabrication was investigated. The electrical and optical properties of 700 -nm-thick ZnO:Al films on glass were analyzed after typical annealing steps occurring during poly-Si film preparation. If the ZnO:Al layer is covered by a 30 nm thin silicon film, the initial sheet resistance of ZnO:Al drops from 4.2 to 2.2 {omega} after 22 h annealing at 600 C and only slightly increases for a 200 s heat treatment at 900 C. A thin-film solar cell concept consisting of poly-Si films on ZnO:Al coated glass is introduced. First solar cell results will be presented using absorber layers either prepared by solid-phase crystallization (SPC) or by direct deposition at 600 C. (author)

Pr and Gd co-doped bismuth ferrite thin films with enhanced ...

Indian Academy of Sciences (India)

in Pr content, the crystal structures of BPGFO thin films retain rhombohedral (R3c) symmetry accompanied by structure distortion. ... Pr and Gd co-modified BiFeO3 thin film; ferroelectric properties; sol-gel. 1. Introduction. In recent years, great attention has been paid to single- phase BiFeO3 (BFO) multiferroic materials ...

Structural characterization of epitaxial LiFe_5O_8 thin films grown by chemical vapor deposition

International Nuclear Information System (INIS)

Loukya, B.; Negi, D.S.; Sahu, R.; Pachauri, N.; Gupta, A.; Datta, R.

2016-01-01

We report on detailed microstructural and atomic ordering characterization by transmission electron microscopy in epitaxial LiFe_5O_8 (LFO) thin films grown by chemical vapor deposition (CVD) on MgO (001) substrates. The experimental results of LFO thin films are compared with those for bulk LFO single crystal. Electron diffraction studies indicate weak long-range ordering in LFO (α-phase) thin films in comparison to bulk crystal where strong ordering is observed in optimally annealed samples. The degree of long-range ordering depends on the growth conditions and the thickness of the film. Annealing experiment along with diffraction study confirms the formation of α-Fe_2O_3 phase in some regions of the films. This suggests that under certain growth conditions γ-Fe_2O_3-like phase forms in some pockets in the as-grown LFO thin films that then convert to α-Fe_2O_3 on annealing. - Highlights: • Atomic ordering in LiFe_5O_8 bulk single crystal and epitaxial thin films. • Electron diffraction studies reveal different level of ordering in the system. • Formation of γ-Fe_2O_3 like phase has been observed.

Effects of flexible substrate thickness on Al-induced crystallization of amorphous Ge thin films

Energy Technology Data Exchange (ETDEWEB)

Oya, Naoki [Institute of Applied Physics, University of Tsukuba, Tsukuba, Ibaraki 305-8573 (Japan); Toko, Kaoru, E-mail: toko@bk.tsukuba.ac.jp [Institute of Applied Physics, University of Tsukuba, Tsukuba, Ibaraki 305-8573 (Japan); Saitoh, Noriyuki; Yoshizawa, Noriko [Electron Microscope Facility, TIA, AIST, 16-1 Onogawa, Tsukuba 305-8569 (Japan); Suemasu, Takashi [Institute of Applied Physics, University of Tsukuba, Tsukuba, Ibaraki 305-8573 (Japan)

2015-05-29

Amorphous germanium (a-Ge) thin films were directly crystallized on flexible plastic substrates at 325 °C using Al-induced crystallization. The thickness of the plastic substrate strongly influenced the crystal quality of the resulting polycrystalline Ge layers. Using a thicker substrate lowered the stress on the a-Ge layer during annealing, which increased the grain size and fraction of (111)-oriented grains within the Ge layer. Employing a 125-μm-thick substrate led to 95% (111)-oriented Ge with grains having an average size of 100 μm. Transmission electron microscopy demonstrated that the Ge grains had a low-defect density. Production of high-quality Ge films on plastic substrates allows for the possibility for developing Ge-based electronic and optical devices on inexpensive flexible substrates. - Highlights: • Polycrystalline Ge thin films are directly formed on flexible plastic substrates. • Al-induced crystallization allows the low-temperature growth (325 °C) of amorphous Ge. • The substrate bending during annealing strongly influences the crystal quality of poly-Ge. • A thick substrate (125 μm) leads to 95% (111)-oriented Ge with grains 100 μm in size.

High-Performance Single-Crystalline Perovskite Thin-Film Photodetector

KAUST Repository

Yang, Zhenqian; Deng, Yuhao; Zhang, Xiaowei; Wang, Suo; Chen, Huazhou; Yang, Sui; Khurgin, Jacob; Fang, Nicholas X.; Zhang, Xiang; Ma, Renmin

2018-01-01

The best performing modern optoelectronic devices rely on single-crystalline thin-film (SC-TF) semiconductors grown epitaxially. The emerging halide perovskites, which can be synthesized via low-cost solution-based methods, have achieved substantial

Residual stress and Young's modulus of pulsed laser deposited PZT thin films: Effect of thin film composition and crystal direction of Si cantilevers

NARCIS (Netherlands)

Nazeer, H.; Nguyen, Duc Minh; Rijnders, Augustinus J.H.M.; Abelmann, Leon; Sardan Sukas, Ö.

2016-01-01

We investigated the residual stress and Young's modulus of Pb(ZrxTi1 - x)O3 (PZT) thin films with a (110) preferred orientation and a composition x ranging from 0.2 to 0.8. The films are grown by pulsed laser deposition on silicon cantilevers aligned along the <110> and <100> silicon crystal

General Space-Confined On-Substrate Fabrication of Thickness-Adjustable Hybrid Perovskite Single-Crystalline Thin Films.

Science.gov (United States)

Chen, Yao-Xuan; Ge, Qian-Qing; Shi, Yang; Liu, Jie; Xue, Ding-Jiang; Ma, Jing-Yuan; Ding, Jie; Yan, Hui-Juan; Hu, Jin-Song; Wan, Li-Jun

2016-12-21

Organic-inorganic hybrid perovskite single-crystalline thin films (SCTFs) are promising for enhancing photoelectric device performance due to high carrier mobility, long diffusion length, and carrier lifetime. However, bulk perovskite single crystals available today are not suitable for practical device application due to the unfavorable thickness. Herein, we report a facile space-confined solution-processed strategy to on-substrate grow various hybrid perovskite SCTFs in a size of submillimeter with adjustable thicknesses from nano- to micrometers. These SCTFs exhibit photoelectric properties comparable to bulk single crystals with low defect density and good air stability. The clear thickness-dependent colors allow fast visual selection of SCTFs with a suitable thickness for specific device application. The present substrate-independent growth of perovskite SCTFs opens up opportunities for on-chip fabrication of diverse high-performance devices.

Thin film pc-Si by aluminium induced crystallization on metallic substrate

Directory of Open Access Journals (Sweden)

Cayron C.

2013-04-01

Full Text Available Thin film polycrystalline silicon (pc-Si on flexible metallic substrates is promising for low cost production of photovoltaic solar cells. One of the attractive methods to produce pc-Si solar cells consists in thickening a large-grained seed layer by epitaxy. In this work, the deposited seed layer is made by aluminium induced crystallization (AIC of an amorphous silicon (a-Si thin film on metallic substrates (Ni/Fe alloy initially coated with a tantalum nitride (TaN conductive diffusion barrier layer. Effect of the thermal budget on the AIC grown pc-Si seed layer was investigated in order to optimize the process (i.e. the quality of the pc-Si thin film. Structural and optical characterizations were carried out using optical microscopy, μ-Raman and Electron Backscatter Diffraction (EBSD. At optimal thermal annealing conditions, the continuous AIC grown pc-Si thin film showed an average grain size around 15 μm. The grains were preferably (001 oriented which is favorable for its epitaxial thickening. This work proves the feasibility of the AIC method to grow large grains pc-Si seed layer on TaN coated metal substrates. These results are, in terms of grains size, the finest obtained by AIC on metallic substrates.

Effect of deposition temperature on electron-beam evaporated polycrystalline silicon thin-film and crystallized by diode laser

Energy Technology Data Exchange (ETDEWEB)

Yun, J., E-mail: j.yun@unsw.edu.au; Varalmov, S.; Huang, J.; Green, M. A. [School of Photovoltaic and Renewable Energy Engineering, University of New South Wales, Sydney, New South Wales 2052 (Australia); Kim, K. [School of Photovoltaic and Renewable Energy Engineering, University of New South Wales, Sydney, New South Wales 2052 (Australia); Suntech R and D Australia, Botany, New South Wales 2019 (Australia)

2014-06-16

The effects of the deposition temperature on the microstructure, crystallographic orientation, and electrical properties of a 10-μm thick evaporated Si thin-film deposited on glass and crystallized using a diode laser, are investigated. The crystallization of the Si thin-film is initiated at a deposition temperature between 450 and 550 °C, and the predominant (110) orientation in the normal direction is found. Pole figure maps confirm that all films have a fiber texture and that it becomes stronger with increasing deposition temperature. Diode laser crystallization is performed, resulting in the formation of lateral grains along the laser scan direction. The laser power required to form lateral grains is higher in case of films deposited below 450 °C for all scan speeds. Pole figure maps show 75% occupancies of the (110) orientation in the normal direction when the laser crystallized film is deposited above 550 °C. A higher density of grain boundaries is obtained when the laser crystallized film is deposited below 450 °C, which limits the solar cell performance by n = 2 recombination, and a performance degradation is expected due to severe shunting.

Effect of medium range order on pulsed laser crystallization of amorphous germanium thin films

Energy Technology Data Exchange (ETDEWEB)

Li, T. T., E-mail: li48@llnl.gov; Bayu Aji, L. B.; Heo, T. W.; Kucheyev, S. O.; Campbell, G. H. [Materials Science Division, Lawrence Livermore National Laboratory, 7000 East Ave., Livermore, California 94551 (United States); Santala, M. K. [Mechanical, Industrial, and Manufacturing Engineering, Oregon State University, 204 Rogers Hall, Corvallis, Oregon 97331 (United States)

2016-05-30

Sputter deposited amorphous Ge thin films had their nanostructure altered by irradiation with high-energy Ar{sup +} ions. The change in the structure resulted in a reduction in medium range order (MRO) characterized using fluctuation electron microscopy. The pulsed laser crystallization kinetics of the as-deposited versus irradiated materials were investigated using the dynamic transmission electron microscope operated in the multi-frame movie mode. The propagation rate of the crystallization front for the irradiated material was lower; the changes were correlated to the MRO difference and formation of a thin liquid layer during crystallization.

Effect of medium range order on pulsed laser crystallization of amorphous germanium thin films

International Nuclear Information System (INIS)

Li, T. T.; Bayu Aji, L. B.; Heo, T. W.; Kucheyev, S. O.; Campbell, G. H.; Santala, M. K.

2016-01-01

Sputter deposited amorphous Ge thin films had their nanostructure altered by irradiation with high-energy Ar"+ ions. The change in the structure resulted in a reduction in medium range order (MRO) characterized using fluctuation electron microscopy. The pulsed laser crystallization kinetics of the as-deposited versus irradiated materials were investigated using the dynamic transmission electron microscope operated in the multi-frame movie mode. The propagation rate of the crystallization front for the irradiated material was lower; the changes were correlated to the MRO difference and formation of a thin liquid layer during crystallization.

Crystal orientation dependent thermoelectric properties of highly oriented aluminum-doped zinc oxide thin films

KAUST Repository

Abutaha, Anas I.

2013-02-06

We demonstrate that the thermoelectric properties of highly oriented Al-doped zinc oxide (AZO) thin films can be improved by controlling their crystal orientation. The crystal orientation of the AZO films was changed by changing the temperature of the laser deposition process on LaAlO3 (100) substrates. The change in surface termination of the LaAlO3 substrate with temperature induces a change in AZO film orientation. The anisotropic nature of electrical conductivity and Seebeck coefficient of the AZO films showed a favored thermoelectric performance in c-axis oriented films. These films gave the highest power factor of 0.26 W m−1 K−1 at 740 K.

Crystal and electronic structures of pentacene thin films from grazing-incidence x-ray diffraction and first-principles calculations

International Nuclear Information System (INIS)

Nabok, Dmitrii; Puschnig, Peter; Ambrosch-Draxl, Claudia; Werzer, Oliver; Resel, Roland; Smilgies, Detlef-M.

2007-01-01

Combined experimental and theoretical investigations on thin films of pentacene are performed in order to determine the structure of the pentacene thin film phase. Grazing incidence x-ray diffraction is used for studying a pentacene thin film with a nominal thickness of 180 nm. The crystal structure is found to exhibit the lattice parameters a=0.592 nm, b=0.754 nm, c=1.563 nm, α=81.5 deg. , β=87.2 deg. , and γ=89.9 deg. . These crystallographic unit cell dimensions are used as the only input parameters for ab initio total-energy calculations within the framework of density functional theory revealing the molecular packing within the crystal structure. Moreover, we calculate the electronic band structure of the thin film phase and compare it to that of the bulk phase. We find the intermolecular bandwidths of the thin film phase to be significantly larger compared to the bulk structure, e.g., the valence bandwidth is twice as large. This remarkable effect is traced back to an enhanced intermolecular π-π overlap due to the upright standing molecules in the thin film phase

Investigation of ferromagnetism in oxygen deficient hafnium oxide thin films

Energy Technology Data Exchange (ETDEWEB)

Hildebrandt, Erwin; Kurian, Jose; Krockenberger, Yoshiharu; Alff, Lambert [Institut fuer Materialwissenschaft, TU Darmstadt (Germany); Suter, Andreas [PSI, Villingen (Switzerland); Wilhelm, Fabrice; Rogalev, Andrei [ESRF, Grenoble (France)

2008-07-01

Oxygen deficient thin films of hafnium oxide were grown on single crystal r-cut and c-cut sapphire by reactive molecular beam epitaxy. RF-activated oxygen was used for the in situ oxidation of hafnium oxide thin films. Oxidation conditions were varied substantially in order to create oxygen deficiency in hafnium oxide films intentionally. The films were characterized by X-ray and magnetic measurements. X-ray diffraction studies show an increase in lattice parameter with increasing oxygen deficiency. Oxygen deficient hafnium oxide thin films also showed a decreasing bandgap with increase in oxygen deficiency. The magnetisation studies carried out with SQUID did not show any sign of ferromagnetism in the whole oxygen deficiency range. X-ray magnetic circular dichroism measurements also confirmed the absence of ferromagnetism in oxygen deficient hafnium oxide thin films.

Non-classical crystallization of thin films and nanostructures in CVD and PVD processes

CERN Document Server

Hwang, Nong Moon

2016-01-01

This book provides a comprehensive introduction to a recently-developed approach to the growth mechanism of thin films and nanostructures via chemical vapour deposition (CVD). Starting from the underlying principles of the low pressure synthesis of diamond films, it is shown that diamond growth occurs not by individual atoms but by charged nanoparticles. This newly-discovered growth mechanism turns out to be general to many CVD and some physical vapor deposition (PVD) processes. This non-classical crystallization is a new paradigm of crystal growth, with active research taking place on growth in solution, especially in biomineralization processes. Established understanding of the growth of thin films and nanostructures is based around processes involving individual atoms or molecules. According to the author’s research over the last two decades, however, the generation of charged gas phase nuclei is shown to be the rule rather than the exception in the CVD process, and charged gas phase nuclei are actively ...

Preparation of TiO2 thin films from autoclaved sol containing needle-like anatase crystals

International Nuclear Information System (INIS)

Ge Lei; Xu Mingxia; Fang Haibo; Sun Ming

2006-01-01

A new inorganic sol-gel method was introduced in this paper to prepare TiO 2 thin films. The autoclaved sol with needle-like anatase crystals was synthesized using titanyl sulfate (TiOSO 4 ) and peroxide (H 2 O 2 ) as starting materials. The transparent anatase TiO 2 thin films were prepared on glass slides from the autoclaved sol by sol-gel dip-coating method. A wide range of techniques such as Fourier transform infrared transmission spectra (FT-IR), X-ray diffraction (XRD), thermogravimetry-differential thermal analysis (TG-DTA), scanning electron microscopes, X-ray photoelectron spectroscopy (XPS) and ultraviolet-visible spectrum were applied to characterize the autoclaved sol and TiO 2 thin films. The results indicate that the autoclaved sol is flavescent, semitransparent and stable at room temperature. The anatase crystals of TiO 2 films connect together to form net-like structure after calcined and the films become uniform with increasing heating temperature. The surface of the TiO 2 films contain not only Ti and O elements, but also a small amount of N and Na elements diffused from substrates during heat treatment. The TiO 2 films are transparent and their maximal light transmittances exceed 80% under visible light region

Epitaxial Oxide Thin Films Grown by Solid Source Metal-Organic Chemical Vapor Deposition.

Science.gov (United States)

Lu, Zihong

1995-01-01

The conventional liquid source metal-organic chemical vapor deposition (MOCVD) technique is capable of producing large area, high quality, single crystal semiconductor films. However, the growth of complex oxide films by this method has been hampered by a lack of suitable source materials. While chemists have been actively searching for new source materials, the research work reported here has demonstrated the successful application of solid metal-organic sources (based on tetramethylheptanedionate) to the growth of high quality thin films of binary compound cerium dioxide (CeO_2), and two more complex materials, the ternary compound lithium niobate (LiNbO_3), with two cations, and the quaternary compound strontium barium niobate (SBN), with three cations. The growth of CeO_2 thin films on (1012)Al_2O_3 substrates has been used as a model to study the general growth behavior of oxides. Factors affecting deposition rate, surface morphology, out-of-plane mosaic structure, and film orientation have been carefully investigated. A kinetic model based on gas phase prereaction is proposed to account for the substrate temperature dependence of film orientation found in this system. Atomically smooth, single crystal quality cerium dioxide thin films have been obtained. Superconducting YBCO films sputtered on top of solid source MOCVD grown thin cerium dioxide buffer layers on sapphire have been shown to have physical properties as good as those of YBCO films grown on single crystal MgO substrates. The thin film growth of LiNbO_3 and Sr_{1-x}Ba _{x}Nb_2 O_6 (SBN) was more complex and challenging. Phase purity, transparency, in-plane orientation, and the ferroelectric polarity of LiNbO _3 films grown on sapphire substrates was investigated. The first optical quality, MOCVD grown LiNbO _3 films, having waveguiding losses of less than 2 dB/cm, were prepared. An important aspect of the SBN film growth studies involved finding a suitable single crystal substrate material. Mg

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.

Synthesis of BiFeO3 thin films on single-terminated Nb : SrTiO3 (111 substrates by intermittent microwave assisted hydrothermal method

Directory of Open Access Journals (Sweden)

Ivan Velasco-Davalos

2016-06-01

Full Text Available We report on a simple and fast procedure to create arrays of atomically flat terraces on single crystal SrTiO3 (111 substrates and the deposition of ferroelectric BiFeO3 thin films on such single-terminated surfaces. A microwave-assisted hydrothermal method in deionized water and ammonia solution selectively removes either (SrO34− or Ti4+ layers to ensure the same chemical termination on all terraces. Measured step heights of 0.225 nm (d111 and uniform contrast in the phase image of the terraces confirm the single termination in pure and Nb doped SrTiO3 single crystal substrates. Multiferroic BiFeO3 thin films were then deposited by the same microwave assisted hydrothermal process on Nb : SrTiO3 (111 substrates. Bi(NO33 and Fe(NO33 along with KOH served as the precursors solution. Ferroelectric behavior of the BiFeO3 films on Nb : SrTiO3 (100 substrates was verified by piezoresponse force microscopy.

Recovery Act : Near-Single-Crystalline Photovoltaic Thin Films on Polycrystalline, Flexible Substrates

Energy Technology Data Exchange (ETDEWEB)

Venkat Selvamanickam; Alex Freundlich

2010-11-29

III-V photovoltaics have exhibited efficiencies above 40%, but have found only a limited use because of the high cost of single crystal substrates. At the other end of the spectrum, polycrystalline and amorphous thin film solar cells offer the advantage of low-cost fabrication, but have not yielded high efficiencies. Our program is based on single-crystalline-like thin film photovoltaics on polycrystalline substrates using biaxially-textured templates made by Ion Beam-Assisted Deposition (IBAD). MgO templates made by IBAD on flexible metal substrate have been successfully used for epitaxial growth of germanium films. In spite of a 4.5% lattice mismatch, heteroepitaxial growth of Ge was achieved on CeO2 that was grown on IBAD MgO template. Room temperature optical bandgap of the Ge films was identified at 0.67 eV indicating minimal residual strain. Refraction index and extinction coefficient values of the Ge films were found to match well with that measured from a reference Ge single crystal. GaAs has been successfully grown epitaxially on Ge on metal substrate by molecular beam epitaxy. RHEED patterns indicate self annihilation of antiphase boundaries and the growth of a single domain GaAs. The GaAs is found to exhibit strong photoluminescence signal and, an existence of a relatively narrow (FWHM~20 meV) band-edge excitons measured in this film indicates a good optoelectronic quality of deposited GaAs. While excellent epitaxial growth has been achieved in GaAs on flexible metal substrates, the defect density of the films as measured by High Resolution X-ray Diffraction and etch pit experiments showed a high value of 5 * 10^8 per cm^2. Cross sectional transmission electron microscopy of the multilayer architecture showed concentration of threading dislocations near the germanium-ceria interface. The defect density was found decrease as the Ge films were made thicker. The defects appear to originate from the MgO layer presumably because of large lattice mismatches

Shape memory characteristics of sputter-deposited Ti-Ni thin films

International Nuclear Information System (INIS)

Miyazaki, Shuichi; Ishida, Akira.

1994-01-01

Ti-Ni shape memory alloy thin films were deposited using an RF magnetron sputtering apparatus. The as-sputtered films were heat-treated in order to crystallize and memorize. After the heat treatment, the shape memory characteristics have been investigated using DSC and thermomechanical tests. Upon cooling the thin films, the solution-treated films showed a single peak in the DSC curve indicating a single stage transformation occurring from B2 to the martensitic phase, while the age-treated films showed double peaks indicating a two-stage transformation, i.e., from B2 to the R-phase, then to the martensitic phase. A perfect shape memory effect was achieved in these sputter-deposited Ti-Ni thin films in association both with the R-phase and martensitic transformations. Transformation temperatures increased linearly with increasing applied stress. The transformation strain also increased with increasing stress. The shape memory characteristics were strongly affected by heat-treatment conditions. (author)

Praseodymium Cuprate Thin Film Cathodes for Intermediate Temperature Solid Oxide Fuel Cells: Roles of Doping, Orientation, and Crystal Structure.

Science.gov (United States)

Mukherjee, Kunal; Hayamizu, Yoshiaki; Kim, Chang Sub; Kolchina, Liudmila M; Mazo, Galina N; Istomin, Sergey Ya; Bishop, Sean R; Tuller, Harry L

2016-12-21

Highly textured thin films of undoped, Ce-doped, and Sr-doped Pr 2 CuO 4 were synthesized on single crystal YSZ substrates using pulsed laser deposition to investigate their area-specific resistance (ASR) as cathodes in solid-oxide fuel cells (SOFCs). The effects of T' and T* crystal structures, donor and acceptor doping, and a-axis and c-axis orientation on ASR were systematically studied using electrochemical impedance spectroscopy on half cells. The addition of both Ce and Sr dopants resulted in improvements in ASR in c-axis oriented films, as did the T* crystal structure with the a-axis orientation. Pr 1.6 Sr 0.4 CuO 4 is identified as a potential cathode material with nearly an order of magnitude faster oxygen reduction reaction kinetics at 600 °C compared to thin films of the commonly studied cathode material La 0.6 Sr 0.4 Co 0.8 Fe 0.2 O 3-δ . Orientation control of the cuprate films on YSZ was achieved using seed layers, and the anisotropy in the ASR was found to be less than an order of magnitude. The rare-earth doped cuprate was found to be a versatile system for study of relationships between bulk properties and the oxygen reduction reaction, critical for improving SOFC performance.

Constructing anisotropic single-Dirac-cones in Bi(1-x)Sb(x) thin films.

Science.gov (United States)

Tang, Shuang; Dresselhaus, Mildred S

2012-04-11

The electronic band structures of Bi(1-x)Sb(x) thin films can be varied as a function of temperature, pressure, stoichiometry, film thickness, and growth orientation. We here show how different anisotropic single-Dirac-cones can be constructed in a Bi(1-x)Sb(x) thin film for different applications or research purposes. For predicting anisotropic single-Dirac-cones, we have developed an iterative-two-dimensional-two-band model to get a consistent inverse-effective-mass-tensor and band gap, which can be used in a general two-dimensional system that has a nonparabolic dispersion relation as in the Bi(1-x)Sb(x) thin film system. © 2012 American Chemical Society

ZnO thin films on single carbon fibres fabricated by Pulsed Laser Deposition (PLD)

Energy Technology Data Exchange (ETDEWEB)

Krämer, André; Engel, Sebastian [Otto Schott Institute of Materials Research (OSIM), Friedrich Schiller University Jena, Löbdergraben 32, 07743 Jena (Germany); Sangiorgi, Nicola [Institute of Science and Technology for Ceramics – National Research Council of Italy (CNR-ISTEC), via Granarolo 64, 48018 Faenza, RA (Italy); Department of Chemical Science and Technologies, University of Rome Tor Vergata, via della Ricerca Scientifica, 00133 Rome (Italy); Sanson, Alessandra [Institute of Science and Technology for Ceramics – National Research Council of Italy (CNR-ISTEC), via Granarolo 64, 48018 Faenza, RA (Italy); Bartolomé, Jose F. [Instituto de Ciencia de Materiales de Madrid (ICMM), Consejo Superior de Investigaciones Científicas (CSIC), C/Sor Juana Inés de la Cruz 3, 28049 Madrid (Spain); Gräf, Stephan, E-mail: stephan.graef@uni-jena.de [Otto Schott Institute of Materials Research (OSIM), Friedrich Schiller University Jena, Löbdergraben 32, 07743 Jena (Germany); Müller, Frank A. [Otto Schott Institute of Materials Research (OSIM), Friedrich Schiller University Jena, Löbdergraben 32, 07743 Jena (Germany); Center for Energy and Environmental Chemistry Jena (CEEC Jena), Friedrich Schiller University Jena, Philosophenweg 7a, 07743 Jena (Germany)

2017-03-31

Highlights: • Carbon fibres were entirely coated with thin films consisting of aligned ZnO crystals. • A Q-switched CO2 laser was utilised as radiation source. • Suitability of ZnO thin films on carbon fibres as photo anodes for DSSC was studied. - Abstract: Single carbon fibres were 360° coated with zinc oxide (ZnO) thin films by pulsed laser deposition using a Q-switched CO{sub 2} laser with a pulse duration τ ≈ 300 ns, a wavelength λ = 10.59 μm, a repetition frequency f{sub rep} = 800 Hz and a peak power P{sub peak} = 15 kW in combination with a 3-step-deposition technique. In a first set of experiments, the deposition process was optimised by investigating the crystallinity of ZnO films on silicon and polished stainless steel substrates. Here, the influence of the substrate temperature and of the oxygen partial pressure of the background gas were characterised by scanning electron microscopy and X-ray diffraction analyses. ZnO coated carbon fibres and conductive glass sheets were used to prepare photo anodes for dye-sensitised solar cells in order to investigate their suitability for energy conversion devices. To obtain a deeper insight of the electronic behaviour at the interface between ZnO and substrate I–V measurements were performed.

Transverse anisotropic magnetoresistance effects in pseudo-single-crystal γ′-Fe4N thin films

Directory of Open Access Journals (Sweden)

Kazuki Kabara

2016-05-01

Full Text Available Transverse anisotropic magnetoresistance (AMR effects, for which magnetization is rotated in an orthogonal plane to the current direction, were investigated at various temperatures, in order to clarify the structural transformation from a cubic to a tetragonal symmetry in a pseudo-single-crystal Fe4N film, which is predicted from the usual in-plane AMR measurements by the theory taking into account the spin-orbit interaction and crystal field splitting of 3d bands. According to a phenomenological theory of AMR, which derives only from the crystal symmetry, a cos 2θ component ( C 2 tr exists in transverse AMR curves for a tetragonal system but does not for a cubic system. In the Fe4N film, the C 2 tr shows a positive small value (0.12% from 300 K to 50 K. However, the C 2 t r increases to negative value below 50 K and reaches to -2% at 5 K. The drastic increasing of the C 2 tr demonstrates the structural transformation from a cubic to a tetragonal symmetry below 50 K in the Fe4N film. In addition, the out-of-plane and in-plane lattice constants (c and a were precisely determined with X-ray diffraction at room temperature using the Nelson-Riely function. As a result, the positive small C 2 t r above 50 K is attributed to a slightly distorted Fe4N lattice (c/a = 1.002.

High-Performance Single-Crystalline Perovskite Thin-Film Photodetector

KAUST Repository

Yang, Zhenqian

2018-01-10

The best performing modern optoelectronic devices rely on single-crystalline thin-film (SC-TF) semiconductors grown epitaxially. The emerging halide perovskites, which can be synthesized via low-cost solution-based methods, have achieved substantial success in various optoelectronic devices including solar cells, lasers, light-emitting diodes, and photodetectors. However, to date, the performance of these perovskite devices based on polycrystalline thin-film active layers lags behind the epitaxially grown semiconductor devices. Here, a photodetector based on SC-TF perovskite active layer is reported with a record performance of a 50 million gain, 70 GHz gain-bandwidth product, and a 100-photon level detection limit at 180 Hz modulation bandwidth, which as far as we know are the highest values among all the reported perovskite photodetectors. The superior performance of the device originates from replacing polycrystalline thin film by a thickness-optimized SC-TF with much higher mobility and longer recombination time. The results indicate that high-performance perovskite devices based on SC-TF may become competitive in modern optoelectronics.

Photonic-Crystal-Based Thin Film Sensor for Detecting Volatile Organic Compounds

Energy Technology Data Exchange (ETDEWEB)

Chang, Hyung Kwan; Park, Jung Yul [Sogang Univ., Seoul (Korea, Republic of)

2016-03-15

Early detection of toxic gases, such as volatile organic compounds (VOCs), is important for safety and environmental protection. However, the conventional detection methods require long-term measurement times and expensive equipment. In this study, we propose a thin-film-type chemical sensor for VOCs, which consists of self assembled monosize nanoparticles for 3-D photonic crystal structures and polydimthylsiloxane (PDMS) film. It is operated without any external power source, is truly portable, and has a fast response time. The structure color of the sensor changes when it is exposed to VOCs, because VOCs induce a swelling of the PDMS. Therefore, using this principle of color change, we can create a thin-film sensor for immediate detection of various types of VOCs. The proposed device evidences that a fast response time of just seconds, along with a clear color change, are successfully observed when the sensor is exposed to gas-phase VOCs.

Coupling of carbon monoxide molecules over oxygen-defected UO2(111) single crystal and thin film surfaces.

Science.gov (United States)

Senanayake, S D; Waterhouse, G I N; Idriss, H; Madey, Theodore E

2005-11-22

While coupling reactions of carbon-containing compounds are numerous in organometallic chemistry, they are very rare on well-defined solid surfaces. In this work we show that the reductive coupling of two molecules of carbon monoxide to C2 compounds (acetylene and ethylene) could be achieved on oxygen-defected UO2(111) single crystal and thin film surfaces. This result allows in situ electron spectroscopic investigation of a typical organometallic reaction such as carbon coupling and extends it to heterogeneous catalysis and solids. By using high-resolution photoelectron spectroscopy (HRXPS) it was possible to track the changes in surface states of the U and O atoms as well as identify the intermediate of the reaction. Upon CO adsorption U cations in low oxidation states are oxidized to U4+ ions; this was accompanied by an increase of the O-to-U surface ratios. The HRXPS C 1s lines show the presence of adsorbed species assigned to diolate species (-OCH=CHO-) that are most likely the reaction intermediate in the coupling of two CO molecules to acetylene and ethylene.

Coupling of Carbon Monoxide Molecules over Oxygen Defected UO2 (111) Single Crystal and Thin Film Surfaces

International Nuclear Information System (INIS)

Senanayake, S.; Waterhouse, G.; Idriss, H.; Madey, T.

2005-01-01

While coupling reactions of carbon-containing compounds are numerous in organometallic chemistry, they are very rare on well-defined solid surfaces. In this work we show that the reductive coupling of two molecules of carbon monoxide to C 2 compounds (acetylene and ethylene) could be achieved on oxygen-defected UO 2 (111) single crystal and thin film surfaces. This result allows in situ electron spectroscopic investigation of a typical organometallic reaction such as carbon coupling and extends it to heterogeneous catalysis and solids. By using high-resolution photoelectron spectroscopy (HRXPS) it was possible to track the changes in surface states of the U and O atoms as well as identify the intermediate of the reaction. Upon CO adsorption U cations in low oxidation states are oxidized to U 4+ ions; this was accompanied by an increase of the O-to-U surface ratios. The HRXPS C 1s lines show the presence of adsorbed species assigned to diolate species (-OCH=CHO-) that are most likely the reaction intermediate in the coupling of two CO molecules to acetylene and ethylene

Organic field-effect transistors using single crystals

International Nuclear Information System (INIS)

Hasegawa, Tatsuo; Takeya, Jun

2009-01-01

Organic field-effect transistors using small-molecule organic single crystals are developed to investigate fundamental aspects of organic thin-film transistors that have been widely studied for possible future markets for 'plastic electronics'. In reviewing the physics and chemistry of single-crystal organic field-effect transistors (SC-OFETs), the nature of intrinsic charge dynamics is elucidated for the carriers induced at the single crystal surfaces of molecular semiconductors. Materials for SC-OFETs are first reviewed with descriptions of the fabrication methods and the field-effect characteristics. In particular, a benchmark carrier mobility of 20-40 cm 2 Vs -1 , achieved with thin platelets of rubrene single crystals, demonstrates the significance of the SC-OFETs and clarifies material limitations for organic devices. In the latter part of this review, we discuss the physics of microscopic charge transport by using SC-OFETs at metal/semiconductor contacts and along semiconductor/insulator interfaces. Most importantly, Hall effect and electron spin resonance (ESR) measurements reveal that interface charge transport in molecular semiconductors is properly described in terms of band transport and localization by charge traps. (topical review)

Thin aligned organic polymer films for liquid crystal devices

International Nuclear Information System (INIS)

Foster, Kathryn Ellen

1997-01-01

This project was designed to investigate the possibility of producing alignment layers for liquid crystal devices by cross-linking thin films containing anisotropic polymer bound chromophores via irradiation with polarised ultraviolet light. Photocross-linkable polymers find use in microelectronics, liquid crystal displays, printing and UV curable lacquers and inks; so there is an increasing incentive for the development of new varieties of photopolymers in general. The synthesis and characterisation of two new photopolymers that are suitable as potential alignment layers for liquid crystal devices are reported in this thesis. The first polymer contains the anthracene chromophore attached via a spacer unit to a methacrylate backbone and the second used a similarly attached aryl azide group. Copolymers of the new monomers with methyl methacrylate were investigated to establish reactivity ratios in order to understand composition drift during polymerisation. (author)

Thin Film Microbatteries

International Nuclear Information System (INIS)

Dudney, Nancy J.

2008-01-01

aerosol spray coating, for one or more components of the battery. The active materials used for the thin film cathodes and anodes are familiar intercalation compounds, but the microstructures and often the cycling properties of the thin films may be quite distinct from those of battery electrodes formed from powders. The thin film cathodes are dense and homogeneous with no added phases such as binders or electrolytes. When deposited at ambient temperatures, the films of cathodes, such as LiCoO 2 , V 2 O 5 , LiMn 2 O4 , LiFePO 4 are amorphous or nanocrystalline. But even in this form, they often act as excellent cathodes with large specific capacities and good stability for hundreds to thousands of cycles. Annealing the cathode films at temperatures of 300 to 800 C may be used to induce crystallization and grain growth of the desired intercalation compound. Crystallizing the cathode film generally improves the Li chemical diffusivity in the electrode material, and hence the power delivered by the battery, by 1-2 orders of magnitude. The microstructure is also tailored by the deposition and heat treatment. Figure 3 shows a fracture edge of an annealed LiCoO 2 cathode film on an alumina substrate. The columnar microstructure, which is typical of a vapor deposited film, sinters at high temperatures leaving small fissures between the dense columns. Such crystalline films also may have a preferred crystallographic orientation. For LiCoO 2 films the crystallographic texture differs for films deposited by sputtering versus pulse laser ablation processes. To improve the manufacturability of the thin film batteries, it would be beneficial to eliminate or minimize the temperature or duration of the annealing step. Several efforts have lead to low temperature fabrication of thin film batteries on polyimide substrates, but the battery capacity and rate are lower than those treated at high temperatures. For the battery anode, many designs use a vapor-deposited metallic lithium film as

Transient phases during crystallization of solution-processed organic thin films

Science.gov (United States)

Wan, Jing; Li, Yang; Ulbrandt, Jeffery; Smilgies, Detlef-M.; Hollin, Jonathan; Whalley, Adam; Headrick, Randall

We report an in-situ study of 2,7-dioctyl[1]benzothieno[3,2-b][1]benzothiophene (C8-BTBT) organic semiconductor thin film deposition from solution via hollow pen writing, which exhibits multiple transient phases during crystallization. Under high writing speed (25 mm/s) the films have an isotropic morphology, although the mobilities range up to 3.0 cm2/V.s. To understand the crystallization in this highly non-equilibrium regime, we employ in-situ microbeam grazing incidence wide-angle X-ray scattering combined with optical video microscopy at different deposition temperatures. A sequence of crystallization was observed in which a layered liquid-crystalline (LC) phase of C8-BTBT precedes inter-layer ordering. For films deposited above 80ºC, a transition from LC phase to a transient crystalline state that we denote as Cr1 occurs after a temperature-dependent incubation time, which is consistent with classical nucleation theory. After an additional ~ 0.5s, Cr1 transforms to the final stable structure Cr2. Based on these results, we demonstrate a method to produce large crystalline grain size and high carrier mobility during high-speed processing by controlling the nucleation rate during the transformation from the LC phase. Nsf DMR-1307017, NSF DMR-1332208.

High-quality EuO thin films the easy way via topotactic transformation

Science.gov (United States)

Mairoser, Thomas; Mundy, Julia A.; Melville, Alexander; Hodash, Daniel; Cueva, Paul; Held, Rainer; Glavic, Artur; Schubert, Jürgen; Muller, David A.; Schlom, Darrell G.; Schmehl, Andreas

2015-07-01

Epitaxy is widely employed to create highly oriented crystalline films. A less appreciated, but nonetheless powerful means of creating such films is via topotactic transformation, in which a chemical reaction transforms a single crystal of one phase into a single crystal of a different phase, which inherits its orientation from the original crystal. Topotactic reactions may be applied to epitactic films to substitute, add or remove ions to yield epitactic films of different phases. Here we exploit a topotactic reduction reaction to provide a non-ultra-high vacuum (UHV) means of growing highly oriented single crystalline thin films of the easily over-oxidized half-metallic semiconductor europium monoxide (EuO) with a perfection rivalling that of the best films of the same material grown by molecular-beam epitaxy or UHV pulsed-laser deposition. As the technique only requires high-vacuum deposition equipment, it has the potential to drastically improve the accessibility of high-quality single crystalline films of EuO as well as other difficult-to-synthesize compounds.

Relaxation in Thin Polymer Films Mapped across the Film Thickness by Astigmatic Single-Molecule Imaging

KAUST Repository

Oba, Tatsuya; Vacha, Martin

2012-01-01

We have studied relaxation processes in thin supported films of poly(methyl acrylate) at the temperature corresponding to 13 K above the glass transition by monitoring the reorientation of single perylenediimide molecules doped into the films

Quartz Crystal Microbalance Coated with Sol-gel-derived Thin Films as Gas Sensor for NO Detection

Directory of Open Access Journals (Sweden)

S. J. O’Shea

2003-10-01

Full Text Available This paper presents the possibilities and properties of Indium tin oxide (ITO-covered quartz crystal as a NOx toxic gas-sensor. The starting sol-gel solution was prepared by mixing indium chloride dissolved in acetylacetone and tin chloride dissolved in ethanol (0-20% by weight. The ITO thin films were deposited on the gold electrodes of quartz crystal by spin-coating technique and subsequently followed a standard photolithography to pattern the derived films to ensure all sensors with the same sensing areas. All heat treatment processes were controlled below 500°C in order to avoid the piezoelectric characteristics degradation of quartz crystal (Quartz will lose its piezoelectricity at ~573°C due to the phase change from α to β. The electrical and structural properties of ITO thin films were characterized with Hall analysis system, TG/DTA, XRD, XPS, SEM and etc. The gas sensor had featured with ITO thin films of ~100nm as the receptor to sense the toxic gas NO and quartz crystal with frequency of 10MHz as the transducer to transfer the surface reactions (mass loading, etc into the frequency shift. A homemade setup had been employed to measure the sensor response under the static mode. The experimental results had indicated that the ITO-coated QCM had a good sensitivity for NO gas, ~12Hz/100ppm within 5mins. These results prove that the ITO-covered quartz crystals are usable as a gas sensor and as an analytical device.

Magnetization of correlated electron systems. MnSi thin films, CrB2 single crystals and two-dimensional electron systems in MgZnO/ZnO

International Nuclear Information System (INIS)

Brasse, Matthias

2014-01-01

Torque magnetometry at low temperature is performed to investigate the magnetic properties of MnSi thin films, of a CrB 2 single crystal and of a two-dimensional electron system (2DESs) formed at the interface of MgZnO/ZnO. The magnetic anisotropy and phase diagram of MnSi as well as information on the electronic structure of CrB 2 are obtained. The MgZnO/ZnO 2DESs exhibits the de Haas-van Alphen effect and non-equilibrium currents which are analyzed in order to determine ground state properties and excited states, respectively.

Crystal structure and thin film morphology of BBL ladder polymer

Energy Technology Data Exchange (ETDEWEB)

Song, H H [Department of Macromolecular Science, Han Nam University, Taejon (Korea, Republic of); Fratini, A V [Department of Chemistry, University of Dayton, Dayton, OH (United States); Chabinyc, M [Department of Chemistry, University of Dayton, Dayton, OH (United States); Price, G E [University of Dayton Research, Dayton, OH (United States); Agrawal, A K [Systran Corporation, Dayton, OH (United States); Wang, C S [University of Dayton Research, Dayton, OH (United States); Burkette, J [University of Dayton Research, Dayton, OH (United States); Dudis, D S [Materials Directorate, Wright Laboratory, Wright-Patterson Air Force Base, OH (United States); Arnold, F E [Materials Directorate, Wright Laboratory, Wright-Patterson Air Force Base, OH (United States)

1995-03-01

Crystal structure and morphology of poly[7-oxo-7H-benz(d,e)imidazo(4`,5`:5,6)-benzimidazo(2,1-a)isoquinoline-3,4:10,11-tetrayl-10-carbonyl] (BBL) ladder-like polymer were studied. The polymer forms a two-dimensional lattice of nematic liquid crystalline structure. An orthorhombic unit cell with cell parameters of a=7.87 b=3.37 c=11.97A was determined from the fiber diffraction pattern. In thin films, the rigid chains spontaneously form a layered structure across the film thickness, but in a very unusual manner, i.e. the very large molecular plane is standing perpendicularly to the film surface plane. The results are identical to our recent results of poly(p-phenylene benzobisthiazole) (PBT) film [7]. The polymer, however, lost its anisotropic order upon extrusion into a film and resulted in a fiber-like structure. (orig.)

Ground Based Experiments in Support of Microgravity Research Results-Vapor Growth of Organic Nonlinear Optical Thin Film

Science.gov (United States)

Zugrav, M. Ittu; Carswell, William E.; Haulenbeek, Glen B.; Wessling, Francis C.

2001-01-01

This work is specifically focused on explaining previous results obtained for the crystal growth of an organic material in a reduced gravity environment. On STS-59, in April 1994, two experiments were conducted with N,N-dimethyl-p-(2,2-dicyanovinyl) aniline (DCVA), a promising nonlinear optical (NLO) material. The space experiments were set to reproduce laboratory experiments that yielded small, bulk crystals of DCVA. The results of the flight experiment, however, were surprising. Rather than producing a bulk single crystal, the result was the production of two high quality, single crystalline thin films. This result was even more intriguing when it is considered that thin films are more desirable for NLO applications than are bulk single crystals. Repeated attempts on the ground to reproduce these results were fruitless. A second set of flight experiments was conducted on STS-69 in September 1995. This time eight DCVA experiments were flown, with each of seven experiments containing a slight change from the first reference experiment. The reference experiment was programmed with growth conditions identical to those of the STS-59 mission. The slight variations in each of the other seven were an attempt to understand what particular parameter was responsible for the preference of thin film growth over bulk crystal growth in microgravity. Once again the results were surprising. In all eight cases thin films were grown again, albeit with varying quality. So now we were faced with a phenomenon that not only takes place in microgravity, but also is very robust, resisting all attempts to force the growth of bulk single crystals.

Nano-crystallization in ZnO-doped In_2O_3 thin films via excimer laser annealing for thin-film transistors

International Nuclear Information System (INIS)

Fujii, Mami N.; Ishikawa, Yasuaki; Bermundo, Juan Paolo Soria; Uraoka, Yukiharu; Ishihara, Ryoichi; Cingel, Johan van der; Mofrad, Mohammad R. T.; Kawashima, Emi; Tomai, Shigekazu; Yano, Koki

2016-01-01

In a previous work, we reported the high field effect mobility of ZnO-doped In_2O_3 (IZO) thin film transistors (TFTs) irradiated by excimer laser annealing (ELA) [M. Fujii et al., Appl. Phys. Lett. 102, 122107 (2013)]. However, a deeper understanding of the effect of ELA on the IZO film characteristics based on crystallinity, carrier concentrations, and optical properties is needed to control localized carrier concentrations for fabricating self-aligned structures in the same oxide film and to adequately explain the physical characteristics. In the case of as-deposited IZO film used as the channel, a high carrier concentration due to a high density of oxygen vacancies was observed; such a film does not show the required TFT characteristics but can act as a conductive film. We achieved a decrease in the carrier concentration of IZO films by crystallization using ELA. This means that ELA can form localized conductive or semi-conductive areas on the IZO film. We confirmed that the reason for the carrier concentration decrease was the decrease of oxygen-deficient regions and film crystallization. The annealed IZO films showed nano-crystalline phase, and the temperature at the substrate was substantially less than the temperature limit for flexible films such as plastic, which is 50°C. This paves the way for the formation of self-aligned structures and separately formed conductive and semi-conductive regions in the same oxide film.

Topography evolution of germanium thin films synthesized by pulsed laser deposition

Directory of Open Access Journals (Sweden)

P. Schumacher

2017-04-01

Full Text Available Germanium thin films were deposited by Pulsed Laser Deposition (PLD onto single crystal Ge (100 and Si (100 substrates with a native oxide film on the surface. The topography of the surface was investigated by Atomic Force Microscopy (AFM to evaluate the scaling behavior of the surface roughness of amorphous and polycrystalline Ge films grown on substrates with different roughnesses. Roughness evolution was interpreted within the framework of stochastic rate equations for thin film growth. Here the Kardar-Parisi-Zhang equation was used to describe the smoothening process. Additionally, a roughening regime was observed in which 3-dimensional growth occurred. Diffusion of the deposited Ge adatoms controlled the growth of the amorphous Ge thin films. The growth of polycrystalline thin Ge films was dominated by diffusion processes only in the initial stage of the growth.

THIN FILMS OF A NEW ORGANIC SINGLE-COMPONENT FERROELECTRIC 2-METHYLBENZIMIDAZOLE

Directory of Open Access Journals (Sweden)

E. V. Balashova

2016-09-01

Full Text Available Subject of Research.We present results of structural and dielectric study of organic ferroelectric 2-methylbenzimidazole (MBI thin films. Method. The films have been grown on substrates of leuco-sapphire, fused and crystalline silica, neodymium gallate, bismuth germanate, gold, aluminium, platinum. The films have been grown by two different methods: substrate covering by ethanol solution of MBI and subsequent ethanol evaporation; sublimation at the temperature near 375 K under atmospheric pressure. Crystallographic orientation studies have been performed by means of «DRON-3» X-ray diffractometer, block structure of the films has been determined by «LaboPol-3» polarizing microscope. Small-signal dielectric response has been received with the use of «MIT 9216A» digital LCR-meter, while strong-signal dielectric response has been studied by Sawyer-Tower circuit. Main Resuts. We have shown that the films obtained by evaporation are continuous and textured. Obtained film structure depends on the concentration of the solution. Films may consist of blocks that are splitted crystals like spherulite. Spontaneous polarization components in such films may be directed both perpendicularly and in the film plane. We have also obtained structures consisting of single-crystal blocks with spontaneous polarization components being allocated in the film plane. Block sizes vary from a few to hundreds of microns. Films obtained by sublimation are amorphous or dendritic. The dielectric properties of the films obtained by evaporation have been studied. We have shown that the dielectric constant and dielectric loss tangent increase under heating. The dielectric hysteresis loops are observed at the temperature equal to 291-379 K. The remnant polarization increases with temperature for constant amplitude of the external electric field, and achieves 4.5mC/cm2, while the coercive field remains constant. We propose that such behavior is explained by increase of the

Microstructure and mechanical behavior of a shape memory Ni-Ti bi-layer thin film

Energy Technology Data Exchange (ETDEWEB)

Mohri, Maryam [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, E-mail: nili@ut.ac.ir [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); Ivanisenko, Julia [Karlsruhe Institute of Technology, Institute of Nanotechnology, 76021 Karlsruhe (Germany); Schwaiger, Ruth [Karlsruhe Institute of Technology, Institute for Applied Materials, 76021 Karlsruhe (Germany); Hahn, Horst; Chakravadhanula, Venkata Sai Kiran [Karlsruhe Institute of Technology, Institute of Nanotechnology, 76021 Karlsruhe (Germany)

2015-05-29

Two different single-layers and a bi-layer Ni-Ti thin films with chemical compositions of Ni{sub 45}Ti{sub 50}Cu{sub 5}, Ni{sub 50.8}Ti{sub 49.2} and Ni{sub 50.8}Ti{sub 49.2}/Ni{sub 45}Ti{sub 50}Cu{sub 5} (numbers indicate at.%) determined by energy dispersive X-ray spectroscopy were deposited on Si (111) substrates using DC magnetron sputtering. The structures, surface morphology and transformation temperatures of annealed thin films at 500 °C for 15 min and 1 h were studied using grazing incidence X-ray diffraction, transmission electron microscopy (TEM), atomic force microscopy and differential scanning calorimetry (DSC), respectively. Nanoindentation was used to characterize the mechanical properties. The DSC and X-ray diffraction results indicated the austenitic structure of the Ni{sub 50.8}Ti{sub 49.2} and martensitic structure of the Ni{sub 45}Ti{sub 50}Cu{sub 5} thin films while the bi-layer was composed of austenitic and martensitic thin films. TEM study revealed that copper encourages crystallization in the bi-layer such that crystal structure containing nano-precipitates in the Ni{sub 45}Ti{sub 50}Cu{sub 5} layer was detected after 15 min annealing while the Ni{sub 50.8}Ti{sub 49.2} layer crystallized after 60 min at 500 °C. Furthermore, after annealing at 500 °C for 15 min, a precipitate free zone and thin layer amorphous were observed closely to the interface in the top layer. The bi-layer was completely crystallized at 500 °C for 1 h and the orientation of the Ni-rich precipitates indicated a stress gradient in the bi-layer. The bi-layer thin film showed different transformation temperatures and mechanical behavior from the single-layers. The developed bi-layer has different phase transformation temperatures, the higher temperatures of shape memory effect and lower temperature of pseudo-elastic behavior compared to the single-layers. Also, the bi-layer thin film exhibited a combined pseudo-elastic behavior and shape memory effect with a reduced

Electron Microscopy Characterization of Vanadium Dioxide Thin Films and Nanoparticles

Science.gov (United States)

Rivera, Felipe

Vanadium dioxide (VO_2) is a material of particular interest due to its exhibited metal to insulator phase transition at 68°C that is accompanied by an abrupt and significant change in its electronic and optical properties. Since this material can exhibit a reversible drop in resistivity of up to five orders of magnitude and a reversible drop in infrared optical transmission of up to 80%, this material holds promise in several technological applications. Solid phase crystallization of VO_2 thin films was obtained by a post-deposition annealing process of a VO_{x,x approx 2} amorphous film sputtered on an amorphous silicon dioxide (SiO_2) layer. Scanning electron microscopy (SEM) and electron-backscattered diffraction (EBSD) were utilized to study the morphology of the solid phase crystallization that resulted from this post-deposition annealing process. The annealing parameters ranged in temperature from 300°C up to 1000°C and in time from 5 minutes up to 12 hours. Depending on the annealing parameters, EBSD showed that this process yielded polycrystalline vanadium dioxide thin films, semi-continuous thin films, and films of isolated single-crystal particles. In addition to these films on SiO_2, other VO_2 thin films were deposited onto a-, c-, and r-cuts of sapphire and on TiO_2(001) heated single-crystal substrates by pulsed-laser deposition (PLD). The temperature of the substrates was kept at ˜500°C during deposition. EBSD maps and orientation imaging microscopy were used to study the epitaxy and orientation of the VO_2 grains deposited on the single crystal substrates, as well as on the amorphous SiO_2 layer. The EBSD/OIM results showed that: 1) For all the sapphire substrates analyzed, there is a predominant family of crystallographic relationships wherein the rutile VO_2{001} planes tend to lie parallel to the sapphire's {10-10} and the rutile VO_2{100} planes lie parallel to the sapphire's {1-210} and {0001}. Furthermore, while this family of

Single-crystal films of a combination of materials (co-crystal) involving DAST and IR-125 for electro-optic applications

Science.gov (United States)

Narayanan, A.; Titus, J.; Rajagopalan, H.; Vippa, P.; Thakur, M.

2006-03-01

Single-crystal film of DAST (4'-dimethylamino-N-methyl-4-stilbazolium tosylate) has been shown [1] to have exceptionally large electro-optic coefficients (r11 ˜ 770 pm/V at 633 nm). In this report, single crystal film of a combination of materials (co-crystal) involving DAST and a dye molecule IR-125 will be discussed. Modified shear method was used to prepare the co-crystal films. The film has been characterized using polarized optical microscopy, optical absorption spectroscopy and x-ray diffraction. The optical absorption spectrum has two major bands: one at about 350--600 nm corresponding to DAST and the other at about 600-900 nm corresponding to IR-125. The x-ray diffraction results show peaks involving the presence of DAST and IR-125 within the co-crystal film. Since the co-crystal has strong absorption at longer wavelengths it is expected to show higher electro-optic coefficients at longer wavelengths. Preliminary measurements at 1.55 μm indicate a high electro-optic coefficient of the co-crystal film. [1] Swamy, Kutty, Titus, Khatavkar, Thakur, Appl. Phys. Lett. 2004, 85, 4025; Kutty, Thakur, Appl. Phys. Lett. 2005, 87, 191111.

Organic field-effect transistors using single crystals

Directory of Open Access Journals (Sweden)

Tatsuo Hasegawa and Jun Takeya

2009-01-01

Full Text Available Organic field-effect transistors using small-molecule organic single crystals are developed to investigate fundamental aspects of organic thin-film transistors that have been widely studied for possible future markets for 'plastic electronics'. In reviewing the physics and chemistry of single-crystal organic field-effect transistors (SC-OFETs, the nature of intrinsic charge dynamics is elucidated for the carriers induced at the single crystal surfaces of molecular semiconductors. Materials for SC-OFETs are first reviewed with descriptions of the fabrication methods and the field-effect characteristics. In particular, a benchmark carrier mobility of 20–40 cm2 Vs−1, achieved with thin platelets of rubrene single crystals, demonstrates the significance of the SC-OFETs and clarifies material limitations for organic devices. In the latter part of this review, we discuss the physics of microscopic charge transport by using SC-OFETs at metal/semiconductor contacts and along semiconductor/insulator interfaces. Most importantly, Hall effect and electron spin resonance (ESR measurements reveal that interface charge transport in molecular semiconductors is properly described in terms of band transport and localization by charge traps.

Structural effects in UO{sub 2} thin films irradiated with U ions

Energy Technology Data Exchange (ETDEWEB)

Popel, A.J., E-mail: apopel@cantab.net [Department of Earth Sciences, University of Cambridge, Downing Street, Cambridge CB2 3EQ (United Kingdom); Adamska, A.M.; Martin, P.G.; Payton, O.D. [Interface Analysis Centre, School of Physics, University of Bristol, Bristol BS8 1TL (United Kingdom); Lampronti, G.I. [Department of Earth Sciences, University of Cambridge, Downing Street, Cambridge CB2 3EQ (United Kingdom); Picco, L.; Payne, L.; Springell, R.; Scott, T.B. [Interface Analysis Centre, School of Physics, University of Bristol, Bristol BS8 1TL (United Kingdom); Monnet, I.; Grygiel, C. [CIMAP, CEA-CNRS-ENSICAEN-Université de Caen, BP 5133, 14070 Caen Cedex5 (France); Farnan, I. [Department of Earth Sciences, University of Cambridge, Downing Street, Cambridge CB2 3EQ (United Kingdom)

2016-11-01

Highlights: • Quantitative characterisation of radiation damage by kernel average misorientation. • UO{sub 2} (1 1 1) plane showed higher irradiation tolerance than (1 1 0) plane. • UO{sub 2} film-YSZ substrate interface is stable under low fluence irradiation. • (0 0 1), (1 1 0), (1 1 1) single crystal UO{sub 2} thin films on YSZ substrates are expected. - Abstract: This work presents the results of a detailed structural characterisation of irradiated and unirradiated single crystal thin films of UO{sub 2}. Thin films of UO{sub 2} were produced by reactive magnetron sputtering onto (0 0 1), (1 1 0) and (1 1 1) single crystal yttria-stabilised zirconia (YSZ) substrates. Half of the samples were irradiated with 110 MeV {sup 238}U{sup 31+} ions to fluences of 5 × 10{sup 10}, 5 × 10{sup 11} and 5 × 10{sup 12} ions/cm{sup 2} to induce radiation damage, with the remainder kept for reference measurements. It was observed that as-produced UO{sub 2} films adopted the crystallographic orientation of their YSZ substrates. The irradiation fluences used in this study however, were not sufficient to cause any permanent change in the crystalline nature of UO{sub 2}. It has been demonstrated that the effect of epitaxial re-crystallisation of the induced radiation damage can be quantified in terms of kernel average misorientation (KAM) and different crystallographic orientations of UO{sub 2} respond differently to ion irradiation.

Fabrication of flexible polymer dispersed liquid crystal films using conducting polymer thin films as the driving electrodes

International Nuclear Information System (INIS)

Kim, Yang-Bae; Park, Sucheol; Hong, Jin-Who

2009-01-01

Conducting polymers exhibit good mechanical and interfacial compatibility with plastic substrates. We prepared an optimized coating formulation based on poly(3,4-ethylenedioxythiophene) (PEDOT) and 3-(trimethoxysilyl)propyl acrylate and fabricated a transparent electrode on poly(ethylene terephthalate) (PET) substrate. The surface resistances and transmittance of the prepared thin films were 500-600 Ω/□ and 87% at 500 nm, respectively. To evaluate the performance of the conducting polymer electrode, we fabricated a five-layer flexible polymer-dispersed liquid crystal (PDLC) device as a PET-PEDOT-PDLC-PEDOT-PET flexible film. The prepared PDLC device exhibited a low driving voltage (15 VAC), high contrast ratio (60:1), and high transmittance in the ON state (60%), characteristics that are comparable with those of conventional PDLC film based on indium tin oxide electrodes. The fabrication of conducting polymer thin films as the driving electrodes in this study showed that such films can be used as a substitute for an indium tin oxide electrode, which further enhances the flexibility of PDLC film

Enhanced electrical properties in bilayered ferroelectric thin films

Science.gov (United States)

Zhang, Hao; Long, WeiJie; Chen, YaQing; Guo, DongJie

2013-03-01

Sr2Bi4Ti5O18 (SBTi) single layered and Sr2Bi4Ti5O18/Pb(Zr0.53Ti0.47)O3 (SBTi/PZT) bilayered thin films have been prepared on Pt/TiO2/SiO2/Si substrates by pulsed-laser deposition (PLD). The related structural characterizations and electrical properties have been comparatively investigated. X-ray diffraction reveals that both films have crystallized into perovskite phases and scanning electron microscopy shows the sharp interfaces. Both films show well-saturated ferroelectric hysteresis loops, however, compared with the single layered SBTi films, the SBTi/PZT bilayered films have significantly increased remnant polarization ( P r) and decreased coercive field ( E c), with the applied field of 260 kV/cm. The measured P r and E c of SBTi and SBTi/PZT films were 7.9 μC/cm2, 88.1 kV/cm and 13.0 μC/cm2, 51.2 kV/cm, respectively. In addition, both films showed good fatigue-free characteristics, the switchable polarization decreased by 9% and 11% of the initial values after 2.2×109 switching cycles for the SBTi single layered films and the SBTi/PZT bilayered films, respectively. Our results may provide some guidelines for further optimization of multilayered ferroelectric thin films.

Influence of the additive Ag for crystallization of amorphous Ge-Sb-Te thin films

Energy Technology Data Exchange (ETDEWEB)

Song, Ki-Ho; Kim, Sung-Won; Seo, Jae-Hee [Faculty of Applied Chemical Engineering, Chonnam National University, 300 Yongbong-dong, Kwangju 500-757 (Korea, Republic of); Lee, Hyun-Yong, E-mail: hyleee@chonnam.ac.k [Faculty of Applied Chemical Engineering, Chonnam National University, 300 Yongbong-dong, Kwangju 500-757 (Korea, Republic of)

2009-05-29

We have investigated the optical and amorphous-to-crystalline transition properties in four-types of chalcogenide thin films; Ge{sub 2}Sb{sub 2}Te{sub 5}, Ge{sub 8}Sb{sub 2}Te{sub 11}, Ag-Ge{sub 2}Sb{sub 2}Te{sub 5} and Ag-Ge{sub 8}Sb{sub 2}Te{sub 11}. Crystallization was caused by nano-pulse illumination ({lambda} = 658 nm) with power (P) of 1-17 mW and pulse duration (t) of 10-460 ns, and the morphologies of crystallized spots were observed by SEM and microscope. It was found that the crystallized spot nearby linearly increases in size with increasing the illuminating energy (E = P {center_dot} t) and eventually ablated out by over illumination. Changes in the optical transmittance of as-deposited and annealed films were measured using a UV-vis-IR spectrophotometer. In addition, a speed of amorphous-to-crystalline transition was evaluated by detecting the reflection response signals for the nano-pulse scanning. Conclusively, the Ge{sub 8}Sb{sub 2}Te{sub 11} film has a faster crystallization speed than the Ge{sub 2}Sb{sub 2}Te{sub 5} film despite its higher crystallization temperature. The crystallization speed was largely improved by adding Ag in Ge{sub 2}Sb{sub 2}Te{sub 5} film but not in Ge{sub 8}Sb{sub 2}Te{sub 11} film. To explain these results, we considered a heat confinement by electron hopping.

Crystallized InBiS3 thin films with enhanced optoelectronic properties

Science.gov (United States)

Ali, N.; Hussain, Arshad; Ahmed, R.; Omar, M. Firdaus Bin; Sultan, M.; Fu, Yong Qing

2018-04-01

In this paper, a one-step thermal evaporation approach was used for fabrication of indium bismuth sulphide thin films, and the synergetic effects of co-evaporation of two sources (indium granules and Bi2S3 powders) were investigated using different characterization techniques. X-ray diffraction (XRD) analysis confirmed the crystalline orthorhombic structure for the post-annealed samples. Surface roughness and crystal size of the obtained film samples were increased with increasing annealing temperatures. Analysis using X-ray photoelectron spectroscopy showed the formation of the InBiS3 structure for the obtained films, which is also confirmed by the XRD results. The optical absorption coefficient value of the annealed samples was found to be in the order of 105 cm-1 in the visible region of the solar spectrum. The optical band gap energy and electrical resistivity of the fabricated samples were observed to decrease (from 2.2 to 1.3 eV, and from 0.3 to 0.01 Ω-cm, respectively) with increasing annealing temperatures (from 200 to 350 °C), indicating the suitability of the prepared InBiS3 thin films for solar cell applications.

Primary and aggregate color centers in proton irradiated LiF crystals and thin films for luminescent solid state detectors

Science.gov (United States)

Piccinini, M.; Ambrosini, F.; Ampollini, A.; Bonfigli, F.; Libera, S.; Picardi, L.; Ronsivalle, C.; Vincenti, M. A.; Montereali, R. M.

2015-04-01

Proton beams of 3 MeV energy, produced by the injector of a linear accelerator for proton therapy, were used to irradiate at room temperature lithium fluoride crystals and polycrystalline thin films grown by thermal evaporation. The irradiation fluence range was 1011-1015 protons/cm2. The proton irradiation induced the stable formation of primary and aggregate color centers. Their formation was investigated by optical absorption and photoluminescence spectroscopy. The F2 and F3+ photoluminescence intensities, carefully measured in LiF crystals and thin films, show linear behaviours up to different maximum values of the irradiation fluence, after which a quenching is observed, depending on the nature of the samples (crystals and films). The Principal Component Analysis, applied to the absorption spectra of colored crystals, allowed to clearly identify the formation of more complex aggregate defects in samples irradiated at highest fluences.

Solvent-induced crystallization for hybrid perovskite thin-film photodetector with high-performance and low working voltage

International Nuclear Information System (INIS)

Hu, Wei; Yang, Shuzhen; Fan, Peng; Pan, Anlian; Wu, Runsheng; Yang, Junliang

2017-01-01

Organometal trihalide perovskites have emerged as a class of solution-processed semiconductors exhibiting remarkable optoelectronic properties. Using a high-quality perovskite thin film prepared by solvent-induced crystallization method and adopting a novel device configuration based on photon recycling effect, a perovskite thin-film photodetector has been constructed with the highest external quantum efficiency of 4.1  ×  10 4 % and responsivity of 219 A W −1 at a low bias of 1 V so far. The device working mechanism was further disclosed based on energy band bending model. The high-performance and low working-voltage perovskite thin-film photodetector will find potential applications in photodetection and optoelectronic integrated circuits. (paper)

Aluminum nitride and nanodiamond thin film microstructures

Energy Technology Data Exchange (ETDEWEB)

Knoebber, Fabian; Bludau, Oliver; Roehlig, Claus-Christian; Williams, Oliver; Sah, Ram Ekwal; Kirste, Lutz; Cimalla, Volker; Lebedev, Vadim; Nebel, Christoph; Ambacher, Oliver [Fraunhofer-Institute for Applied Solid State Physics, Freiburg (Germany)

2010-07-01

In this work, aluminum nitride (AlN) and nanocrystalline diamond (NCD) thin film microstructures have been developed. Freestanding NCD membranes were coated with a piezoelectrical AlN layer in order to build tunable micro-lens arrays. For the evaluation of the single material quality, AlN and NCD thin films on silicon substrates were fabricated using RF magnetron sputtering and microwave chemical vapor deposition techniques, respectively. The crystal quality of AlN was investigated by X-ray diffraction. The piezoelectric constant d{sub 33} was determined by scanning laser vibrometry. The NCD thin films were optimized with respect to surface roughness, mechanical stability, intrinsic stress and transparency. To determine the mechanical properties of the materials, both, micromechanical resonator and membrane structures were fabricated and measured by magnetomotive resonant frequency spectroscopy and bulging experiments, respectively. Finally, the behavior of AlN/NCD heterostructures was modeled using the finite element method and the first structures were characterized by piezoelectrical measurements.

Metal-insulator transition induced in CaVO3 thin films

International Nuclear Information System (INIS)

Gu Man; Laverock, Jude; Chen, Bo; Smith, Kevin E.; Wolf, Stuart A.; Lu Jiwei

2013-01-01

Stoichiometric CaVO 3 (CVO) thin films of various thicknesses were grown on single crystal SrTiO 3 (STO) (001) substrates using a pulsed electron-beam deposition technique. The CVO films were capped with a 2.5 nm STO layer. We observed a temperature driven metal-insulator transition (MIT) in CVO films with thicknesses below 4 nm that was not observed in either thick CVO films or STO films. The emergence of this MIT can be attributed to the reduction in effective bandwidth due to a crossover from a three-dimensional metal to a two-dimensional insulator. The insulating phase was only induced with a drive current below 0.1 μA. X-ray absorption measurements indicated different electronic structures for thick and very thin films of CVO. Compared with the thick film (∼60 nm), thin films of CVO (2–4 nm) were more two-dimensional with the V charge state closer to V 4+ .

Advances in thin-film solar cells for lightweight space photovoltaic power

Science.gov (United States)

Landis, Geoffrey A.; Bailey, Sheila G.; Flood, Dennis J.

1989-01-01

The development of photovoltaic arrays beyond the next generation is discussed with attention given to the potentials of thin-film polycrystalline and amorphous cells. Of particular importance is the efficiency (the fraction of incident solar energy converted to electricity) and specific power (power to weight ratio). It is found that the radiation tolerance of thin-film materials is far greater than that of single crystal materials. CuInSe2 shows no degradation when exposed to 1-MeV electrons.

UV detectors based on epitaxial diamond films grown on single-crystal diamond substrates by vapor-phase synthesis

International Nuclear Information System (INIS)

Sharonov, G.V.; Petrov, S.A.; Bol'shakov, A.P.; Ral'chenko, V.G.; Kazyuchits, N.M.

2010-01-01

The prospects for use of CVD-technology for epitaxial growth of single-crystal diamond films of instrumental quality in UHF plasma for the production of optoelectronic devices are discussed. A technology for processing diamond single crystals that provides a perfect surface crystal structure with roughness less than 0,5 nm was developed. It was demonstrated that selective UV detectors based on synthetic single-crystal diamond substrates coated with single-crystal films can be produced. A criterion for selecting clean and structurally perfect single crystals of synthetic diamond was developed for the epitaxial growth technology. (authors)

Optical constants of CH3NH3PbBr3 perovskite thin films measured by spectroscopic ellipsometry

KAUST Repository

Alias, Mohd Sharizal; Dursun, Ibrahim; Saidaminov, Makhsud I.; Diallo, Elhadj Marwane; Mishra, Pawan; Ng, Tien Khee; Bakr, Osman; Ooi, Boon S.

2016-01-01

function) of CH3NH3PbBr3 perovskite thin films using spectroscopic ellipsometry. Due to the existence of voids, the refractive index of the thin films is around 8% less than the single crystals counterpart. The energy bandgap is around 2.309 eV as obtained

Antiphase inversion domains in lithium cobaltite thin films deposited on single-crystal sapphire substrates

International Nuclear Information System (INIS)

Zheng, S.J.; Fisher, C.A.J.; Hitosugi, T.; Kumatani, A.; Shiraki, S.; Ikuhara, Y.H.; Kuwabara, A.; Moriwake, H.; Oki, H.; Ikuhara, Y.

2013-01-01

Antiphase inversion domains in LiCoO 2 thin films prepared by pulsed laser deposition on sapphire single-crystal substrates are analyzed using a combination of (scanning) transmission electron microscopy and first-principles calculations. Domains form epitaxially on the substrates with orientation relationships of [112 ¯ 0] LiCoO 2 (0001) LiCoO 2 //[11 ¯ 00] α-Al 2 O 3 (0001) α-Al 2 O 3 and [1 ¯ 1 ¯ 20] LiCoO 2 (0001) LiCoO 2 //[11 ¯ 00] α-Al 2 O 3 (0001) α-Al 2 O 3 . In addition, substrate/film interfaces with the above orientation relationships always have the same stacking sequence of Al–O–Co–O–Li–O. This is confirmed to be the most energetically stable stacking arrangement according to first-principles calculations. Individual domains form as a result of steps one (0 0 0 1) O–Al–O spacing in height on the otherwise flat substrate surface. Because the orientation of adjacent (0 0 0 1) AlO 6 octahedra in Al 2 O 3 are rotated by 180°, while LiO 6 and CoO 6 octahedra in LiCoO 2 are all aligned in the same direction, substrate steps produce LiCoO 2 domains rotated 180° relative to their neighbors. The similar size of oxygen octahedra in the two materials also means that the step height is close to the layer spacing in LiCoO 2 , so that (0 0 0 1) Li and Co layers of adjacent domains are shifted by one layer relative to each other at each domain boundary, aligning Li layers with Co layers across the boundary. The combination of these two effects generates antiphase inversion domains. The domain boundaries effectively sever Li-ion diffusion pathways in the (0 0 0 1) planes between domains and thus are expected to have a detrimental effect on Li-ion conductivity

Textured indium tin oxide thin films by chemical solution deposition and rapid thermal processing

International Nuclear Information System (INIS)

Mottern, Matthew L.; Tyholdt, Frode; Ulyashin, Alexander; Helvoort, Antonius T.J. van; Verweij, Henk; Bredesen, Rune

2007-01-01

The microstructure of state-of-the-art chemical solution deposited indium tin oxide thin films typically consists of small randomly oriented grains, high porosity and poor homogeneity. The present study demonstrates how the thin film microstructure can be improved significantly by tailoring the precursor solutions and deposition conditions to be kinetically and thermodynamically favorable for generation of homogeneous textured thin films. This is explained by the occurrence of a single heterogeneous nucleation mechanism. The as-deposited thin films, crystallized at 800 deg. C, have a high apparent density, based on a refractive index of ∼ 1.98 determined by single wavelength ellipsometry at 633 nm. The microstructure of the films consists of columnar grains with preferred orientation as determined by X-ray diffraction and transmission electron microscopy. The resistivity, measured by the four point probe method, is ∼ 2 x 10 -3 Ω cm prior to post-deposition treatments

Photon emission by electrons and positrons traversing thin single crystal

International Nuclear Information System (INIS)

Ol'chak, A.S.

1984-01-01

Radiation emission by planar channeled particles (electrons, positrons) in a thin single crystal of thickness L is considered. It is shown that for L approximately πb/THETAsub(L) (b is the lattice constant, THETA sub(L) the Lindhard angle) besides the main spontaneous channeling maxima there exist auxiliary interference maxima, the positions of all the maxima depending on L. The dependence of the radiation spectral intensity on crystal thickness is discussed

Primary and aggregate color centers in proton irradiated LiF crystals and thin films for luminescent solid state detectors

International Nuclear Information System (INIS)

Piccinini, M; Ambrosini, F; Ampollini, A; Bonfigli, F; Libera, S; Picardi, L; Ronsivalle, C; Vincenti, M A; Montereali, R M

2015-01-01

Proton beams of 3 MeV energy, produced by the injector of a linear accelerator for proton therapy, were used to irradiate at room temperature lithium fluoride crystals and polycrystalline thin films grown by thermal evaporation. The irradiation fluence range was 10 11 -10 15 protons/cm 2 . The proton irradiation induced the stable formation of primary and aggregate color centers. Their formation was investigated by optical absorption and photoluminescence spectroscopy. The F 2 and F 3 + photoluminescence intensities, carefully measured in LiF crystals and thin films, show linear behaviours up to different maximum values of the irradiation fluence, after which a quenching is observed, depending on the nature of the samples (crystals and films). The Principal Component Analysis, applied to the absorption spectra of colored crystals, allowed to clearly identify the formation of more complex aggregate defects in samples irradiated at highest fluences. (paper)

Thin-film magnetless Faraday rotators for compact heterogeneous integrated optical isolators

Science.gov (United States)

Karki, Dolendra; Stenger, Vincent; Pollick, Andrea; Levy, Miguel

2017-06-01

This report describes the fabrication, characterization, and transfer of ultra-compact thin-film magnetless Faraday rotators to silicon photonic substrates. Thin films of magnetization latching bismuth-substituted rare-earth iron garnets were produced from commercially available materials by mechanical lapping, dice polishing, and crystal-ion-slicing. Eleven- μ m -thick films were shown to retain the 45 ° Faraday rotation of the bulk material to within 2 ° at 1.55 μ m wavelength without re-poling. Anti-reflection coated films evince 0.09 dB insertion loses and better than -20 dB extinction ratios. Lower extinction ratios than the bulk are ascribed to multimode propagation. Significantly larger extinction ratios are predicted for single-mode waveguides. Faraday rotation, extinction ratios, and insertion loss tests on He-ion implanted slab waveguides of the same material yielded similar results. The work culminated with bond alignment and transfer of 7 μ m -thick crystal-ion-sliced 50 × 480 μ m 2 films onto silicon photonic substrates.

Synthesis of BiFeO{sub 3} thin films on single-terminated Nb : SrTiO{sub 3} (111) substrates by intermittent microwave assisted hydrothermal method

Energy Technology Data Exchange (ETDEWEB)

Velasco-Davalos, Ivan; Ambriz-Vargas, Fabian; Kolhatkar, Gitanjali; Thomas, Reji, E-mail: ruediger@emt.inrs.ca, E-mail: reji.thomas@emt.inrs.ca; Ruediger, Andreas, E-mail: ruediger@emt.inrs.ca, E-mail: reji.thomas@emt.inrs.ca [Centre Énergie, Matériaux et Télécommunications, INRS, 1650 Lionel-Boulet, Varennes, Québec, J3X1S2 (Canada)

2016-06-15

We report on a simple and fast procedure to create arrays of atomically flat terraces on single crystal SrTiO{sub 3} (111) substrates and the deposition of ferroelectric BiFeO{sub 3} thin films on such single-terminated surfaces. A microwave-assisted hydrothermal method in deionized water and ammonia solution selectively removes either (SrO{sub 3}){sup 4−} or Ti{sup 4+} layers to ensure the same chemical termination on all terraces. Measured step heights of 0.225 nm (d{sub 111}) and uniform contrast in the phase image of the terraces confirm the single termination in pure and Nb doped SrTiO{sub 3} single crystal substrates. Multiferroic BiFeO{sub 3} thin films were then deposited by the same microwave assisted hydrothermal process on Nb : SrTiO{sub 3} (111) substrates. Bi(NO{sub 3}){sub 3} and Fe(NO{sub 3}){sub 3} along with KOH served as the precursors solution. Ferroelectric behavior of the BiFeO{sub 3} films on Nb : SrTiO{sub 3} (100) substrates was verified by piezoresponse force microscopy.

Self-assembly morphology effects on the crystallization of semicrystalline block copolymer thin film

Science.gov (United States)

Wei, Yuhan; Pan, Caiyuan; Li, Binyao; Han, Yanchun

2007-03-01

Self-assembly morphology effects on the crystalline behavior of asymmetric semicrystalline block copolymer polystyrene-block-poly(L-lactic acid) thin film were investigated. Firstly, a series of distinctive self-assembly aggregates, from spherical to ellipsoid and rhombic lamellar micelles (two different kinds of rhombic micelles, defined as rhomb 1 and rhomb 2) was prepared by means of promoting the solvent selectivity. Then, the effects of these self-assembly aggregates on crystallization at the early stage of film evolution were investigated by in situ hot stage atomic force microscopy. Heterogeneous nucleation initiated from the spherical micelles and dendrites with flat on crystals appeared with increasing temperature. At high temperature, protruding structures were observed due to the thickening of the flat-on crystals and finally more thermodynamically stable crystallization formed. Annealing the rhombic lamellar micelles resulted in different phenomena. Turtle-shell-like crystalline structure initiated from the periphery of the rhombic micelle 1 and spread over the whole film surface in the presence of mostly noncrystalline domain interior. Erosion and small hole appeared at the surface of the rhombic lamellar micelle 2; no crystallization like that in rhomb 1 occurred. It indicated that the chain-folding degree was different in these two micelles, which resulted in different annealing behaviors.

Nano-crystallization in ZnO-doped In{sub 2}O{sub 3} thin films via excimer laser annealing for thin-film transistors

Energy Technology Data Exchange (ETDEWEB)

Fujii, Mami N., E-mail: f-mami@ms.naist.jp; Ishikawa, Yasuaki; Bermundo, Juan Paolo Soria; Uraoka, Yukiharu [Nara Institute of Science and Technology, 8916-5 Takayama, Ikoma, Nara 630-0192 (Japan); Ishihara, Ryoichi; Cingel, Johan van der; Mofrad, Mohammad R. T. [Delft University of Technology, Feldmannweg 17, P.O. Box 5053, 2600 GB Delft (Netherlands); Kawashima, Emi; Tomai, Shigekazu; Yano, Koki [Idemitsu Kosan Co., Ltd., 1280 Kami-izumi, Sodegaura, Chiba, 299-0293 (Japan)

2016-06-15

In a previous work, we reported the high field effect mobility of ZnO-doped In{sub 2}O{sub 3} (IZO) thin film transistors (TFTs) irradiated by excimer laser annealing (ELA) [M. Fujii et al., Appl. Phys. Lett. 102, 122107 (2013)]. However, a deeper understanding of the effect of ELA on the IZO film characteristics based on crystallinity, carrier concentrations, and optical properties is needed to control localized carrier concentrations for fabricating self-aligned structures in the same oxide film and to adequately explain the physical characteristics. In the case of as-deposited IZO film used as the channel, a high carrier concentration due to a high density of oxygen vacancies was observed; such a film does not show the required TFT characteristics but can act as a conductive film. We achieved a decrease in the carrier concentration of IZO films by crystallization using ELA. This means that ELA can form localized conductive or semi-conductive areas on the IZO film. We confirmed that the reason for the carrier concentration decrease was the decrease of oxygen-deficient regions and film crystallization. The annealed IZO films showed nano-crystalline phase, and the temperature at the substrate was substantially less than the temperature limit for flexible films such as plastic, which is 50°C. This paves the way for the formation of self-aligned structures and separately formed conductive and semi-conductive regions in the same oxide film.

Influences of annealing temperature on sprayed CuFeO2 thin films

Science.gov (United States)

Abdelwahab, H. M.; Ratep, A.; Abo Elsoud, A. M.; Boshta, M.; Osman, M. B. S.

2018-06-01

Delafossite CuFeO2 thin films were successfully prepared onto quartz substrates using simple spray pyrolysis technique. Post annealing under nitrogen atmosphere for 2 h was necessary to form delafossite CuFeO2 phase. The effect of alteration in annealing temperature (TA) 800, 850 and 900 °C was study on structural, morphology and optical properties. The XRD results for thin film annealed at TA = 850 °C show single phase CuFeO2 with rhombohedral crystal system and R 3 bar m space group with preferred orientation along (0 1 2). The prepared copper iron oxide thin films have an optical transmission ranged ∼40% in the visible region. The optical direct optical band gap of the prepared thin films was ranged ∼2.9 eV.

"Silicon millefeuille": From a silicon wafer to multiple thin crystalline films in a single step

Science.gov (United States)

Hernández, David; Trifonov, Trifon; Garín, Moisés; Alcubilla, Ramon

2013-04-01

During the last years, many techniques have been developed to obtain thin crystalline films from commercial silicon ingots. Large market applications are foreseen in the photovoltaic field, where important cost reductions are predicted, and also in advanced microelectronics technologies as three-dimensional integration, system on foil, or silicon interposers [Dross et al., Prog. Photovoltaics 20, 770-784 (2012); R. Brendel, Thin Film Crystalline Silicon Solar Cells (Wiley-VCH, Weinheim, Germany 2003); J. N. Burghartz, Ultra-Thin Chip Technology and Applications (Springer Science + Business Media, NY, USA, 2010)]. Existing methods produce "one at a time" silicon layers, once one thin film is obtained, the complete process is repeated to obtain the next layer. Here, we describe a technology that, from a single crystalline silicon wafer, produces a large number of crystalline films with controlled thickness in a single technological step.

Excimer Laser Deposition of PLZT Thin Films

National Research Council Canada - National Science Library

Petersen, GAry

1991-01-01

.... In order to integrate these devices into optical systems, the production of high quality thin films with high transparency and perovskite crystal structure is desired. This requires development of deposition technologies to overcome the challenges of depositing and processing PLZT thin films.

Automatic identification of single- and/or few-layer thin-film material

DEFF Research Database (Denmark)

2014-01-01

One or more digital representations of single- (101) and/or few-layer (102) thin- film material are automatically identified robustly and reliably in a digital image (100), the digital image (100) having a predetermined number of colour components, by - determining (304) a background colour...... component of the digital image (100) for each colour component, and - determining or estimating (306) a colour component of thin-film material to be identified in the digital image (100) for each colour component by obtaining a pre-determined contrast value (C R; C G; C B) for each colour component...

Pulsed Laser Deposition of BaTiO3 Thin Films on Different Substrates

Directory of Open Access Journals (Sweden)

Yaodong Yang

2010-01-01

Full Text Available We have studied the deposition of BaTiO3 (BTO thin films on various substrates. Three representative substrates were selected from different types of material systems: (i SrTiO3 single crystals as a typical oxide, (ii Si wafers as a semiconductor, and (iii Ni foils as a magnetostrictive metal. We have compared the ferroelectric properties of BTO thin films obtained by pulsed laser deposition on these diverse substrates.

Low-temperature growth of polycrystalline Ge thin film on glass by in situ deposition and ex situ solid-phase crystallization for photovoltaic applications

International Nuclear Information System (INIS)

Tsao, Chao-Yang; Weber, Juergen W.; Campbell, Patrick; Widenborg, Per I.; Song, Dengyuan; Green, Martin A.

2009-01-01

Poly-crystalline germanium (poly-Ge) thin films have potential for lowering the manufacturing cost of photovoltaic devices especially in tandem solar cells, but high crystalline quality would be required. This work investigates the crystallinity of sputtered Ge thin films on glass prepared by in situ growth and ex situ solid-phase crystallization (SPC). Structural properties of the films were characterized by Raman, X-ray diffraction and ultraviolet-visible reflectance measurements. The results show the transition temperature from amorphous to polycrystalline is between 255 deg. C and 280 deg. C for in situ grown poly-Ge films, whereas the transition temperature is between 400 deg. C and 500 deg. C for films produced by SPC for a 20 h annealing time. The in situ growth in situ crystallized poly-Ge films at 450 deg. C exhibit significantly better crystalline quality than those formed by solid-phase crystallization at 600 deg. C. High crystalline quality at low substrate temperature obtained in this work suggests the poly-Ge films could be promising for use in thin film solar cells on glass.

Metal-insulator transition induced in CaVO{sub 3} thin films

Energy Technology Data Exchange (ETDEWEB)

Gu Man [Department of Physics, University of Virginia, 382 McCormick Rd., Charlottesville, Virginia 22904 (United States); Laverock, Jude; Chen, Bo; Smith, Kevin E. [Department of Physics, Boston University, 590 Commonwealth Avenue, Boston, Massachusetts 02215 (United States); Wolf, Stuart A. [Department of Physics, University of Virginia, 382 McCormick Rd., Charlottesville, Virginia 22904 (United States); Department of Materials Science and Engineering, University of Virginia, 395 McCormick Rd., Charlottesville, Virginia 22904 (United States); Lu Jiwei [Department of Materials Science and Engineering, University of Virginia, 395 McCormick Rd., Charlottesville, Virginia 22904 (United States)

2013-04-07

Stoichiometric CaVO{sub 3} (CVO) thin films of various thicknesses were grown on single crystal SrTiO{sub 3} (STO) (001) substrates using a pulsed electron-beam deposition technique. The CVO films were capped with a 2.5 nm STO layer. We observed a temperature driven metal-insulator transition (MIT) in CVO films with thicknesses below 4 nm that was not observed in either thick CVO films or STO films. The emergence of this MIT can be attributed to the reduction in effective bandwidth due to a crossover from a three-dimensional metal to a two-dimensional insulator. The insulating phase was only induced with a drive current below 0.1 {mu}A. X-ray absorption measurements indicated different electronic structures for thick and very thin films of CVO. Compared with the thick film ({approx}60 nm), thin films of CVO (2-4 nm) were more two-dimensional with the V charge state closer to V{sup 4+}.

Electrochemically modified crystal orientation, surface morphology and optical properties using CTAB on Cu2O thin films

Directory of Open Access Journals (Sweden)

Karupanan Periyanan Ganesan

Full Text Available Cuprous oxide (Cu2O thin films with different crystal orientations were electrochemically deposited in the presence of various molar concentrations of cetyl trimethyl ammonium bromide (CTAB on fluorine doped tin oxide (FTO glass substrate using standard three electrodes system. X-ray diffraction (XRD studies reveal cubic structure of Cu2O with (111 plane orientation, after addition of CTAB in deposition solution, the orientation of crystal changes from (111 into (200 plane. Scanning electron microscope (SEM images explored significant variation on morphology of Cu2O thin films deposited with addition of CTAB compared to without addition of CTAB. Photoluminescence (PL spectra illustrate that the emission peak around at 650 nm is attributed to near band edge emission, and the film prepared at the 3 mM of CTAB exhibits much higher intensity than that of the all other films. UV–Visible spectra show optical absorption in the range of 480–610 nm and the highest transparency of Cu2O film prepared at the concentration of 3 mM CTAB. The optical band gap is increased in the range between 2.16 and 2.45 eV with increasing the CTAB concentrations. Keywords: Cuprous oxide, Crystal orientation, Electrodeposition and cubic structure

Defect studies of thin ZnO films prepared by pulsed laser deposition

International Nuclear Information System (INIS)

Vlček, M; Čížek, J; Procházka, I; Novotný, M; Bulíř, J; Lančok, J; Anwand, W; Brauer, G; Mosnier, J-P

2014-01-01

Thin ZnO films were grown by pulsed laser deposition on four different substrates: sapphire (0 0 0 1), MgO (1 0 0), fused silica and nanocrystalline synthetic diamond. Defect studies by slow positron implantation spectroscopy (SPIS) revealed significantly higher concentration of defects in the studied films when compared to a bulk ZnO single crystal. The concentration of defects in the films deposited on single crystal sapphire and MgO substrates is higher than in the films deposited on amorphous fused silica substrate and nanocrystalline synthetic diamond. Furthermore, the effect of deposition temperature on film quality was investigated in ZnO films deposited on synthetic diamond substrates. Defect studies performed by SPIS revealed that the concentration of defects firstly decreases with increasing deposition temperature, but at too high deposition temperatures it increases again. The lowest concentration of defects was found in the film deposited at 450° C.

Solid phase epitaxial growth of high mobility La:BaSnO_3 thin films co-doped with interstitial hydrogen

International Nuclear Information System (INIS)

Niedermeier, Christian A.; Rhode, Sneha; Fearn, Sarah; Moram, Michelle A.; Ide, Keisuke; Hiramatsu, Hidenori; Hosono, Hideo; Kamiya, Toshio

2016-01-01

This work presents the solid phase epitaxial growth of high mobility La:BaSnO_3 thin films on SrTiO_3 single crystal substrates by crystallization through thermal annealing of nanocrystalline thin films prepared by pulsed laser deposition at room temperature. The La:BaSnO_3 thin films show high epitaxial quality and Hall mobilities up to 26 ± 1 cm"2/Vs. Secondary ion mass spectroscopy is used to determine the La concentration profile in the La:BaSnO_3 thin films, and a 9%–16% La doping activation efficiency is obtained. An investigation of H doping to BaSnO_3 thin films is presented employing H plasma treatment at room temperature. Carrier concentrations in previously insulating BaSnO_3 thin films were increased to 3 × 10"1"9" cm"−"3 and in La:BaSnO_3 thin films from 6 × 10"1"9" cm"−"3 to 1.5 × 10"2"0" cm"−"3, supporting a theoretical prediction that interstitial H serves as an excellent n-type dopant. An analysis of the free electron absorption by infrared spectroscopy yields a small (H,La):BaSnO_3 electron effective mass of 0.27 ± 0.05 m_0 and an optical mobility of 26 ± 7 cm"2/Vs. As compared to La:BaSnO_3 single crystals, the smaller electron mobility in epitaxial thin films grown on SrTiO_3 substrates is ascribed to threading dislocations as observed in high resolution transmission electron micrographs.

Influence of Substrate on Crystal Orientation of Large-Grained Si Thin Films Formed by Metal-Induced Crystallization

Directory of Open Access Journals (Sweden)

Kaoru Toko

2015-01-01

Full Text Available Producing large-grained polycrystalline Si (poly-Si film on glass substrates coated with conducting layers is essential for fabricating Si thin-film solar cells with high efficiency and low cost. We investigated how the choice of conducting underlayer affected the poly-Si layer formed on it by low-temperature (500°C Al-induced crystallization (AIC. The crystal orientation of the resulting poly-Si layer strongly depended on the underlayer material: (100 was preferred for Al-doped-ZnO (AZO and indium-tin-oxide (ITO; (111 was preferred for TiN. This result suggests Si heterogeneously nucleated on the underlayer. The average grain size of the poly-Si layer reached nearly 20 µm for the AZO and ITO samples and no less than 60 µm for the TiN sample. Thus, properly electing the underlayer material is essential in AIC and allows large-grained Si films to be formed at low temperatures with a set crystal orientation. These highly oriented Si layers with large grains appear promising for use as seed layers for Si light-absorption layers as well as for advanced functional materials.

On crystallization of bisphenol-A polycarbonate thin films upon annealing

Energy Technology Data Exchange (ETDEWEB)

Yang, Chunhong; Li, Qichao; Mao, Wenfeng; Wang, Peng; He, Chunqing, E-mail: hecq@whu.edu.cn

2015-10-16

Crystallization of polycarbonate (PC) films as a function of annealing time has been investigated by various methods. A distinct diffraction peak at 17.56°, a sharp decrease of film thickness, an increase of refractive index and branch-type structures on the surface are found merely for the film after crystallization. Interestingly, positron annihilation parameters demonstrate fractional free-volumes in PC films vary significantly not only before crystallization but also at the early stage of annealing, which are not found by other methods. The results show that free-volumes in PC film must be increased remarkably before crystallization, which enables the occurrence of molecule rearrangement. - Highlights: • Fractional free-volume in PC film decreased of early stage of annealing. • Crystallization of PC film on Si substrate occurred after annealed for ∼48 hours. • Fractional free-volume in PC film increased remarkably before crystallization. • Positron diffusion length and S parameter revealed the variation of free volumes.

On crystallization of bisphenol-A polycarbonate thin films upon annealing

International Nuclear Information System (INIS)

Yang, Chunhong; Li, Qichao; Mao, Wenfeng; Wang, Peng; He, Chunqing

2015-01-01

Crystallization of polycarbonate (PC) films as a function of annealing time has been investigated by various methods. A distinct diffraction peak at 17.56°, a sharp decrease of film thickness, an increase of refractive index and branch-type structures on the surface are found merely for the film after crystallization. Interestingly, positron annihilation parameters demonstrate fractional free-volumes in PC films vary significantly not only before crystallization but also at the early stage of annealing, which are not found by other methods. The results show that free-volumes in PC film must be increased remarkably before crystallization, which enables the occurrence of molecule rearrangement. - Highlights: • Fractional free-volume in PC film decreased of early stage of annealing. • Crystallization of PC film on Si substrate occurred after annealed for ∼48 hours. • Fractional free-volume in PC film increased remarkably before crystallization. • Positron diffusion length and S parameter revealed the variation of free volumes

Chemical solution deposition of YBCO thin film by different polymer additives

International Nuclear Information System (INIS)

Wang, W.T.; Li, G.; Pu, M.H.; Sun, R.P.; Zhou, H.M.; Zhang, Y.; Zhang, H.; Yang, Y.; Cheng, C.H.; Zhao, Y.

2008-01-01

A polymer-assisted chemical solution deposition approach has been proposed for the preparation of YBCO thin film. Different additives like PVB (polyvinyl butyral), PEG (polyethylene glycol) and PVP (polyvinylpyrrolidone) have been used to adjust the final viscosity of the precursor solution and thus the film formation. In this fluorine-free approach, YBCO has been deposited on single crystal substrates with metal acetates being starting materials. Biaxially textured YBCO thin films have been obtained. However, different additives lead to different microstructure. Dense, smooth and crack-free YBCO film prepared with PVB as additive yields sharp superconducting transition around T c = 90 K as well as high J c (0 T, 77 K) over 3 MA/cm 2

Chemical solution deposition of YBCO thin film by different polymer additives

Energy Technology Data Exchange (ETDEWEB)

Wang, W.T.; Li, G.; Pu, M.H.; Sun, R.P.; Zhou, H.M.; Zhang, Y. [Key Laboratory of Magnetic Levitation Technologies and Maglev Trains, Ministry of Education of China, Superconductivity R and D Center (SRDC), Mail Stop 165, Southwest Jiaotong University, Chengdu 610031 (China); Zhang, H. [Department of Physics, Peking University, Beijing 100871 (China); Yang, Y. [Key Laboratory of Magnetic Levitation Technologies and Maglev Trains, Ministry of Education of China, Superconductivity R and D Center (SRDC), Mail Stop 165, Southwest Jiaotong University, Chengdu 610031 (China); Cheng, C.H. [Key Laboratory of Magnetic Levitation Technologies and Maglev Trains, Ministry of Education of China, Superconductivity R and D Center (SRDC), Mail Stop 165, Southwest Jiaotong University, Chengdu 610031 (China); School of Materials Science and Engineering, University of New South Wale, Sydney, 2052 NSW (Australia); Zhao, Y. [Key Laboratory of Magnetic Levitation Technologies and Maglev Trains, Ministry of Education of China, Superconductivity R and D Center (SRDC), Mail Stop 165, Southwest Jiaotong University, Chengdu 610031 (China); School of Materials Science and Engineering, University of New South Wale, Sydney, 2052 NSW (Australia)], E-mail: yzhao@swjtu.edu.cn

2008-09-15

A polymer-assisted chemical solution deposition approach has been proposed for the preparation of YBCO thin film. Different additives like PVB (polyvinyl butyral), PEG (polyethylene glycol) and PVP (polyvinylpyrrolidone) have been used to adjust the final viscosity of the precursor solution and thus the film formation. In this fluorine-free approach, YBCO has been deposited on single crystal substrates with metal acetates being starting materials. Biaxially textured YBCO thin films have been obtained. However, different additives lead to different microstructure. Dense, smooth and crack-free YBCO film prepared with PVB as additive yields sharp superconducting transition around T{sub c} = 90 K as well as high J{sub c} (0 T, 77 K) over 3 MA/cm{sup 2}.

Synthesis of single phase of CuTl-1234 thin films

CERN Document Server

Khan, N A; Ishida, K; Tateai, F; Kojima, T; Terada, N; Ihara, H

1999-01-01

Thin films of CuTl-1234 superconductor have been prepared for the first time using an amorphous phase epitaxy method (APE). In this method, an amorphous phase is sputtered from a target of stoichiometric composition CuBa/sub 2/Ca/sub 3/Cu/sub 4/O/sub x/. Thin films on the SrTiO/sub 3/ substrate after the thallium treatment are biaxially oriented. The XRD reflected a predominant single phase with c-axis 18.7 AA and pole figure measurements of (103) reflections showed a-axis oriented films with Delta phi =0.8 degrees . Resistivity measurements showed T/sub c/=113 K and preliminary J/sub c/ measurements manifested a current density of 1.0*10/sup 6/ A/cm (77 K, 0 T). The composition of films after EDX measurements is Cu /sub 0.3/Tl/sub 0.7/CuBa/sub 2/Ca/sub 3/Cu/sub 4/O/sub 12-y/. (8 refs).

Breakthrough to Non-Vacuum Deposition of Single-Crystal, Ultra-Thin, Homogeneous Nanoparticle Layers: A Better Alternative to Chemical Bath Deposition and Atomic Layer Deposition

Directory of Open Access Journals (Sweden)

Yu-Kuang Liao

2017-04-01

Full Text Available Most thin-film techniques require a multiple vacuum process, and cannot produce high-coverage continuous thin films with the thickness of a few nanometers on rough surfaces. We present a new ”paradigm shift” non-vacuum process to deposit high-quality, ultra-thin, single-crystal layers of coalesced sulfide nanoparticles (NPs with controllable thickness down to a few nanometers, based on thermal decomposition. This provides high-coverage, homogeneous thickness, and large-area deposition over a rough surface, with little material loss or liquid chemical waste, and deposition rates of 10 nm/min. This technique can potentially replace conventional thin-film deposition methods, such as atomic layer deposition (ALD and chemical bath deposition (CBD as used by the Cu(In,GaSe2 (CIGS thin-film solar cell industry for decades. We demonstrate 32% improvement of CIGS thin-film solar cell efficiency in comparison to reference devices prepared by conventional CBD deposition method by depositing the ZnS NPs buffer layer using the new process. The new ZnS NPs layer allows reduction of an intrinsic ZnO layer, which can lead to severe shunt leakage in case of a CBD buffer layer. This leads to a 65% relative efficiency increase.

Relaxation in Thin Polymer Films Mapped across the Film Thickness by Astigmatic Single-Molecule Imaging

KAUST Repository

Oba, Tatsuya

2012-06-19

We have studied relaxation processes in thin supported films of poly(methyl acrylate) at the temperature corresponding to 13 K above the glass transition by monitoring the reorientation of single perylenediimide molecules doped into the films. The axial position of the dye molecules across the thickness of the film was determined with a resolution of 12 nm by analyzing astigmatic fluorescence images. The average relaxation times of the rotating molecules do not depend on the overall thickness of the film between 20 and 110 nm. The relaxation times also do not show any dependence on the axial position within the films for the film thickness between 70 and 110 nm. In addition to the rotating molecules we observed a fraction of spatially diffusing molecules and completely immobile molecules. These molecules indicate the presence of thin (<5 nm) high-mobility surface layer and low-mobility layer at the interface with the substrate. (Figure presented) © 2012 American Chemical Society.

Preparation of a Non-Polar ZnO Film on a Single-Crystal NdGaO3 Substrate by the RF Sputtering Method

Science.gov (United States)

Kashiwaba, Y.; Tanaka, Y.; Sakuma, M.; Abe, T.; Imai, Y.; Kawasaki, K.; Nakagawa, A.; Niikura, I.; Kashiwaba, Y.; Osada, H.

2018-04-01

Preparation of non-polar ZnO ( 11\\overline{2} 0 ) films on single-crystal NdGaO3 (NGO) (001) substrates was successfully achieved by the radio frequency (RF) sputtering method. Orientation, deposition rate, and surface roughness of ZnO films strongly depend on the working pressure. Characteristics of ZnO films deposited on single-crystal NGO (001) substrates were compared with those of ZnO films deposited on single-crystal sapphire ( 01\\overline{1} 2 ) substrates. An x-ray diffraction peak of the ZnO ( 11\\overline{2} 0 ) plane was observed on ZnO films deposited on single-crystal NGO (001) substrates under working pressure of less than 0.5 Pa. On the other hand, uniaxially oriented ZnO ( 11\\overline{2} 0 ) films on single-crystal sapphire ( 01\\overline{1} 2 ) substrates were observed under working pressure of 0.1 Pa. The mechanism by which the diffraction angle of the ZnO ( 11\\overline{2} 0 ) plane on single-crystal NGO (001) substrates was shifted is discussed on the basis of anisotropic stress of lattice mismatch. The deposition rate of ZnO films decreased with an increase in working pressure, and the deposition rate on single-crystal NGO (001) substrates was larger than that on single-crystal sapphire ( 01\\overline{1} 2 ) substrates. Root mean square (RMS) roughness of ZnO films increased with an increase in working pressure, and RMS roughness of ZnO films on single-crystal NGO (001) substrates was smaller than that of ZnO films on single-crystal sapphire ( 01\\overline{1} 2 ) substrates even though the film thickness on single-crystal NGO (001) substrates was greater than that on sapphire substrates. It is thought that a single-crystal NGO (001) substrate is useful for deposition of non-polar ZnO ( 11\\overline{2} 0 ) films.

Tips pentacene crystal alignment for improving performance of solution processed organic thin film transistors

Science.gov (United States)

He, Zhengran

A newly-developed p-type organic semiconductor 6,13-bis (triisopropylsilylethynyl) pentacene (TIPS pentacene) demonstrates various advantages such as high mobility, air stability and solution processibility, but at the same time its application is restricted by major issues, such as crystal misorientation and performance variation of organic thin-film transistors (OTFTs). This dissertation demonstrates several different approaches to address these issues. As a result, both crystal orientation and areal coverage can be effectively improved, leading to an enhancement of average mobility and performance consistency of OTFTs. Chapter 1 presents an introduction and background of this dissertation. Chapter 2 explores the usage of inorganic silica nanoparticles to manipulate the morphology of TIPS pentacene thin films and the performance of solution-processed organic OTFTs. The resultant drop-cast films yield improved morphological uniformity at ~10% SiO2 loading, which also leads to a 3-fold increase in average mobility and nearly 4-times reduction in the ratio of standard deviation of mobility (μStdev) to average mobility (μAvg). The experimental results suggest that the SiO2 nanoparticles mostly aggregate at TIPS pentacene grain boundaries, and that 10% nanoparticle concentration effectively reduces the undesirable crystal misorientation without considerably compromising TIPS pentacene crystallinity. Chapter 3 discusses the utilization of air flow to effectively reduce the TIPS pentacene crystal anisotropy and enhance performance consistency in OTFTs. Under air-flow navigation (AFN), TIPS pentacene forms thin films with improved crystal orientation and increased areal coverage, which subsequently lead to a four-fold increase of average hole mobility and one order of magnitude enhancement in performance consistency. Chapter 4 investigates the critical roles of lateral and vertical phase separation in the performance of the next-generation organic and hybrid electronic

Sputtering materials for VLSI and thin film devices

CERN Document Server

Sarkar, Jaydeep

2010-01-01

An important resource for students, engineers and researchers working in the area of thin film deposition using physical vapor deposition (e.g. sputtering) for semiconductor, liquid crystal displays, high density recording media and photovoltaic device (e.g. thin film solar cell) manufacturing. This book also reviews microelectronics industry topics such as history of inventions and technology trends, recent developments in sputtering technologies, manufacturing steps that require sputtering of thin films, the properties of thin films and the role of sputtering target performance on overall p

Growth of conductive HfO{sub 2-x} thin films by reactive molecular beam epitaxy

Energy Technology Data Exchange (ETDEWEB)

Hildebrandt, Erwin; Kurian, Jose; Alff, Lambert [Institut fuer Materialwissenschaft, TU Darmstadt (Germany); Kleebe, Hans-Joachim [Institut fuer Angewandte Geowissenschaften, TU Darmstadt (Germany)

2009-07-01

Thin films of oxygen deficient hafnium oxide were grown on single crystal c-cut and r-cut sapphire substrates by reactive molecular beam epitaxy. The oxidation conditions during growth were varied within a wide range using RF-activated oxygen. Hafnium oxide thin films were characterized using X-ray diffraction, resistivity measurements ({rho}-T) and transmission electron microscopy (TEM). The results show a dramatic increase in conductivity of the deposited oxygen deficient hafnium oxide thin films with decreasing oxidation conditions during growth. The electrical properties of deficient hafnium oxide thin films varied from insulating over semiconducting to conducting. X-ray diffraction data as well as TEM data rule out the possibility of conductivity due to metallic hafnium.

Dielectric loss of strontium titanate thin films

Science.gov (United States)

Dalberth, Mark Joseph

1999-12-01

Interest in strontium titanate (STO) thin films for microwave device applications continues to grow, fueled by the telecommunications industry's interest in phase shifters and tunable filters. The optimization of these devices depends upon increasing the phase or frequency tuning and decreasing the losses in the films. Currently, the dielectric response of thin film STO is poorly understood through lack of data and a theory to describe it. We have studied the growth of STO using pulsed laser deposition and single crystal substrates like lanthanum aluminate and neodymium gallate. We have researched ways to use ring resonators to accurately measure the dielectric response as a function of temperature, electric field, and frequency from low radio frequencies to a few gigahertz. Our films grown on lanthanum aluminate show marked frequency dispersion in the real part of the dielectric constant and hints of thermally activated loss behavior. We also found that films grown with conditions that optimized the dielectric constant showed increased losses. In an attempt to simplify the system, we developed a technique called epitaxial lift off, which has allowed us to study films removed from their growth substrates. These free standing films have low losses and show obvious thermally activated behavior. The "amount of tuning," as measured by a figure of merit, KE, is greater in these films than in the films still attached to their growth substrates. We have developed a theory that describes the real and imaginary parts of the dielectric constant. The theory models the real part using a mean field description of the ionic motion in the crystal and includes the loss by incorporating the motion of charged defects in the films.

Single Crystals of Organolead Halide Perovskites: Growth, Characterization, and Applications

KAUST Repository

Peng, Wei

2017-04-01

With the soaring advancement of organolead halide perovskite solar cells rising from a power conversion efficiency of merely 3% to more than 22% shortly in five years, researchers’ interests on this big material family have been greatly spurred. So far, both in-depth studies on the fundamental properties of organolead halide perovskites and their extended applications such as photodetectors, light emitting diodes, and lasing have been intensively reported. The great successes have been ascribed to various superior properties of organolead halide hybrid perovskites such as long carrier lifetimes, high carrier mobility, and solution-processable high quality thin films, as will be discussed in Chapter 1. Notably, most of these studies have been limited to their polycrystalline thin films. Single crystals, as a counter form of polycrystals, have no grain boundaries and higher crystallinity, and thus less defects. These characteristics gift single crystals with superior optical, electrical, and mechanical properties, which will be discussed in Chapter 2. For example, organolead halide perovskite single crystals have been reported with much longer carrier lifetimes and higher carrier mobilities, which are especially intriguing for optoelectronic applications. Besides their superior optoelectronic properties, organolead halide perovskites have shown large composition versatility, especially their organic components, which can be controlled to effectively adjust their crystal structures and further fundamental properties. Single crystals are an ideal platform for such composition-structure-property study since a uniform structure with homogeneous compositions and without distraction from grain boundaries as well as excess defects can provide unambiguously information of material properties. As a major part of work of this dissertation, explorative work on the composition-structure-property study of organic-cation-alloyed organolead halide perovskites using their single

RHEED transmission mode and pole figures thin film and nanostructure texture analysis

CERN Document Server

Wang, Gwo-Ching

2014-01-01

This unique book covers the fundamental principle of electron diffraction, basic instrumentation of RHEED, definitions of textures in thin films and nanostructures, mechanisms and control of texture formation, and examples of RHEED transmission mode measurements of texture and texture evolution of thin films and nanostructures. Also presented is a new application of RHEED in the transmission mode called RHEED pole figure technique that can be used to monitor the texture evolution in thin film growth and nanostructures and is not limited to single crystal epitaxial film growth. Details of the construction of RHEED pole figures and the interpretation of observed pole figures are presented.  Materials covered include metals, semiconductors, and thin insulators. This book also: Presents a new application of RHEED in the transmission mode Introduces a variety of textures from metals, semiconductors, compound semiconductors, and their characteristics in RHEED pole figures Provides examples of RHEED measurements o...

Enhanced magnetoelectric coupling in a composite multiferroic system via interposing a thin film polymer

Science.gov (United States)

Xiao, Zhuyun; Mohanchandra, Kotekar P.; Lo Conte, Roberto; Ty Karaba, C.; Schneider, J. D.; Chavez, Andres; Tiwari, Sidhant; Sohn, Hyunmin; Nowakowski, Mark E.; Scholl, Andreas; Tolbert, Sarah H.; Bokor, Jeffrey; Carman, Gregory P.; Candler, Rob N.

2018-05-01

Enhancing the magnetoelectric coupling in a strain-mediated multiferroic composite structure plays a vital role in controlling magnetism by electric fields. An enhancement of magnetoelastic coupling between ferroelectric single crystal (011)-cut [Pb(Mg1/3Nb2/3)O3](1-x)-[PbTiO3]x (PMN-PT, x≈ 0.30) and ferromagnetic polycrystalline Ni thin film through an interposed benzocyclobutene polymer thin film is reported. A nearly twofold increase in sensitivity of remanent magnetization in the Ni thin film to an applied electric field is observed. This observation suggests a viable method of improving the magnetoelectric response in these composite multiferroic systems.

Intercalation crystallization of phase-pure α-HC(NH₂)₂PbI₃ upon microstructurally engineered PbI₂ thin films for planar perovskite solar cells.

Science.gov (United States)

Zhou, Yuanyuan; Yang, Mengjin; Kwun, Joonsuh; Game, Onkar S; Zhao, Yixin; Pang, Shuping; Padture, Nitin P; Zhu, Kai

2016-03-28

The microstructure of the solid-PbI2 precursor thin film plays an important role in the intercalation crystallization of the formamidinium lead triiodide perovskite (α-HC(NH2)2PbI3). It is shown that microstructurally engineered PbI2 thin films with porosity and low crystallinity are the most favorable for conversion into uniform-coverage, phase-pure α-HC(NH2)2PbI3 perovskite thin films. Planar perovskite solar cells fabricated using these thin films deliver power conversion efficiency (PCE) up to 13.8%.

Influence of metal induced crystallization parameters on the performance of polycrystalline silicon thin film transistors

International Nuclear Information System (INIS)

Pereira, L.; Barquinha, P.; Fortunato, E.; Martins, R.

2005-01-01

In this work, metal induced crystallization using nickel was employed to obtain polycrystalline silicon by crystallization of amorphous films for thin film transistor applications. The devices were produced through only one lithographic process with a bottom gate configuration using a new gate dielectric consisting of a multi-layer of aluminum oxide/titanium oxide produced by atomic layer deposition. The best results were obtained for TFTs with the active layer of poly-Si crystallized for 20 h at 500 deg. C using a nickel layer of 0.5 nm where the effective mobility is 45.5 cm 2 V -1 s -1 . The threshold voltage, the on/off current ratio and the sub-threshold voltage are, respectively, 11.9 V, 5.55x10 4 and 2.49 V/dec

Bi-Sr-Ca-Cu-O superconducting thin films: theory and experiment

Energy Technology Data Exchange (ETDEWEB)

Yavuz, M [Department of Mechanical Engineering and Mechatronics Engineering Program, University of Waterloo, Waterloo, Ontario N2L 3G1 (Canada); Boybay, M S [Department of Mechanical Engineering and Mechatronics Engineering Program, University of Waterloo, Waterloo, Ontario N2L 3G1 (Canada); Elbuken, C [Department of Mechanical Engineering and Mechatronics Engineering Program, University of Waterloo, Waterloo, Ontario N2L 3G1 (Canada); Andrews, M J [Los Alamos National Lab, PO Box 1663, Mail Stop B 296, Los Alamos, NM 87545 (United States); Hu, C R [Department of Physics, Texas A and M University, College Station, Texas 77843 (United States); Ross, J H [Department of Physics, Texas A and M University, College Station, Texas 77843 (United States)

2006-06-01

The interest of this paper centers on fabrication and characterization and modeling of vortices in high temperature superconducting thin films. As a first step, the magnetic vertices of the superconducting matrix were modeled. As a second, Bi-Sr-Ca-Cu-O thin films were grown using Pulsed Laser Ablation (PLD) on single crystal MgO substrates as magnetic templates for the potential use for Nano and Microelectronic circuits, and were characterized by x-ray diffraction, electron, and atomic force microscopy. The third step (future work) will be observation and pinning of these vortices using Bitter decoration.

Crystallization of sol-gel derived lead zirconate titanate thin films in argon and oxygen atmospheres

International Nuclear Information System (INIS)

Bursill, L.A.

1994-01-01

Electron diffraction and high-resolution electron microscopic techniques are applied to reveal the mechanisms of crystallization of 75 nm thin films of ferroelectric lead-zirconate-titanate (PZT). Sol-gel methods, followed by pyrolysis at 350 deg C, were used to provide a common starting point after which a variety of rapid-thermal annealing (RTA) experiments in the temperature range 400-700 deg C were made in argon, oxygen and nitrogen/hydrogen atmospheres. The results are interpreted in terms of the crystal chemical analysis, which points out that partial pressure of oxygen and heating rate are important experimental parameters which must be controlled if ferroelectric perovskite-type Pb 2 ZrTiO 6 , rather than pyrochlore-type Pb 2 ZrTiO 6+x , where O < X < 1 or -1 < X < O, is to be obtained after the RTA step. Thus significant improvements in the crystallization of perovskite-type PZT were clearly demonstrated by using argon atmospheres for the RTA step. The results have significance for the production of high-quality ferroelectric thin films, with improved switching and fatigue characteristics, since even small amounts of the pyrochlore phase prove detrimental for these properties. 18 refs., 1 tab., 10 figs

Visualization of nanosecond laser-induced dewetting, ablation and crystallization processes in thin silicon films

Science.gov (United States)

Qi, Dongfeng; Zhang, Zifeng; Yu, Xiaohan; Zhang, Yawen

2018-06-01

In the present work, nanosecond pulsed laser crystallization, dewetting and ablation of thin amorphous silicon films are investigated by time-resolved imaging. Laser pulses of 532 nm wavelength and 7 ns temporal width are irradiated on silicon film. Below the dewetting threshold, crystallization process happens after 400 ns laser irradiation in the spot central region. With the increasing of laser fluence, it is observed that the dewetting process does not conclude until 300 ns after the laser irradiation, forming droplet-like particles in the spot central region. At higher laser intensities, ablative material removal occurs in the spot center. Cylindrical rims are formed in the peripheral dewetting zone due to solidification of transported matter at about 500 ns following the laser pulse exposure.

PLD of X7R for thin film capacitors

International Nuclear Information System (INIS)

Hino, Takanori; Matsumoto, Noriyuki; Nishida, Minoru; Araki, Takao

2008-01-01

Thin film capacitors with a thickness of 200 nm were prepared on SrTiO 3 (1 0 0), (1 1 0) and (1 1 1) single crystal substrates at a temperature of 973 K by pulsed laser deposition (PLD) using a KrF excimer laser in an O 2 -O 3 atmosphere with a gas pressure of 1 Pa using an X7R sintered target. As a result, perovskite BaTiO 3 solid solution films were obtained. In the X7R thin films on (1 0 0) and (1 1 0) SrTiO 3 , only diffraction peaks with strong intensities from BaTiO 3 (1 0 0) and (1 1 0), respectively, were observed. X7R films on SrTiO 3 (1 1 1) were grown epitaxially oriented to the crystal plane direction of the substrate by inserting an initial homoepitaxial SrTiO 3 layer with a thickness of 4 nm. The X7R/SrTiO 3 film capacitors yielded a large volumetric efficiency of 50 μF/mm 3 and a temperature coefficient of capacitance (TCC) of -1.3% to 1.3% which satisfies the EIA standard specifications for X7R

Chemical state analysis of oxide thin films using a high resolution double crystal X-ray fluorescence spectrometer

International Nuclear Information System (INIS)

Masuda, Hirohisa; Morinaga, Kenji; Ohta, Yoshio.

1995-01-01

The chemical state analysis of r.f.-sputtered amorphous oxide thin films was determined by a high resolution X-ray fluorescence spectrometer with double crystals. The polymerization degree of silicate anions in the silicate film was as same as a target (α-Quartz). The oxygen coordination number of Al 3+ ions in the aluminate film was different from a target (α-Al 2 O 3 ), and it was a mixture of 4 and 6 in a spinel-like structure. In CaO-SiO 2 and CaO-Al 2 O 3 films, when the film thickness is thin at the beginning of sputtering, the composition of films are in the shortage of CaO. But when the film thickness become thicker, the composition of films become as same as the target. From the results above, the chemical state of films and their variations with film thickness can be clarified by using the apparatus. (author)

All-organic polymer-dispersed liquid crystal light-valves integrated with electroactive anthraquinone-2-sulfonate-doped polypyrrole thin films as driving electrodes

International Nuclear Information System (INIS)

Wang, Pen-Cheng; Yu, Jing-Yu; Li, Kuan-Hsun

2011-01-01

Highlights: → Fabrication of flexible semi-transparent all-polymer electrodes under ambient conditions without using a CVD system. → Characterization of the above electrodes based on anthraquinone-2-sulfonate-doped polypyrrole thin films. → Demonstration of all-organic liquid crystal light-valves with polypyrrole thin films as the driving electrodes. - Abstract: All-organic PDLC (polymer-dispersed liquid crystal) light-valves using all-polymer conductive substrates containing thin films of polypyrrole doped with anthraquinone-2-sulfonate (AQSA - ) as the driving electrodes were fabricated in this study. The all-polymer conductive substrates were prepared under ambient conditions by in situ depositing polypyrrole thin films on blank flexible poly(ethylene terephthalate), or PET, substrates from aqueous media in which oxidative polymerization of pyrrole was taking place. The obtained flexible all-polymer conductive substrates were semi-transparent with cohesive coatings of AQSA - doped polypyrrole thin films (thickness ∼55 nm). The all-polymer flexible conductive substrates had sheet resistivity ∼40 kΩ □ -1 and T% transparency against air ∼78% at 600 nm. The light-valves fabricated using the above all-polymer conductive substrates showed ∼50% transparency against air at 600 nm when 4 V μm -1 electric field was applied.

Mechanical and optical nanodevices in single-crystal quartz

Science.gov (United States)

Sohn, Young-Ik; Miller, Rachel; Venkataraman, Vivek; Lončar, Marko

2017-12-01

Single-crystal α-quartz, one of the most widely used piezoelectric materials, has enabled a wide range of timing applications. Owing to the fact that an integrated thin-film based quartz platform is not available, most of these applications rely on macroscopic, bulk crystal-based devices. Here, we show that the Faraday cage angled-etching technique can be used to realize nanoscale electromechanical and photonic devices in quartz. Using this approach, we demonstrate quartz nanomechanical cantilevers and ring resonators featuring Qs of 4900 and 8900, respectively.

Printable Thin Film Supercapacitors Using Single-Walled Carbon Nanotubes

KAUST Repository

Kaempgen, Martti

2009-05-13

Thin film supercapacitors were fabricated using printable materials to make flexible devices on plastic. The active electrodes were made from sprayed networks of single-walled carbon nanotubes (SWCNTs) serving as both electrodes and charge collectors. Using a printable aqueous gel electrolyte as well as an organic liquid electrolyte, the performances of the devices show very high energy and power densities (6 W h/kg for both electrolytes and 23 and 70 kW/kg for aqueous gel electrolyte and organic electrolyte, respectively) which is comparable to performance in other SWCNT-based supercapacitor devices fabricated using different methods. The results underline the potential of printable thin film supercapacitors. The simplified architecture and the sole use of printable materials may lead to a new class of entirely printable charge storage devices allowing for full integration with the emerging field of printed electronics. © 2009 American Chemical Society.

Rapid thermal annealing of Ti-rich TiNi thin films: A new approach to fabricate patterned shape memory thin films

International Nuclear Information System (INIS)

Motemani, Y.; Tan, M.J.; White, T.J.; Huang, W.M.

2011-01-01

This paper reports the rapid thermal annealing (RTA) of Ti-rich TiNi thin films, synthesized by the co-sputtering of TiNi and Ti targets. Long-range order of aperiodic alloy could be achieved in a few seconds with the optimum temperature of 773 K. Longer annealing (773 K/240 s), transformed the film to a poorly ordered vitreous phase, suggesting a novel method for solid state amorphization. Reitveld refinement analyses showed significant differences in structural parameters of the films crystallized by rapid and conventional thermal annealing. Dependence of the elastic modulus on the valence electron density (VED) of the crystallized films was studied. It is suggested that RTA provides a new approach to fabricate patterned shape memory thin films.

Improvement in crystallization and electrical properties of barium strontium titanate thin films by gold doping using metal-organic deposition method

International Nuclear Information System (INIS)

Wang, H.-W.; Nien, S.-W.; Lee, K.-C.; Wu, M.-C.

2005-01-01

The effect of gold (Au) on the crystallization, dielectric constant and leakage current density of barium strontium titanate (BST) thin films was investigated. BST thin films with various gold concentrations were prepared via a metal-organic deposition process. The X-ray diffraction shows enhanced crystallization as well as expanded lattice constants for the gold-doped BST films. Thermal analysis reveals that the gold dopant induces more complete decomposition of precursor for the doped films than those of undoped ones. The leakage current density of BST films is greatly reduced by the gold dopant over a range of biases (1-5 V). The distribution of gold was confirmed by electron energy loss spectroscopy and found to be inside the BST grains, not in the grain-boundaries. Gold acted as a catalyst, inducing the nucleation of crystallites and improving the crystallinity of the structure. Its addition is shown to be associated to the improvement of the electrical properties of BST films

Phase transition in lead titanate thin films: a Brillouin study

International Nuclear Information System (INIS)

Kuzel, P; Dugautier, C; Moch, P; Marrec, F Le; Karkut, M G

2002-01-01

The elastic properties of both polycrystalline and epitaxial PbTiO 3 (PTO) thin films are studied using Brillouin scattering spectroscopy. The epitaxial PTO films were prepared by pulsed laser ablation on (1) a [0 0 1] single crystal of SrTiO 3 (STO) doped with Nb and (2) a [0 0 1] STO buffered with a layer of YBa 2 Cu 3 O 7 . The polycrystalline PTO films were prepared by sol-gel on a Si substrate buffered with TiO 2 and Pt layers. The data analysis takes into account the ripple and the elasto-optic contributions. The latter significantly affects the measured spectra since it gives rise to a Love mode in the p-s scattering geometry. At room temperature, the spectra of the epitaxially grown samples are interpreted using previously published elastic constants of PTO single crystals. Sol-gel samples exhibit appreciable softening of the effective elastic properties compared to PTO single crystals: this result is explained by taking into account the random orientation of the microscopic PTO grains. For both the polycrystalline and the epitaxial films we have determined that the piezoelectric terms do not contribute to the spectra. The temperature dependence of the spectra shows strong anomalies of the elastic properties near the ferroelectric phase transition. Compared to the bulk, T C is higher in the sol-gel films, while in the epitaxial films the sign of the T C shift depends on the underlying material

Velocities of dislocation groups in very thin neutron-irradiated copper single crystals measured by slip line cinematography

Energy Technology Data Exchange (ETDEWEB)

Potthoff, H.H. (Technische Univ. Braunschweig (Germany, F.R.). Inst. fuer Metallphysik und Nukleare Festkoerperphysik)

1983-05-16

Slip line development on very thin flat single crystals of neutron-irradiated Cu (thickness down to only 15 to 20 ..mu..m, orientation for single glide, yield region, room temperature) is recorded by high-speed cinematography during tensile deformation. In such very thin crystals glide dislocations on the slip plane must be arranged in a rather simple way. Drops in tensile load occuring during initiation of single slip lines at the Lueders band front indicate that in the beginning of a slip line development dislocation groups traverse the whole glide plane in very short times. Evaluating the data measured for the slip line growth v/sub s/ >= 10 cm/s is found for screw dislocations and v/sub e/ >= v/sub s/ for edge dislocations. For later stages on thin crystals and for all stages on thick crystals (>= several 100 ..mu..m) slip line development is much slower and slip line show many cross slip events which then appear to control the mean velocity of the dislocations.

Single-domain epitaxial silicene on diboride thin films

Energy Technology Data Exchange (ETDEWEB)

Fleurence, A., E-mail: antoine@jaist.ac.jp; Friedlein, R.; Aoyagi, K.; Yamada-Takamura, Y. [School of Materials Science, Japan Advanced Institute of Science and Technology (JAIST), 1-1 Asahidai, Nomi, Ishikawa 923-1292 (Japan); Gill, T. G. [School of Materials Science, Japan Advanced Institute of Science and Technology (JAIST), 1-1 Asahidai, Nomi, Ishikawa 923-1292 (Japan); London Centre for Nanotechnology, University College London (UCL), London WC1H 0AH (United Kingdom); Department of Chemistry, UCL, London WC1H 0AJ (United Kingdom); Sadowski, J. T. [Center for Functional Nanomaterials, Brookhaven National Laboratory, Upton, New York 11973 (United States); Copel, M.; Tromp, R. M. [IBM Research Division, Thomas J. Watson Research Center, Yorktown Heights, New York 10598 (United States); Hirjibehedin, C. F. [London Centre for Nanotechnology, University College London (UCL), London WC1H 0AH (United Kingdom); Department of Chemistry, UCL, London WC1H 0AJ (United Kingdom); Department of Physics and Astronomy, UCL, London WC1E 6BT (United Kingdom)

2016-04-11

Epitaxial silicene, which forms spontaneously on ZrB{sub 2}(0001) thin films grown on Si(111) wafers, has a periodic stripe domain structure. By adsorbing additional Si atoms on this surface, we find that the domain boundaries vanish, and a single-domain silicene sheet can be prepared without altering its buckled honeycomb structure. The amount of Si required to induce this change suggests that the domain boundaries are made of a local distortion of the silicene honeycomb lattice. The realization of a single domain sheet with structural and electronic properties close to those of the original striped state demonstrates the high structural flexibility of silicene.

Sputtered highly oriented PZT thin films for MEMS applications

Science.gov (United States)

Kalpat, Sriram S.

Recently there has been an explosion of interest in the field of micro-electro-mechanical systems (MEMS). MEMS device technology has become critical in the growth of various fields like medical, automotive, chemical, and space technology. Among the many applications of ferroelectric thin films in MEMS devices, microfluidics is a field that has drawn considerable amount of research from bio-technology industries as well as chemical and semiconductor manufacturing industries. PZT thin films have been identified as best suited materials for micro-actuators and micro-sensors used in MEMS devices. A promising application for piezoelectric thin film based MEMS devices is disposable drug delivery systems that are capable of sensing biological parameters, mixing and delivering minute and precise amounts of drugs using micro-pumps or micro mixers. These devices call for low driving voltages, so that they can be battery operated. Improving the performance of the actuator material is critical in achieving battery operated disposal drug delivery systems. The device geometry and power consumption in MEMS devices largely depends upon the piezoelectric constant of the films, since they are most commonly used to convert electrical energy into a mechanical response of a membrane or cantilever and vice versa. Phenomenological calculation on the crystal orientation dependence of piezoelectric coefficients for PZT single crystal have reported a significant enhancement of the piezoelectric d33 constant by more than 3 times along [001] in the rhombohedral phase as compared to the conventionally used orientation PZT(111) since [111] is the along the spontaneous polarization direction. This could mean considerable improvement in the MEMS device performance and help drive the operating voltages lower. The motivation of this study is to investigate the crystal orientation dependence of both dielectric and piezoelectric coefficients of PZT thin films in order to select the appropriate

Investigation of phase transformation for ferrite–austenite structure in stainless steel thin films

Energy Technology Data Exchange (ETDEWEB)

Merakeb, Noureddine [Laboratory of Physical Metallurgy and Property of Materials (LM2PM), Metallurgy and Materials Engineering Department, Badji Mokhtar University, P.O. Box 12, Annaba 23000 (Algeria); Messai, Amel [Laboratoire d' Ingénierie et Sciences des Matériaux Avancés (ISMA), Institut des Sciences et Technologie, Abbès Laghrour University, Khenchela 40000 (Algeria); Ayesh, Ahmad I., E-mail: ayesh@qu.edu.qa [Department of Mathematics, Statistics and Physics, Qatar University, Doha (Qatar)

2016-05-01

In this work we report on phase transformation of 304 stainless steel thin films due to heat treatment. Ex-situ annealing was applied for evaporated 304 stainless steel thin films inside an ultra-high vacuum chamber with a pressure of 3 × 10{sup −7} Pa at temperatures of 500 °C and 600 °C. The structure of thin films was studied by X-ray diffraction (XRD) and conversion electron Mössbauer spectroscopy (CEMS) techniques. The results revealed a transformation from α-phase that exhibits a body-centered cubic structure (BCC) to γ-phase that exhibits a face-centered cubic (FCC) due to annealing. In addition, the percentage of γ-phase structure increased with the increase of annealing temperature. Annealing thin films increased the crystal size of both phases (α and γ), however, the increase was nonlinear. The results also showed that phase transformation was produced by recrystallization of α and γ crystals with a temporal evolution at each annealing temperature. The texture degree of thin films was investigated by XRD rocking curve method, while residual stress was evaluated using curvature method. - Highlights: • Stainless steel thin films were fabricated by thermal evaporation on quartz. • Alpha to gamma phase transformation of thin films was investigated. • Annealing of thin films reduces disruption in crystal lattice. • The stress of as-grown thin films was independent on the thin film thickness. • The stress of the thin films was reduced due to annealing.

GAGG:ce single crystalline films: New perspective scintillators for electron detection in SEM

International Nuclear Information System (INIS)

Bok, Jan; Lalinský, Ondřej; Hanuš, Martin; Onderišinová, Zuzana; Kelar, Jakub; Kučera, Miroslav

2016-01-01

Single crystal scintillators are frequently used for electron detection in scanning electron microscopy (SEM). We report gadolinium aluminum gallium garnet (GAGG:Ce) single crystalline films as a new perspective scintillators for the SEM. For the first time, the epitaxial garnet films were used in a practical application: the GAGG:Ce scintillator was incorporated into a SEM scintillation electron detector and it showed improved image quality. In order to prove the GAGG:Ce quality accurately, the scintillation properties were examined using electron beam excitation and compared with frequently used scintillators in the SEM. The results demonstrate excellent emission efficiency of the GAGG:Ce single crystalline films together with their very fast scintillation decay useful for demanding SEM applications. - Highlights: • First practical application of epitaxial garnet films demonstrated in SEM. • Improved image quality of SEM equipped with GAGG:Ce single crystalline thin film scintillator. • Scintillation properties of GAGG:Ce films compared with standard bulk crystal scintillators.

Growth of n-alkane films on a single-crystal substrate

DEFF Research Database (Denmark)

Wu, Z. U.; Ehrlich, S. N.; Matthies, B.

2001-01-01

The structure and growth mode of alkane films (n-C/sub n/H/sub 2n+2/; n=4, 6, 7) adsorbed on a Ag(111) surface have been investigated by synchrotron X-ray scattering. New models are proposed for the butane (n=4) and hexane (n=6) monolayer and butane bilayer structures. Specular reflectivity scans...... reveal that growth of all films is preempted between two and three layers by nucleation of bulk particles oriented with a single bulk crystal plane parallel to the film. In the case of butane, the bulk particles also have a fixed azimuthal relationship with the film resulting in complete epitaxy....

Self-Limited Growth in Pentacene Thin Films.

Science.gov (United States)

Pachmajer, Stefan; Jones, Andrew O F; Truger, Magdalena; Röthel, Christian; Salzmann, Ingo; Werzer, Oliver; Resel, Roland

2017-04-05

Pentacene is one of the most studied organic semiconducting materials. While many aspects of the film formation have already been identified in very thin films, this study provides new insight into the transition from the metastable thin-film phase to bulk phase polymorphs. This study focuses on the growth behavior of pentacene within thin films as a function of film thickness ranging from 20 to 300 nm. By employing various X-ray diffraction methods, combined with supporting atomic force microscopy investigations, one crystalline orientation for the thin-film phase is observed, while three differently tilted bulk phase orientations are found. First, bulk phase crystallites grow with their 00L planes parallel to the substrate surface; second, however, crystallites tilted by 0.75° with respect to the substrate are found, which clearly dominate the former in ratio; third, a different bulk phase polymorph with crystallites tilted by 21° is found. The transition from the thin-film phase to the bulk phase is rationalized by the nucleation of the latter at crystal facets of the thin-film-phase crystallites. This leads to a self-limiting growth of the thin-film phase and explains the thickness-dependent phase behavior observed in pentacene thin films, showing that a large amount of material is present in the bulk phase much earlier during the film growth than previously thought.

Field emission mechanism from a single-layer ultra-thin semiconductor film cathode

International Nuclear Information System (INIS)

Duan Zhiqiang; Wang Ruzhi; Yuan Ruiyang; Yang Wei; Wang Bo; Yan Hui

2007-01-01

Field emission (FE) from a single-layer ultra-thin semiconductor film cathode (SUSC) on a metal substrate has been investigated theoretically. The self-consistent quantum FE model is developed by synthetically considering the energy band bending and electron scattering. As a typical example, we calculate the FE properties of ultra-thin AlN film with an adjustable film thickness from 1 to 10 nm. The calculated results show that the FE characteristic is evidently modulated by varying the film thickness, and there is an optimum thickness of about 3 nm. Furthermore, a four-step FE mechanism is suggested such that the distinct FE current of a SUSC is rooted in the thickness sensitivity of its quantum structure, and the optimum FE properties of the SUSC should be attributed to the change in the effective potential combined with the attenuation of electron scattering

Electrical properties of single crystal Yttrium Iron Garnet ultra-thin films at high temperatures

OpenAIRE

Thiery, Nicolas; Naletov, Vladimir V.; Vila, Laurent; Marty, Alain; Brenac, Ariel; Jacquot, Jean-François; de Loubens, Grégoire; Viret, Michel; Anane, Abdelmadjid; Cros, Vincent; Youssef, Jamal Ben; Demidov, Vladislav E.; Demokritov, Sergej O.; Klein, Olivier

2017-01-01

We report a study on the electrical properties of 19 nm thick Yttrium Iron Garnet (YIG) films grown by liquid phase epitaxy. The electrical conductivity and Hall coefficient are measured in the high temperature range [300,400]~K using a Van der Pauw four-point probe technique. We find that the electrical resistivity decreases exponentially with increasing temperature following an activated behavior corresponding to a band-gap of $E_g\\approx 2$ eV, indicating that epitaxial YIG ultra-thin film...

Electrically Anisotropic Layered Perovskite Single Crystal

KAUST Repository

Li, Ting-You

2016-04-01

Organic-inorganic hybrid perovskites (OIHPs), which are promising materials for electronic and optoelectronic applications (1-10), have made into layered organic-inorganic hybrid perovskites (LOIHPs). These LOIHPs have been applied to thin-film transistors, solar cells and tunable wavelength phosphors (11-18). It is known that devices fabricated with single crystal exhibit the superior performance, which makes the growth of large-sized single crystals critical for future device applications (19-23). However, the difficulty in growing large-sized LOIHPs single crystal with superior electrical properties limits their practical applications. Here, we report a method to grow the centimeter-scaled LOIHP single crystal of [(HOC2H4NH3)2PbI4], demonstrating the potentials in mass production. After that, we reveal anisotropic electrical and optoelectronic properties which proved the carrier propagating along inorganic framework. The carrier mobility of in-inorganic-plane (in-plane) devices shows the average value of 45 cm2 V–1 s–1 which is about 100 times greater than the record of LOIHP devices (15), showing the importance of single crystal in device application. Moreover, the LOIHP single crystals show its ultra-short carrier lifetime of 42.7 ps and photoluminescence quantum efficiency (PLQE) of 25.4 %. We expect this report to be a start of LOIHPs for advanced applications in which the anisotropic properties are needed (24-25), and meets the demand of high-speed applications and fast-response applications.

Reduction of crystallization temperature of the Nd-Fe-B thin films by Cu addition

International Nuclear Information System (INIS)

Ma Yungui; Yang Zheng; Matsumoto, M.; Morisako, A.; Takei, S.

2004-01-01

Nonmagnetic Cu element has been doped into the sputtered Nd-Fe-B thin films. It is found that the introduction of suitable amount of copper atoms could reduce the crystallization temperature of the 2:14:1 phase by near 100 deg. C, compared with that without Cu. For the 15 nm Nd 16 Fe 70.2 Cu 1.8 B 12 film deposited at 340 deg. C, perpendicular coercivity and remanent magnetization ratio of 350 kA/m and 0.96 have been successfully obtained. Cu addition would lead to the grain growth, but the average grain size in the films could be greatly decreased through lowering the deposition temperature. These results are compared with those found in the fabrication of FePtCu films

Ultra-thin distributed Bragg reflectors via stacked single-crystal silicon nanomembranes

Energy Technology Data Exchange (ETDEWEB)

Cho, Minkyu; Seo, Jung-Hun; Lee, Jaeseong; Mi, Hongyi; Kim, Munho; Ma, Zhenqiang, E-mail: mazq@engr.wisc.edu [Department of Electrical and Computer Engineering, University of Wisconsin-Madison, Madison, Wisconsin 53706 (United States); Zhao, Deyin; Zhou, Weidong [Nanophotonics Lab, Department of Electrical Engineering, University of Texas at Arlington, Arlington, Texas 76019 (United States); Yin, Xin; Wang, Xudong [Department of Material Science and Engineering, University of Wisconsin-Madison, Madison, Wisconsin 53706 (United States)

2015-05-04

In this paper, we report ultra-thin distributed Bragg reflectors (DBRs) via stacked single-crystal silicon (Si) nanomembranes (NMs). Mesh hole-free single-crystal Si NMs were released from a Si-on-insulator substrate and transferred to quartz and Si substrates. Thermal oxidation was applied to the transferred Si NM to form high-quality SiO{sub 2} and thus a Si/SiO{sub 2} pair with uniform and precisely controlled thicknesses. The Si/SiO{sub 2} layers, as smooth as epitaxial grown layers, minimize scattering loss at the interface and in between the layers. As a result, a reflection of 99.8% at the wavelength range from 1350 nm to 1650 nm can be measured from a 2.5-pair DBR on a quartz substrate and 3-pair DBR on a Si substrate with thickness of 0.87 μm and 1.14 μm, respectively. The high reflection, ultra-thin DBRs developed here, which can be applied to almost any devices and materials, holds potential for application in high performance optoelectronic devices and photonics applications.

Origin of thermally stable ferroelectricity in a porous barium titanate thin film synthesized through block copolymer templating

Directory of Open Access Journals (Sweden)

Norihiro Suzuki

2017-07-01

Full Text Available A porous barium titanate (BaTiO3 thin film was chemically synthesized using a surfactant-assisted sol-gel method in which micelles of amphipathic diblock copolymers served as structure-directing agents. In the Raman spectrum of the porous BaTiO3 thin film, a peak corresponding to the ferroelectric tetragonal phase was observed at around 710 cm−1, and it remained stable at much higher temperature than the Curie temperature of bulk single-crystal BaTiO3 (∼130 °C. Measurements revealed that the ferroelectricity of the BaTiO3 thin film has high thermal stability. By analyzing high-resolution transmission electron microscope images of the BaTiO3 thin film by the fast Fourier transform mapping method, the spatial distribution of stress in the BaTiO3 framework was clearly visualized. Careful analysis also indicated that the porosity in the BaTiO3 thin film introduced anisotropic compressive stress, which deformed the crystals. The resulting elongated unit cell caused further displacement of the Ti4+ cation from the center of the lattice. This displacement increased the electric dipole moment of the BaTiO3 thin film, effectively enhancing its ferro(piezoelectricity.

Temperature dependence of LRE-HRE-TM thin films

Science.gov (United States)

Li, Zuoyi; Cheng, Xiaomin; Lin, Gengqi; Li, Zhen; Huang, Zhixin; Jin, Fang; Wang, Xianran; Yang, Xiaofei

2003-04-01

Temperature dependence of the properties of RE-TM thin films is very important for MO recording. In this paper, we studied the temperature dependence of the magnetic and magneto-optical properties of the amorphous LRE-HRE-TM single layer thin films and LRE-HRE-TM/HRE-TM couple-bilayered thin films. For LRE-HRE-TM single layer thin films, the temperature dependence of the magnetization was investigated by using the mean field theory. The experimental and theoretical results matched very well. With the LRE substitution in HRE-TM thin film, the compensation temperature Tcomp decreased and the curie temperature Tc remained unchanged. Kerr rotation angle became larger and the saturation magnetization Ms at room temperature increased. For LRE-HRE-TM/HRE-TM couple-bilayered thin films, comparisons of the temperature dependences of the coercivities and Kerr rotation angles were made between isolated sublayers and couple-bilayered thin film.

Excimer laser assisted re-oxidation of BaTiO3 thin films on Ni metal foils

International Nuclear Information System (INIS)

Bharadwaja, S. S. N.; Ko, S. W.; Qu, W.; Clark, T.; Rajashekhar, A.; Motyka, M.; Podraza, N.; Randall, C. A.; Trolier-McKinstry, S.

2016-01-01

Excimer laser assisted re-oxidation for reduced, crystallized BaTiO 3 thin films on Ni-foils was investigated. It was found that the BaTiO 3 can be re-oxidized at an oxygen partial pressure of ∼50 mTorr and substrate temperature of 350 °C without forming a NiO x interface layer between the film and base metal foil. The dielectric permittivity of re-oxidized films was >1000 with loss tangent values <2% at 100 Hz, 30 mV rms excitation signal. Electron Energy Loss Spectroscopy indicated that BaTiO 3 thin films can be re-oxidized to an oxygen stoichiometry close to ∼3 (e.g., stoichiometric). High resolution cross sectional transmission electron microscopy showed no evidence of NiO x formation between the BaTiO 3 and the Ni foil upon excimer laser re-oxidation. Spectroscopic ellipsometry studies on laser re-oxidized [001] C and [111] C BaTiO 3 single crystals indicate that the re-oxidation of BaTiO 3 single crystals is augmented by photo-excitation of the ozone, as well as laser pulse induced temperature and local stress gradients

Hall coefficients and optical properties of La/sub 2-//sub x/Sr/sub x/CuO4 single-crystal thin films

International Nuclear Information System (INIS)

Suzuki, M.

1989-01-01

The low-field Hall coefficient R/sub H/, optical reflectance and transmittance of the La/sub 2-//sub x/Sr/sub x/CuO 4 system with various Sr concentrations from x = 0 to 0.36 are systematically studied using single-crystal thin films epitaxially grown on (100) face SrTiO 3 substrates with the c axis normal to the film surface. For the x range measured, R/sub H/ is positive and decreases more rapidly than that expected from the Sr concentration but more slowly than reported earlier for polycrystalline specimens, indicating anisotropy of R/sub H/. Furthermore, the x dependence indicates deviation from that expected from a simple band model. Within the superconducting composition range, R/sub H/ exhibits characteristic temperature dependence. The optical reflectance spectrum changes from that of a semiconductor at x = 0 to a typical metallic one characterized by the Drude model for x>0.1, indicating the development of itinerant holes in the Cu-O planes. In the optical transmission spectra, an anomalous absorption band is seen in addition to the fundamental absorption corresponding to an energy gap of about 2 eV. This band, which develops with Sr doping, implies an enhancement of the density of states near the Fermi level. Taking these observations into account, the normal-state transport properties are explained with a qualitative consistence

Crystallization of sol-gel derived lead zirconate titanate thin films in argon and oxygen atmospheres

Energy Technology Data Exchange (ETDEWEB)

Bursill, L A [Melbourne Univ., Parkville, VIC (Australia). School of Physics; Brooks, K G [Ecole Polytechnique Federale, Lausanne (Switzerland)

1994-12-31

Electron diffraction and high-resolution electron microscopic techniques are applied to reveal the mechanisms of crystallization of 75 nm thin films of ferroelectric lead-zirconate-titanate (PZT). Sol-gel methods, followed by pyrolysis at 350 deg C, were used to provide a common starting point after which a variety of rapid-thermal annealing (RTA) experiments in the temperature range 400-700 deg C were made in argon, oxygen and nitrogen/hydrogen atmospheres. The results are interpreted in terms of the crystal chemical analysis, which points out that partial pressure of oxygen and heating rate are important experimental parameters which must be controlled if ferroelectric perovskite-type Pb{sub 2}ZrTiO{sub 6}, rather than pyrochlore-type Pb{sub 2}ZrTiO{sub 6+x}, where O < X < 1 or -1 < X < O, is to be obtained after the RTA step. Thus significant improvements in the crystallization of perovskite-type PZT were clearly demonstrated by using argon atmospheres for the RTA step. The results have significance for the production of high-quality ferroelectric thin films, with improved switching and fatigue characteristics, since even small amounts of the pyrochlore phase prove detrimental for these properties. 18 refs., 1 tab., 10 figs.

Annealing Effect on the Structural and Optical Properties of Sputter-Grown Bismuth Titanium Oxide Thin Films

Directory of Open Access Journals (Sweden)

José E. Alfonso

2014-04-01

Full Text Available The aim of this work is to assess the evolution of the structural and optical properties of BixTiyOz films grown by rf magnetron sputtering upon post-deposition annealing treatments in order to obtain good quality films with large grain size, low defect density and high refractive index similar to that of single crystals. Films with thickness in the range of 220–250 nm have been successfully grown. After annealing treatment at 600 °C the films show excellent transparency and full crystallization. It is shown that to achieve larger crystallite sizes, up to 17 nm, it is better to carry the annealing under dry air than under oxygen atmosphere, probably because the nucleation rate is reduced. The refractive index of the films is similar under both atmospheres and it is very high (n =2.5 at 589 nm. However it is still slightly lower than that of the single crystal value due to the polycrystalline morphology of the thin films.

Relationship between tribology and optics in thin films of mechanically oriented nanocrystals.

Science.gov (United States)

Wong, Liana; Hu, Chunhua; Paradise, Ruthanne; Zhu, Zina; Shtukenberg, Alexander; Kahr, Bart

2012-07-25

Many crystalline dyes, when rubbed unidirectionally with cotton on glass slides, can be organized as thin films of highly aligned nanocrystals. Commonly, the linear birefringence and linear dichroism of these films resemble the optical properties of single crystals, indicating precisely oriented particles. Of 186 colored compounds, 122 showed sharp extinction and 50 were distinctly linearly dichroic. Of the latter 50 compounds, 88% were more optically dense when linearly polarized light was aligned with the rubbing axis. The mechanical properties of crystals that underlie the nonstatistical correlation between tribological processes and the direction of electron oscillations in absorption bands are discussed. The features that give rise to the orientation of dye crystallites naturally extend to colorless molecular crystals.

Fabrication and analysis of single-crystal KTiOPO₄ films with thicknesses in the micrometer range.

Science.gov (United States)

Ma, Changdong; Lu, Fei; Xu, Bo; Fan, Ranran

2016-02-01

Single-crystal potassium titanyl phosphate (KTiOPO4, KTP) films with thicknesses less than 5 μm are obtained by using helium (He) implantation combined with ion-beam-enhanced etching. A heavily damaged layer created by a 4×10(16)  cm(-2) fluence of 2 MeV He implantation is removed by means of wet chemical etching in hydrofluoric acid (HF). Thus, free-standing films of KTP with thicknesses in the range of 3-5 μm are obtained. The etching rate can be adjusted over a wide range by choosing temperature and HF concentration, as well as annealing conditions. Sharp etching edges and the smooth surface of the film indicate that a high selective-etching rate is achieved in the damaged layer, and the remaining part of the crystal is undamaged. X-ray and Raman-scattering results prove that KTP films have good single-crystal properties.

Velocities of dislocation groups in very thin neutron-irradiated copper single crystals measured by slip line cinematography

International Nuclear Information System (INIS)

Potthoff, H.H.

1983-01-01

Slip line development on very thin flat single crystals of neutron-irradiated Cu (thickness down to only 15 to 20 μm, orientation for single glide, yield region, room temperature) is recorded by high-speed cinematography during tensile deformation. In such very thin crystals glide dislocations on the slip plane must be arranged in a rather simple way. Drops in tensile load occuring during initiation of single slip lines at the Lueders band front indicate that in the beginning of a slip line development dislocation groups traverse the whole glide plane in very short times. Evaluating the data measured for the slip line growth v/sub s/ >= 10 cm/s is found for screw dislocations and v/sub e/ >= v/sub s/ for edge dislocations. For later stages on thin crystals and for all stages on thick crystals (>= several 100 μm) slip line development is much slower and slip line show many cross slip events which then appear to control the mean velocity of the dislocations. (author)

The structure of ultrathin iron films on tungsten single-crystal surfaces

International Nuclear Information System (INIS)

Gardiner, T.M.

1983-01-01

Ultrathin iron films vapour deposited onto the surface of a cylindrical tungsten single crystal are discussed. Results from work function change, Auger electron spectroscopic and low energy electron diffraction techniques are combined for a comparison of the initial stages of film growth on four low index planes. Advantage is taken of the opportunity to evaporate onto and simultaneously to make measurements on all surface orientations of the zone. (Auth.)

Fiscal 1974 Sunshine Project result report. R and D on photovoltaic power generation system (R and D on particle non-accelerating growth Si thin film crystal); 1974 nendo taiyoko hatsuden system no kenkyu kaihatsu seika hokokusho. Ryushi hikasoku seichogata silicon usumaku kessho no kenkyu kaihatsu

Energy Technology Data Exchange (ETDEWEB)

NONE

1975-05-28

This research aims at development of the technology for producing photovoltaic power generation systems at a cost less than 1/100 of those by current technology. In fiscal 1974, basic study was made on formation technology of particle non-accelerating growth Si thin film crystals. In addition, evaluation was made on formed thin film crystal characteristics, and studies were also made on junction formation for thin film crystals, and on thin film formation and junction formation for indium phosphide compound semiconductor thin films. The research includes (1) study on formation technology for particle non-accelerating growth Si thin film crystals, (2) evaluation on Si thin film crystals, (3) study on junction formation technology for Si thin film crystals, and (4) study on indium phosphide compound semiconductors. Evaluations were made on thin film formation technology by CVD, and on crystallographical and electrical characteristics of the formed thin films. The evaluation results clarified the compatibility between substrates and Si thin films, the formation condition of columnar structure films, and the effect of growth conditions on a carrier density or mobility. (NEDO)

Thin films and nanomaterials

International Nuclear Information System (INIS)

Jayakumar, S.; Kannan, M.D.; Prasanna, S.

2012-01-01

The objective of this book is to disseminate the most recent research in Thin Films, Nanomaterials, Corrosion and Metallurgy presented at the International Conference on Advanced Materials (ICAM 2011) held in PSG College of Technology, Coimbatore, India during 12-16 December 2011. The book is a compilation of 113 chapters written by active researchers providing information and critical insights into the recent advancements that have taken place. Important new applications are possible today in the fields of microelectronics, opto-electronics, metallurgy and energy by the application of thin films on solid surfaces. Recent progress in high vacuum technology and new materials has a remarkable effect in thin film quality and cost. This has led to the development of new single or multi-layered thin film devices with diverse applications in a multitude of production areas, such as optics, thermal barrier coatings and wear protections, enhancing service life of tools and to protect materials against thermal and atmospheric influence. On the other hand, thin film process techniques and research are strongly related to the basic research activities in nano technology, an increasingly important field with countless opportunities for applications due to the emergence of new properties at the nanoscale level. Materials and structures that are designed and fabricated at the nano scale level, offer the potential to produce new devices and processes that may enhance efficiencies and reduce costs in many areas, as photovoltaic systems, hydrogen storage, fuel cells and solar thermal systems. In the book, the contributed papers are classified under two sections i) thin films and ii) nanomaterials. The thin film section includes single or multi layer conducting, insulating or semiconducting films synthesized by a wide variety of physical or chemical techniques and characterized or analyzed for different applications. The nanomaterials section deals with novel or exciting materials

Cellulose triacetate, thin film dielectric capacitor

Science.gov (United States)

Yen, Shiao-Ping S. (Inventor); Jow, T. Richard (Inventor)

1995-01-01

Very thin films of cellulose triacetate are cast from a solution containing a small amount of high boiling temperature, non-solvent which evaporates last and lifts the film from the casting surface. Stretched, oriented, crystallized films have high electrical breakdown properties. Metallized films less than about 2 microns in thickness form self-healing electrodes for high energy density, pulsed power capacitors. Thicker films can be utilized as a dielectric for a capacitor.

Scintillation efficiency and X-ray imaging with the RE-Doped LuAG thin films grown by liquid phase epitaxy

International Nuclear Information System (INIS)

Tous, Jan; Blazek, Karel; Kucera, Miroslav; Nikl, Martin; Mares, Jiri A.

2012-01-01

Very thin scintillator imaging plates have recently become of great interest. In high resolution X-ray radiography, very thin scintillator layers of about 5–20 μm are used to achieve 2D-spatial resolutions below 1 μm. Thin screens can be prepared by mechanical polishing from single crystals or by epitaxial growth on single-crystal substrates using the Liquid Phase Epitaxy technique (LPE). Other types of screens (e.g. deposited powder) do no reach required spatial resolutions. This work compares LPE-grown YAG and LuAG scintillator films doped with different rare earth ions (Cerium, Terbium and Europium). Two different fluxes were used in the LPE growth procedure. These LPE films are compared to YAG:Ce and LuAG:Ce screens made from bulk single crystals. Relative light yield was detected by a highly sensitive CCD camera. Scintillator screens were excited by a micro-focus X-ray source and the generated light was gathered by the CCD camera’s optical system. Scintillator 2D-homogeneity is examined in an X-ray imaging setup also using the CCD camera.

Analysis of Crystal Structure of Fe3O4 Thin Films Based on Iron Sand Growth by Spin Coating Method

Science.gov (United States)

Rianto, D.; Yulfriska, N.; Murti, F.; Hidayati, H.; Ramli, R.

2018-04-01

Recently, iron sand used as one of base materials in the steel industry. However, the content of iron sand can be used as starting materials in sensor technology in the form of thin films. In this paper, we report the analysis of crystal structure of magnetite thin film based on iron sand from Tiram’s Beach. The magnetic content of sand separated by a permanent magnet, then it was milled at 30 hours milling time. In order to increase the purity of magnetite, it washed after milling using aquades under magnetic separation by a magnet permanent. The thin film has been prepared using iron (III) nitrate by sol–gel technique. The precursor is resulted by dissolving magnetite in oxalic acid and nitric acid. Then, solution of iron (III) nitrate dissolved in ethylene glycol was applied on glass substrates by spin coating. The X-Ray Diffraction is operated thin film characterization. The structure of magnetite has been studied based on X-Ray Peaks that correspond to magnetite content of thin films.

Time-resolved luminescent spectroscopy of YAG:Ce single crystal and single crystalline films

International Nuclear Information System (INIS)

Zorenko, Yu.; Gorbenko, V.; Savchyn, V.; Vozniak, T.; Puzikov, V.; Danko, A.; Nizhankovski, S.

2010-01-01

The peculiarities of the luminescence and energy transfer from YAG host to the emission centers formed by the Y Al antisite defects and Ce 3+ ions have been studied in YAG:Ce single crystals, grown from the melt by modified Bridgman method in Ar and CO 2 + H 2 atmospheres, and YAG:Ce single crystalline film, grown by liquid phase epitaxy method, using the comparative time-resolved luminescent spectroscopy under excitation by synchrotron radiation in the range of fundamental adsorption of this garnet.

Crystal Structure of AgBi2I7 Thin Films.

Science.gov (United States)

Xiao, Zewen; Meng, Weiwei; Mitzi, David B; Yan, Yanfa

2016-10-06

Synthesis of cubic-phase AgBi 2 I 7 iodobismuthate thin films and fabrication of air-stable Pb-free solar cells using the AgBi 2 I 7 absorber have recently been reported. On the basis of X-ray diffraction (XRD) analysis and nominal composition, it was suggested that the synthesized films have a cubic ThZr 2 H 7 crystal structure with AgBi 2 I 7 stoichiometry. Through careful examination of the proposed structure and computational evaluation of the phase stability and bandgap, we find that the reported "AgBi 2 I 7 " films cannot be forming with the ThZr 2 H 7 -type structure, but rather more likely adopt an Ag-deficient AgBiI 4 type. Both the experimental X-ray diffraction pattern and bandgap can be better explained by the AgBiI 4 structure. Additionally, the proposed AgBiI 4 structure, with octahedral bismuth coordination, removes unphysically short Bi-I bonding within the [BiI 8 ] hexahedra of the ThZr 2 I 7 model. Our results provide critical insights for assessing the photovoltaic properties of AgBi 2 I 7 iodobismuthate materials.

Crystal structure determination of solar cell materials: Cu2ZnSnS4 thin films using X-ray anomalous dispersion

International Nuclear Information System (INIS)

Nozaki, Hiroshi; Fukano, Tatsuo; Ohta, Shingo; Seno, Yoshiki; Katagiri, Hironori; Jimbo, Kazuo

2012-01-01

Highlights: ► Cu 2 ZnSnS 4 thin films as a solar cell material were synthesized. ► The wavelength dependences of the diffraction intensity were measured. ► The crystal structures were clearly identified as kesterite structure for all samples. ► Crystal structure analysis revealed that the atomic compositions were Cu/(Zn + Sn) = 0.97 and Zn/Sn = 1.42 for the sample synthesized using stoichiometric amount of starting materials. - Abstract: The crystal structure of Cu 2 ZnSnS 4 (CZTS) thin films fabricated by vapor-phase sulfurization was determined using X-ray anomalous dispersion. High statistic synchrotron radiation X-ray diffraction data were collected from very small amounts of powder. By analyzing the wavelength dependencies of the diffraction peak intensities, the crystal structure was clearly identified as kesterite. Rietveld analysis revealed that the atomic composition deviated from stoichiometric composition, and the compositions were Cu/(Zn + Sn) = 0.97, and Zn/Sn = 1.42.

Thickness-modulated anisotropic ferromagnetism in Fe-doped epitaxial HfO2 thin films

Science.gov (United States)

Liu, Wenlong; Liu, Ming; Zhang, Ruyi; Ma, Rong; Wang, Hong

2017-10-01

Epitaxial tetragonal Fe-doped Hf0.95Fe0.05O2 (FHO) thin films with various thicknesses were deposited on (001)-oriented NdCaAlO4 (NCAO) substrates by using a pulsed laser deposition (PLD) system. The crystal structure and epitaxial nature of the FHO thin films were confirmed by typical x-ray diffraction (XRD) θ-2θ scan and reciprocal space mapping (RSM). The results indicate that two sets of lattice sites exist with two different crystal orientations [(001) and (100)] in the thicker FHO thin films. Further, the intensity of the (100) direction increases with the increase in thicknesses, which should have a significant effect on the anisotropic magnetization of the FHO thin films. Meanwhile, all the FHO thin films possess a tetragonal phase structure. An anisotropy behavior in magnetization has been observed in the FHO thin films. The anisotropic magnetization of the FHO thin films is slowly weakened as the thickness increases. Meanwhile, the saturation magnetization (Ms) of both in-plane and out-of-plane decreases with the increase in the thickness. The change in the anisotropic magnetization and Ms is attributed to the crystal lattice and the variation in the valence of Fe ions. These results indicate that the thickness-modulated anisotropic ferromagnetism of the tetragonal FHO epitaxial thin films is of potential use for the integration of metal-oxide semiconductors with spintronics.

Optical constants of CH3NH3PbBr3 perovskite thin films measured by spectroscopic ellipsometry

KAUST Repository

Alias, Mohd Sharizal

2016-07-14

The lack of optical constants information for hybrid perovskite of CH3NH3PbBr3 in thin films form can delay the progress of efficient LED or laser demonstration. Here, we report on the optical constants (complex refractive index and dielectric function) of CH3NH3PbBr3 perovskite thin films using spectroscopic ellipsometry. Due to the existence of voids, the refractive index of the thin films is around 8% less than the single crystals counterpart. The energy bandgap is around 2.309 eV as obtained from photoluminescence and spectrophotometry spectra, and calculated from the SE analysis. The precise measurement of optical constants will be useful in designing optical devices using CH3NH3PbBr3 thin films.

In situ differential reflectance spectroscopy of thin crystalline films of PTCDA on different substrates

International Nuclear Information System (INIS)

Proehl, Holger; Nitsche, Robert; Dienel, Thomas; Leo, Karl; Fritz, Torsten

2005-01-01

We report an investigation of the excitonic properties of thin crystalline films of the archetypal organic semiconductor PTCDA (3,4,9,10-perylenetetracarboxylic dianhydride) grown on poly- and single crystalline surfaces. A sensitive setup capable of measuring the optical properties of ultrathin organic molecular crystals via differential reflectance spectroscopy (DRS) is presented. This tool allows to carry out measurements in situ, i.e., during the actual film growth, and over a wide spectral range, even on single crystalline surfaces with high symmetry or metallic surfaces, where widely used techniques like reflection anisotropy spectroscopy (RAS) or fluorescence excitation spectroscopy fail. The spectra obtained by DRS resemble mainly the absorption of the films if transparent substrates are used, which simplifies the analysis. In the case of mono- to multilayer films of PTCDA on single crystalline muscovite mica(0001) and Au(111) substrates, the formation of the solid state absorption from monomer to dimer and further to crystal-like absorption spectra can be monitored

The α-particle excited scintillation response of YAG:Ce thin films grown by liquid phase epitaxy

International Nuclear Information System (INIS)

Prusa, Petr; Nikl, Martin; Mares, Jiri A.; Nitsch, Karel; Beitlerova, Alena; Kucera, Miroslav

2009-01-01

Y 3 Al 5 O 12 :Ce (YAG:Ce) thin films were grown from PbO-,BaO-, and MoO 3 -based fluxes using the liquid phase epitaxy (LPE) method. Photoelectron yield, its time dependence within 0.5-10 μs shaping time, and energy resolution of these samples were measured under α-particle excitation. For comparison a sample of the Czochralski grown bulk YAG:Ce single crystal was measured as well. Photoelectron yield values of samples grown from the BaO-based flux were found superior to other LPE films and comparable with that of the bulk single crystal. The same is valid also for the time dependence of photoelectron yield. Obtained results are discussed taking into account the influence of the flux and technology used. Additionally, α particle energy deposition in very thin films is modelled and discussed. (copyright 2009 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

Threshold fluence measurement for laser liftoff of InP thin films by selective absorption

NARCIS (Netherlands)

Jan, A.; Reeves, B.A.; Van De Burgt, Y.B.; Hayes, G.J.; Clemens, B.M.

2018-01-01

e explore conditions for achieving laser liftoff in epitaxially grown heterojunctions, in which single crystal thin films can be separated from their growth substrates using a selectively absorbing buried intermediate layer. Because this highly non-linear process is subject to a variety of process

Growth and structure of thermally evaporated Bi{sub 2}Te{sub 3} thin films

Energy Technology Data Exchange (ETDEWEB)

Rogacheva, E.I., E-mail: rogacheva@kpi.kharkov.ua [National Technical University “Kharkov Polytechnic Institute”, 21 Frunze St., Kharkov 61002 (Ukraine); Budnik, A.V. [National Technical University “Kharkov Polytechnic Institute”, 21 Frunze St., Kharkov 61002 (Ukraine); Dobrotvorskaya, M.V.; Fedorov, A.G.; Krivonogov, S.I.; Mateychenko, P.V. [Institute for Single Crystals of NAS of Ukraine, 60 Lenin Prospect, Kharkov 61001 (Ukraine); Nashchekina, O.N.; Sipatov, A.Yu. [National Technical University “Kharkov Polytechnic Institute”, 21 Frunze St., Kharkov 61002 (Ukraine)

2016-08-01

The growth mechanism, microstructure, and crystal structure of the polycrystalline n-Bi{sub 2}Te{sub 3} thin films with thicknesses d = 15–350 nm, prepared by thermal evaporation in vacuum onto glass substrates, were studied. Bismuth telluride with Te excess was used as the initial material for the thin film preparation. The thin film characterization was performed using X-ray diffraction, X-ray photoelectron spectroscopy, energy-dispersive X-ray spectroscopy, scan electron microscopy, and electron force microscopy. It was established that the chemical composition of the prepared films corresponded rather well to the starting material composition and the films did not contain any phases apart from Bi{sub 2}Te{sub 3}. It was shown that the grain size and the film roughness increased with increasing film thickness. The preferential growth direction changed from [00l] to [015] under increasing d. The X-ray photoelectron spectroscopy studies showed that the thickness of the oxidized surface layer did not exceed 1.5–2.0 nm and practically did not change in the process of aging at room temperature, which is in agreement with the results reported earlier for single crystals. The obtained data show that using simple and inexpensive method of thermal evaporation in vacuum and appropriate technological parameters, one can grow n-Bi{sub 2}Te{sub 3} thin films of a sufficiently high quality. - Highlights: • The polycrystalline n-Bi{sub 2}Te{sub 3} thin films were grown thermal evaporation onto glass. • The growth mechanism and film structure were studied by different structure methods. • The grain size and film roughness increased with increasing film thickness. • The growth direction changes from [00l] to [015] under film thickness increasing. • The oxidized layer thickness (1–2 nm) did not change under aging at room temperature.

Observation of two regions of selective light reflection from a thin film of a cholesteric liquid crystal

International Nuclear Information System (INIS)

Alaverdyan, R B; Dadalyan, T K; Chilingaryan, Yurii S

2013-01-01

Two regions of selective light reflection (in the short- and long- wavelength parts of the visible spectrum) from a thin film of a cholesteric liquid crystal (CLC), consisting of the mixture of two CLCs with opposite chirality and a nematic liquid crystal, are experimentally found for the first time. The spectral position of the reflection regions and the separation between them varies depending on the CLC composition and the temperature. The long-wavelength region of reflection corresponds to the region of Bragg reflection from the CLC helix, while the short-wavelength region is probably due to the defects in the structure of the CLC film. (letters)

Chapter 23. Single and Heterostructure Multiferroic Thin Films

OpenAIRE

Barbier , Antoine

2018-01-01

International audience; Multiferroic oxide materials exhibiting several long range ferroic orders are of high interest because of their wide range of potential applications. The incorporation of their genuine properties in new devices, offering additional physical properties, requires often elaborating them in form of thin films. Retaining their multiferroic characteristics is very challenging. However, thin films can be structured on the nanometer scale and additional degrees of freedom, suc...

Enhancement of Jc of MgB2 thin films by introduction of oxygen during deposition

International Nuclear Information System (INIS)

Mori, Zon; Doi, Toshiya; Hakuraku, Yoshinori; Kitaguchi, Hitoshi

2006-01-01

The introduction of various pinning center are examined as the effective means for improvement of J c of MgB 2 thin films. We have investigated the effects of introduction of oxygen during deposition on the superconducting properties of MgB 2 thin films. MgB 2 thin films were prepared on polished sapphire C(0001) single crystal substrates by using electron beam evaporation technique (EB) without any post-annealing. The background pressure was less than 1.3x10 -6 Pa. The evaporation flux ratio of Mg was set at 30 times as high as that of B, and the growth rate of MgB 2 film was 1nm/s. The film thickness was typically 300nm at 5min deposition. The substrate temperature was 245 deg. C. Under these conditions, we controlled the oxygen partial pressure (P O 2 ) within the range from 1.3x10 -6 to 1.3x10 -3 Pa by using a quadrapole mass spectrometer. Although T c of deposited thin film decreased in order of P O 2 , ΔM in the magnetization hysteresis loops measured from 0 to 6T at 4.2K increased up to 1.3x10 -5 . On the other hand, thin film prepared under P O 2 of 1.3x10 -3 Pa does not show superconducting transition. Between these films, there is no difference in the crystal structure from X-ray diffraction (XRD). These results suggest that the pinning center in the thin films increased by introduction of oxygen. Extremely small amount of oxygen introduction has enabled the control of growth of oxide

Soft chemistry routes to transparent metal oxide thin films. The case of sol–gel synthesis and structural characterization of Ta2O5 thin films from tantalum chloromethoxide

International Nuclear Information System (INIS)

Epifani, Mauro; Zamani, Reza; Arbiol, Jordi; Fabrega, Cristian; Andreu, Teresa; Pace, Giovanni Battista; Siciliano, Pietro; Morante, Joan R.

2014-01-01

Ta 2 O 5 thin films were prepared by spin-coating methanol solutions of Ta chloromethoxide. It was prepared by reacting TaCl 5 with methanol, followed by water addition (H 2 O: Ta molar ratio was 16). Thin films were deposited by spin-coating onto SiO 2 /Si substrates, followed by drying at 90 °C and heat-treatment up to 700 °C. The films were characterized by X-ray diffraction, transmission electron microscopy and field emission scanning electron microscopy. Crystallization was obtained only after heating at 700 °C, in the Ta 2 O 5 orthorhombic phase. The resulting films had a thickness of 100 nm. Their structure was constituted by porous crystals with size up to 50 nm, while the pores had a size of about 10 nm. The results demonstrated that TaCl 5 is very convenient precursor for the wet chemical synthesis of Ta 2 O 5 thin films. - Highlights: • Development of convenient solution synthesis of Ta 2 O 5 thin films; • The precursor chemistry was established and related to the synthesis process; • Uniform films crystallized in the most stable orthorombic Ta 2 O 5 phase;

The Structure and Stability of Molybdenum Ditelluride Thin Films

Directory of Open Access Journals (Sweden)

Zhouling Wang

2014-01-01

Full Text Available Molybdenum-tellurium alloy thin films were fabricated by electron beam evaporation and the films were annealed in different conditions in N2 ambient. The hexagonal molybdenum ditelluride thin films with well crystallization annealed at 470°C or higher were obtained by solid state reactions. Thermal stability measurements indicate the formation of MoTe2 took place at about 350°C, and a subtle weight-loss was in the range between 30°C and 500°C. The evolution of the chemistry for Mo-Te thin films was performed to investigate the growth of the MoTe2 thin films free of any secondary phase. And the effect of other postdeposition treatments on the film characteristics was also investigated.

Epitaxial growth and control of the sodium content in Na{sub x}CoO{sub 2} thin films

Energy Technology Data Exchange (ETDEWEB)

Hildebrandt, Sandra; Komissinskiy, Philipp [Institute for Materials Science, Technische Universität Darmstadt, 64287 Darmstadt (Germany); Major, Marton [Institute for Materials Science, Technische Universität Darmstadt, 64287 Darmstadt (Germany); WIGNER RCP, RMKI, H-1525 Budapest, P.O.B. 49 (Hungary); Donner, Wolfgang [Institute for Materials Science, Technische Universität Darmstadt, 64287 Darmstadt (Germany); Alff, Lambert, E-mail: alff@oxide.tu-darmstadt.de [Institute for Materials Science, Technische Universität Darmstadt, 64287 Darmstadt (Germany)

2013-10-31

Single-phase c-axis oriented Na{sub x}CoO{sub 2} thin films were grown on (001) SrTiO{sub 3} single-crystal substrates, using pulsed laser deposition. X-ray diffraction analysis indicates the epitaxial growth of Na{sub x}CoO{sub 2} thin films in two domains, rotated in-plane by 15 and 45 degrees relative to [100] SrTiO{sub 3}. The sodium stoichiometry x of the films can be controlled in a range of 0.38 < x < 0.84 by in-situ post-deposition annealing the Na{sub x}CoO{sub 2} films at 720 – 760 °C in oxygen for 10 – 30 min. γ - Na{sub x}CoO{sub 2} films are obtained with a full width at half maximum of the (002) Na{sub x}CoO{sub 2} rocking curve below 0.2 degrees. The post-deposition annealing can substitute commonly used chemical deintercalation of Na which is typically associated with a loss in crystallinity. - Highlights: • Single phase Na{sub x}CoO{sub 2} thin films grown by pulsed laser deposition • Epitaxial relations of Na{sub x}CoO{sub 2} thin films on (001) SrTiO{sub 3} substrates • Multi-domain thin films • Control of sodium content by in-situ annealing of Na{sub x}CoO{sub 2} thin films.

Texture analysis by the Schulz reflection method: Defocalization corrections for thin films

International Nuclear Information System (INIS)

Chateigner, D.; Germi, P.; Pernet, M.

1992-01-01

A new method is described for correcting experimental data obtained from the texture analysis of thin films. The analysis employed for correcting the data usually requires the experimental curves of defocalization for a randomly oriented specimen. In view of difficulties in finding non-oriented films, a theoretical method for these corrections is proposed which uses the defocalization evolution for a bulk sample, the film thickness and the penetration depth of the incident beam in the material. This correction method is applied to a film of YBa 2 CU 3 O 7-δ on an SrTiO 3 single-crystal substrate. (orig.)

Solid phase crystallized polycrystalline thin-films on glass from evaporated silicon for photovoltaic applications

International Nuclear Information System (INIS)

Song Dengyuan; Inns, Daniel; Straub, Axel; Terry, Mason L.; Campbell, Patrick; Aberle, Armin G.

2006-01-01

Polycrystalline silicon (poly-Si) thin-films are made on planar and textured glass substrates by solid phase crystallization (SPC) of in situ doped amorphous silicon (a-Si) deposited by electron-beam evaporation. These materials are referred to by us as EVA materials (SPC of evaporated a-Si). The properties of EVA poly-Si films are characterised by Raman microscopy, transmission electron microscopy, and X-ray diffraction. A narrow and symmetrical Raman peak at a wave number of about 520 cm -1 is observed for all samples, showing that the films are fully crystallized. X-ray diffraction (XRD) reveals that the films are preferentially (111)-oriented. Furthermore, the full width at half maximum of the dominant (111) XRD peaks indicates that the structural quality of the films is affected by the a-Si deposition temperature and the surface morphology of the glass substrates. A-Si deposition at 200 instead of 400 deg. C leads to an enhanced poly-Si grain size. On textured glass, the addition of a SiN barrier layer between the glass and the Si improves the poly-Si material quality. No such effect occurs on planar glass. Mesa-type solar cells are made from these EVA films on planar and textured glass. A strong correlation between the cells' current-voltage characteristics and their crystalline material quality is observed

Photoelectrocatrocatalytic hydrolysis of starch by using sprayed ZnO thin films

Science.gov (United States)

Sapkal, R. T.; Shinde, S. S.; Rajpure, K. Y.; Bhosale, C. H.

2013-05-01

Thin films of zinc oxide have been deposited onto glass/FTO substrates at optimized 400 °C by using a chemical spray pyrolysis technique. Deposited films are character photocatalytic activity by using XRD, an SEM, a UV-vis spectrophotometer, and a PEC single-cell reactor. Films are polycrystalline and have a hexagonal (wurtzite) crystal structure with c-axis (002) orientation growth perpendicular to the substrate surface. The observed direct band gap is about 3.22 eV for typical films prepared at 400 °C. The photocatalytic activity of starch with a ZnO photocatalyst has been studied by using a novel photoelectrocatalytic process.

Photoelectrocatrocatalytic hydrolysis of starch by using sprayed ZnO thin films

International Nuclear Information System (INIS)

Sapkal, R. T.; Shinde, S. S.; Rajpure, K.Y.; Bhosale, C. H.

2013-01-01

Thin films of zinc oxide have been deposited onto glass/FTO substrates at optimized 400 °C by using a chemical spray pyrolysis technique. Deposited films are character photocatalytic activity by using XRD, an SEM, a UV-vis spectrophotometer, and a PEC single-cell reactor. Films are polycrystalline and have a hexagonal (wurtzite) crystal structure with c-axis (002) orientation growth perpendicular to the substrate surface. The observed direct band gap is about 3.22 eV for typical films prepared at 400 °C. The photocatalytic activity of starch with a ZnO photocatalyst has been studied by using a novel photoelectrocatalytic process. (semiconductor materials)

Composition and structural analysis of Sm-Co thin films on (100)Si

International Nuclear Information System (INIS)

Ghantasala, M.; Sood, D.K.; Mohan, S.

1998-01-01

Full text: The necessity of integration of magnetics with silicon processing technology became essential with the advent of Micro Electromechanical Systems (MEMS). The need to control the crystalline and magnetic properties of the magnetic thin films on silicon substrates has been the primary motivation for this work. The major objective of this work is to prepare the stoichiometric and crystalline SmCo 5 thin films with good magnetic properties on single crystal silicon substrate. We have prepared the SmCo think films on single crystal (100) silicon substrates using DC magnetron sputtering. Films have been prepared in pure argon as the sputter media at two different pressures 2 x 10 -2 torr and 2 x 10 3 torr with the substrates kept at room temperature, 500 and 700 deg C separately. These films have been characterised using RBS, XRD and SEM. RBS analysis showed that the films are nearly stoichiometric (1:4.9) and have significant amounts of oxygen as impurity. But XRD studies indicated that the as deposited films (at all substrate temperatures) are yet to form the crystalline structure. Some of the films have been subjected to rapid thermal annealing at two different temperatures at 800 and 1000 deg C for 30 secs in an effort to crystallise the films. RBS analysis of these films indicated that the room temperature and post annealed films at 1000 deg C resulted in considerable interdiffusion characteristics, whereas the high temperature deposited (500 and 700 deg C) and annealed films showed relatively very stable characteristics with minimal diffusion between the film and the substrate. XRD and SEM analysis of the films is in progress. The detailed results of these investigations will be presented

Photodiode Based on CdO Thin Films as Electron Transport Layer

Science.gov (United States)

Soylu, M.; Kader, H. S.

2016-11-01

Cadmium oxide (CdO) thin films were synthesized by the sol-gel method. The films were analyzed by means of XRD, AFM, and UV/Vis spectrophotometry. X-ray diffraction patterns confirm that the films are formed from CdO with cubic crystal structure and consist of nano-particles. The energy gap of the prepared film was found to be 2.29 eV. The current-voltage ( I- V) characteristics of the CdO/ p-Si heterojunction were examined in the dark and under different illumination intensities. The heterojunction showed high rectifying behavior and a strong photoresponse. Main electrical parameters of the photodiode such as series and shunt resistances ( R s and R sh), saturation current I 0, and photocurrent I ph, were extracted considering a single diode equivalent circuit of a photovoltaic cell. Results indicate that the application of CdO thin films as an electron transport layer on p-Si acts as a photodetector in the field of the UV/visible.

Morphology evolution of thin Ni film on MgO(100) substrate

International Nuclear Information System (INIS)

Lin, C.; Xu, Y.H.; Naramoto, H.; Wei, P.; Kitazawa, S.; Narumi, K.

2002-01-01

Thin Ni films with various thicknesses were deposited onto the MgO(100) single crystal substrate at 400 deg. C. The morphology measured by atomic force microscope shows an apparent correlation with the thickness. The initial 10 A film is composed of small round Ni islands. In the 25 A film, pinholes with narrow size distribution occur, which show local periodic distribution in some regions when the thickness of the film reaches 75 A. The driving force for such a structure is attributed to the elastic strain energy. When the film is about 100 A thick, the pinholes begin to disappear, due to filling by the late-coming atoms and covering of upper islands. (author)

Microstructure of thin film platinum electrodes on yttrium stabilized zirconia prepared by sputter deposition

Energy Technology Data Exchange (ETDEWEB)

Toghan, Arafat, E-mail: arafat.toghan@pci.uni-hannover.de [Institute of Physical Chemistry and Electrochemistry, Leibniz University of Hannover, Callinstrasse 3-3a, D-30167 Hannover (Germany); Khodari, M. [Chemistry Department, Faculty of Science, South Valley University, Qena, 83523 (Egypt); Steinbach, F.; Imbihl, R. [Institute of Physical Chemistry and Electrochemistry, Leibniz University of Hannover, Callinstrasse 3-3a, D-30167 Hannover (Germany)

2011-09-01

(111) oriented thin film Pt electrodes were prepared on single crystals of yttrium-stabilized zirconia (YSZ) by sputter deposition of platinum. The electrodes were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), selected area electron diffraction (SAED), X-ray diffraction (XRD), energy-dispersive X-ray analysis (EDX), atomic force microscopy (AFM) and by profilometry. SEM images of the as-sputtered platinum film show a compact amorphous Pt film covering uniformly the substrate. Upon annealing at 1123 K, gaps and pores at the interface develop leading to a partial dewetting of the Pt film. Increasing the annealing temperature to 1373 K transforms the polycrystalline Pt film into single crystalline grains exhibiting a (111) orientation towards the substrate.

Solid-state dewetting of single- and bilayer Au-W thin films: Unraveling the role of individual layer thickness, stacking sequence and oxidation on morphology evolution

Directory of Open Access Journals (Sweden)

A. Herz

2016-03-01

Full Text Available Self-assembly of ultrathin Au, W, and Au-W bilayer thin films is investigated using a rapid thermal annealing technique in an inert ambient. The solid-state dewetting of Au films is briefly revisited in order to emphasize the role of initial film thickness. W films deposited onto SiO2 evolve into needle-like nanocrystals rather than forming particle-like agglomerates upon annealing at elevated temperatures. Transmission electron microscopy reveals that such nanocrystals actually consist of tungsten (VI oxide (WO3 which is related to an anisotropic oxide crystal growth out of the thin film. The evolution of W films is highly sensitive to the presence of any residual oxygen. Combination of both the dewetting of Au and the oxide crystal growth of WO3 is realized by using various bilayer film configurations of the immiscible Au and W. At low temperature, Au dewetting is initiated while oxide crystal growth is still suppressed. Depending on the stacking sequence of the Au-W bilayer thin film, W acts either as a substrate or as a passivation layer for the dewetting of Au. Being the ground layer, W changes the wettability of Au which clearly modifies its initial state for the dewetting. Being the top layer, W prevents Au from dewetting regardless of Au film thickness. Moreover, regular pattern formation of Au-WO3 nanoparticles is observed at high temperature demonstrating how bilayer thin film dewetting can create unique nanostructure arrangements.

Solid-state dewetting of single- and bilayer Au-W thin films: Unraveling the role of individual layer thickness, stacking sequence and oxidation on morphology evolution

Energy Technology Data Exchange (ETDEWEB)

Herz, A., E-mail: andreas.herz@tu-ilmenau.de, E-mail: dong.wang@tu-ilmenau.de; Franz, A.; Theska, F.; Hentschel, M.; Kups, Th.; Wang, D., E-mail: andreas.herz@tu-ilmenau.de, E-mail: dong.wang@tu-ilmenau.de; Schaaf, P. [Department of Materials for Electronics and Electrical Engineering, Institute of Materials Science and Engineering and Institute of Micro- and Nanotechnologies MacroNano, TU Ilmenau, D-98693 Ilmenau (Germany)

2016-03-15

Self-assembly of ultrathin Au, W, and Au-W bilayer thin films is investigated using a rapid thermal annealing technique in an inert ambient. The solid-state dewetting of Au films is briefly revisited in order to emphasize the role of initial film thickness. W films deposited onto SiO{sub 2} evolve into needle-like nanocrystals rather than forming particle-like agglomerates upon annealing at elevated temperatures. Transmission electron microscopy reveals that such nanocrystals actually consist of tungsten (VI) oxide (WO{sub 3}) which is related to an anisotropic oxide crystal growth out of the thin film. The evolution of W films is highly sensitive to the presence of any residual oxygen. Combination of both the dewetting of Au and the oxide crystal growth of WO{sub 3} is realized by using various bilayer film configurations of the immiscible Au and W. At low temperature, Au dewetting is initiated while oxide crystal growth is still suppressed. Depending on the stacking sequence of the Au-W bilayer thin film, W acts either as a substrate or as a passivation layer for the dewetting of Au. Being the ground layer, W changes the wettability of Au which clearly modifies its initial state for the dewetting. Being the top layer, W prevents Au from dewetting regardless of Au film thickness. Moreover, regular pattern formation of Au-WO{sub 3} nanoparticles is observed at high temperature demonstrating how bilayer thin film dewetting can create unique nanostructure arrangements.

Structure and electrical properties of Pb(ZrxTi1-x)O3 deposited on textured Pt thin films

International Nuclear Information System (INIS)

Hong, Jongin; Song, Han Wook; Lee, Hee Chul; Lee, Won Jong; No, Kwangsoo

2001-01-01

The texturing of the bottom electrode plays a key role in the structure and electrical properties of Pb(Zr,Ti)O 3 (PZT) thin films. We fabricated Pt bottom electrodes having a different thickness on MgO single crystals at 600 o C by rf magnetron sputtering. As the thickness of platinum (Pt) thin film increased, the preferred orientation of Pt thin film changed from (200) to (111). PZT thin films were fabricated at 450 o C by electron cyclotron resonance-plasma enhanced metal organic chemical vapor deposition on the textured Pt thin films. The texturing of the bottom electrode caused drastic changes in the C--V characteristics, P--E characteristics, and fatigue characteristics of metal/ferroelectric material/metal (MFM) capacitors. The difference of the electrical properties between the PZT thin films having different texturing was discussed in terms-of the x--y alignment and the interface between electrode and PZT in MFM capacitors. copyright 2001 American Institute of Physics

Single source precursors for fabrication of I-III-VI{sub 2} thin-film solar cells via spray CVD

Energy Technology Data Exchange (ETDEWEB)

Hollingsworth, J.A.; Banger, K.K.; Jin, M.H.-C.; Harris, J.D.; Cowen, J.E.; Bohannan, E.W.; Switzer, J.A.; Buhro, W.E.; Hepp, A.F

2003-05-01

The development of thin-film solar cells on flexible, lightweight, space-qualified substrates provides an attractive cost solution to fabricating solar arrays with high specific power (W/kg). Thin-film fabrication studies demonstrate that ternary single source precursors can be used in either a hot, or cold-wall spray chemical vapour deposition reactor, for depositing CuInS{sub 2}, CuGaS{sub 2} and CuGaInS{sub 2} at reduced temperatures (400-450 sign C), which display good electrical and optical properties suitable for photovoltaic devices. X-ray diffraction studies, energy dispersive spectroscopy and scanning electron microscopy confirmed the formation of the single phase CIS, CGS, CIGS thin-films on various substrates at reduced temperatures.

Hydrothermal crystallization of amorphous titania films deposited using low temperature atomic layer deposition

Energy Technology Data Exchange (ETDEWEB)

Mitchell, D.R.G. [Institute of Materials Engineering, ANSTO, PMB 1, Menai, NSW 2234 (Australia)], E-mail: drm@ansto.gov.au; Triani, G.; Zhang, Z. [Institute of Materials Engineering, ANSTO, PMB 1, Menai, NSW 2234 (Australia)

2008-10-01

A two stage process (atomic layer deposition, followed by hydrothermal treatment) for producing crystalline titania thin films at temperatures compatible with polymeric substrates (< 130 deg. C) has been assessed. Titania thin films were deposited at 80 deg. C using atomic layer deposition. They were extremely flat, uniform and almost entirely amorphous. They also contained relatively high levels of residual Cl from the precursor. After hydrothermal treatment at 120 deg. C for 1 day, > 50% of the film had crystallized. Crystallization was complete after 10 days of hydrothermal treatment. Crystallization of the film resulted in the formation of coarse grained anatase. Residual Cl was completely expelled from the film upon crystallization. As a result of the amorphous to crystalline transformation voids formed at the crystallization front. Inward and lateral crystal growth resulted in voids being localized to the film/substrate interface and crystallite perimeters resulting in pinholing. Both these phenomena resulted in films with poor adhesion and film integrity was severely compromised.

Unit cell determination of epitaxial thin films based on reciprocal space vectors by high-resolution X-ray diffractometry

OpenAIRE

Yang, Ping; Liu, Huajun; Chen, Zuhuang; Chen, Lang; Wang, John

2013-01-01

A new approach, based on reciprocal space vectors (RSVs), is developed to determine Bravais lattice types and accurate lattice parameters of epitaxial thin films by high-resolution X-ray diffractometry (HR-XRD). The lattice parameters of single crystal substrates are employed as references to correct the systematic experimental errors of RSVs of thin films. The general procedure is summarized, involving correction of RSVs, derivation of raw unit cell, subsequent conversion to the Niggli unit ...

Spiro-OMeTAD single crystals: Remarkably enhanced charge-carrier transport via mesoscale ordering

KAUST Repository

Shi, Dong

2016-04-15

We report the crystal structure and hole-transport mechanism in spiro-OMeTAD [2,2′,7,7′-tetrakis(N,N-di-p-methoxyphenyl-amine)9,9′-spirobifluorene], the dominant hole-transporting material in perovskite and solid-state dye-sensitized solar cells. Despite spiro-OMeTAD’s paramount role in such devices, its crystal structure was unknown because of highly disordered solution-processed films; the hole-transport pathways remained ill-defined and the charge carrier mobilities were low, posing a major bottleneck for advancing cell efficiencies. We devised an antisolvent crystallization strategy to grow single crystals of spiro-OMeTAD, which allowed us to experimentally elucidate its molecular packing and transport properties. Electronic structure calculations enabled us to map spiro-OMeTAD’s intermolecular charge-hopping pathways. Promisingly, single-crystal mobilities were found to exceed their thin-film counterparts by three orders of magnitude. Our findings underscore mesoscale ordering as a key strategy to achieving breakthroughs in hole-transport material engineering of solar cells.

Studies of Second Order Optical Nonlinearities of 4-Aminobenzophenone (ABP) Single Crystal Films

Science.gov (United States)

Bhowmik, Achintya; Thakur, Mrinal

1998-03-01

Specific organic materials exhibit very high second order optical susceptibilities. Growth of single crystal films of these materials and characterization of nonlinear optical properties are necessary for implementation of device applications. We have grown large-area films ( 1 cm^2 area, 4 μm thick) of ABP by a modification of the shear method. Single crystal nature of the films was confirmed by polarized optical microscopy. X-ray diffraction analysis showed a [100] surface orientation. The absorption spectra revealed transparency from 390 nm to 1940 nm. Significant elements of the second order optical susceptibility tensor were measured by detailed SHG experiments using a Nd:YAG laser (1064 nm, 100 ps, 82 MHz). Second-harmonic power was measured using lock-in detection with carefully selected polarization conditions while the film was rotated about the propagation direction. Using LiNbØas the reference, d-coefficients of ABP were found to be d_23=7.2 pm/V and d_22=0.7 pm/V. Type-I and type-II phase-matching directions were identified on the film by analyzing the optical indicatrix surfaces at fundamental and second-harmonic frequencies.

Effect of arc suppression on the physical properties of low temperature dc magnetron sputtered tantalum thin films

International Nuclear Information System (INIS)

Subrahmanyam, A.; Valleti, Krishna; Joshi, Srikant V.; Sundararajan, G.

2007-01-01

Arcing is a common phenomenon in the sputtering process. Arcs and glow discharges emit electrons which may influence the physical properties of films. This article reports the properties of tantalum (Ta) thin films prepared by continuous dc magnetron sputtering in normal and arc-suppression modes. The substrate temperature was varied in the range of 300-673 K. The tantalum films were ∼1.8 μm thick and have good adherence to 316 stainless steel and single-crystal silicon substrates. The phase of the Ta thin film determines the electrical and tribological properties. The films deposited at 300 K using both methods were crystallized in a tetragonal structure (β phase) with a smooth surface (grain size of ∼10 nm) and exhibited an electrical resistivity of ∼194 μΩ cm and a hardness of ∼20 GPa. When the substrate temperature was 473 K and higher, the arc-suppression mode appears to influence the films to crystallize in the α phase with a grain size of ∼40 nm, whereas the normal power mode gave mixed phases β and α beyond 473 K, the arc-suppression mode yields larger grain sizes in the Ta thin films and the hardness decreases. These changes in the physical properties in arc-suppression mode are attributed to either the change in plasma characteristics or the energetic particle bombardment onto the substrate, or both

Epitaxial growth of thin single-crystals and their quality study by Rutherford scattering in channeling conditions

International Nuclear Information System (INIS)

Kirsch, Robert.

1975-01-01

Some aspects of thin crystalline layers are reminded: vacuum deposition, epitaxial growth, annealing and interdiffusion ion channeling and scattering of 1-2MeV helium ions are used to study the crystalline quality, the annealing effects and in some cases the interdiffusion in epitaxial multilayers of silver, copper gold and nickel. Thin single-crystals of gold and nickel oriented (III) plan parallel to the surface were obtained by successive epitaxial growth from muscovite mica clivages. The mounting techniques of single crystalline, self-supporting, 300 to 1200 Angstroems thick, gold and nickel targets of 3mm diameter are described. The gold single-crystals have dislocation densities of 10 8 cm -2 and the various epitaxial layers are obtained without twinning [fr

Formation of nano-sized pinholes array in thin Ni film on MgO(100) substrate

Energy Technology Data Exchange (ETDEWEB)

Lin Chuan; Naramoto, Hiroshi; Xu Yonghua; Kitazawa, Sin-iti; Narumi, Kazumasa; Sakai, Seiji

2003-10-22

We have grown thin Ni films with various thicknesses on polished MgO(100) single crystal substrates in an e-gun evaporation system. The morphology of the as-deposited films was characterized with atomic force microscopy. Pinholes with average diameter of 5-10 nm are found in the film with thickness from 1 to 15 nm, and pinholes array was observed in the film 10 nm thick. The origin of such structure formation is discussed in terms of the elastic strain energy.

Structural transformations in MoOx thin films grown by pulsed laser deposition

International Nuclear Information System (INIS)

Camacho-Lopez, M.A.; Haro-Poniatowski, E.; Escobar-Alarcon, L.

2004-01-01

In this work, laser-induced crystallization in MoO x thin films (1.8≤x≤2.1) is reported. This transformation involves a MoO x oxidation and subsequently a crystallization process from amorphous MoO 3 to crystalline αMoO 3 . For comparison purposes crystallization is induced thermally, in an oven, as well. The crystallization kinetics is monitored by Raman spectroscopy; a threshold in the energy density necessary to induce the phase transformation is determined in the case of photo-crystallization. This threshold depends on the type of substrate on which the film is deposited. For the thin films deposited on glass substrates, the structural transformation is from amorphous MoO x to the thermodynamically stable αMoO 3 crystalline phase. For the thin films deposited on Si(100) the structural transformation is from amorphous MoO x to a mixture of αMoO 3 and the thermodynamically unstable βMoO 3 crystalline phases. The structural transformations are also characterized by scanning electron microscopy and light-transmission experiments. (orig.)

Three-dimensional photonic crystals as intermediate filter for thin-film tandem solar cells

Science.gov (United States)

Bielawny, Andreas; Miclea, Paul T.; Wehrspohn, Ralf B.; Lee, Seung-Mo; Knez, Mato; Rockstuhl, Carsten; Lisca, Marian; Lederer, Falk L.; Carius, Reinhard

2008-04-01

The concept of a 3D photonic crystal structure as diffractive and spectrally selective intermediate filter within 'micromorphous' (a-Si/μc-Si) tandem solar cells has been investigated numerically and experimentally. Our device aims for the enhancement of the optical pathway of incident light within the amorphous silicon top cell in its spectral region of low absorption. From our previous simulations, we expect a significant improvement of the tandem cell efficiency of about absolutely 1.3%. This increases the efficiency for a typical a-Si / μc-Si tandem cell from 11.1% to 12.4%, as a result of the optical current-matching of the two junctions. We suggest as wavelength-selective optical element a 3D-structured optical thin-film, prepared by self-organized artificial opal templates and replicated with atomic layer deposition. The resulting samples are highly periodic thin-film inverted opals made of conducting and transparent zinc-oxide. We describe the fabrication processes and compare experimental data on the optical properties in reflection and transmission with our simulations and photonic band structure calculations.

Biocompatibility of GaSb thin films grown by RF magnetron sputtering

Science.gov (United States)

Nishimoto, Naoki; Fujihara, Junko; Yoshino, Katsumi

2017-07-01

GaSb may be suitable for biological applications, such as cellular sensors and bio-medical instrumentation because of its low toxicity compared with As (III) compounds and its band gap energy. Therefore, the biocompatibility and the film properties under physiological conditions were investigated for GaSb thin films with or without a surface coating. GaSb thin films were grown on quartz substrates by RF magnetron sputtering, and then coated with (3-mercaptopropyl) trimethoxysilane (MPT). The electrical properties, surface morphology, and crystal structure of the GaSb thin film were unaffected by the MPT coating. The cell viability assay suggested that MPT-coated GaSb thin films are biocompatible. Bare GaSb was particularly unstable in pH9 buffer. Ga elution was prevented by the MPT coating, although the Ga concentration in the pH 9 buffer was higher than that in the other solutions. The surface morphology and crystal structure were not changed by exposure to the solutions, except for the pH 9 buffer, and the thin film properties of MPT-coated GaSb exposed to distilled water and H2O2 in saline were maintained. These results indicate that MPT-coated GaSb thin films are biocompatible and could be used for temporary biomedical devices.

Epitaxial patterning of thin-films: conventional lithographies and beyond

International Nuclear Information System (INIS)

Zhang, Wei; Krishnan, Kannan M

2014-01-01

Thin-film based novel magnetic and electronic devices have entered a new era in which the film crystallography, structural coherence, and epitaxy play important roles in determining their functional properties. The capabilities of controlling such structural and functional properties are being continuously developed by various physical deposition technologies. Epitaxial patterning strategies further allow the miniaturization of such novel devices, which incorporates thin-film components into nanoscale architectures while keeping their functional properties unmodified from their ideal single-crystal values. In the past decade, epitaxial patterning methods on the laboratory scale have been reported to meet distinct scientific inquires, in which the techniques and processes used differ from one to the other. In this review we summarize many of these pioneering endeavors in epitaxial patterning of thin-film devices that use both conventional and novel lithography techniques. These methods demonstrate epitaxial patterning for a broad range of materials (metals, oxides, and semiconductors) and cover common device length scales from micrometer to sub-hundred nanometer. Whilst we have been motivated by magnetic materials and devices, we present our outlook on developing systematic-strategies for epitaxial patterning of functional materials which will pave the road for the design, discovery and industrialization of next-generation advanced magnetic and electronic nano-devices. (topical review)

Mechanical design of thin-film diamond crystal mounting apparatus for coherence preservation hard x-ray optics

International Nuclear Information System (INIS)

Shu, Deming; Shvyd’ko, Yuri V.; Stoupin, Stanislav; Kim, Kwang-Je

2016-01-01

A new thin-film diamond crystal mounting apparatus has been designed at the Advanced Photon Source (APS) for coherence preservation hard x-ray optics with optimized thermal contact and minimized crystal strain. This novel mechanical design can be applied to new development in the field of: x-ray optics cavities for hard x-ray free-electron laser oscillators (XFELOs), self-seeding monochromators for hard x-ray free-electron laser (XFEL) with high average thermal loading, high heat load diamond crystal monochromators and beam-sharing/beam-split-and-delay devices for XFEL facilities and future upgraded high-brightness coherent x-ray source in the MBA lattice configuration at the APS.

Mechanical design of thin-film diamond crystal mounting apparatus for coherence preservation hard x-ray optics

Energy Technology Data Exchange (ETDEWEB)

Shu, Deming, E-mail: shu@aps.anl.gov; Shvyd’ko, Yuri V.; Stoupin, Stanislav; Kim, Kwang-Je [Advanced Photon Source, Argonne National Laboratory, Argonne, IL 60439, U.S.A (United States)

2016-07-27

A new thin-film diamond crystal mounting apparatus has been designed at the Advanced Photon Source (APS) for coherence preservation hard x-ray optics with optimized thermal contact and minimized crystal strain. This novel mechanical design can be applied to new development in the field of: x-ray optics cavities for hard x-ray free-electron laser oscillators (XFELOs), self-seeding monochromators for hard x-ray free-electron laser (XFEL) with high average thermal loading, high heat load diamond crystal monochromators and beam-sharing/beam-split-and-delay devices for XFEL facilities and future upgraded high-brightness coherent x-ray source in the MBA lattice configuration at the APS.

Surface phase separation, dewetting feature size, and crystal morphology in thin films of polystyrene/poly(ε-caprolactone) blend.

Science.gov (United States)

Ma, Meng; He, Zhoukun; Li, Yuhan; Chen, Feng; Wang, Ke; Zhang, Qing; Deng, Hua; Fu, Qiang

2012-12-01

Thin films of polystyrene (PS)/poly(ε-caprolactone) (PCL) blends were prepared by spin-coating and characterized by tapping mode force microscopy (AFM). Effects of the relative concentration of PS in polymer solution on the surface phase separation and dewetting feature size of the blend films were systematically studied. Due to the coupling of phase separation, dewetting, and crystallization of the blend films with the evaporation of solvent during spin-coating, different size of PS islands decorated with various PCL crystal structures including spherulite-like, flat-on individual lamellae, and flat-on dendritic crystal were obtained in the blend films by changing the film composition. The average distance of PS islands was shown to increase with the relative concentration of PS in casting solution. For a given ratio of PS/PCL, the feature size of PS appeared to increase linearly with the square of PS concentration while the PCL concentration only determined the crystal morphology of the blend films with no influence on the upper PS domain features. This is explained in terms of vertical phase separation and spinodal dewetting of the PS rich layer from the underlying PCL rich layer, leading to the upper PS dewetting process and the underlying PCL crystalline process to be mutually independent. Copyright © 2012 Elsevier Inc. All rights reserved.

Crystal Structure, Optical, and Electrical Properties of SnSe and SnS Semiconductor Thin Films Prepared by Vacuum Evaporation Techniques for Solar Cell Applications

Science.gov (United States)

Ariswan; Sutrisno, H.; Prasetyawati, R.

2017-05-01

Thin films of SnSe and SnS semiconductors had been prepared by vacuum evaporation techniques. All prepared samples were characterized on their structure, optical, and electrical properties in order to know their application in technology. The crystal structure of SnSe and SnS was determined by X-Ray Diffraction (XRD) instrument. The morphology and chemical composition were obtained by Scanning Electron Microscopy (SEM) coupled with Energy Dispersive of X-Ray Analysis (EDAX). The optical property such as band gap was determined by DR-UV-Vis (Diffuse Reflectance-Ultra Violet-Visible) spectroscopy, while the electrical properties were determined by measuring the conductivity by four probes method. The characterization results indicated that both SnSe and SnS thin films were polycrystalline. SnSe crystallized in an orthorhombic crystal system with the lattice parameters of a = 11.47 Å, b = 4.152 Å and c = 4.439 Å, while SnS had an orthorhombic crystal system with lattice parameters of a = 4.317 Å, b = 11.647 Å and c = 3.981 Å. Band gaps (Eg) of SnSe and SnS were 1.63 eV and 1.35 eV, respectively. Chemical compositions of both thin films were non-stoichiometric. Molar ratio of Sn : S was close to ideal which was 1 : 0.96, while molar ratio of Sn : S was 1 : 0.84. The surface morphology described the arrangement of the grains on the surface of the thin film with sizes ranging from 0.2 to 0.5 microns. Color similarity on the surface of the SEM images proved a homogenous thin layer.

High mobility single-crystalline-like GaAs thin films on inexpensive flexible metal substrates by metal-organic chemical vapor deposition

International Nuclear Information System (INIS)

Dutta, P.; Rathi, M.; Gao, Y.; Yao, Y.; Selvamanickam, V.; Zheng, N.; Ahrenkiel, P.; Martinez, J.

2014-01-01

We demonstrate heteroepitaxial growth of single-crystalline-like n and p-type doped GaAs thin films on inexpensive, flexible, and light-weight metal foils by metal-organic chemical vapor deposition. Single-crystalline-like Ge thin film on biaxially textured templates made by ion beam assisted deposition on metal foil served as the epitaxy enabling substrate for GaAs growth. The GaAs films exhibited strong (004) preferred orientation, sharp in-plane texture, low grain misorientation, strong photoluminescence, and a defect density of ∼10 7  cm −2 . Furthermore, the GaAs films exhibited hole and electron mobilities as high as 66 and 300 cm 2 /V-s, respectively. High mobility single-crystalline-like GaAs thin films on inexpensive metal substrates can pave the path for roll-to-roll manufacturing of flexible III-V solar cells for the mainstream photovoltaics market.

High mobility single-crystalline-like GaAs thin films on inexpensive flexible metal substrates by metal-organic chemical vapor deposition

Energy Technology Data Exchange (ETDEWEB)

Dutta, P., E-mail: pdutta2@central.uh.edu; Rathi, M.; Gao, Y.; Yao, Y.; Selvamanickam, V. [Department of Mechanical Engineering, University of Houston, Houston, Texas 77204 (United States); Zheng, N.; Ahrenkiel, P. [Department of Nanoscience and Nanoengineering, South Dakota School of Mines and Technology, Rapid City, South Dakota 57701 (United States); Martinez, J. [Materials Evaluation Laboratory, NASA Johnson Space Center, Houston, Texas 77085 (United States)

2014-09-01

We demonstrate heteroepitaxial growth of single-crystalline-like n and p-type doped GaAs thin films on inexpensive, flexible, and light-weight metal foils by metal-organic chemical vapor deposition. Single-crystalline-like Ge thin film on biaxially textured templates made by ion beam assisted deposition on metal foil served as the epitaxy enabling substrate for GaAs growth. The GaAs films exhibited strong (004) preferred orientation, sharp in-plane texture, low grain misorientation, strong photoluminescence, and a defect density of ∼10{sup 7 }cm{sup −2}. Furthermore, the GaAs films exhibited hole and electron mobilities as high as 66 and 300 cm{sup 2}/V-s, respectively. High mobility single-crystalline-like GaAs thin films on inexpensive metal substrates can pave the path for roll-to-roll manufacturing of flexible III-V solar cells for the mainstream photovoltaics market.

Elastic properties of amorphous thin films studied by Rayleigh waves

International Nuclear Information System (INIS)

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

1993-01-01

Physical vapor deposition in ultra-high vacuum was used to co-deposit nickel and zirconium onto quartz single crystals and grow amorphous Ni 1-x Zr 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

Characterisation of magnetron sputtered SmCo5 thin films

International Nuclear Information System (INIS)

Wang, Y.; Sood, D.K.; Kothari

1999-01-01

SmCo 5 thin films were deposited using DC magnetron sputtering on single crystal silicon substrate with chromium and SiO 2 top layers. Deposition was carried out at three different substrate temperatures: room temperature, 400 deg C and 600 deg C. Films were characterised by using Rutherford Backscattering Spectroscopy (RBS), X-ray Diffraction (XRD), Secondary Ion Mass Spectrometry (SIMS) and SQUID magnetometer. RBS analysis indicated that the films have excellent stoichiometry with the Sm to Co ratio of 1:5. This analysis also showed that the films deposited or annealed at high temperatures (≥600 deg C) indicated significant inter-diffusion at the interface between the barrier layer and the film. Oxygen was found to be the major impurity in the films. XRD data indicated that the films formed 1:5 and 2:17 phases under different deposition conditions. The preliminary studies of these films using magnetic force microscopy revealed the presence of magnetic domains

Understanding polymorphism in organic semiconductor thin films through nanoconfinement.

Science.gov (United States)

Diao, Ying; Lenn, Kristina M; Lee, Wen-Ya; Blood-Forsythe, Martin A; Xu, Jie; Mao, Yisha; Kim, Yeongin; Reinspach, Julia A; Park, Steve; Aspuru-Guzik, Alán; Xue, Gi; Clancy, Paulette; Bao, Zhenan; Mannsfeld, Stefan C B

2014-12-10

Understanding crystal polymorphism is a long-standing challenge relevant to many fields, such as pharmaceuticals, organic semiconductors, pigments, food, and explosives. Controlling polymorphism of organic semiconductors (OSCs) in thin films is particularly important given that such films form the active layer in most organic electronics devices and that dramatic changes in the electronic properties can be induced even by small changes in the molecular packing. However, there are very few polymorphic OSCs for which the structure-property relationships have been elucidated so far. The major challenges lie in the transient nature of metastable forms and the preparation of phase-pure, highly crystalline thin films for resolving the crystal structures and evaluating the charge transport properties. Here we demonstrate that the nanoconfinement effect combined with the flow-enhanced crystal engineering technique is a powerful and likely material-agnostic method to identify existing polymorphs in OSC materials and to prepare the individual pure forms in thin films at ambient conditions. With this method we prepared high quality crystal polymorphs and resolved crystal structures of 6,13-bis(triisopropylsilylethynyl)pentacene (TIPS-pentacene), including a new polymorph discovered via in situ grazing incidence X-ray diffraction and confirmed by molecular mechanic simulations. We further correlated molecular packing with charge transport properties using quantum chemical calculations and charge carrier mobility measurements. In addition, we applied our methodology to a [1]benzothieno[3,2-b][1]1benzothiophene (BTBT) derivative and successfully stabilized its metastable form.

Thin films prepared from tungstate glass matrix

Energy Technology Data Exchange (ETDEWEB)

Montanari, B.; Ribeiro, S.J.L.; Messaddeq, Y. [Departamento de Quimica Geral e Inorganica, Instituto de Quimica, Sao Paulo State University-UNESP, CP 355, CEP 14800-900, Araraquara, SP (Brazil); Li, M.S. [Instituto de Fisica, USP, CP 369, CEP 13560-970, Sao Carlos, SP (Brazil); Poirier, G. [Departamento de Ciencias Exatas, UNIFAL-MG, CEP 37130-000, Alfenas-MG (Brazil)], E-mail: gael@unifal-mg.edu.br

2008-01-30

Vitreous samples containing high concentrations of WO{sub 3} (above 40% M) have been used as a target to prepare thin films. Such films were deposited using the electron beam evaporation method onto soda-lime glass substrates. These films were characterized by X-ray diffraction (XRD), perfilometry, X-ray energy dispersion spectroscopy (EDS), M-Lines and UV-vis absorption spectroscopy. In this work, experimental parameters were established to obtain stable thin films showing a chemical composition close to the glass precursor composition and with a high concentration of WO{sub 3}. These amorphous thin films of about 4 {mu}m in thickness exhibit a deep blue coloration but they can be bleached by thermal treatment near the glass transition temperature. Such bleached films show several guided modes in the visible region and have a high refractive index. Controlled crystallization was realized and thus it was possible to obtain WO{sub 3} microcrystals in the amorphous phase.

Nucleation of fcc Ta when heating thin films

International Nuclear Information System (INIS)

Janish, Matthew T.; Mook, William M.; Carter, C. Barry

2015-01-01

Thin tantalum films have been studied during in situ heating in a transmission electron microscope. Diffraction patterns from the as-deposited films were typical of amorphous materials. Crystalline grains were observed to form when the specimen was annealed in situ at 450 °C. Particular attention was addressed to the formation and growth of grains with the face-centered cubic (fcc) crystal structure. These observations are discussed in relation to prior work on the formation of fcc Ta by deformation and during thin film deposition

Effects of Sb-doping on the grain growth of Cu(In, Ga)Se2 thin films fabricated by means of single-target sputtering

International Nuclear Information System (INIS)

Zhang, Shu; Wu, Lu; Yue, Ruoyu; Yan, Zongkai; Zhan, Haoran; Xiang, Yong

2013-01-01

To investigate the effects of Sb doping on the kinetics of grain growth in Cu(In,Ga)Se 2 (CIGS) thin films during annealing, CIGS thin films were sputtered onto Mo coated substrates from a single CIGS alloy target, followed by chemical bath deposition of Sb 2 S 3 thin layers on top of CIGS layers and subsequent annealing at different temperatures for 30 min in Se vapors. X-ray diffraction results showed that CIGS thin films were obtained directly using the single-target sputtering method. After annealing, the In/Ga ratio in Sb-doped CIGS thin films remained stable compared to undoped film, possibly because Sb can promote the incorporation of Ga into CIGS. The grain growth in CIGS thin films was enhanced after Sb doping, exhibiting significantly larger grains after annealing at 400 °C or 450 °C compared to films without Sb. In particular, the effect was strikingly significant in grain growth across the film thickness, resulting in columnar grain structure in Sb-doped films. This grain growth improvement may be led by the diffusion of Sb from the front surface to the CIGS-Mo back interface, which promoted the mass transport process in CIGS thin films. - Highlights: ► Cu(In,Ga)Se 2 (CIGS) thin films made by sputtering from a single CIGS target. ► Chemical bath deposition used to introduce antimony into CIGS absorber layers. ► In/Ga ratio decreases in Sb-doped annealed films, comparatively to undoped films. ► Sb-doped CIGS films are superior to undoped films in terms of grain-growth kinetics

High field properties of superconducting BaFe{sub 2-x}Ni{sub x}As{sub 2} thin films

Energy Technology Data Exchange (ETDEWEB)

Richter, Stefan [Institute for Metallic Materials, IFW Dresden (Germany); Technical University Dresden (Germany); Kurth, Fritz; Grinenko, Vadim; Nielsch, Kornelius; Huehne, Ruben [Institute for Metallic Materials, IFW Dresden (Germany); Iida, Kazumasa [Nagoya University (Japan); Pervakov, Kirill [Russian Academy of Sciences (Russian Federation); Tarantini, Chiara; Jaroszynski, Jan [National High Magnetic Field Laboratory (United States); Pukenas, Aurimas; Skrotzki, Werner [Technical University Dresden (Germany)

2016-07-01

Fe based superconductors combine the advantages of cuprates (high upper critical field) with the small Hc{sub 2} anisotropy of classic low temperature superconductors, which makes them suitable candidates for high field applications. The study of Fe-based superconducting thin films is one crucial step to explore this potential in more detail. We present results for epitaxial BaFe{sub 2-x}Ni{sub x}As{sub 2} thin films, which have been successfully grown for the first time using pulsed laser deposition. Superconducting transition temperatures of up to 19 K have been realized in slightly overdoped films, which is in good agreement with results obtained for single crystals. The behavior of the upper critical field and critical current density has been measured in high magnetic fields up to 35 T. The results will be correlated to the observed microstructure and compared to high field data for single crystals with similar composition.

Thermal annealing of amorphous Ti-Si-O thin films

OpenAIRE

Hodroj , Abbas; Chaix-Pluchery , Odette; Audier , Marc; Gottlieb , Ulrich; Deschanvres , Jean-Luc

2008-01-01

International audience; Ti-Si-O thin films were deposited using an aerosol chemical vapor deposition process at atmospheric pressure. The film structure and microstructure were analysed using several techniques before and after thermal annealing. Diffraction results indicate that the films remain X-ray amorphous after annealing whereas Fourier transform infrared spectroscopy gives evidence of a phase segregation between amorphous SiO2 and well crystallized anatase TiO2. Crystallization of ana...

A thermodynamic model for predicting surface melting and overheating of different crystal planes in BCC, FCC and HCP pure metallic thin films

International Nuclear Information System (INIS)

Jahangir, Vafa; Riahifar, Reza; Sahba Yaghmaee, Maziar

2016-01-01

In order to predict as well as study the surface melting phenomena in contradiction to surface overheating, a generalized thermodynamics model including the surface free energy of solid and the melt state along with the interfacial energy of solid–liquid (melt on substrate) has been introduced. In addition, the effect of different crystal structures of surfaces in fcc, bcc and hcp metals was included in surface energies as well as in the atomistic model. These considerations lead us to predict surface melting and overheating as two contradictory melting phenomena. The results of the calculation are demonstrated on the example of Pb and Al thin films in three groups of (100), (110) and (111) surface planes. Our conclusions show good agreement with experimental results and other theoretical investigations. Moreover, a computational algorithm has been developed which enables users to investigate the surface melt or overheating of single component metallic thin film with variable crystal structures and different crystalline planes. This model and developed software can be used for studying all related surface phenomena. - Highlights: • Investigating the surface melting and overheating phenomena • Effect of crystal orientations, surface energies, geometry and different atomic surface layers • Developing a computational algorithm and its related code (free-software SMSO-Ver1) • Thickness and orientation of surface plane dominate the surface melting or overheating. • Total excess surface energy as a function of thickness and temperature explains melting.

A thermodynamic model for predicting surface melting and overheating of different crystal planes in BCC, FCC and HCP pure metallic thin films

Energy Technology Data Exchange (ETDEWEB)

Jahangir, Vafa, E-mail: vafa.jahangir@yahoo.com; Riahifar, Reza, E-mail: reza_rfr@yahoo.com; Sahba Yaghmaee, Maziar, E-mail: fkmsahba@uni-miskolc.hu

2016-03-31

In order to predict as well as study the surface melting phenomena in contradiction to surface overheating, a generalized thermodynamics model including the surface free energy of solid and the melt state along with the interfacial energy of solid–liquid (melt on substrate) has been introduced. In addition, the effect of different crystal structures of surfaces in fcc, bcc and hcp metals was included in surface energies as well as in the atomistic model. These considerations lead us to predict surface melting and overheating as two contradictory melting phenomena. The results of the calculation are demonstrated on the example of Pb and Al thin films in three groups of (100), (110) and (111) surface planes. Our conclusions show good agreement with experimental results and other theoretical investigations. Moreover, a computational algorithm has been developed which enables users to investigate the surface melt or overheating of single component metallic thin film with variable crystal structures and different crystalline planes. This model and developed software can be used for studying all related surface phenomena. - Highlights: • Investigating the surface melting and overheating phenomena • Effect of crystal orientations, surface energies, geometry and different atomic surface layers • Developing a computational algorithm and its related code (free-software SMSO-Ver1) • Thickness and orientation of surface plane dominate the surface melting or overheating. • Total excess surface energy as a function of thickness and temperature explains melting.

Crystal and electronic structure study of AgAu and AgCu bimetallic alloy thin films by X-ray techniques

Energy Technology Data Exchange (ETDEWEB)

Ozkendir, O. Murat, E-mail: ozkendir@gmail.com [Mersin University, Faculty of Technology, Energy Systems Engineering, Tarsus (Turkey); Mersin University, Institute of Natural Science, Department of Nanotechnology and Advanced Materials, Mersin (Turkey); Cengiz, E. [Karadeniz Technical University, Faculty of Science, Department of Physics, Trabzon (Turkey); Yalaz, E. [Mersin University, Institute of Natural Science, Department of Nanotechnology and Advanced Materials, Mersin (Turkey); Söğüt, Ö.; Ayas, D.H. [Kahramanmaraş Sütçü İmam Üniversitesi, Faculty of Science and Letters, Department of Physics, Kahramanmaraş (Turkey); Thammajak, B. Nirawat [Synchrotron Light Research Institute (Public Organisation), 111 University Avenue, T. Suranaree, A. Muang, Nakhon Ratchasima 30000 (Thailand)

2016-05-15

Highlights: • Crystal and electronic properties of bimetallic AgCu and AgAu alloy thin films were studied. • Both AgCu and AgAu bimetallic samples were determined to have cubic crystal geometry. • Strong influence of Cu and Au atoms on the electronic structure of the Ag atoms were determined. - Abstract: Crystal and electronic structure properties of bimetallic AgAu and AgCu alloy thin films were investigated by X-ray spectroscopic techniques. The aim of this study is to probe the influence of Au or Cu atoms on the electronic behaviors of Ag ions in bimetallic alloy materials that yields different crystal properties. To identify the mechanisms causing crystal phase transitions, study were supported by the collected EXAFS (Extended X-ray Absorption Fine Structure) data. Crystal structures of both Cu and Au doped bimetallic Ag samples were determined mainly in cubic geometry with “Fm3m” space group. Through the Ag–Au and Ag–Cu molecular interactions during bimetallic alloy formations, highly overlapped electronic levels that supports large molecular band formations were observed with different ionization states. Besides, traces of the d–d interactions in Au rich samples were determined as the main interplay in the broad molecular bond formations. The exact atomic locations and types in the samples were determined by EXAFS studies and supported by the performed calculations with FEFF scientific code.

Kinetics and Mechanisms of Oxygen Surface Exchange on La0.6Sr0.4FeO3-delta Thin Films

OpenAIRE

Mosleh, Majid; Søgaard, Martin; Hendriksen, Peter Vang

2009-01-01

The thermodynamic properties as well as oxygen exchange kinetics were examined on mixed ionic and electronic conducting (La0.6Sr0.4)0.99FeO3− (LSF64) thin films deposited on MgO single crystals. It is found that thin films and bulk material have the same oxygen stoichiometry for a given temperature and oxygen partial pressure [i.e., the incorporation reaction has the same reaction enthalpy (H0=−105 KJ/mol) and entropy (S0=−75.5 J/mol/K) as found for bulk material]. The thin film shows smaller...

Direct observation of phase transition of GeSbTe thin films by Atomic Force Microscope

Energy Technology Data Exchange (ETDEWEB)

Yang Fei [National Laboratory of Solid State Microstructures and Jiangsu Provincial Key Laboratory of Photonic and Electronic Materials Sciences and Technology, School of Electronic Science and Engineering, Nanjing University, Nanjing 210093 (China); Xu Ling, E-mail: xuling@nju.edu.cn [National Laboratory of Solid State Microstructures and Jiangsu Provincial Key Laboratory of Photonic and Electronic Materials Sciences and Technology, School of Electronic Science and Engineering, Nanjing University, Nanjing 210093 (China); Zhang Rui; Geng Lei; Tong Liang; Xu Jun [National Laboratory of Solid State Microstructures and Jiangsu Provincial Key Laboratory of Photonic and Electronic Materials Sciences and Technology, School of Electronic Science and Engineering, Nanjing University, Nanjing 210093 (China); Su Weining; Yu Yao [National Laboratory of Solid State Microstructures and Department of Physics, Nanjing University, Nanjing 210093 (China); Ma Zhongyuan; Chen Kunji [National Laboratory of Solid State Microstructures and Jiangsu Provincial Key Laboratory of Photonic and Electronic Materials Sciences and Technology, School of Electronic Science and Engineering, Nanjing University, Nanjing 210093 (China)

2012-10-01

Graphical abstract: Nano-sized marks on GST thin film were fabricated using Conductive-AFM (Atomic Force Microscope). The AFM morphology images show that the marks are ablated at the center and a raised ring surrounding it. Highlights: Black-Right-Pointing-Pointer Microstructure of GeSbTe thin films was characterized by XRD and AFM. Black-Right-Pointing-Pointer Annealing and applying electrical field can induce crystallization on thin film. Black-Right-Pointing-Pointer Conductive-AFM was used to modify the surface of GeSbTe thin film. - Abstract: GeSbTe (GST) thin films were deposited on quartz substrates using electron beam evaporation system and then annealed in nitrogen atmosphere at different temperatures, ranging from 20 Degree-Sign C to 300 Degree-Sign C. X-ray diffraction (XRD) and Atomic Force microscope (AFM) measurements were used to characterize the as-deposited and post-annealed thin films. Annealing treatment was found to induce changes on microstructure, surface roughness and grain size, indicating that with the increase of annealing temperature, the amorphous GST films first changed to face-centered-cubic (fcc) phase and then the stable hexagonal (hex) phase. Meanwhile, conductive-AFM (C-AFM) was used to produce crystallized GST dots on thin films. I-V spectroscopy results show that GST films can switch from amorphous state to crystalline state at threshold voltage. After switching, I-V curve exhibits ohmic characteristic, which is usually observed in crystallized GST films. By applying repeated I-V spectroscopies on the thin films, crystallized nuclei were observed. As the times of I-V spectroscopies increases, the area of written dots increases, and the center of the mark begin to ablate. The AFM images show that the shape of marks is an ablated center with a raised ring surrounding it.

Investigation of cosputtered W--C thin films as diffusion barriers

International Nuclear Information System (INIS)

Yang, H.Y.; Zhao, X.

1988-01-01

Polycrystalline thin films of W--C were deposited on single-crystal Si or SiO 2 substrates by rf planar magnetron cosputtering of graphite (C) and W targets. The performance of cosputtered W 75 C 25 thin films as diffusion barriers between a Si substrate and metallic overlayers of Ag, Au, or Al was investigated. Backscattering spectrometry and x-ray diffraction are used to detect metallurgical interactions. Four-point probe measurement of resistance is employed to monitor the electrical stability of the metallization schemes upon thermal annealing in a vacuum for 30 min in temperature ranges from 500 to 700 0 C. The electrical resistivity of W 75 C 25 films is 140 μΩ cm. A W 75 C 25 layer 1100 A thick prevents metallurgical interdiffusion and reaction between Au or Ag overlayers and the Si substrates up to 700 0 C, and between an Al overlayer and the Si substrate up to 450 0 C.tential

Growth and Characterisation of Pulsed-Laser Deposited Tin Thin Films on Cube-Textured Copper at Different Temperatures

Directory of Open Access Journals (Sweden)

Szwachta G.

2016-06-01

Full Text Available High-quality titanium nitride thin films have been grown on a cube-textured copper surface via pulsed laser deposition. The growth of TiN thin films has been very sensitive to pre-treatment procedure and substrate temperature. It is difficult to grow heteroexpitaxial TiN films directly on copper tape due to large differences in lattice constants, thermal expansion coefficients of the two materials as well as polycrystalline structure of substrate. The X-Ray diffraction measurement revealed presence of high peaks belonged to TiN(200 and TiN(111 thin films, depending on used etcher of copper surface. The electron diffraction patterns of TiN(200/Cu films confirmed the single-crystal nature of the films with cube-on-cube epitaxy. The high-resolution microscopy on our films revealed sharp interfaces between copper and titanium nitride with no presence of interfacial reaction.

Structural, electrical, and optical properties of polycrystalline NbO_2 thin films grown on glass substrates by solid phase crystallization

International Nuclear Information System (INIS)

Nakao, Shoichiro; Kamisaka, Hideyuki; Hirose, Yasushi; Hasegawa, Tetsuya

2017-01-01

We investigated the structural, electrical, and optical properties of polycrystalline NbO_2 thin films on glass substrates. The NbO_2 films were crystallized from amorphous precursor films grown by pulsed laser deposition at various oxygen partial pressures (P_O_2). The electrical and optical properties of the precursor films systematically changed with P_O_2, demonstrating that the oxygen content of the precursor films can be finely controlled with P_O_2. The precursors were crystallized into polycrystalline NbO_2 films by annealing under vacuum at 600 C. The NbO_2 films possessed extremely flat surfaces with branching patterns. Even optimized films showed a low resistivity (ρ) of 2 x 10"2 Ω cm, which is much lower than the bulk value of 1 x 10"4 Ω cm, probably because of the inferior crystallinity of the films compared with that of a bulk NbO_2 crystal. Both oxygen-rich and -poor NbO_2 films showed lower ρ than that of the stoichiometric film. The NbO_2 film with the highest ρ showed an indirect bandgap of 0.7 eV. (copyright 2016 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

Growth and structural properties of indium sesquitelluride (In2Te3) thin films

International Nuclear Information System (INIS)

Desai, R.R.; Lakshminarayana, D.; Patel, P.B.; Patel, P.K.; Panchal, C.J.

2005-01-01

Indium sesquitelluride (In 2 Te 3 ) compound was synthesized by mixing and melting the pure individual elements in stoichiometric proportions. The synthesized compound was utilized for the deposition of In 2 Te 3 thin films on glass and freshly cleaved NaCl substrates using flash evaporation technique. The structure of In 2 Te 3 thin films has been studied on the glass substrates by X-ray diffraction technique and on the cleavage faces of NaCl by electron diffraction technique. It was observed that the deposition from an ordered α-phase compound results in polycrystalline films on glass substrate at 473 K which are predominant α-phase and random β-phase compounds resulting in single crystal films on NaCl substrate at 523 K. Effect of source and substrate temperature on the composition of In 2 Te 3 was also studied

Atmospheric Pressure Plasma Jet-Assisted Synthesis of Zeolite-Based Low-k Thin Films.

Science.gov (United States)

Huang, Kai-Yu; Chi, Heng-Yu; Kao, Peng-Kai; Huang, Fei-Hung; Jian, Qi-Ming; Cheng, I-Chun; Lee, Wen-Ya; Hsu, Cheng-Che; Kang, Dun-Yen

2018-01-10

Zeolites are ideal low-dielectric constant (low-k) materials. This paper reports on a novel plasma-assisted approach to the synthesis of low-k thin films comprising pure-silica zeolite MFI. The proposed method involves treating the aged solution using an atmospheric pressure plasma jet (APPJ). The high reactivity of the resulting nitrogen plasma helps to produce zeolite crystals with high crystallinity and uniform crystal size distribution. The APPJ treatment also remarkably reduces the time for hydrothermal reaction. The zeolite MFI suspensions synthesized with the APPJ treatment are used for the wet deposition to form thin films. The deposited zeolite thin films possessed dense morphology and high crystallinity, which overcome the trade-off between crystallinity and film quality. Zeolite thin films synthesized using the proposed APPJ treatment achieve low leakage current (on the order of 10 -8 A/cm 2 ) and high Young's modulus (12 GPa), outperforming the control sample synthesized without plasma treatment. The dielectric constant of our zeolite thin films was as low as 1.41. The overall performance of the low-k thin films synthesized with the APPJ treatment far exceed existing low-k films comprising pure-silica MFI.

Effects of DC gate and drain bias stresses on the degradation of excimer laser crystallized polysilicon thin film transistors

International Nuclear Information System (INIS)

Kouvatsos, D N; Michalas, L; Voutsas, A T; Papaioannou, G J

2005-01-01

The effects of gate and drain bias stresses on thin film transistors fabricated in polysilicon films crystallized using the advanced sequential lateral solidification excimer laser annealing (SLS ELA) process, which yields very elongated polysilicon grains and allows the fabrication of TFTs without grain boundary barriers to current flow, are investigated as a function of the active layer thickness and of the TFT orientation relative to the grains. The application of hot carrier stress, with a condition of V GS = V DS /2, was determined to induce threshold voltage, subthreshold swing and transconductance degradation for TFTs in thicker polysilicon films and the associated stress-induced increase in the active layer trap density was evaluated. However, this device degradation was drastically reduced for TFTs fabricated in ultra-thin films. Furthermore, the application of the same stress condition to TFTs oriented vertically to the elongated grains resulted in similar threshold voltage shift but in substantially decreased subthreshold swing and transconductance degradation. The immunity of ultra-thin active layer devices to degradation under hot carrier stress clearly suggests the implementation of ultra thin SLS ELA polysilicon films for the fabrication of TFTs exhibiting not only high performance but, especially, the high reliability needed for integrated systems on panel

Crystallization of Sr0.5Ba0.5Nb2O6 Thin Films on LaNiO3 Electrodes by RF Magnetron Reactive Sputtering

Science.gov (United States)

Jong, Chao-An; Gan, Jon-Yiew

2000-02-01

Strontium barium niobium (Sr0.5Ba0.5Nb2O6) (SBN) thin films are prepared on conductive-oxide LNO (LaNiO3) electrodes by the rf magnetron sputtering system. Instead of conventional furnace annealing, SBN thin films are crystallized by rapid thermal annealing (RTA) above 700°C for 5 min. The textured SBN films are crystallized with two orientations: one is the (001) or (310) direction, and the other is the (002) or (620) direction. Films compositions measured by the electron spectroscopy of chemical analysis (ESCA) quantitative analysis method show nearly the same stoichiometric ratio as the target. The depth profiles of SBN films and the target are examined by secondary ion mass spectrometer (SIMS). The concentrations of the films are quite uniform. After being heat treated at 800°C for 5 min by RTA, La and Ni diffuse into the SBN film. The diffusion coefficient of La in SBN films is also calculated.

Post-annealing effects on pulsed laser deposition-grown GaN thin films

International Nuclear Information System (INIS)

Cheng, Yu-Wen; Wu, Hao-Yu; Lin, Yu-Zhong; Lee, Cheng-Che; Lin, Ching-Fuh

2015-01-01

In this work, the post-annealing effects on gallium nitride (GaN) thin films grown from pulsed laser deposition (PLD) are investigated. The as-deposited GaN thin films grown from PLD are annealed at different temperatures in nitrogen ambient. Significant changes of the GaN crystal properties are observed. Raman spectroscopy is used to observe the crystallinity, the change of residual stress, and the thermal decomposition of the annealed GaN thin films. X-ray diffraction is also applied to identify the crystal phase of GaN thin films, and the surface morphology of GaN thin films annealed at different temperatures is observed by scanning electron microscopy. Through the above analyses, the GaN thin films grown by PLD undergo three stages: phase transition, stress alteration, and thermal decomposition. At a low annealing temperature, the rock salt GaN in GaN films is transformed into wurtzite. The rock salt GaN diminishes with increasing annealing temperature. At a medium annealing temperature, the residual stress of the film changes significantly from compressive strain to tensile strain. As the annealing temperature further increases, the GaN undergoes thermal decomposition and the surface becomes granular. By investigating the annealing temperature effects and controlling the optimized annealing temperature of the GaN thin films, we are able to obtain highly crystalline and strain-free GaN thin films by PLD. - Highlights: • The GaN thin film is grown on sapphire by pulsed laser deposition. • The GaN film undergoes three stages with increasing annealing temperature. • In the first stage, the film transfers from rock salt to wurtzite phase. • In the second stage, the stress in film changes from compressive to tensile. • In the final stage, the film thermally decomposes and becomes granular

Micro-Raman spectroscopy studies of bulk and thin films of CuInTe2

International Nuclear Information System (INIS)

Ananthan, M R; Mohanty, Bhaskar Chandra; Kasiviswanathan, S

2009-01-01

Micro-Raman spectroscopy measurements were made on polycrystalline and amorphous thin films of CuInTe 2 as well as bulk polycrystalline CuInTe 2 . Various vibrational modes exhibited by the bulk and polycrystalline thin films were attributed to those expected for single crystal CuInTe 2 . Raman spectra of amorphous films presented a broad spectrum, decomposition of which revealed the presence of elemental tellurium on the film surface. Laser-induced changes on CuInTe 2 thin films were studied by acquiring spectra with higher laser beam power. Modes due to tellurium appeared when the spectra were acquired during laser–sample interaction, indicating tellurium segregation. The Raman spectra measured from polycrystalline films during high laser power irradiation did not show decrease in the intensity of the A 1 mode of CuInTe 2 in spite of loss of tellurium from the lattice. This has been interpreted as related to an increased contribution from the undistorted subsurface CuInTe 2 region at higher excitation power

Thermionic vacuum arc (TVA) technique for magnesium thin film deposition

Energy Technology Data Exchange (ETDEWEB)

Balbag, M.Z., E-mail: zbalbag@ogu.edu.t [Eskisehir Osmangazi University, Education Faculty, Primary Education, Meselik Campus, Eskisehir 26480 (Turkey); Pat, S.; Ozkan, M.; Ekem, N. [Eskisehir Osmangazi University, Art and Science Faculty, Physics Department, Eskisehir 26480 (Turkey); Musa, G. [Ovidius University, Physics Department, Constanta (Romania)

2010-08-15

In this study, magnesium thin films were deposited on glass substrate by the Thermionic Vacuum Arc (TVA) technique for the first time. We present a different technique for deposition of high-quality magnesium thin films. By means of this technique, the production of films is achieved by condensing the plasma of anode material generated using Thermionic Vacuum Arc (TVA) under high vacuum conditions onto the surface to be coated. The crystal orientation and morphology of the deposited films were investigated by using XRD, EDX, SEM and AFM. The aim of this study is to search the use of TVA technique to coat magnesium thin films and to determine some of the physical properties of the films generated. Furthermore, this study will contribute to the scientific studies which search the thin films of magnesium or the compounds containing magnesium. In future, this study will be preliminary work to entirely produce magnesium diboride (MgB{sub 2}) superconductor thin film with the TVA technique.

Perovskite oxynitride LaTiOxNy thin films: Dielectric characterization in low and high frequencies

International Nuclear Information System (INIS)

Lu, Y.; Ziani, A.; Le Paven-Thivet, C.; Benzerga, R.; Le Gendre, L.; Fasquelle, D.; Kassem, H.

2011-01-01

Lanthanum titanium oxynitride (LaTiO x N y ) thin films are studied with respect to their dielectric properties in low and high frequencies. Thin films are deposited by radio frequency magnetron sputtering on different substrates. Effects of nitrogen content and crystalline quality on dielectric properties are investigated. In low-frequency range, textured LaTiO x N y thin films deposited on conductive single crystal Nb–STO show a dielectric constant ε′ ≈ 140 with low losses tanδ = 0.012 at 100 kHz. For the LaTiO x N y polycrystalline films deposited on conductive silicon substrates with platinum (Pt/Ti/SiO 2 /Si), the tunability reached up to 57% for a weak electric field of 50 kV/cm. In high-frequency range, epitaxial LaTiO x N y films deposited on MgO substrate present a high dielectric constant with low losses (ε′ ≈ 170, tanδ = 0.011, 12 GHz).

Crystallization behavior and domain structure in textured Pb(Zr0.52Ti0.48)O3 thin films by different annealing processes

International Nuclear Information System (INIS)

Huang, W.; Jiang, S.W.; Li, Y.R.; Zhu, J.; Zhang, Y.; Wei, X.H.; Zeng, H.Z.

2006-01-01

Amorphous Pb(Zr 0.52 Ti 0.48 )O 3 (PZT) thin films were prepared on the Pt/Ti/SiO 2 /Si substrates by radio-frequency magnetron sputtering at room temperature. After rapid thermal annealing (RTA) and conventional furnace annealing (CFA) at different temperatures, the films were transformed into polycrystalline PZT thin films with (111) and (100) orientation, respectively. The phase formation and ferroelectric domains correlated with different orientation were systematically investigated by X-ray diffraction and piezoresponse force microscopy. The results showed that the perovskite PZT crystal with [111] orientation hetero-nucleated preferentially on top of the PtPb intermetallic phase at the PZT/Pt interface during RTA process. It is of interest to find that the domain self-organized into a structure with rounded shape at the early stage of crystallization. While the nucleation of the films treated by CFA dominantly homo-nucleated, thus the (100) orientation grains with minimum surface energy were easy to grow. The texture effects on ferroelectric properties of PZT films were also discussed in relation to the domain structure

Effects of ZnO addition on electrical and structural properties of amorphous SnO2 thin films

International Nuclear Information System (INIS)

Ko, J.H.; Kim, I.H.; Kim, D.; Lee, K.S.; Lee, T.S.; Jeong, J.-H.; Cheong, B.; Baik, Y.J.; Kim, W.M.

2006-01-01

Amorphous Zn-Sn-O (ZTO) thin films with relative Zn contents (= [at.% Zn]/([at.% Zn] + [at.% Sn])) of 0, 0.08 and 0.27 were fabricated by co-sputtering of SnO 2 and ZnO targets at room temperature. Changes in structural, electrical and optical properties together with electron transport properties were examined upon post-annealing treatment in the temperature range from 200 to 600 deg. C in vacuum and in air. Characterization by XRD showed that an amorphous ZTO thin film crystallized at higher temperatures with increasing Zn content. Crystallized ZTO films with a relative Zn content of 0.27 might not contain a single SnO 2 phase which is observed in the films of the other compositions. Amorphous ZTO films showed decreasing electrical resistivities with increasing annealing temperature, having a minimum value of 1 x 10 - 3 Ω cm. Upon crystallization, the resistivities increased drastically, which was attributed to poor crystallinity of the crystallized films. All the ZTO films were found to be degenerate semiconductors with non-parabolic conduction bands having effective masses varying from 0.15 to 0.3 in the carrier concentration range of 6 x 10 18 to 2 x 10 2 cm - 3 . As for a ZTO film with a relative Zn content of 0.27, the degree of non-parabolicity was much lower compared with films of the other compositions, leading to a relatively stable mobility over a wide range of carrier concentration

Preparation and properties of KCl-doped Cu2O thin film by electrodeposition

International Nuclear Information System (INIS)

Yu, Xiaojiao; Li, Xinming; Zheng, Gang; Wei, Yuchen; Zhang, Ama; Yao, Binghua

2013-01-01

With the indium tin oxide-coated glass as working electrode, cuprous oxide thin film is fabricated by means of electrodeposition. The effects of KCl doped and annealing treatment upon Cu 2 O thin film morphology, surface resistivity, open-circuit voltage, electric conduction types and visible light response are studied. The research results indicate that KCl doped has a great effect upon Cu 2 O crystal morphology, thus, making Cu 2 O thin film surface resistivity drop, and the open-circuit voltage increase and that electric conduction types are transformed from p type into n type, and the visible light (400–500 nm) absorption rate is slightly reduced. Annealing treatment can obviously decrease Cu 2 O thin film surface resistivity and improve its open-circuit voltage. When KCl concentration in electrolytic solution reaches 7 mmol/L, Cu 2 O thin film morphology can be changed from the dendritic crystal into the cubic crystal and Cu 2 O thin film surface resistivity decreases from the initial 2.5 × 10 6 Ω cm to 8.5 × 10 4 Ω cm. After annealing treatment at 320 °C for 30 min, the surface resistivity decreases to 8.5 × 10 2 Ω cm, and the open-circuit voltage increases from the initial 3.1 mV to 79.2 mV.

Channel formation in single-monolayer pentacene thin film transistors

International Nuclear Information System (INIS)

Park, B-N; Seo, Soonjoo; Evans, Paul G

2007-01-01

The geometrical arrangement of single-molecule-high islands and the contact between them have large roles in determining the electrical properties of field effect transistors (FETs) based on monolayer-scale pentacene thin films. As the pentacene coverage increases through the submonolayer regime there is a percolation transition where islands come into contact and a simultaneous rapid onset of current. At coverages just above the percolation threshold, the electrical properties vary with geometrical changes in the contacts between the pentacene islands. At higher coverages, the FET mobility is much lower than the mobility measured by the van der Pauw method because of high contact resistances in monolayer-scale pentacene film devices. An increase in the van der Pauw mobility of holes as a function of pentacene coverage shows that second layer islands take part in charge transport

Soft chemistry routes to transparent metal oxide thin films. The case of sol–gel synthesis and structural characterization of Ta{sub 2}O{sub 5} thin films from tantalum chloromethoxide

Energy Technology Data Exchange (ETDEWEB)

Epifani, Mauro, E-mail: mauro.epifani@le.imm.cnr.it [Istituto per la Microelettronica e i Microsistemi, IMM-CNR, Via Monteroni, 73100 Lecce (Italy); Zamani, Reza [Catalonia Institute for Energy Research, IREC c/Jardins de les Dones de Negre, 1, 08930-Sant Adria del Besos, Barcelona (Spain); Institut de Ciència de Materials de Barcelona, ICMAB-CSIC, 08193 Bellaterra, CAT (Spain); Arbiol, Jordi [Institut de Ciència de Materials de Barcelona, ICMAB-CSIC, 08193 Bellaterra, CAT (Spain); Institucio Catalana de Recerca i Estudis Avançats, ICREA, 08010, Barcelona (Spain); Fabrega, Cristian; Andreu, Teresa [Catalonia Institute for Energy Research, IREC c/Jardins de les Dones de Negre, 1, 08930-Sant Adria del Besos, Barcelona (Spain); Pace, Giovanni Battista; Siciliano, Pietro [Istituto per la Microelettronica e i Microsistemi, IMM-CNR, Via Monteroni, 73100 Lecce (Italy); Morante, Joan R. [Catalonia Institute for Energy Research, IREC c/Jardins de les Dones de Negre, 1, 08930-Sant Adria del Besos, Barcelona (Spain); M2E-IN2UB-XaRMAE, Departament d’Electrònica, Universitat de Barcelona, C. Martí i Franquès 1, 08028 Barcelona, CAT (Spain)

2014-03-31

Ta{sub 2}O{sub 5} thin films were prepared by spin-coating methanol solutions of Ta chloromethoxide. It was prepared by reacting TaCl{sub 5} with methanol, followed by water addition (H{sub 2}O: Ta molar ratio was 16). Thin films were deposited by spin-coating onto SiO{sub 2}/Si substrates, followed by drying at 90 °C and heat-treatment up to 700 °C. The films were characterized by X-ray diffraction, transmission electron microscopy and field emission scanning electron microscopy. Crystallization was obtained only after heating at 700 °C, in the Ta{sub 2}O{sub 5} orthorhombic phase. The resulting films had a thickness of 100 nm. Their structure was constituted by porous crystals with size up to 50 nm, while the pores had a size of about 10 nm. The results demonstrated that TaCl{sub 5} is very convenient precursor for the wet chemical synthesis of Ta{sub 2}O{sub 5} thin films. - Highlights: • Development of convenient solution synthesis of Ta{sub 2}O{sub 5} thin films; • The precursor chemistry was established and related to the synthesis process; • Uniform films crystallized in the most stable orthorombic Ta{sub 2}O{sub 5} phase;.

Dye sensitized solar cell applications of CdTiO{sub 3}–TiO{sub 2} composite thin films deposited from single molecular complex

Energy Technology Data Exchange (ETDEWEB)

Ehsan, Muhammad Ali [Nanotechnology and Catalysis Centre (NANOCAT), University of Malaya, Lembah Pantai, 50603 Kuala Lumpur (Malaysia); Khaledi, Hamid [Department of Chemistry, Faculty of Science, University of Malaya, Lembah Pantai, 50603 Kuala Lumpur (Malaysia); Pandikumar, Alagarsamy; Huang, Nay Ming [Department of Physics, Faculty of Science, University of Malaya, Lembah Pantai, 50603 Kuala Lumpur (Malaysia); Arifin, Zainudin [Department of Chemistry, Faculty of Science, University of Malaya, Lembah Pantai, 50603 Kuala Lumpur (Malaysia); Mazhar, Muhammad, E-mail: mazhar42pk@yahoo.com [Department of Chemistry, Faculty of Science, University of Malaya, Lembah Pantai, 50603 Kuala Lumpur (Malaysia)

2015-10-15

A heterobimetallic complex [Cd{sub 2}Ti{sub 4}(μ-O){sub 6}(TFA){sub 8}(THF){sub 6}]·1.5THF (1) (TFA=trifluoroacetato, THF=tetrahydrofuran) comprising of Cd:Ti (1:2) ratio was synthesized by a chemical reaction of cadmium (II) acetate with titanium (IV) isopropoxide and triflouroacetic acid in THF. The stoichiometry of (1) was recognized by single crystal X-ray diffraction, spectroscopic and elemental analyses. Thermal studies revealed that (1) neatly decomposes at 450 °C to furnish 1:1 ratio of cadmium titanate:titania composite oxides material. The thin films of CdTiO{sub 3}–TiO{sub 2} composite oxides were deposited at 550 °C on fluorine doped tin oxide coated conducting glass substrate in air ambient. The micro-structure, crystallinity, phase identification and chemical composition of microspherical architectured CdTiO{sub 3}–TiO{sub 2} composite thin film have been determined by scanning electron microscopy, X-ray diffraction, Raman spectroscopy and energy dispersive X-ray analysis. The scope of composite thin film having band gap of 3.1 eV was explored as photoanode for dye-sensitized solar cell application. - Graphical abstarct: Microspherical designed CdTiO{sub 3}–TiO{sub 2} composite oxides photoanode film has been fabricated from single source precursor [Cd{sub 2}Ti{sub 4}(μ-O){sub 6}(TFA){sub 8}(THF){sub 6}]·1.5THF via aerosol assisted chemical vapor deposition technique for dye sensitized solar cell application. - Highlights: • Synthesis and characterization of a heterobimetallic Cd–Ti complex. • Fabrication of CdTiO{sub 3}–TiO{sub 2} thin film photoelectrode. • Application as dye sensitized photoanode for solar application.

Transient phases during fast crystallization of organic thin films from solution

Science.gov (United States)

Wan, Jing; Li, Yang; Ulbrandt, Jeffrey G.; Smilgies, Detlef-M.; Hollin, Jonathan; Whalley, Adam C.; Headrick, Randall L.

2016-01-01

We report an in situ microbeam grazing incidence X-ray scattering study of 2,7-dioctyl[1]benzothieno[3,2-b][1]benzothiophene (C8-BTBT) organic semiconductor thin film deposition by hollow pen writing. Multiple transient phases are observed during the crystallization for substrate temperatures up to ≈93 °C. The layered smectic liquid-crystalline phase of C8-BTBT initially forms and preceedes inter-layer ordering, followed by a transient crystalline phase for temperature >60 °C, and ultimately the stable phase. Based on these results, we demonstrate a method to produce extremely large grain size and high carrier mobility during high-speed processing. For high writing speed (25 mm/s), mobility up to 3.0 cm2/V-s has been observed.

Crystallinity of the epitaxial heterojunction of C60 on single crystal pentacene

Science.gov (United States)

Tsuruta, Ryohei; Mizuno, Yuta; Hosokai, Takuya; Koganezawa, Tomoyuki; Ishii, Hisao; Nakayama, Yasuo

2017-06-01

The structure of pn heterojunctions is an important subject in the field of organic semiconductor devices. In this work, the crystallinity of an epitaxial pn heterojunction of C60 on single crystal pentacene is investigated by non-contact mode atomic force microscopy and high-resolution grazing incidence x-ray diffraction. Analysis shows that the C60 molecules assemble into grains consisting of single crystallites on the pentacene single crystal surface. The in-plane mean crystallite size exceeds 0.1 μm, which is at least five time larger than the size of crystallites deposited onto polycrystalline pentacene thin films grown on SiO2. The results indicate that improvement in the crystal quality of the underlying molecular substrate leads to drastic promotion of the crystallinity at the organic semiconductor heterojunction.

High-frequency Lamb wave device composed of MEMS structure using LiNbO3 thin film and air gap.

Science.gov (United States)

Kadota, Michio; Ogami, Takashi; Yamamoto, Kansho; Tochishita, Hikari; Negoro, Yasuhiro

2010-11-01

High-frequency devices operating at 3 GHz or higher are required, for instance, for future 4th generation mobile phone systems in Japan. Using a substrate with a high acoustic velocity is one method to realize a high-frequency acoustic or elastic device. A Lamb wave has a high velocity when the substrate thickness is thin. To realize a high-frequency device operating at 3 GHz or higher using a Lamb wave, a very thin (less than 0.5 μm thick) single-crystal plate must be used. It is difficult to fabricate such a very thin single crystal plate. The authors have attempted to use a c-axis orientated epitaxial LiNbO(3) thin film deposited by a chemical vapor deposition system (CVD) instead of using a thin LiNbO(3) single crystal plate. Lamb wave resonators composed of a interdigital transducer (IDT)/the LiNbO(3) film/air gap/base substrate structure like micro-electromechanical system (MEMS) transducers were fabricated. These resonators have shown a high frequency of 4.5 and 6.3 GHz, which correspond to very high acoustic velocities of 14,000 and 12,500 m/s, respectively, have excellent characteristics such as a ratio of resonant and antiresonant impedance of 52 and 38 dB and a wide band of 7.2% and 3.7%, respectively, and do not have spurious responses caused by the 0th modes of shear horizontal (SH(0)) and symmetric (S(0)) modes.

Strain engineering of perovskite thin films using a single substrate

International Nuclear Information System (INIS)

Janolin, P-E; Guiblin, N; Dkhil, B; Anokhin, A S; Mukhortov, V M; Golovko, Yu I; Gui, Z; Bellaiche, L; Ravy, S; El Marssi, M; Yuzyuk, Yu I

2014-01-01

Combining temperature-dependent x-ray diffraction, Raman spectroscopy and first-principles-based effective Hamiltonian calculations, we show that varying the thickness of (Ba 0.8 Sr 0.2 )TiO 3 (BST) thin films deposited on the same single substrate (namely, MgO) enables us to change not only the magnitude but also the sign of the misfit strain. Such previously overlooked control of the strain allows several properties of these films (e.g. Curie temperature, symmetry of ferroelectric phases, dielectric response) to be tuned and even optimized. Surprisingly, such desired control of the strain (and of the resulting properties) originates from an effect that is commonly believed to be detrimental to functionalities of films, namely the existence of misfit dislocations. The present study therefore provides a novel route to strain engineering, as well as leading us to revisit common beliefs. (fast track communication)

Structural effects in UO{sub 2} thin films irradiated with fission-energy Xe ions

Energy Technology Data Exchange (ETDEWEB)

Popel, A.J., E-mail: apopel@cantab.net [Department of Earth Sciences, University of Cambridge, Downing Street, Cambridge, CB2 3EQ (United Kingdom); Lebedev, V.A. [Lomonosov Moscow State University, Moscow, 119991 (Russian Federation); Martin, P.G. [Interface Analysis Centre, School of Physics, University of Bristol, Bristol, BS8 1TL (United Kingdom); Shiryaev, A.A. [Frumkin Institute of Physical Chemistry and Electrochemistry RAS, Moscow (Russian Federation); Lomonosov Moscow State University, Moscow, 119991 (Russian Federation); Lampronti, G.I. [Department of Earth Sciences, University of Cambridge, Downing Street, Cambridge, CB2 3EQ (United Kingdom); Springell, R. [Interface Analysis Centre, School of Physics, University of Bristol, Bristol, BS8 1TL (United Kingdom); Kalmykov, S.N. [Lomonosov Moscow State University, Moscow, 119991 (Russian Federation); National Research Centre “Kurchatov Institute”, 123098, Moscow (Russian Federation); Scott, T.B. [Interface Analysis Centre, School of Physics, University of Bristol, Bristol, BS8 1TL (United Kingdom); Monnet, I.; Grygiel, C. [CIMAP, CEA-CNRS-ENSICAEN-Université de Caen, BP 5133, 14070, Caen, Cedex5 (France); Farnan, I. [Department of Earth Sciences, University of Cambridge, Downing Street, Cambridge, CB2 3EQ (United Kingdom)

2016-12-15

Uranium dioxide thin films have been successfully grown on LSAT (Al{sub 10}La{sub 3}O{sub 51}Sr{sub 14}Ta{sub 7}) substrates by reactive magnetron sputtering. Irradiation by 92 MeV {sup 129}Xe{sup 23+} ions to simulate fission damage that occurs within nuclear fuels caused microstructural and crystallographic changes. Initially flat and continuous thin films were produced by magnetron sputtering with a root mean square roughness of 0.35 nm determined by AFM. After irradiation, this roughness increased to 60–70 nm, with the films developing discrete microstructural features: small grains (∼3 μm), along with larger circular (up to 40 μm) and linear formations with non-uniform composition according to the SEM, AFM and EDX results. The irradiation caused significant restructuring of the UO{sub 2} films that was manifested in significant film-substrate mixing, observed through EDX analysis. Diffusion of Al from the substrate into the film in unirradiated samples was also observed. - Highlights: • Flat (001) single crystal UO{sub 2} thin films on LSAT (001) substrates produced. • Ion irradiation induced topographical and structural rearrangements in UO{sub 2} films.

Superconducting properties of iron chalcogenide thin films

Directory of Open Access Journals (Sweden)

Paolo Mele

2012-01-01

Full Text Available Iron chalcogenides, binary FeSe, FeTe and ternary FeTexSe1−x, FeTexS1−x and FeTe:Ox, are the simplest compounds amongst the recently discovered iron-based superconductors. Thin films of iron chalcogenides present many attractive features that are covered in this review, such as: (i easy fabrication and epitaxial growth on common single-crystal substrates; (ii strong enhancement of superconducting transition temperature with respect to the bulk parent compounds (in FeTe0.5Se0.5, zero-resistance transition temperature Tc0bulk = 13.5 K, but Tc0film = 19 K on LaAlO3 substrate; (iii high critical current density (Jc ~ 0.5 ×106 A cm2 at 4.2 K and 0 T for FeTe0.5Se0.5 film deposited on CaF2, and similar values on flexible metallic substrates (Hastelloy tapes buffered by ion-beam assisted deposition with a weak dependence on magnetic field; (iv high upper critical field (~50 T for FeTe0.5Se0.5, Bc2(0, with a low anisotropy, γ ~ 2. These highlights explain why thin films of iron chalcogenides have been widely studied in recent years and are considered as promising materials for applications requiring high magnetic fields (20–50 T and low temperatures (2–10 K.

Aggregate linear properties of ferroelectric ceramics and polycrystalline thin films: Calculation by the method of effective piezoelectric medium

Science.gov (United States)

Pertsev, N. A.; Zembilgotov, A. G.; Waser, R.

1998-08-01

The effective dielectric, piezoelectric, and elastic constants of polycrystalline ferroelectric materials are calculated from single-crystal data by an advanced method of effective medium, which takes into account the piezoelectric interactions between grains in full measure. For bulk BaTiO3 and PbTiO3 polarized ceramics, the dependences of material constants on the remanent polarization are reported. Dielectric and elastic constants are computed also for unpolarized c- and a-textured ferroelectric thin films deposited on cubic or amorphous substrates. It is found that the dielectric properties of BaTiO3 and PbTiO3 polycrystalline thin films strongly depend on the type of crystal texture. The influence of two-dimensional clamping by the substrate on the dielectric and piezoelectric responses of polarized films is described quantitatively and shown to be especially important for the piezoelectric charge coefficient of BaTiO3 films.

Oxygen engineering of HfO{sub 2-x} thin films grown by reactive molecular beam epitaxy

Energy Technology Data Exchange (ETDEWEB)

Hildebrandt, Erwin; Kurian, Jose; Alff, Lambert [Institut fuer Materialwissenschaft, TU-Darmstadt (Germany); Zaumseil, Peter; Schroeder, Thomas [IHP, Frankfurt, Oder (Germany)

2010-07-01

Reactive molecular beam epitaxy (R-MBE) is an ideal tool for tailoring physical properties of thin films to specific needs. For the development of cutting-edge oxides for thin film applications a precise control of oxygen defects is crucial. R-MBE in combination with rf-activated oxygen allows reproducibly growing oxide thin films with precise oxidation conditions enabling oxygen engineering. R-MBE was used to grow Hf and HfO{sub 2{+-}}{sub x} thin films with different oxidation conditions on sapphire single crystal substrates. Structural characterization was carried out using rotating anode x-ray diffraction revealing highly textured to epitaxial thin films on c-cut sapphire. Furthermore, switching of film orientation by varying the oxidation conditions was observed demonstrating the role of oxygen in the growth procedure. The investigation of electrical properties using a four probe measurement setup showed conductivities in the range of 1000 {mu}{omega}cm for oxygen deficient HfO{sub 2-x} thin films. Optical properties were investigated using a photospectrometer and additionally x-ray photoelectron spectroscopy was carried out to study the band gap and valence states. Both techniques were used to monitor the oxygen content in deficient HfO{sub 2-x} thin films. Our results demonstrate the importance of oxygen engineering even in the case of 'simple' oxides.

Effect of cerium substitution on microstructure and Faraday rotation of Ce{sub x}Y{sub 3-x}Fe{sub 5}O{sub 12} thin films

Energy Technology Data Exchange (ETDEWEB)

Shahrokhvand, S.M.; Mozaffari, M.; Rozatian, A.S.H. [University of Isfahan, Department of Physics, Faculty of Science, Isfahan (Iran, Islamic Republic of); Hamidi, S.M. [Shahid Beheshti University, Laser and Plasma Research Institute, Evin, Tehran (Iran, Islamic Republic of); Tehranchi, M.M. [Shahid Beheshti University, Laser and Plasma Research Institute, Evin, Tehran (Iran, Islamic Republic of); Shahid Beheshti University, Department of Physics, Evin, Tehran (Iran, Islamic Republic of)

2016-01-15

In this work, cerium-substituted yttrium iron garnet (Ce{sub x}Y{sub 3-x}Fe{sub 5}O{sub 12}, x = 0.25-1) targets were fabricated by conventional ceramic method at different temperatures, and their crystal structures were investigated by X-ray diffraction method. The results showed that the minimum calcining temperature required to get single-phase targets depends on x value and decreased by increasing x value. Then, thin films of the targets were deposited on GGG (444) single-crystal substrates by pulsed laser deposition technique. Based on the previous studies, preferred (444) oriented Ce{sub x}Y{sub 3-x}Fe{sub 5}O{sub 12} thin films were fabricated under optimum conditions. Faraday rotation of the thin films was measured at 635 nm wavelength, and the results showed that Faraday rotation and sensitivity constant increased by increasing x value. Scanning electron microscope images showed that by increasing x value, cracks on the thin films' surface increased. Atomic force microscopy images showed that the films have smooth surfaces and the surface roughness decreased by increasing the x value. (orig.)

Physical and chemical properties of YBa2Cu3O7 thin films

International Nuclear Information System (INIS)

El-Samahi, M.I.

1991-12-01

Investigations were carried out to determine the influence of different annealing processes on the superconducting properties of the YBa 2 Cu 3 O 7 thin films. The samples were produced by means of coevaporation of Cu, Y and Ba on polycrystalline yttria stabilized (YSZ) ZrO 2 and single crystal SrTiO 3 (001) substrates. Subsequently, the as-deposited films were subjected to two different annealing methods to crystallize the superconducting phase YBa 2 Cu 3 O 7 : (i) heating up, annealing and cooling in an oxygen atmosphere and (ii) heating up in an innert gas atmosphere up to the maximum annealing temperature (T max ) and then annealing and cooling under oxygen. (orig.)

A sensor of alcohol vapours based on thin polyaniline base film and quartz crystal microbalance.

Science.gov (United States)

Ayad, Mohamad M; El-Hefnawey, Gad; Torad, Nagy L

2009-08-30

Thin films of polyaniline base, emeraldine base (EB), coating on the quartz crystal microbalance (QCM) electrode were used as a sensitive layer for the detection of a number of primary aliphatic alcohols such as ethanol, methanol, 2-propanol and 1-propanol vapours. The frequency shifts (Deltaf) of the QCM were increased due to the vapour adsorption into the EB film. Deltaf were found to be linearly correlated with the concentrations of alcohols vapour in part per million (ppm). The sensitivity of the sensor was found to be governed by the chemical structure of the alcohol. The sensor shows a good reproducibility and reversibility. The diffusions of different alcohols vapour were studied and the diffusion coefficients (D) were calculated. It is concluded that the diffusion of the vapours into the EB film follows Fickian kinetics.

Preparation and characterization of Cu2SnS3 thin films by electrodeposition

Science.gov (United States)

Patel, Biren; Narasimman, R.; Pati, Ranjan K.; Mukhopadhyay, Indrajit; Ray, Abhijit

2018-05-01

Cu2SnS3 thin films were electrodeposited on F:SnO2/Glass substrates at room temperature by using aqueous solution. Copper and tin were first electrodeposited from single bath and post annealed in the presence of sulphur atmosphere to obtain the Cu2SnS3 phase. The Cu2SnS3 phase with preferred orientation along the (112) crystal direction grows to greater extent by the post annealing of the film. Raman analysis confirms the monoclinic crystal structure of Cu2SnS3 with principle mode of vibration as A1 (symmetric breathing mode) corresponding to the band at 291 cm-1. It also reveals the benign coexistence of orthorhombic Cu3SnS4 and Cu2SnS7 phases. Optical properties of the film show direct band gap of 1.25 eV with a high absorption coefficient of the order of 104 cm-1 in the visible region. Photo activity of the electrodeposited film was established in two electrode photoelectro-chemical cell, where an open circuit voltage of 91.6 mV and a short circuit current density of 10.6 µA/cm2 were recorded. Fabrication of Cu2SnS3 thin film heterojunction solar cell is underway.

Tuning polymorphism and orientation in organic semiconductor thin films via post-deposition processing.

Science.gov (United States)

Hiszpanski, Anna M; Baur, Robin M; Kim, Bumjung; Tremblay, Noah J; Nuckolls, Colin; Woll, Arthur R; Loo, Yueh-Lin

2014-11-05

Though both the crystal structure and molecular orientation of organic semiconductors are known to impact charge transport in thin-film devices, separately accessing different polymorphs and varying the out-of-plane molecular orientation is challenging, typically requiring stringent control over film deposition conditions, film thickness, and substrate chemistry. Here we demonstrate independent tuning of the crystalline polymorph and molecular orientation in thin films of contorted hexabenzocoronene, c-HBC, during post-deposition processing without the need to adjust deposition conditions. Three polymorphs are observed, two of which have not been previously reported. Using our ability to independently tune the crystal structure and out-of-plane molecular orientation in thin films of c-HBC, we have decoupled and evaluated the effects that molecular packing and orientation have on device performance in thin-film transistors (TFTs). In the case of TFTs comprising c-HBC, polymorphism and molecular orientation are equally important; independently changing either one affects the field-effect mobility by an order of magnitude.

Deposition of thin films by retardation of an isotope separator beam

International Nuclear Information System (INIS)

Colligon, J.S.; Grant, W.A.; Williams, J.S.; Lawson, R.P.W.

1976-01-01

An ion optical lens system capable of retarding and focusing a mass-analysed ion beam, produced in the University of Salford isotope separator, from an energy of 20 keV to 50-60 eV is described. Using this system it is technically feasible to deposit spectroscopically pure ions of all species onto a substrate to produce thin film for devices and junctions. Preliminary investigations of the technique have been carried out using lead and copper ions which were deposited onto silicon single-crystal substrates. These ions were selected because their high mass relative to silicon allowed analyses of the deposited films by low-angle Rutherford backscattering of 2 MeV He ions; the single-crystal silicon substrate enabled the extent of damage due to unretarded neutral particles to be estimated from channelling data. Results for lead films showed that films less than 150 A in thickness were discontinuous and scanning electron microscopy confirmed their 'island' structure. For thicker deposits, of order 600 A, the films were continuous. Results are also presented for copper-lead sandwich layers produced by successive depositions. Channelling experiments indicated that the neutral component was less than 5% of the total ion-beam intensity. Investigations of the spatial distribution of the lead films indicated a non-uniformity which, it is suggested, arises from a fault in the retardation lens design. (author)

Solution-printed organic semiconductor blends exhibiting transport properties on par with single crystals.

Science.gov (United States)

Niazi, Muhammad R; Li, Ruipeng; Qiang Li, Er; Kirmani, Ahmad R; Abdelsamie, Maged; Wang, Qingxiao; Pan, Wenyang; Payne, Marcia M; Anthony, John E; Smilgies, Detlef-M; Thoroddsen, Sigurdur T; Giannelis, Emmanuel P; Amassian, Aram

2015-11-23

Solution-printed organic semiconductors have emerged in recent years as promising contenders for roll-to-roll manufacturing of electronic and optoelectronic circuits. The stringent performance requirements for organic thin-film transistors (OTFTs) in terms of carrier mobility, switching speed, turn-on voltage and uniformity over large areas require performance currently achieved by organic single-crystal devices, but these suffer from scale-up challenges. Here we present a new method based on blade coating of a blend of conjugated small molecules and amorphous insulating polymers to produce OTFTs with consistently excellent performance characteristics (carrier mobility as high as 6.7 cm(2) V(-1) s(-1), low threshold voltages oforganic semiconductor films with transport properties and other figures of merit on par with their single-crystal counterparts.

Piezoresistivity of mechanically drawn single-walled carbon nanotube (SWCNT) thin films-: mechanism and optimizing principle

Science.gov (United States)

Obitayo, Waris

The individual carbon nanotube (CNT) based strain sensors have been found to have excellent piezoresistive properties with a reported gauge factor (GF) of up to 3000. This GF on the other hand, has been shown to be structurally dependent on the nanotubes. In contrast, to individual CNT based strain sensors, the ensemble CNT based strain sensors have very low GFs e.g. for a single walled carbon nanotube (SWCNT) thin film strain sensor, GF is ~1. As a result, studies which are mostly numerical/analytical have revealed the dependence of piezoresistivity on key parameters like concentration, orientation, length and diameter, aspect ratio, energy barrier height and Poisson ratio of polymer matrix. The fundamental understanding of the piezoresistive mechanism in an ensemble CNT based strain sensor still remains unclear, largely due to discrepancies in the outcomes of these numerical studies. Besides, there have been little or no experimental confirmation of these studies. The goal of my PhD is to study the mechanism and the optimizing principle of a SWCNT thin film strain sensor and provide experimental validation of the numerical/analytical investigations. The dependence of the piezoresistivity on key parameters like orientation, network density, bundle diameter (effective tunneling area), and length is studied, and how one can effectively optimize the piezoresistive behavior of a SWCNT thin film strain sensors. To reach this goal, my first research accomplishment involves the study of orientation of SWCNTs and its effect on the piezoresistivity of mechanically drawn SWCNT thin film based piezoresistive sensors. Using polarized Raman spectroscopy analysis and coupled electrical-mechanical test, a quantitative relationship between the strain sensitivity and SWCNT alignment order parameter was established. As compared to randomly oriented SWCNT thin films, the one with draw ratio of 3.2 exhibited ~6x increase on the GF. My second accomplishment involves studying the

Growth and giant coercive field of spinel-structured Co3- x Mn x O4 thin films

Science.gov (United States)

Kwak, Yongsu; Song, Jonghyun; Koo, Taeyeong

2016-08-01

We grew epitaxial thin films of CoMn2O4 and Co2MnO4 on Nb-doped SrTiO3(011) and SrTiO3(001) single crystal substrates using pulsed laser deposition. The magnetic Curie temperature ( T c ) of the Co2MnO4 thin films was ~176 K, which is higher than that of the bulk whereas CoMn2O4 thin films exhibited a value of T c (~151 K) lower than that of the bulk. For the Co2MnO4 thin films, the M - H loop showed a coercive field of ~0.7 T at 10 K, similar to the value for the bulk. However, the M -H loop of the CoMn2O4(0 ll) thin film grown on a Nb-doped SrTiO3(011) substrate exhibited a coercive field of ~4.5 T at 30 K, which is significantly higher than those of the Co2MnO4 thin film and bulk. This giant coercive field, only observed for the CoMn2O4(0 ll) thin film, can be attributed to the shape anisotropy and strong spin-orbit coupling.

Effects of high-temperature thermal annealing on the electronic properties of In-Ga-Zn oxide thin films

Energy Technology Data Exchange (ETDEWEB)

Li, Qin; Song, Zhong Xiao; Ma, Fei, E-mail: mafei@mail.xjtu.edu.cn, E-mail: liyhemail@gmail.com; Li, Yan Huai, E-mail: mafei@mail.xjtu.edu.cn, E-mail: liyhemail@gmail.com [State Key Laboratory for Mechanical Behavior of Materials, Xi' an Jiaotong University, Xi' an, Shaanxi 710049 (China); Xu, Ke Wei [State Key Laboratory for Mechanical Behavior of Materials, Xi' an Jiaotong University, Xi' an, Shaanxi 710049, China and Department of Physics and Opt-electronic Engineering, Xi' an University of Arts and Science, Xi' an, Shaanxi 710065 (China)

2015-03-15

Indium gallium zinc oxide (IGZO) thin films were deposited by radio-frequency magnetron sputtering at room-temperature. Then, thermal annealing was conducted to improve the structural ordering. X-ray diffraction and high-resolution transmission electron microscopy demonstrated that the as-deposited IGZO thin films were amorphous and crystallization occurred at 800 and 950 °C. As a result of crystallization at high temperature, the carrier concentration and the Hall mobility of IGZO thin films were sharply increased, which could be ascribed to the increased oxygen vacancies and improved structural ordering of the thin films.

Mesoscopic layered structure in conducting polymer thin film fabricated by potential-programmed electropolymerization

Energy Technology Data Exchange (ETDEWEB)

Fujitsuka, Mamoru (Div. of Molecular Engineering, Kyoto Univ. (Japan)); Nakahara, Reiko (Div. of Molecular Engineering, Kyoto Univ. (Japan)); Iyoda, Tomokazu (Div. of Molecular Engineering, Kyoto Univ. (Japan)); Shimidzu, Takeo (Div. of Molecular Engineering, Kyoto Univ. (Japan)); Tomita, Shigehisa (Toray Research Center Co., Ltd., Shiga (Japan)); Hatano, Yayoi (Toray Research Center Co., Ltd., Shiga (Japan)); Soeda, Fusami (Toray Research Center Co., Ltd., Shiga (Japan)); Ishitani, Akira (Toray Research Center Co., Ltd., Shiga (Japan)); Tsuchiya, Hajime (Nitto Technical Information Center Co., Ltd., Shimohozumi Ibaraki, Osaka (Japan)); Ohtani, Akira (Central Research Lab., Nitto Denko Co., Ltd., Shimohozumi Ibaraki, Osaka (Japan))

1992-11-01

Mesoscopic layered structures in conducting polymer thin films are fabricated by the potential-programmed electropolymerization method. High lateral quality in the layered structure is realized by the improvement of polymerization conditions, i.e., a mixture of pyrrole and bithiophene as monomers, a silicon single-crystal wafer as a working electrode and propylene carbonate as a solvent. SIMS depth profiling of the resulting layered films indicates a significant linear correlation between the electric charge passed and the thickness of the individual layers on a 100 A scale. (orig.)

Microstructure and optical properties of nanocrystalline ZnO and ZnO:(Li or Al) thin films

Energy Technology Data Exchange (ETDEWEB)

Oral, A. Yavuz [Department of Materials Science and Engineering, Gebze Institute of Technology, Gebze 41400 (Turkey)]. E-mail: aoral@gyte.edu.tr; Bahsi, Z. Banu [Department of Materials Science and Engineering, Gebze Institute of Technology, Gebze 41400 (Turkey); Aslan, M. Hasan [Department of Physics, Gebze Institute of Technology, Gebze 41400 (Turkey)

2007-03-15

Zinc oxide thin films (ZnO, ZnO:Li, ZnO:Al) were deposited on glass substrates by a sol-gel technique. Zinc acetate, lithium acetate, and aluminum chloride were used as metal ion sources in the precursor solutions. XRD analysis revealed that Li doped and undoped ZnO films formed single phase zincite structure in contrast to Al:ZnO films which did not fully crystallize at the annealing temperature of 550 deg. C. Crystallized films had a grain size under 50 nm and showed c-axis grain orientation. All films had a very smooth surface with RMS surface roughness values between 0.23 and 0.35 nm. Surface roughness and optical band tail values increased by Al doping. Compared to undoped ZnO films, Li doping slightly increased the optical band gap of the films.

All-metallic electrically gated 2H-TaSe2 thin-film switches and logic circuits

International Nuclear Information System (INIS)

Renteria, J.; Jiang, C.; Yan, Z.; Samnakay, R.; Goli, P.; Pope, T. R.; Salguero, T. T.; Wickramaratne, D.; Lake, R. K.; Khitun, A. G.; Balandin, A. A.

2014-01-01

We report the fabrication and performance of all-metallic three-terminal devices with tantalum diselenide thin-film conducting channels. For this proof-of-concept demonstration, the layers of 2H-TaSe 2 were exfoliated mechanically from single crystals grown by the chemical vapor transport method. Devices with nanometer-scale thicknesses exhibit strongly non-linear current-voltage characteristics, unusual optical response, and electrical gating at room temperature. We have found that the drain-source current in thin-film 2H-TaSe 2 –Ti/Au devices reproducibly shows an abrupt transition from a highly resistive to a conductive state, with the threshold tunable via the gate voltage. Such current-voltage characteristics can be used, in principle, for implementing radiation-hard all-metallic logic circuits. These results may open new application space for thin films of van der Waals materials

All-metallic electrically gated 2H-TaSe2 thin-film switches and logic circuits

Science.gov (United States)

Renteria, J.; Samnakay, R.; Jiang, C.; Pope, T. R.; Goli, P.; Yan, Z.; Wickramaratne, D.; Salguero, T. T.; Khitun, A. G.; Lake, R. K.; Balandin, A. A.

2014-01-01

We report the fabrication and performance of all-metallic three-terminal devices with tantalum diselenide thin-film conducting channels. For this proof-of-concept demonstration, the layers of 2H-TaSe2 were exfoliated mechanically from single crystals grown by the chemical vapor transport method. Devices with nanometer-scale thicknesses exhibit strongly non-linear current-voltage characteristics, unusual optical response, and electrical gating at room temperature. We have found that the drain-source current in thin-film 2H-TaSe2-Ti/Au devices reproducibly shows an abrupt transition from a highly resistive to a conductive state, with the threshold tunable via the gate voltage. Such current-voltage characteristics can be used, in principle, for implementing radiation-hard all-metallic logic circuits. These results may open new application space for thin films of van der Waals materials.

Structural, electrical, and optical properties of polycrystalline NbO{sub 2} thin films grown on glass substrates by solid phase crystallization

Energy Technology Data Exchange (ETDEWEB)

Nakao, Shoichiro [Kanagawa Academy of Science and Technology (KAST), Kawasaki (Japan); Kamisaka, Hideyuki [Department of Chemistry, The University of Tokyo (Japan); Hirose, Yasushi; Hasegawa, Tetsuya [Kanagawa Academy of Science and Technology (KAST), Kawasaki (Japan); Department of Chemistry, The University of Tokyo (Japan)

2017-03-15

We investigated the structural, electrical, and optical properties of polycrystalline NbO{sub 2} thin films on glass substrates. The NbO{sub 2} films were crystallized from amorphous precursor films grown by pulsed laser deposition at various oxygen partial pressures (P{sub O2}). The electrical and optical properties of the precursor films systematically changed with P{sub O2}, demonstrating that the oxygen content of the precursor films can be finely controlled with P{sub O2}. The precursors were crystallized into polycrystalline NbO{sub 2} films by annealing under vacuum at 600 C. The NbO{sub 2} films possessed extremely flat surfaces with branching patterns. Even optimized films showed a low resistivity (ρ) of 2 x 10{sup 2} Ω cm, which is much lower than the bulk value of 1 x 10{sup 4} Ω cm, probably because of the inferior crystallinity of the films compared with that of a bulk NbO{sub 2} crystal. Both oxygen-rich and -poor NbO{sub 2} films showed lower ρ than that of the stoichiometric film. The NbO{sub 2} film with the highest ρ showed an indirect bandgap of 0.7 eV. (copyright 2016 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

Preparation of biaxially oriented TlCu-1234 thin films

CERN Document Server

Khan, N A; Tateai, F; Kojima, T; Ishida, K; Terada, N; Ihara, H

1999-01-01

The single phase of TlCu-1234 superconductor thin films is prepared for the first time by the amorphous phase epitaxy (APE) method, which is thallium treatment of sputtered amorphous phase at 900 degrees C for 1 h. The amorphous $9 phase is prepared by sputtering from the stoichiometric target composition CuBa/sub 2/Ca/sub 3/Cu/sub 4/O/sub 12-y/. The films on the SrTiO/sub 3/ substrate are aligned biaxially after the thallium treatment. Highly reproducible $9 TlCu-1234 films are prepared by this method. The XRD reflected a predominant single phase with the c-axis lattice constant of 18.74 AA. This lattice constant value is in between that of Cu-1234 (17.99 AA) and Tl-1234 (19.11 AA) . The $9 pole figure measurements of (103) reflection of the films showed a-axis-oriented crystals with Delta phi =0.8 degrees . The composition of the films after energy dispersive X-ray (EDX) measurements is Tl/sub 0.8/Cu/sub 0.2/Ba/sub $9 2/Ca/sub 3/Cu/sub 4/O /sub 12-y/. From the resistivity measurements, the T/sub c/ is 113 K...

Analysis of thin-film photonic crystal microstructures

International Nuclear Information System (INIS)

Pottage, John Mark

2003-01-01

Optical-scale microstructures containing thin-film photonic crystals (TFPCs) are modelled by transfer/scattering matrix methods, based on Fourier-series expansion of the optical Bloch eigenmodes. The majority of the TFPCs considered consist of 2D arrays of holes arranged in a triangular lattice, etched into high-index Al x Ga 1-x As and placed on a low-index oxidised substrate. These TFPCs can be easily fabricated by standard electron-beam lithography techniques. Unlike most photonic crystal devices that have been proposed, our 'intra-pass-band' TFPCs would work by exploiting the somewhat surprising properties of propagating optical Bloch waves rather than directly relying on photonic bandgaps. By numerical modelling, it is demonstrated that 2D-patterned TFPCs can support highly dispersive high-Q quasi-guided and truly-guided resonant modes, and the unusual properties of these modes are explained in terms of their Bloch-wave compositions. Modal dispersion diagrams of TFPCs, showing the loci of the resonant modes in in-plane wavevector space at fixed frequency, are calculated. These so-called 'resonance diagrams' and variants thereof, are shown to be a useful design tool for TFPC-based integrated optical components. It is suggested that TFPCs may be a viable alternative to distributed Bragg reflectors in semiconductor vertical cavity surface-emitting lasers, possessing potential advantages in terms of compactness and ease of fabrication. The high angular and spectral dispersion of the resonant modes implies that TFPCs could form the basis of a new family of compact devices for performing such functions as wavelength-division multiplexing/demultiplexing, beam-steering and frequency-selective filtering. Enhancement of nonlinear effects could also be achieved in TFPC resonators, because in them a high cavity Q-factor and a low in-plane group-velocity can be attained simultaneously. (author)

Angular dependencies of longitudinal magnetoresistivity and planar Hall effect of single and multilayered thin films

International Nuclear Information System (INIS)

Ko, T.W.; Lee, J.H.; Park, B.K.; Rhie, K.; Jang, P.W.; Hwang, D.G.; Lee, S.S.; Kim, M.Y.; Rhee, J.R.