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Sample records for sio2 film grown

  1. Photoluminescent characteristics of ion beam synthesized Ge nanoparticles in thermally grown SiO2 films

    International Nuclear Information System (INIS)

    Yu, C.F.; Chao, D.S.; Chen, Y.-F.; Liang, J.H.

    2013-01-01

    Prospects of developing into numerous silicon-based optoelectronic applications have prompted many studies on the optical properties of Ge nanoparticles within a silicon oxide (SiO 2 ) matrix. Even with such abundant studies, the fundamental mechanism underlying the Ge nanoparticle-induced photoluminescence (PL) is still an open question. In order to elucidate the mechanism, we dedicate this study to investigating the correlation between the PL properties and microstructure of the Ge nanoparticles synthesized in thermally grown SiO 2 films. Our spectral data show that the peak position, at ∼3.1 eV or 400 nm, of the PL band arising from the Ge nanoparticles was essentially unchanged under different Ge implantation fluences and the temperatures of the following annealing process, whereas the sample preparation parameters modified or even fluctuated (in the case of the annealing temperature) the peak intensity considerably. Given the microscopically observed correlation between the nanoparticle structure and the sample preparation parameters, this phenomenon is consistent with the mechanism in which the oxygen-deficiency-related defects in the Ge/SiO 2 interface act as the major luminescence centers; this mechanism also successfully explains the peak intensity fluctuation with the annealing temperature. Moreover, our FTIR data indicate the formation of GeO x upon ion implantation. Since decreasing of the oxygen-related defects by the GeO x formation is expected to be correlated with the annealing temperature, presence of the GeO x renders further experimental support to the oxygen defect mechanism. This understanding may assist the designing of the manufacturing process to optimize the Ge nanoparticle-based PL materials for different technological applications

  2. Influence of CO annealing in metal-oxide-semiconductor capacitors with SiO2 films thermally grown on Si and on SiC

    Science.gov (United States)

    Pitthan, E.; dos Reis, R.; Corrêa, S. A.; Schmeisser, D.; Boudinov, H. I.; Stedile, F. C.

    2016-01-01

    Understanding the influence of SiC reaction with CO, a by-product of SiC thermal oxidation, is a key point to elucidate the origin of electrical defects in SiC metal-oxide-semiconductor (MOS) devices. In this work, the effects on electrical, structural, and chemical properties of SiO2/Si and SiO2/SiC structures submitted to CO annealing were investigated. It was observed that long annealing times resulted in the incorporation of carbon from CO in the Si substrate, followed by deterioration of the SiO2/Si interface, and its crystallization as SiC. Besides, this incorporated carbon remained in the Si surface (previous SiO2/Si region) after removal of the silicon dioxide film by HF etching. In the SiC case, an even more defective surface region was observed due to the CO interaction. All MOS capacitors formed using both semiconductor materials presented higher leakage current and generation of positive effective charge after CO annealings. Such results suggest that the negative fixed charge, typically observed in SiO2/SiC structures, is not originated from the interaction of the CO by-product, formed during SiC oxidation, with the SiO2/SiC interfacial region.

  3. Enhancement of carrier mobility in pentacene thin-film transistor on SiO 2 by controlling the initial film growth modes

    Science.gov (United States)

    Qi, Qiong; Yu, Aifang; Jiang, Peng; Jiang, Chao

    2009-02-01

    Pentacene thin-film transistors (TFTs) were fabricated on thermally grown SiO 2 gate insulator under the conditions of various pre-cleaning treatments. Initial nucleation and growth of the material films on treated substrates were observed by atomic force microscope. The performance of fabricated TFT devices with different surface cleaning approaches was found to be highly related to the initial film morphologies. In contrast to the three-dimensional island-like growth mode on SiO 2 under an organic cleaning process, a layer-by-layer initial growth occurred on the SiO 2 insulator cleaned with ammonia solution, which was believed to be the origination of the excellent electrical properties of the TFT device. Field effect mobility of the TFT device could achieve as high as 1.0 cm 2/Vs on the bared SiO 2/Si substrate and the on/off ratio was over 10 6.

  4. Synthesis of TiO 2-doped SiO 2 composite films and its applications

    Indian Academy of Sciences (India)

    In XRD, FT–IR, and TEM investigations of these TiO2-doped SiO2 composite films, the titanium oxide species are highly dispersed in the SiO2 matrixes and exist in a ... Anhui Key Laboratory of Functional Molecular Solids, College of Chemistry and Materials Science, Anhui Normal University, Wuhu 241000, P.R. China ...

  5. Characterisation of NdFeB thin films prepared on (100)Si substrates with SiO2 barrier layers

    International Nuclear Information System (INIS)

    Sood, D.K.; Muralidhar, G.K.

    1998-01-01

    This work presents a systematic study of the deposition and characterization of NdFeB films on substrates of Si(100) and of SiO2 layer thermally grown on Si(100) held at RT, 360 deg C or 440 deg C. The post-deposition annealing is performed at 600 or 800 deg C in vacuum. The films are characterised using the analytical techniques of RBS, SIMS, XRD, OM and SEM. Results indicate that SiO2 is, in deed, an excellent diffusion barrier layer till 600 deg C but becomes relatively less effective at 800 deg C. Without this barrier layer, interdiffusion at the Si-NdFeB film interface leads to formation of iron silicides, α-Fe and B exclusion from the diffusion zone, in competition with the formation of the magnetic NdFeB phase. (authors)

  6. Structural colors of the SiO2/polyethyleneimine thin films on poly(ethylene terephthalate) substrates

    International Nuclear Information System (INIS)

    Jia, Yanrong; Zhang, Yun; Zhou, Qiubao; Fan, Qinguo; Shao, Jianzhong

    2014-01-01

    The SiO 2 /polyethyleneimine (PEI) films with structural colors on poly(ethylene terephthalate) (PET) substrates were fabricated by an electrostatic self-assembly method. The morphology of the films was characterized by Scanning Electron Microscopy. The results showed that there was no distinguishable multilayered structure found of SiO 2 /PEI films. The optical behaviors of the films were investigated through the color photos captured by a digital camera and the color measurement by a multi-angle spectrophotometer. Different hue and brightness were observed at various viewing angles. The structural colors were dependent on the SiO 2 particle size and the number of assembly cycles. The mechanism of the structural colors generated from the assembled films was elucidated. The morphological structures and the optical properties proved that the SiO 2 /PEI film fabricated on PET substrate formed a homogeneous inorganic/organic SiO 2 /PEI composite layer, and the structural colors were originated from single thin film interference. - Highlights: • SiO 2 /PEI thin films were electrostatic self-assembled on PET substrates. • The surface morphology and optical behavior of the film were investigated. • The structural colors varied with various SiO 2 particle sizes and assembly cycles. • Different hue and lightness of SiO 2 /PEI film were observed at various viewing angles. • Structural color of the SiO 2 /PEI film originated from single thin film interference

  7. Ion assisted deposition of SiO2 film from silicon

    Science.gov (United States)

    Pham, Tuan. H.; Dang, Cu. X.

    2005-09-01

    Silicon dioxide, SiO2, is one of the preferred low index materials for optical thin film technology. It is often deposited by electron beam evaporation source with less porosity and scattering, relatively durable and can have a good laser damage threshold. Beside these advantages the deposition of critical optical thin film stacks with silicon dioxide from an E-gun was severely limited by the stability of the evaporation pattern or angular distribution of the material. The even surface of SiO2 granules in crucible will tend to develop into groove and become deeper with the evaporation process. As the results, angular distribution of the evaporation vapor changes in non-predicted manner. This report presents our experiments to apply Ion Assisted Deposition process to evaporate silicon in a molten liquid form. By choosing appropriate process parameters we can get SiO2 film with good and stable property.

  8. Synthesis of crystalline Ge nanoclusters in PE-CVD-deposited SiO2 films

    DEFF Research Database (Denmark)

    Leervad Pedersen, T.P.; Skov Jensen, J.; Chevallier, J.

    2005-01-01

    The synthesis of evenly distributed Ge nanoclusters in plasma-enhanced chemical-vapour-deposited (PE-CVD) SiO2 thin films containing 8 at. % Ge is reported. This is of importance for the application of nanoclusters in semiconductor technology. The average diameter of the Ge nanoclusters can...

  9. Synthesis of TiO2-doped SiO2 composite films and its applications

    Indian Academy of Sciences (India)

    Wintec

    And special attention has been focused on the relationship between the local structure of the titanium oxide species in the TiO2-doped SiO2 composite films and the photocatalytic reactiv- ity in order to provide vital information for the design and application of such highly efficient photocatalytic systems in the degradation of ...

  10. Atmospheric Plasma Deposition of SiO2 Films for Adhesion Promoting Layers on Titanium

    Directory of Open Access Journals (Sweden)

    Liliana Kotte

    2014-12-01

    Full Text Available This paper evaluates the deposition of silica layers at atmospheric pressure as a pretreatment for the structural bonding of titanium (Ti6Al4V, Ti15V3Cr3Sn3Al in comparison to an anodizing process (NaTESi process. The SiO2 film was deposited using the LARGE plasma source, a linearly extended DC arc plasma source and applying hexamethyldisiloxane (HMDSO as a precursor. The morphology of the surface was analyzed by means of SEM, while the characterization of the chemical composition of deposited plasma layers was done by XPS and FTIR. The long-term durability of bonded samples was evaluated by means of a wedge test in hot/wet condition. The almost stoichiometric SiO2 film features a good long-term stability and a high bonding strength compared to the films produced with the wet-chemical NaTESi process.

  11. Uniform fabrication of Ge nanocrystals embedded into SiO2 film via neutron transmutation doping

    Directory of Open Access Journals (Sweden)

    Wei Liu

    2014-06-01

    Full Text Available Nanocrystalline 74Ge embedded SiO2 films were prepared by employing ion implantation and neutron transmutation doping methods. Transmission electron microscopy, energy dispersive x-ray spectroscopy, and photoluminescence of the obtained samples were measured. The existence of As dopants transmuted from 74Ge is significant to guarantee the uniformity and higher volume density of Ge nanocrystals by tuning the system׳s crystallinity and activating mass transfer process. It was observed that the photoluminescence intensity of Ge nanocrystals increased first then decreased with the increase of arsenic concentration. The optimized fluence of neutron transmutation doping was found to be 5.5×1017 cm−2 to achieve maximum photoluminescence emission in Ge embedded SiO2 film. This work opens a route in the three-dimensional nanofabrication of uniform Ge nanocrystals.

  12. A novel growth mode of alkane films on a SiO2 surface

    DEFF Research Database (Denmark)

    Mo, H.; Taub, H.; Volkmann, U.G.

    2003-01-01

    Synchrotron X-ray specular scattering measurements confirm microscopically a structural model recently inferred by very-high-resolution ellipsometry of a solid dotriacontane (n-C32H66 or C32) film formed by adsorption from solution onto a SiO2 surface. Sequentially, one or two layers adsorb on th...... previously for shorter alkanes deposited from the vapor phase onto solid surfaces....

  13. Direct fabrication of graphene on SiO2 enabled by thin film stress engineering

    Science.gov (United States)

    McNerny, Daniel Q.; Viswanath, B.; Copic, Davor; Laye, Fabrice R.; Prohoda, Christophor; Brieland-Shoultz, Anna C.; Polsen, Erik S.; Dee, Nicholas T.; Veerasamy, Vijayen S.; Hart, A. John

    2014-01-01

    We demonstrate direct production of graphene on SiO2 by CVD growth of graphene at the interface between a Ni film and the SiO2 substrate, followed by dry mechanical delamination of the Ni using adhesive tape. This result is enabled by understanding of the competition between stress evolution and microstructure development upon annealing of the Ni prior to the graphene growth step. When the Ni film remains adherent after graphene growth, the balance between residual stress and adhesion governs the ability to mechanically remove the Ni after the CVD process. In this study the graphene on SiO2 comprises micron-scale domains, ranging from monolayer to multilayer. The graphene has >90% coverage across centimeter-scale dimensions, limited by the size of our CVD chamber. Further engineering of the Ni film microstructure and stress state could enable manufacturing of highly uniform interfacial graphene followed by clean mechanical delamination over practically indefinite dimensions. Moreover, our findings suggest that preferential adhesion can enable production of 2-D materials directly on application-relevant substrates. This is attractive compared to transfer methods, which can cause mechanical damage and leave residues behind. PMID:24854632

  14. Effect of Si and SiO2 Substrates on the Geometries of As-Grown Carbon Coils

    Directory of Open Access Journals (Sweden)

    Semi Park

    2012-01-01

    Full Text Available Carbon coils could be synthesized using C2H2/H2 as source gases and SF6 as an incorporated additive gas under thermal chemical vapor deposition system. Si substrate, SiO2 thin film deposited Si substrate (SiO2 substrate, and quartz substrate were employed to elucidate the effect of substrate on the formation of carbon coils. The characteristics (formation densities, morphologies, and geometries of the deposited carbon coils on the substrate were investigated. In case of Si substrate, the microsized carbon coils were dominant on the substrate surface. While, in case of SiO2 substrate, the nanosized carbon coils were prevailing on the substrate surface. The surface morphologies of samples were investigated step by step during the reaction process. The cause for the different geometry formation of carbon coils according to the different substrates was discussed in association with the different thermal expansion coefficient values of Si and SiO2 substrates and the different etched characteristics of Si and SiO2 substrates by SF6 + H2 flow.

  15. Thermally tunable VO2-SiO2 nanocomposite thin-film capacitors

    Science.gov (United States)

    Sun, Yifei; Narayanachari, K. V. L. V.; Wan, Chenghao; Sun, Xing; Wang, Haiyan; Cooley, Kayla A.; Mohney, Suzanne E.; White, Doug; Duwel, Amy; Kats, Mikhail A.; Ramanathan, Shriram

    2018-03-01

    We present a study of co-sputtered VO2-SiO2 nanocomposite dielectric thin-film media possessing continuous temperature tunability of the dielectric constant. The smooth thermal tunability is a result of the insulator-metal transition in the VO2 inclusions dispersed within an insulating matrix. We present a detailed comparison of the dielectric characteristics of this nanocomposite with those of a VO2 control layer and of VO2/SiO2 laminate multilayers of comparable overall thickness. We demonstrated a nanocomposite capacitor that has a thermal capacitance tunability of ˜60% between 25 °C and 100 °C at 1 MHz, with low leakage current. Such thermally tunable capacitors could find potential use in applications such as sensing, thermal cloaks, and phase-change energy storage devices.

  16. Effect of annealing time and NH3 flow on GaN films deposited on amorphous SiO2 by MOCVD

    Science.gov (United States)

    Li, Tianbao; Liu, Chenyang; Zhang, Zhe; Yu, Bin; Dong, Hailiang; Jia, Wei; Jia, Zhigang; Yu, Chunyan; Xu, Bingshe

    2018-05-01

    GaN polycrystalline films were successfully grown on amorphous SiO2 by metal-organic chemical vapour deposition to fabricate transferable devices using inorganic films. Field-emission scanning electron microscopy images show that by prolonging the annealing time, re-evaporation is enhanced, which reduced the uniformity of the nucleation layer and GaN films. X-ray diffraction patterns indicate that the decomposition rate of the nucleation layer increases when the annealing flow rate of NH3 is 500 sccm, which makes the unstable plane and amorphous domains decompose rapidly, thereby improving the crystallinity of the GaN films. Photoluminescence spectra also indicate the presence of fewer defects when the annealing flow rate of NH3 is 500 sccm. The excellent crystal structure of the GaN films grown under optimized conditions was revealed by transmission electron microscopy analysis. More importantly, the crystal structure and orientation of GaN grown on SiO2 are the same as that of GaN grown on conventional sapphire substrate when a buffer layer is used. This work can aid in the development of transferable devices using GaN films.

  17. Formation of thin DLC films on SiO2/Si substrate using FCVAD technique

    International Nuclear Information System (INIS)

    Bootkul, D.; Intarasiri, S.; Aramwit, C.; Tippawan, U.; Yu, L.D.

    2013-01-01

    Diamond-like carbon (DLC) films deposited on SiO 2 /Si substrate are attractive for novel sensitive and selective chemical sensors. According to the almost never ending of size reduction, a nm-thickness layer of the film is greatly required. However, formation of such a very thin DLC film on SiO 2 /Si substrate is challenging. In this experiment, DLC films were formed using our in-house Filtered Cathodic Vacuum Arc Deposition (FCVAD) facility by varying the bias voltage of 0 V, −250 V and −450 V with the arc voltage of 350 V, 450 V, 550 V, 650 V and 750 V for 10 min. Raman spectroscopy was applied for characterization of the film qualities and Transmission Electron Microscopy (TEM) was applied for cross sectional analysis. Results showed that films of thickness ranging from 10–50 nm were easily acquired depending on deposition conditions. Deconvolution of Raman spectra of these samples revealed that, when fixing the substrate bias but increasing the arc voltage from 350 to 750 V, the ratio between D-peak and G-peak intensity, namely I D /I G ratio, tended to reduce up to the arc voltage of 450 V, then increased up to the arc voltage of 650 V and finally decreased again. On the other hand, when fixing the arc voltage, the I D /I G ratio tended to decrease continuously as the increasing of bias voltage. It can be concluded that the bonding structure would evolve from a graphitic-like structure to a diamond-like structure as the substrate bias increases. Additionally, the sp 3 site should be maximized at the arc voltage ∼450 V for fixed bias voltage. It is expected that, at −450 V bias and 450 V arc, sp 3 fractions could be higher than 60%. However, in some cases, e.g. at low arc voltages, voids formed between the film and the amorphous SiO 2 substrate. Electron energy loss spectroscopy (EELS) of the C edge across the DLC indicated that the thicker DLC film had uniform chemistry and structure, whereas the thin DLC film showed changes in the edge shape

  18. Effects of Mev Si Ions and Thermal Annealing on Thermoelectric and Optical Properties of SiO2/SiO2+Ge Multi-nanolayer thin Films

    Science.gov (United States)

    Budak, S.; Alim, M. A.; Bhattacharjee, S.; Muntele, C.

    Thermoelectric generator devices have been prepared from 200 alternating layers of SiO2/SiO2+Ge superlattice films using DC/RF magnetron sputtering. The 5 MeV Si ionsbombardmenthasbeen performed using the AAMU Pelletron ion beam accelerator to formquantum dots and / or quantum clusters in the multi-layer superlattice thin films to decrease the cross-plane thermal conductivity, increase the cross-plane Seebeck coefficient and increase the cross-plane electrical conductivity to increase the figure of merit, ZT. The fabricated devices have been annealed at the different temperatures to tailor the thermoelectric and optical properties of the superlattice thin film systems. While the temperature increased, the Seebeck coefficient continued to increase and reached the maximum value of -25 μV/K at the fluenceof 5x1013 ions/cm2. The decrease in resistivity has been seen between the fluence of 1x1013 ions/cm2 and 5x1013 ions/cm2. Transport properties like Hall coefficient, density and mobility did not change at all fluences. Impedance spectroscopy has been used to characterize the multi-junction thermoelectric devices. The loci obtained in the C*-plane for these data indicate non-Debye type relaxation displaying the presence of the depression parameter.

  19. SiO2 sol-gel films after ammonia and heat two-step treatments

    International Nuclear Information System (INIS)

    Zhang Chunlai; Wang Biyi; Tian Dongbin; Yin Wei; Jiang Xiaodong; Yuan Xiaodong; Yan Lianghong; Zhang Hongliang; Zhao Songnan; Lv Haibing

    2008-01-01

    SiO 2 thin films were deposited using tetraethoxylsilane as precursor, ammonia as catalyst on K9 glass by sol-gel method. These films were post-treated by ammonia and heat. The properties of the coatings were characterized by ellipsometer, UV-vis spectrophotometry, FTIR-spectroscopy, scanning probe microscope and contact angle measurement apparatus. The resuits indicate that the thickness of the films with ammonia and heat treatment tend to decrease. Both the refractive index and water contact angle increase after ammonia treatment. However, they both decrease after heat treatment. The former increases by 0.236 for the first step, then decreases by 0.202 for the second. The latter increases to 58.92 degree, then decreases to 38.07 degree. The transmittance of the coatings turn to be better and continuously shift to short wave by UV-vis spectrophotometry. The surface becomes smoother by AFM after the two-step treatment. (authors)

  20. CMOS Compatible Nonvolatile Memory Devices Based on SiO2/Cu/SiO2 Multilayer Films

    Science.gov (United States)

    Wang, Yan; Liu, Qi; Lu, Hang-Bing; Long, Shi-Bing; Zhang, Sen; Li, Ying-Tao; Lian, Wen-Tai; Yang, Jian-Hong; Liu, Ming

    2011-07-01

    We systematically investigate the resistive switching characteristics of SiO2 films with a Cu/SiO2/Cu/SiO2/Pt multilayer structure. The device exhibits good resistive switching performances, including a high ON/OFF resistance ratio (>103), good retention characteristic (>104s), satisfactory switching endurance (>200 cycles), a fast programming speed (<100 ns) and a high device yield (~100%). Considering these results, SiO2-based memories have highly promising applications for nonvolatile memory devices.

  1. Tunable Anisotropic Absorption of Ag-Embedded SiO2 Thin Films by Oblique Angle Deposition

    International Nuclear Information System (INIS)

    Xiu-Di, Xiao; Guo-Ping, Dong; Jian-Da, Shao; Zheng-Xiu, Fan; Hong-Bo, He; Hong-Ji, Qi

    2009-01-01

    Ag-embedded SiO 2 thin films are prepared by oblique angle deposition. Through field emission scanning electron microscopy (SEM), an orientated slanted columnar structure is observed. Energy-dispersive x-ray (EDX) analysis shows the Ag concentration is about 3% in the anisotropic SiO 2 matrix. Anisotropic surface plasma resonance (SPR) absorption is observed in the Ag-embedded SiO 2 thin films, which is dependent on polarization state and incidence angle of two orthogonal polarized lights and the deposition angle. This means that optical properties and anisotropic SPR absorption can be tunable in Ag-embedded SiO 2 thin films. Broadband polarization splitting is also observed and the transmission ratio T p /T s between p- and s-polarized lights is up to 2.7 for thin films deposited at α = 70°, which means that Ag-embedded SiO 2 thin films are a promising candidate for thin film polarizers. (condensed matter: structure, mechanical and thermal properties)

  2. Boosting light emission from Si-based thin film over Si and SiO(2) nanowires architecture.

    Science.gov (United States)

    Yu, Zhongwei; Qian, Shengyi; Yu, Linwei; Misra, Soumyadeep; Zhang, Pei; Wang, Junzhuan; Shi, Yi; Xu, Ling; Xu, Jun; Chen, Kunji; Roca i Cabarrocas, Pere

    2015-03-09

    Silicon (Si)-based light emitting thin film has been a key ingredient for all-Si-based optoelectronics. Besides material engineering, adopting a novel 3D photonic architecture represents an effective strategy to boost light excitation and extraction from Si-based thin film material. We here explore the use of a nanowires (NW) framework, grown via vapor-liquid-solid mode, to achieve strongly enhanced yellow-green luminescence from SiN(x)O(y)/NW core-shell structure, with an order of magnitude enhancement compared to co-deposited planar references. We found that choosing geometrically-identical but different NW cores (Si or SiO(2)) can lead to profound influence on the overall light emission performance. Combining parametric investigation and theoretical modeling, we have been able to evaluate the key contributions arising from different mechanisms that include near-field enhancement, 3D light trapping and enhanced light extraction. These new findings indicate a new and effective strategy for strong Si-based thin film light emitting source, while being generic enough to be applicable in a wide variety of other thin film materials.

  3. Regulating effect of SiO2 interlayer on optical properties of ZnO thin films

    International Nuclear Information System (INIS)

    Xu, Linhua; Zheng, Gaige; Miao, Juhong; Su, Jing; Zhang, Chengyi; Shen, Hua; Zhao, Lilong

    2013-01-01

    ZnO/SiO 2 nanocomposite films with periodic structure were prepared by electron beam evaporation technique. Regulating effect of SiO 2 interlayer with various thicknesses on the optical properties of ZnO/SiO 2 thin films was investigated deeply. The analyses of X-ray diffraction show that the ZnO layers in ZnO/SiO 2 nanocomposite films have a wurtzite structure and are preferentially oriented along the c-axis while the SiO 2 layers are amorphous. The scanning electron microscope images display that the ZnO layers are composed of columnar grains and the thicknesses of ZnO and SiO 2 layers are all very uniform. The SiO 2 interlayer presents a significant modulation effect on the optical properties of ZnO thin films, which is reflected in the following two aspects: (1) the transmittance of ZnO/SiO 2 nanocomposite films is increased; (2) the photoluminescence (PL) of ZnO/SiO 2 nanocomposite films is largely enhanced compared with that of pure ZnO thin films. The ZnO/SiO 2 nanocomposite films have potential applications in light-emitting devices and flat panel displays. -- Highlights: ► ZnO/SiO 2 nanocomposite films with periodic structure were prepared by electron beam evaporation technique. ► The SiO 2 interlayer presents a significant modulation effect on the optical properties of ZnO thin films. ► The photoluminescence of ZnO/SiO 2 nanocomposite films is largely enhanced compared with that of pure ZnO thin films. ► The ZnO/SiO 2 nanocomposite films have potential applications in light-emitting devices and flat panel displays

  4. Effect of SiO2, PVA and glycerol concentrations on chemical and mechanical properties of alginate-based films.

    Science.gov (United States)

    Yang, Manli; Shi, Jinsheng; Xia, Yanzhi

    2018-02-01

    Sodium alginate (SA)/polyvinyl alcohol (PVA)/SiO 2 nanocomposite films were prepared by in situ polymerization through solution casting and solvent evaporation. The effect of different SA/PVA ratios, SiO 2 , and glycerol content on the mechanical properties, water content, water solubility, and water vapor permeability were studied. The nanocomposite films were characterized by Fourier transform infrared, X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and thermal stability (thermogravimetric analysis/differential thermogravimetry) analyses. The nanocomposites showed the highest values of mechanical properties, such as SA/PVA ratio, SiO 2 , and glycerol content was 7:3, 6wt.%, and 0.25g/g SA, respectively. The tensile strength and elongation at break (E%) of the nanocomposites increased by 525.7% and 90.7%, respectively, compared with those of the pure alginate film. The Fourier transform infrared spectra showed a new SiOC band formed in the SA/PVA/SiO 2 nanocomposite film. The scanning electron microscopy image revealed good adhesion between SiO 2 and SA/PVA matrix. After the incorporation of PVA and SiO 2 , the water resistance of the SA/PVA/SiO 2 nanocomposite film was markedly improved. Transparency decreased with increasing PVA content but was enhanced by adding SiO 2 . Copyright © 2017. Published by Elsevier B.V.

  5. Hole trapping in E-beam irradiated SiO2 films

    Science.gov (United States)

    Aitken, J. M.; Dekeersmaecker, R. F.

    1990-07-01

    Low energy (25 kV) electron beam irradiation of MOS capacitors is shown to produce neutral hole traps in thin ‘radiation hardened’ SiO2 films. These traps are found in an uncharged state after irradiation and are populated by passing a small hole current, generated by avalanche breakdown of the n-type silicon substrate, through the oxide. From the time dependence of the observed trapping, a capture cross-section between 1 × 10˜-13 and 1 × 10-14 cm2 is deduced. The trap density is found to depend on the annealing conditions and incident electron beam dosage. The density of traps increases with incident electron beam exposure. Once introduced into the oxide by the radiation the traps can be removed by thermal anneals at temperatures above 500° C. Parallels between electron and hole trapping on these neutral centers are strong evidence for an amphoteric uncharged trap generated by ionizing radiation.

  6. Enhanced Visible Transmittance of Thermochromic VO2 Thin Films by SiO2 Passivation Layer and Their Optical Characterization

    Directory of Open Access Journals (Sweden)

    Jung-Hoon Yu

    2016-07-01

    Full Text Available This paper presents the preparation of high-quality vanadium dioxide (VO2 thermochromic thin films with enhanced visible transmittance (Tvis via radio frequency (RF sputtering and plasma enhanced chemical vapor deposition (PECVD. VO2 thin films with high Tvis and excellent optical switching efficiency (Eos were successfully prepared by employing SiO2 as a passivation layer. After SiO2 deposition, the roughness of the films was decreased 2-fold and a denser structure was formed. These morphological changes corresponded to the results of optical characterization including the haze, reflectance and absorption spectra. In spite of SiO2 coating, the phase transition temperature (Tc of the prepared films was not affected. Compared with pristine VO2, the total layer thickness after SiO2 coating was 160 nm, which is an increase of 80 nm. Despite the thickness change, the VO2 thin films showed a higher Tvis value (λ 650 nm, 58% compared with the pristine samples (λ 650 nm, 43%. This enhancement of Tvis while maintaining high Eos is meaningful for VO2-based smart window applications.

  7. Research of high-hardness and wear-resistant SiO2 film coating on acrylic substrates

    Science.gov (United States)

    Yao, Yu-ting; Cheng, Yan; Deng, Xiu-mei; Jiang, Jin-hu; Zhu, Xiao-bo; Gu, Wen-hua

    2017-10-01

    Acrylic (PMMA) possesses excellent optical transparency, good chemical stability as well as many other merits such as the feasibilities in dyeing and manufacturing. But its poor hardness and wear resistance restrict its industrialized applications. In order to improve the hardness and wear resistance, SiO2 films were coated on PMMA substrates by both dip coating method and aerosol spraying method in this work. Heating curing method was carried out after the coating of SiO2 film, and consequently, the mechanical properties, optical properties and surface morphology were characterized and compared. The experimental results showed that the SiO2 films prepared by aerosol spraying method has a better performance in both hardness and wear resistance, compared with the films prepared by dip coating method. In the optimized conditions, the hardness of the PMMA was improved from 3H to 8H, and the non-abrasion rubbing times increased from less than 100 times to 5000 times with a loading of 500g weight after the coating of SiO2 film, indicating the improvement of the wear resistance.

  8. Synthis and Phisical And Chemical; Properties of SiO2 - B2O3 and SiO2 - P2O5 Thin Film Systems and Powders

    Science.gov (United States)

    Mal'chik, A. G.; Litovkin, S. V.; Seregin, V. I.; Rodionov, P. V.; Kryuchkova, S. O.

    2016-08-01

    The SiO2 - B2O3 and SiO2 - P2O5 films were synthesized by using film forming solutions having a P2O5 content of up to 30% and B2O3 up to 40%. Properties of the filmforming solutions and binary oxides were examined. The physical and chemical processes occurring in the solution during the heat treatment of films were examined. The conditions for producing films of different thicknesses were determined. The kinetic parameters were calculated.

  9. SiO $ _2 $/TiO $ _2 $ multi-layered thin films with self-cleaning and ...

    Indian Academy of Sciences (India)

    Self-cleaning, high transmittance glazing was obtained by cold spray deposition for glazings. The thin films contain TiO 2 , SiO 2 and Au nanoparticles in different structures which allow for tailoring the optical, hydrophilic and photocatalytic properties. The crystallinity, morphology and surface energy were correlated with the ...

  10. Application of high-quality SiO2 grown by multipolar ECR source to Si/SiGe MISFET

    Science.gov (United States)

    Sung, K. T.; Li, W. Q.; Li, S. H.; Pang, S. W.; Bhattacharya, P. K.

    1993-01-01

    A 5 nm-thick SiO2 gate was grown on an Si(p+)/Si(0.8)Ge(0.2) modulation-doped heterostructure at 26 C with an oxygen plasma generated by a multipolar electron cyclotron resonance source. The ultrathin oxide has breakdown field above 12 MV/cm and fixed charge density about 3 x 10 exp 10/sq cm. Leakage current as low as 1/micro-A was obtained with the gate biased at 4 V. The MISFET with 0.25 x 25 sq m gate shows maximum drain current of 41.6 mA/mm and peak transconductance of 21 mS/mm.

  11. SiO2/TiO2 multi-layered thin films with self-cleaning and enhanced ...

    Indian Academy of Sciences (India)

    using a TEOS:EtOH:HCl:H2O in 1:8:3:0.5 volume ratio. The as-prepared SiO2 gel was then calcinated at 600 ... 0.25 g SiO2 powder in 50 ml ethanol:water (1:1 v/v), respec- tively, 0.05 g TiO2 powder in 50 ml ethanol. ... cleaned by ultra-sonication in alcohol and then dried using compressed air. The multi-layered thin films ...

  12. Preparation and optical properties of SiO2 stablized SnO2 quantum dot films

    International Nuclear Information System (INIS)

    Peng Qiangxiang; Li Zhijie; Zu Xiaotao

    2009-01-01

    SiO 2 stabilized SnO 2 quantum dot were prepared by sol-gel-hydrothermal process. Then SnO 2 quantum dot thin films were obtained by spin-coating with preprocess of well dispersing SnO 2 quantum dots in SiO 2 sol. The as-prepared SnO 2 quantum dots showed tetragonal rutile crystal structure and quantum dot radius of about 4.0 nm. The optical bad gap of the thin films was derived from UV-vis transmission spectra, with value of about 3.96 eV. The SnO 2 quantum dot thin films showed multi-peak photoluminescence properties at room temperature, mainly excitation emission at 356 nm and defect emission at 388 nm. (authors)

  13. Lateral protonic/electronic hybrid oxide thin-film transistor gated by SiO2 nanogranular films

    International Nuclear Information System (INIS)

    Zhu, Li Qiang; Chao, Jin Yu; Xiao, Hui

    2014-01-01

    Ionic/electronic interaction offers an additional dimension in the recent advancements of condensed materials. Here, lateral gate control of conductivities of indium-zinc-oxide (IZO) films is reported. An electric-double-layer (EDL) transistor configuration was utilized with a phosphorous-doped SiO 2 nanogranular film to provide a strong lateral electric field. Due to the strong lateral protonic/electronic interfacial coupling effect, the IZO EDL transistor could operate at a low-voltage of 1 V. A resistor-loaded inverter is built, showing a high voltage gain of ∼8 at a low supply voltage of 1 V. The lateral ionic/electronic coupling effects are interesting for bioelectronics and portable electronics

  14. Gate-tunable coherent transport in Se-capped Bi2Se3 grown on amorphous SiO2/Si

    International Nuclear Information System (INIS)

    Liu, Y. H.; Chong, C. W.; Huang, S. Y.; Jheng, J. L.; Huang, S. M.; Huang, J. C. A.; Li, Z.; Qiu, H.; Marchenkov, V. V.

    2015-01-01

    A topological insulator (TI) is an exotic material that has a bulk insulating gap and metallic surface states with unique spin-momentum locking characteristics. Despite its various important applications, large scale integration of TI into MOSFET technologies and its coherent transport study are still rarely explored. Here, we report the growth of high quality Bi 2 Se 3 thin film on amorphous SiO 2 /Si substrate using MBE. By controlling the thickness of the film at ∼7 nm and capping the as grown film in situ with a 2 nm-thick Se layer, largest electrostatic field effect is obtained and the resistance is changed by almost 300%. More importantly, pronounced gate-tunable weak antilocalization (WAL) is observed, which refers to modulation of α from ∼−0.55 to ∼−0.2 by applying a back gate voltage. The analysis herein suggests that the significant gate-tunable WAL is attributable to the transition from weak disorder into intermediate disorder regime when the Fermi level is shifted downward by increasing the negative back gate voltage. Our findings may pave the ways towards the development of TI-based MOSFET and are promising for the applications of electric-field controlled spintronic and magnetic device

  15. Study of sputtered ZnO thin films on SiO2 and GaP substrates

    International Nuclear Information System (INIS)

    Brath, T.; Buc, D.; Kovac, J.; Hrnciar, V.; Caplovic, L.

    2011-01-01

    We have investigated n-ZnO polycrystalline thin films prepared on SiO 2 and p-GaP substrate using magnetron sputtering technique. The structural and electrical properties of these structures were studied. The measured parameters give promising results with a possibility to utilize n-ZnO/p-GaP heterostructure for application in the solar cells development especially in the field of nanostructures. The prepared structures will be a subject of further research. (authors)

  16. Defect induced phonon scattering for tuning the lattice thermal conductivity of SiO2 thin films

    Directory of Open Access Journals (Sweden)

    Sen Cao

    2017-01-01

    Full Text Available In this work, the thermal properties of nanoscale SiO2 thin films have been systematically investigated with respect to the thickness, crystal orientations and the void defects using non-equilibrium molecular-dynamics (NEMD simulation. Size effect for the lattice thermal conductivity of nanoscale SiO2 thin films was observed. Additionally, SiO2 thin films with [001] oriented exhibited greater thermal conductivity compared with other crystal orientations which was discussed in terms of phonon density of states (PDOS. Furthermore, the porosity of void defects was introduced to quantify the influence of defects for thermal conductivity. Results exhibited that the thermal conductivity degraded with the increase of porosity. Two thermal conductivity suppression mechanisms, namely, void defects induced material loss interdicting heat conduction and phonon scattering enhanced by the boundary of defects, were proposed. Then, a further simulation was deployed to find that the effect of boundary scattering of defects was dominant in thermal conductivity degradation compared with material loss mechanism. The conclusion suggests that the thermal conductivity could be configured via regulating the distribution of PDOS directly associated with void defects.

  17. Síntese e caracterização de nanocompósitos Ni: SiO2 processados na forma de filmes finos Synthesis and characterization of Ni: SiO2 nanocomposites processed as thin films

    Directory of Open Access Journals (Sweden)

    Paulo Sérgio Gouveia

    2005-10-01

    Full Text Available We have produced nanocomposite films of Ni:SiO2 by an alternative polymeric precursor route. Films, with thickness of ~ 1000 nm, were characterized by several techniques including X-ray diffraction, scanning electron microscopy, atomic force microscopy, flame absorption atomic spectrometry, and dc magnetization. Results from the microstructural characterizations indicated that metallic Ni-nanoparticles with average diameter of ~ 3 nm are homogeneously distributed in an amorphous SiO2 matrix. Magnetization measurements revealed a blocking temperature T B ~ 7 K for the most diluted sample and the absence of an exchange bias suggesting that Ni nanoparticles are free from an oxide layer.

  18. The Effects of SiO2 Nanoparticles on Mechanical and Physicochemical Properties of Potato Starch Films

    Directory of Open Access Journals (Sweden)

    Z. Torabi

    2013-06-01

    Full Text Available In this paper effect of SiO2 nanoparticles was investigated on potato starch films. Potato starch films were prepared by casting method with addition of nano-silicon dioxide and a mixture of sorbitol/glycerol (weight ratio of 3 to 1 as plasticizers. SiO2 nanoparticles incorporated to the potato starch films at different concentrations 0, 1, 2, 3, and 5% of total solid, and the films were dried under controlled conditions.  Physicochemical properties such as water absorption capacity (WAC, water vapor permeability (WVP and mechanical properties of the films were measured. Results show that by increasing the concentration of silicon dioxide nanoparticles, mechanical properties of films can be improved. Also incorporation of silicon dioxide nanoparticles in the structure of biopolymer decrease permeability of the gaseous molecules such as water vapor. In summary, addition of silicon dioxide nanoparticles improves functional properties of potato starch films and these bio Nano composites can be used in food packaging.

  19. Gas plasma etching of Si and SiO2 films

    International Nuclear Information System (INIS)

    Koyama, Satoshi; Kajiwara, Yoshinori; Nanjo, Junji; Nomura, Shigeru; Hara, Shin-ichi

    1978-01-01

    The dependence of etching depth on the positions and on the quantity of materials to be etched, for plasma ething, has been investigated. When N identical wafers of silicon are etched simultaneously, the etching depth is subject to the following experimental formula D = 9600Nsup(-0.79) (A), where D is etching depth and N is the number of identical wafers. It has been shown that for uniform etching of all wafers, spaces between wafers need over 2.5 cm. Plasma etching characteristics of anodically oxidized silicon and thermally grown silicon dioxide are studied compared with the conventional chemical etching. Etching rate of anodically oxidized silicon in plasma etching is smaller than that of the thermally grown silicon dioxide, but in chemical etching, this relation becomes reverse. It has been suggested that the presence of the water molecules and OH radicals in the anodic oxide films prevents the role of fluorine radicals (F*) in plasma. (author)

  20. Nanomechanical and Macrotribological Properties of CVD-Grown Graphene as a Middle Layer between Metal Pt Cylinders and SiO2/Si Substrate

    Directory of Open Access Journals (Sweden)

    Hongyan Wu

    2015-01-01

    Full Text Available The CVD-grown graphene as a middle layer was introduced between Pt cylinders and SiO2/Si to extend the application of graphene for improving the wear performance of microelectromechanical systems. Periodic arrays of Pt cylinders were prepared on the graphene/SiO2/Si (Pt/graphene and SiO2/Si substrate (Pt/SiO2 using the magnetron sputtering technique. To characterize Pt/graphene and Pt/SiO2, nanoindentation and macrotribological tests were performed. The results showed that the friction coefficient was lower and the wear lifetime of Pt/graphene was longer than those of Pt/SiO2. Graphene, as a middle layer, was not only observed to have significant influence on the mechanical properties (i.e., microhardness and elastic modulus, but also found to improve the adhesive strength between SiO2/Si and Pt cylinders.

  1. Size dependence of non-linear optical properties of SiO2 thin films containing InP nanocrystals

    Science.gov (United States)

    Zheng, M. J.; Zhang, L. D.; Zhang, J. G.

    SiO2 composite thin films containing InP nanocrystals were fabricated by radio-frequency magnetron co-sputtering technique. The microstructure of the composite thin films was characterized by X-ray diffraction and Raman spectrum. The optical absorption band edges exhibit marked blueshift with respect to bulk InP due to strong quantum confinement effect. Non-linear optical absorption and non-linear optical refraction were studied by a Z-scan technique using a single Gaussian beam of a He-Ne laser (632.8 nm). We observed the saturation absorption and two-photon absorption in the composite films. An enhanced third-order non-linear optical absorption coefficient and non-linear optical refractive index were achieved in the composite films. The nonlinear optical properties of the films display the dependence on InP nanocrystals size.

  2. Annealing temperature effect on structure and electrical properties of films formed of Ge nanoparticles in SiO2

    International Nuclear Information System (INIS)

    Stavarache, Ionel; Lepadatu, Ana-Maria; Stoica, Toma; Ciurea, Magdalena Lidia

    2013-01-01

    Ge–SiO 2 films with high Ge/Si atomic ratio of about 1.86 were obtained by co-sputtering of Ge and SiO 2 targets and subsequently annealed at different temperatures between 600 and 1000 °C in a conventional furnace in order to show how the annealing process influences the film morphology concerning the Ge nanocrystal and/or amorphous nanoparticle formation and to study their electrical behaviour. Atomic force microscopy (AFM) imaging, Raman spectroscopy and electrical conductance measurements were performed in order to find out the annealing effect on the film surface morphology, as well as the Ge nanoparticle formation in correlation with the hopping conductivity of the films. AFM images show that the films annealed at 600 and 700 °C present a granular surface with particle height of about 15 nm, while those annealed at higher temperatures have smoother surface. The Raman investigations evidence Ge nanocrystals (including small ones) coexisting with amorphous Ge in the films annealed at 600 °C and show that almost all Ge is crystallized in the films annealed at 700 °C. The annealing at 800 °C disadvantages the Ge nanocrystal formation due to the strong Ge diffusion. This transition in Ge nanocrystals formation process by annealing temperature increase from 700 to 800 °C revealed by AFM and Raman spectroscopy measurements corresponds to a change in the electrical transport mechanism. Thus, in the 700 °C annealed films, the current depends on temperature according to a T −1/2 law which is typical for a tunnelling mechanism between neighbour Ge nanocrystals. In the 800 °C annealed films, the current–temperature characteristic has a T −1/4 dependence showing a hopping mechanism within an electronic band of localized states related to diffused Ge in SiO 2 .

  3. Formation of SiO2 film by chemical vapor deposition enhanced by atomic species extracted from a surface-wave generated plasma

    Science.gov (United States)

    Okada, H.; Baba, M.; Furukawa, M.; Yamane, K.; Sekiguchi, H.; Wakahara, A.

    2017-01-01

    In this study, we have investigated SiO2 deposition by chemical vapor deposition enhanced by neutral oxygen at the ground state extracted from a surface-wave generated plasma proposed by our group at 350°C using hexamethyldisilane (HMDS) as a precursor. Good properties of deposited SiO2 having refractive index of n = 1.45-1.46 have been confirmed by ellipsometry. Stoichiometric SiO2 was also confirmed by X-ray photoelectron spectroscopy (XPS) with single peak of Si 2p and O 1s. High quality SiO2 film deposition was also confirmed by Fourier transform infrared spectrometer (FT-IR) analysis indicating formation of chemical bonding in SiO2 with no unwanted bonds due to -OH or -CH3 groups.

  4. Water Sorption in Electron-Beam Evaporated SiO2 on QCM Crystals and Its Influence on Polymer Thin Film Hydration Measurements.

    Science.gov (United States)

    Kushner, Douglas I; Hickner, Michael A

    2017-05-30

    Spectroscopic ellipsometry (SE) and quartz crystal microbalance (QCM) measurements are two critical characterization techniques routinely employed for hydration studies of polymer thin films. Water uptake by thin polymer films is an important area of study to investigate antifouling surfaces, to probe the swelling of thin water-containing ionomer films, and to conduct fundamental studies of polymer brush hydration and swelling. SiO 2 -coated QCM crystals, employed as substrates in many of these hydration studies, show porosity in the thin electron-beam (e-beam) evaporated SiO 2 layer. The water sorption into this porous SiO 2 layer requires correction of the optical and mass characterization of the hydrated polymer due to changes in the SiO 2 layer as it sorbs water. This correction is especially important when experiments on SiO 2 -coated QCM crystals are compared to measurements on Si wafers with dense native SiO 2 layers. Water adsorption filling void space during hydration in ∼200-260 nm thick SiO 2 layers deposited on a QCM crystal resulted in increased refractive index of the layer during water uptake experiments. The increased refractive index led to artificially higher polymer swelling in the optical modeling of the hydration experiments. The SiO 2 -coated QCM crystals showed between 6 and 8% void as measured by QCM and SE, accounting for 60%-85% of the measured polymer swelling in the low humidity regime (70% RH) from optical modeling for 105 and 47 nm thick sulfonated polymer films. Correcting the refractive index of the SiO 2 layer for its water content resulted in polymer swelling that successfully resembled swelling measured on a silicon wafer with nonporous native oxide.

  5. Void Shapes Controlled by Using Interruption-Free Epitaxial Lateral Overgrowth of GaN Films on Patterned SiO2 AlN/Sapphire Template

    Directory of Open Access Journals (Sweden)

    Yu-An Chen

    2014-01-01

    Full Text Available GaN epitaxial layers with embedded air voids grown on patterned SiO2 AlN/sapphire templates were proposed. Using interruption-free epitaxial lateral overgrowth technology, we realized uninterrupted growth and controlled the shape of embedded air voids. These layers showed improved crystal quality using X-ray diffraction and measurement of etching pits density. Compared with conventional undoped-GaN film, the full width at half-maximum of the GaN (0 0 2 and (1 0 2 peaks decreased from 485 arcsec to 376 arcsec and from 600 arcsec to 322 arcsec, respectively. Transmission electron microscopy results showed that the coalesced GaN growth led to bending threading dislocation. We also proposed a growth model based on results of scanning electron microscopy.

  6. Humidity sensor based on a long-period fiber grating coated with a SiO2-nanosphere film

    Science.gov (United States)

    Viegas, D.; Goicoechea, J.; Corres, J. M.; Santos, J. L.; Ferreira, L. A.; Araújo, F. M.; Matias, I. R.

    2008-04-01

    This work addresses a humidity sensor using long-period fiber gratings (LPG) coated with silica nanospheres film. SiO2-nanospheres coating is deposited onto the LPG using the electrostatic self-assembly technique (ESA). The polymeric overlay changes its optical properties when exposed to different humidity levels, resulting in a shift of the resonance wavelength of the LPG. The obtained results are accordant with the theoretical simulations. Wavelength shifts up to 12nm in a humidity range from 20% to 80% are reported, maintaining the same dependence at different temperatures.

  7. Microstructure and magnetic properties of FePt:Ag nanocomposite films on SiO2/Si(1 0 0)

    International Nuclear Information System (INIS)

    Wang Hao; Yang, F.J.; Wang, H.B.; Cao, X.; Xue, S.X.; Wang, J.A.; Gao, Y.; Huang, Z.B.; Yang, C.P.; Chiah, M.F.; Cheung, W.Y.; Wong, S.P.; Li, Q.; Li, Z.Y.

    2006-01-01

    FePt:Ag nanocomposite films were prepared by pulsed filtered vacuum arc deposition system and subsequent rapid thermal annealing on SiO 2 /Si(1 0 0) substrates. The microstructure and magnetic properties were investigated. A strong dependence of coercivity and ordering of the face-central tetragonal structure on both Ag concentration and annealing temperature was observed. With Ag concentration of 22% in atomic ratio, the coercivity got to 6.0 kOe with a grain size of 6.7 nm when annealing temperature was 400 deg. C

  8. IrO2-SiO2 binary oxide films: Preparation, physiochemical characterization and their electrochemical properties

    International Nuclear Information System (INIS)

    Wang Xiaomei; Hu Jiming; Zhang Jianqing

    2010-01-01

    Mixed IrO 2 -SiO 2 oxide films were prepared on titanium substrate by the thermo-decomposition of hexachloroiridate (H 2 IrCl 6 ) and tetraethoxysilane (TEOS) mixed precursors in organic solvents. The solution chemistry and thermal decomposition kinetics of the mixed precursors were investigated by ultra violet/visible (UV/vis) spectroscopy and thermogravimetry (TGA) and differential thermal analysis (DTA), respectively. The physiochemical characterization of the resulting materials was conducted by X-ray diffraction (XRD), scanning electron microscopy (SEM) and electrochemical measurements. It is shown from the UV/vis spectra that the electronic absorption intensity of IrCl 6 2- complexes in the precursors decreases in the presence of TEOS, indicating the interaction between these two components. Thermal analysis shows the decomposition reaction of H 2 IrCl 6 is inhibited by TEOS in the low temperature range, but the further oxidation reaction at high temperatures of formed intermediates is independent of the presence of silane component. Physical measurements show a restriction effect of silica on the crystallization and crystal growth processes of IrO 2 , leading to the formation of finer oxide particles and the porous morphology of the binary oxide films. The porous composite films exhibit high apparent electrocatalytic activity toward the oxygen evolution reaction. In addition, the long-term stability of Ti-supported IrO 2 electrodes is found to apparently improve with appropriate amount of SiO 2 incorporation, as tested under galvanostatic electrolysis.

  9. Atomic force microscopy measurements of topography and friction on dotriacontane films adsorbed on a SiO2 surface

    DEFF Research Database (Denmark)

    Trogisch, S.; Simpson, M.J.; Taub, H.

    2005-01-01

    We report comprehensive atomic force microscopy (AFM) measurements at room temperature of the nanoscale topography and lateral friction on the surface of thin solid films of an intermediate-length normal alkane, dotriacontane (n-C32H66), adsorbed onto a SiO2 surface. Our topographic and frictional...... their location. Above a minimum size, the bulk particles are separated from islands of perpendicularly oriented molecules by regions of exposed parallel layers that most likely extend underneath the particles. We find that the lateral friction is sensitive to the molecular orientation in the underlying...... crystalline film and can be used effectively with topographic measurements to resolve uncertainties in the film structure. We measure the same lateral friction on top of the bulk particles as on the perpendicular layers, a value that is about 2.5 times smaller than on a parallel layer. Scans on top...

  10. Paramagnetic point defects in amorphous thin films of SiO2 and Si3N4: An update

    Science.gov (United States)

    Poindexter, E. H.; Warren, W. L.

    Recent research on point defects in thin films of SiO2 and Si3SN4 on Si is presented and reviewed. In SiO2 it is now clear that no one type of E(prime) center is the sole source of radiation-induced positive charge; hydrogenous moieties or other types of E(prime) are proposed. Molecular orbital theory and easy passivation of E(prime) by H2 suggest that released H might depassivate P(sub b) sites. A charged E(prime)(sub delta) center has been seen in Cl-free SIMOX and thermal oxide film, and it is reassigned to an electron delocalized over four O3 triple bond Si units around a fifth Si. In Si3N4 a new model for the amphoteric charging of Si triple bond N3 moieties is based on local shifts in defect energy with respect to the Fermi level, arising from nonuniform composition; it does not assume negative-U electron correlation. A new defect NN(sub 2)(sup 0) has been identified, with dangling orbital on a 2-coordinated N atom bonded to another N.

  11. Effectively Improved SiO2-TiO2 Composite Films Applied in Commercial Multicrystalline Silicon Solar Cells

    Directory of Open Access Journals (Sweden)

    Chih-Hsiang Yang

    2013-01-01

    Full Text Available Composite silicon dioxide-titanium dioxide (SiO2-TiO2 films are deposited on a large area of 15.6 × 15.6 cm2 textured multicrystalline silicon solar cells to increase the incident light trapped within the device. For further improvement of the antireflective coatings (ARCs quality, dimethylformamide (DMF solution is added to the original SiO2-TiO2 solutions. DMF solution solves the cracking problem, thus effectively decreasing reflectance as well as surface recombination. The ARCs prepared by sol-gel process and plasma-enhanced chemical vapor deposition (PECVD on multicrystalline silicon substrate are compared. The average efficiency of the devices with improved sol-gel ARCs is 16.3%, only 0.5% lower than that of devices with PECVD ARCs (16.8%. However, from equipment depreciation point of view (the expiration date of equipment is generally considered as 5 years, the running cost (USD/watt of sol-gel technique is 80% lower than that of PECVD method for the first five years and 66% lower than that of PECVD method from the start of the sixth year. This result proves that sol-gel-deposited ARCs process has potential applications in manufacturing low-cost, large-area solar cells.

  12. A polycrystalline SiO2 colloidal crystal film with ultra-narrow reflections.

    Science.gov (United States)

    Fu, Qianqian; Chen, Ang; Shi, Lei; Ge, Jianping

    2015-04-30

    This work reported a high quality photonic crystal film with an ultra-narrow photonic bandgap obtained via a chemical synthetic route. The bandgap is much narrower than that of traditional colloidal crystals, which makes the film qualified for use in optical devices. The narrow PBG originates from not only the high crystallinity and uniform orientations of microcrystals within the film but also the very close refractive indices between the silica and the polymer matrix. Due to the matching of the refractive index, the amorphous contents of the film are optically transparent and do not interfere with the reflection, so that the photonic crystal film is tolerant of the existence of disordered contents.

  13. Negative differential resistance effect induced by metal ion implantation in SiO2 film for multilevel RRAM application

    Science.gov (United States)

    Wu, Facai; Si, Shuyao; Shi, Tuo; Zhao, Xiaolong; Liu, Qi; Liao, Lei; Lv, Hangbing; Long, Shibing; Liu, Ming

    2018-02-01

    Pt/SiO2:metal nanoparticles/Pt sandwich structure is fabricated with the method of metal ion (Ag) implantation. The device exhibits multilevel storage with appropriate R off/R on ratio, good endurance and retention properties. Based on transmission electron microscopy and energy dispersive spectrometer analysis, we confirm that Pt nanoparticles are spurted into SiO2 film from Pt bottom electrode by Ag implantation; during electroforming, the local electric field can be enhanced by these Pt nanoparticles, meanwhile the Ag nanoparticles constantly migrate toward the Pt nanoparticles. The implantation induced nanoparticles act as trap sites in the resistive switching layer and play critical roles in the multilevel storage, which is evidenced by the negative differential resistance effect in the current–voltage (I–V) measurements.

  14. Surface morphology of amorphous germanium thin films following thermal outgassing of SiO2/Si substrates

    International Nuclear Information System (INIS)

    Valladares, L. de los Santos; Dominguez, A. Bustamante; Llandro, J.; Holmes, S.; Quispe, O. Avalos; Langford, R.; Aguiar, J. Albino; Barnes, C.H.W.

    2014-01-01

    Highlights: • Annealing promotes outgassing of SiO 2 /Si wafers. • Outgassing species embed in the a-Ge film forming bubbles. • The density of bubbles obtained by slow annealing is smaller than by rapid annealing. • The bubbles explode after annealing the samples at 800 °C. • Surface migration at higher temperatures forms polycrystalline GeO 2 islands. - Abstract: In this work we report the surface morphology of amorphous germanium (a-Ge) thin films (140 nm thickness) following thermal outgassing of SiO 2 /Si substrates. The thermal outgassing was performed by annealing the samples in air at different temperatures from 400 to 900 °C. Annealing at 400 °C in slow (2 °C/min) and fast (10 °C/min) modes promotes the formation of bubbles on the surface. A cross sectional view by transmission electron microscope taken of the sample slow annealed at 400 °C reveals traces of gas species embedded in the a-Ge film, allowing us to propose a possible mechanism for the formation of the bubbles. The calculated internal pressure and number of gas molecules for this sample are 30 MPa and 38 × 10 8 , respectively. Over an area of 22 × 10 −3 cm 2 the density of bubbles obtained at slow annealing (9 × 10 3 cm −2 ) is smaller than that at rapid annealing (6.4 × 10 4 cm −2 ), indicating that the amount of liberated gas in both cases is only a fraction of the total gas contained in the substrate. After increasing the annealing temperature in the slow mode, bubbles of different diameters (from tens of nanometers up to tens of micrometers) randomly distribute over the Ge film and they grow with temperature. Vertical diffusion of the outgas species through the film dominates the annealing temperature interval 400–600 °C, whereas coalescence of bubbles caused by lateral diffusion is detected after annealing at 700 °C. The bubbles explode after annealing the samples at 800 °C. Annealing at higher temperatures, such as 900 °C, leads to surface migration of the

  15. Low-temperature atomic layer deposition of SiO2/Al2O3 multilayer structures constructed on self-standing films of cellulose nanofibrils

    Science.gov (United States)

    Putkonen, Matti; Sippola, Perttu; Svärd, Laura; Sajavaara, Timo; Vartiainen, Jari; Buchanan, Iain; Forsström, Ulla; Simell, Pekka; Tammelin, Tekla

    2017-12-01

    In this paper, we have optimized a low-temperature atomic layer deposition (ALD) of SiO2 using AP-LTO® 330 and ozone (O3) as precursors, and demonstrated its suitability to surface-modify temperature-sensitive bio-based films of cellulose nanofibrils (CNFs). The lowest temperature for the thermal ALD process was 80°C when the silicon precursor residence time was increased by the stop-flow mode. The SiO2 film deposition rate was dependent on the temperature varying within 1.5-2.2 Å cycle-1 in the temperature range of 80-350°C, respectively. The low-temperature SiO2 process that resulted was combined with the conventional trimethyl aluminium + H2O process in order to prepare thin multilayer nanolaminates on self-standing CNF films. One to six stacks of SiO2/Al2O3 were deposited on the CNF films, with individual layer thicknesses of 3.7 nm and 2.6 nm, respectively, combined with a 5 nm protective SiO2 layer as the top layer. The performance of the multilayer hybrid nanolaminate structures was evaluated with respect to the oxygen and water vapour transmission rates. Six stacks of SiO2/Al2O with a total thickness of approximately 35 nm efficiently prevented oxygen and water molecules from interacting with the CNF film. The oxygen transmission rates analysed at 80% RH decreased from the value for plain CNF film of 130 ml m-2 d-1 to 0.15 ml m-2 d-1, whereas the water transmission rates lowered from 630 ± 50 g m-2 d-1 down to 90 ± 40 g m-2 d-1. This article is part of a discussion meeting issue `New horizons for cellulose nanotechnology'.

  16. Surface properties of SiO2 with and without H2O2 treatment as gate dielectrics for pentacene thin-film transistor applications

    Science.gov (United States)

    Hung, Cheng-Chun; Lin, Yow-Jon

    2018-01-01

    The effect of H2O2 treatment on the surface properties of SiO2 is studied. H2O2 treatment leads to the formation of Si(sbnd OH)x at the SiO2 surface that serves to reduce the number of trap states, inducing the shift of the Fermi level toward the conduction band minimum. H2O2 treatment also leads to a noticeable reduction in the value of the SiO2 capacitance per unit area. The effect of SiO2 layers with H2O2 treatment on the behavior of carrier transports for the pentacene/SiO2-based organic thin-film transistor (OTFT) is also studied. Experimental identification confirms that the shift of the threshold voltage towards negative gate-source voltages is due to the reduced number of trap states in SiO2 near the pentacene/SiO2 interface. The existence of a hydrogenated layer between pentacene and SiO2 leads to a change in the pentacene-SiO2 interaction, increasing the value of the carrier mobility.

  17. Enhancement of Electrical Conductance for Pentacene Thin Film Transistor by Controlling an Initial Layer-by-Layer Growth Mode Directly on SiO2 Insulator

    Science.gov (United States)

    Qi, Qiong; Jiang, Yeping; Yu, Aifang; Qiu, Xiaohui; Jiang, Chao

    2009-04-01

    Initial nucleation and growth of pentacene films on various pre-cleaning treated SiO2 gate insulators were systematically examined by atomic force microscope. The performance of fabricated pentacene thin film transistor devices was found to be highly related to the initial film growth modes. In contrast to the film in the three-dimensional island-like growth mode on SiO2 under an organic cleaning process, a layer-by-layer initial growth mode occurred on the SiO2 insulator cleaned with ammonia solution which has shown much improved electrical properties of the thin film transistors. Field effect mobility of the thin film transistor devices could be achieved as high as 1.0 cm2 V-1 s-1 on the bared SiO2/Si substrate and the on/off ratio was over 106. The enhanced electrical conductance was further confirmed by an electrostatic force microscopic observation of quantized electrical potentials via charge-injection to the submonolayer pentacene islands with layer-by-layer growth mode.

  18. Low-temperature PZT thin-film ferroelectric memories fabricated on SiO2/Si and glass substrates

    Directory of Open Access Journals (Sweden)

    D.H. Minh

    2016-03-01

    Full Text Available In a ferroelectric-gate thin film transistor memory (FGT type structure, the gate-insulator layer is extremely important for inducing the charge when accumulating or depleting. We concentrated on the application of low-temperature PZT films crystallized at 450, 500 and 550 °C, instead of at conventional high temperatures (≥600 °C. Investigation of the crystalline structure and electrical properties indicated that the PZT film, crystallized at 500 °C, was suitable for FGT fabrication because of a high (111 orientation, large remnant polarization of 38 μC/cm2 on SiO2/Si substrate and 17.8 μC/cm2 on glass, and low leakage current of 10−6 A/cm2. In sequence, we successfully fabricated FGT with all processes below 500 °C on a glass substrate, whose operation exhibits a memory window of 4 V, ON/OFF current ratio of 105, field-effect mobility of 0.092 cm2 V−1 s−1, and retention time of 1 h.

  19. Microporous SiO2 with huge electric-double-layer capacitance for low-voltage indium tin oxide thin-film transistors

    International Nuclear Information System (INIS)

    Lu Aixia; Sun Jia; Jiang Jie; Wan Qing

    2009-01-01

    Electric-double-layer (EDL) effect is observed in microporous SiO 2 dielectric films deposited at room temperature by plasma-enhanced chemical vapor deposition method. Indium tin oxide thin-film transistors gated by such microporous SiO 2 gate dielectric are fabricated at room temperature, and a low operating voltage of 1.5 V is obtained due to the huge EDL specific capacitance (2.14 μF/cm 2 ). The field-effect electron mobility is estimated to be 118 cm 2 V -1 s -1 . Current on/off ratio and subthreshold gate voltage swing are estimated to be 5x10 6 and 92 mV/decade, respectively. Room-temperature deposited microporous SiO 2 dielectric is promising for low-power field-effect transistors on temperature sensitive substrates.

  20. Surface texture modification of spin-coated SiO2 xerogel thin films ...

    Indian Academy of Sciences (India)

    water and alcohol product formed in the hydrolysis reaction. ∗. Author for correspondence (ammahajan@nmu.ac.in; ammahajan.ele@rediffmail.com) get polymerized and form siloxane bonds. The microstruc- ture of the silica film can be easily modified by controlling the sol–gel process parameters. Hydrolysis reaction:.

  1. Surface texture modification of spin-coated SiO2 xerogel thin films ...

    Indian Academy of Sciences (India)

    Condensation reaction: Si–OR + HO–Si → Si–O–Si + ROH. (b). Si–OH + HO–Si → Si–O–Si + H2O. (c). (Brinker and Scherrer 1990). The synthesized porous silica films usually are hydrophilic nature which can absorb moisture under the atmospheric con- dition due to the presence of the polar OH radical on the surface that ...

  2. Optical transparency and mechanical properties of semi-refined iota carrageenan film reinforced with SiO2 as food packaging material

    Science.gov (United States)

    Aji, Afifah Iswara; Praseptiangga, Danar; Rochima, Emma; Joni, I. Made; Panatarani, Camellia

    2018-02-01

    Food packaging is important for protecting food from environmental influences such as heat, light, water vapor, oxygen, dirt, dust particles, gas emissions and so on, which leads to decrease the quality of food. The most widely used type of packaging in the food industry is plastic which is made from synthetic polymers and takes hundreds of years to biodegrade. Recently, food packaging with high bio-degradability is being developed using biopolymer combined with nanoparticles as reinforcing agent (filler) to improve its properties. In this study, semi-refined iota carrageenan films were prepared by incorporating SiO2 nanoparticles as filler at different concentrations (0%, 0.5%, 1.0% and 1.5% w/w carrageenan) using solution casting method. The optical transparency and mechanical properties (tensile strength and elongation at break) of the films were analyzed. The results showed that incorporation of SiO2 nanoparticles to carrageenan matrix on optical transparency of the films. For the mechanical properties, the highest tensile strength was found for incorporation of 0.5% SiO2, while the elongation at break of the films improved with increasing SiO2 concentration.

  3. High performance a-IGZO thin-film transistors with mf-PVD SiO2 as an etch-stop-layer

    NARCIS (Netherlands)

    Nag, M.; Steudel, S.; Bhoolokam, A.; Chasin, A.; Rockele, M.; Myny, K.; Maas, J.; Fritz, T.; Trube, J.; Groeseneken, G.; Heremans, P.

    2014-01-01

    In this work, we report on high-performance bottom-gate top-contact (BGTC) amorphous-Indium-Gallium-Zinc-Oxide (a-IGZO) thin-film transistor (TFT) with SiO2 as an etch-stop-layer (ESL) deposited by medium frequency physical vapor deposition (mf-PVD). The TFTs show field-effect mobility (μFE) of

  4. Two-component transparent TiO2/SiO2 and TiO2/PDMS films as efficient photocatalysts for environmental cleaning

    Czech Academy of Sciences Publication Activity Database

    Novotná, P.; Zita, J.; Krýsa, J.; Kalousek, Vít; Rathouský, Jiří

    2007-01-01

    Roč. 79, č. 2 (2007), s. 179-185 ISSN 0926-3373 R&D Projects: GA MŠk 1M0577 Institutional research plan: CEZ:AV0Z40400503 Keywords : TiO2 * SiO2 * PDMS * thin film Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 4.651, year: 2007

  5. Periodically ordered meso – and macroporous SiO2 thin films and their induced electrochemical activity as a function of pore hierarchy

    Czech Academy of Sciences Publication Activity Database

    Sel, O.; Sallard, S.; Brezesinski, T.; Rathouský, Jiří; Dunphy, D. R.; Collord, A.; Smarsly, B. M.

    2007-01-01

    Roč. 17, č. 16 (2007), s. 3241-3250 ISSN 1616-301X Institutional research plan: CEZ:AV0Z40400503 Keywords : SiO2 * thin films * pore hierarchy * electrochemistry Subject RIV: CG - Electrochemistry Impact factor: 7.496, year: 2007

  6. A Nonvolatile MOSFET Memory Device Based on Mobile Protons in SiO(2) Thin Films

    Energy Technology Data Exchange (ETDEWEB)

    Vanheusden, K.; Warren, W.L.; Devine, R.A.B.; Fleetwood, D.M.; Draper, B.L.; Schwank, J.R.

    1999-03-02

    It is shown how mobile H{sup +} ions can be generated thermally inside the oxide layer of Si/SiO{sub 2}/Si structures. The technique involves only standard silicon processing steps: the nonvolatile field effect transistor (NVFET) is based on a standard MOSFET with thermally grown SiO{sub 2} capped with a poly-silicon layer. The capped thermal oxide receives an anneal at {approximately}1100 C that enables the incorporation of the mobile protons into the gate oxide. The introduction of the protons is achieved by a subsequent 500-800 C anneal in a hydrogen-containing ambient, such as forming gas (N{sub 2}:H{sub 2} 95:5). The mobile protons are stable and entrapped inside the oxide layer, and unlike alkali ions, their space-charge distribution can be controlled and rapidly rearranged at room temperature by an applied electric field. Using this principle, a standard MOS transistor can be converted into a nonvolatile memory transistor that can be switched between normally on and normally off. Switching speed, retention, endurance, and radiation tolerance data are presented showing that this non-volatile memory technology can be competitive with existing Si-based non-volatile memory technologies such as the floating gate technologies (e.g. Flash memory).

  7. Film growth, adsorption and desorption kinetics of indigo on SiO2

    International Nuclear Information System (INIS)

    Scherwitzl, Boris; Resel, Roland; Winkler, Adolf

    2014-01-01

    Organic dyes have recently been discovered as promising semiconducting materials, attributable to the formation of hydrogen bonds. In this work, the adsorption and desorption behavior, as well as thin film growth was studied in detail for indigo molecules on silicon dioxide with different substrate treatments. The material was evaporated onto the substrate by means of physical vapor deposition under ultra-high vacuum conditions and was subsequently studied by Thermal Desorption Spectroscopy (TDS), Auger Electron Spectroscopy, X-Ray Diffraction, and Atomic Force Microscopy. TDS revealed initially adsorbed molecules to be strongly bonded on a sputter cleaned surface. After further deposition a formation of dimers is suggested, which de-stabilizes the bonding mechanism to the substrate and leads to a weakly bonded adsorbate. The dimers are highly mobile on the surface until they get incorporated into energetically favourable three-dimensional islands in a dewetting process. The stronger bonding of molecules within those islands could be shown by a higher desorption temperature. On a carbon contaminated surface no strongly bonded molecules appeared initially, weakly bonded monomers rather rearrange into islands at a surface coverage that is equivalent to one third of a monolayer of flat-lying molecules. The sticking coefficient was found to be unity on both substrates. The desorption energies from carbon covered silicon dioxide calculated to 1.67 ± 0.05 eV for multilayer desorption from the islands and 0.84 ± 0.05 eV for monolayer desorption. Corresponding values for desorption from a sputter cleaned surface are 1.53 ± 0.05 eV for multilayer and 0.83 ± 0.05 eV for monolayer desorption

  8. Film growth, adsorption and desorption kinetics of indigo on SiO2

    Science.gov (United States)

    Scherwitzl, Boris; Resel, Roland; Winkler, Adolf

    2014-05-01

    Organic dyes have recently been discovered as promising semiconducting materials, attributable to the formation of hydrogen bonds. In this work, the adsorption and desorption behavior, as well as thin film growth was studied in detail for indigo molecules on silicon dioxide with different substrate treatments. The material was evaporated onto the substrate by means of physical vapor deposition under ultra-high vacuum conditions and was subsequently studied by Thermal Desorption Spectroscopy (TDS), Auger Electron Spectroscopy, X-Ray Diffraction, and Atomic Force Microscopy. TDS revealed initially adsorbed molecules to be strongly bonded on a sputter cleaned surface. After further deposition a formation of dimers is suggested, which de-stabilizes the bonding mechanism to the substrate and leads to a weakly bonded adsorbate. The dimers are highly mobile on the surface until they get incorporated into energetically favourable three-dimensional islands in a dewetting process. The stronger bonding of molecules within those islands could be shown by a higher desorption temperature. On a carbon contaminated surface no strongly bonded molecules appeared initially, weakly bonded monomers rather rearrange into islands at a surface coverage that is equivalent to one third of a monolayer of flat-lying molecules. The sticking coefficient was found to be unity on both substrates. The desorption energies from carbon covered silicon dioxide calculated to 1.67 ± 0.05 eV for multilayer desorption from the islands and 0.84 ± 0.05 eV for monolayer desorption. Corresponding values for desorption from a sputter cleaned surface are 1.53 ± 0.05 eV for multilayer and 0.83 ± 0.05 eV for monolayer desorption.

  9. Role of HfO2/SiO2 thin-film interfaces in near-ultraviolet absorption and pulsed laser damage

    Science.gov (United States)

    Papernov, Semyon; Kozlov, Alexei A.; Oliver, James B.; Smith, Chris; Jensen, Lars; Günster, Stefan; Mädebach, Heinrich; Ristau, Detlev

    2017-01-01

    The role of thin-film interfaces in the near-ultraviolet (near-UV) absorption and pulsed laser-induced damage was studied for ion-beam-sputtered and electron-beam-evaporated coatings comprised from HfO2 and SiO2 thin-film pairs. To separate contributions from the bulk of the film and from interfacial areas, absorption and damage threshold measurements were performed for a one-wave (355-nm wavelength) thick, HfO2 single-layer film and for a film containing seven narrow HfO2 layers separated by SiO2 layers. The seven-layer film was designed to have a total optical thickness of HfO2 layers, equal to one wave at 355 nm and an E-field peak and average intensity similar to a single-layer HfO2 film. Absorption in both types of films was measured using laser calorimetry and photothermal heterodyne imaging. The results showed a small contribution to total absorption from thin-film interfaces as compared to HfO2 film material. The relevance of obtained absorption data to coating near-UV, nanosecond-pulse laser damage was verified by measuring the damage threshold and characterizing damage morphology. The results of this study revealed a higher damage resistance in the seven-layer coating as compared to the single-layer HfO2 film in both sputtered and evaporated coatings. The results are explained through the similarity of interfacial film structure with structure formed during the codeposition of HfO2 and SiO2 materials.

  10. Adsorption and self-assembly of M13 phage into directionally organized structures on C and SiO2 films.

    Science.gov (United States)

    Moghimian, Pouya; Srot, Vesna; Rothenstein, Dirk; Facey, Sandra J; Harnau, Ludger; Hauer, Bernhard; Bill, Joachim; van Aken, Peter A

    2014-09-30

    A versatile method for the directional assembly of M13 phage using amorphous carbon and SiO2 thin films was demonstrated. A high affinity of the M13 phage macromolecules for incorporation into aligned structures on an amorphous carbon surface was observed at the concentration range, in which the viral nanofibers tend to disorder. In contrast, the viral particles showed less freedom to adopt an aligned orientation on SiO2 films when deposited in close vicinity. Here an interpretation of the role of the carbon surface in significant enhancement of adsorption and generation of viral arrays with a high orientational order was proposed in terms of surface chemistry and competitive electrostatic interactions. This study suggests the use of amorphous carbon substrates as a template for directional organization of a closely-packed and two-dimensional M13 viral film, which can be a promising route to mineralize a variety of smooth and homogeneous inorganic nanostructure layers.

  11. In-situ grown CNTs modified SiO2/C composites as anode with improved cycling stability and rate capability for lithium storage

    Science.gov (United States)

    Wang, Siqi; Zhao, Naiqin; Shi, Chunsheng; Liu, Enzuo; He, Chunnian; He, Fang; Ma, Liying

    2018-03-01

    Silica (SiO2) is regarded as one of the most promising anode materials for lithium ion batteries owing to its high theoretical specific capacity, relatively low operation potentials, abundance, environmental benignity and low cost. However, the low intrinsic electrical conductivity and large volume change of SiO2 during the discharge/charge cycles usually results in poor electrochemical performance. In this work, carbon nanotubes (CNTs) modified SiO2/C composites have been fabricated through an in-situ chemical vapor deposition method. The results show that the electrical conductivity of the SiO2/C/CNTs is visibly enhanced through a robust connection between the CNTs and SiO2/C particles. Compared with the pristine SiO2 and SiO2/C composites, the SiO2/C/CNTs composites display a high initial capacity of 1267.2 mA h g-1. Besides, an excellent cycling stability with the capacity of 315.7 mA h g-1 is achieved after 1000th cycles at a rate of 1 A g-1. The significantly improved electrochemical properties of the SiO2/C/CNTs composites are mainly attributed to the formation of three dimensional CNT networks in the SiO2/C substrate, which can not only shorten the Li-ion diffusion path but also relieve the volume change during the lithium-ion insertion/extraction processes.

  12. New intelligent multifunctional SiO2/VO2 composite films with enhanced infrared light regulation performance, solar modulation capability, and superhydrophobicity.

    Science.gov (United States)

    Wang, Chao; Zhao, Li; Liang, Zihui; Dong, Binghai; Wan, Li; Wang, Shimin

    2017-01-01

    Highly transparent, energy-saving, and superhydrophobic nanostructured SiO 2 /VO 2 composite films have been fabricated using a sol-gel method. These composite films are composed of an underlying infrared (IR)-regulating VO 2 layer and a top protective layer that consists of SiO 2 nanoparticles. Experimental results showed that the composite structure could enhance the IR light regulation performance, solar modulation capability, and hydrophobicity of the pristine VO 2 layer. The transmittance of the composite films in visible region ( T lum ) was higher than 60%, which was sufficient to meet the requirements of glass lighting. Compared with pristine VO 2 films and tungsten-doped VO 2 film, the near IR control capability of the composite films was enhanced by 13.9% and 22.1%, respectively, whereas their solar modulation capability was enhanced by 10.9% and 22.9%, respectively. The water contact angles of the SiO 2 /VO 2 composite films were over 150°, indicating superhydrophobicity. The transparent superhydrophobic surface exhibited a high stability toward illumination as all the films retained their initial superhydrophobicity even after exposure to 365 nm light with an intensity of 160 mW . cm -2 for 10 h. In addition, the films possessed anti-oxidation and anti-acid properties. These characteristics are highly advantageous for intelligent windows or solar cell applications, given that they can provide surfaces with anti-fogging, rainproofing, and self-cleaning effects. Our technique offers a simple and low-cost solution to the development of stable and visible light transparent superhydrophobic surfaces for industrial applications.

  13. A pentacene thin film transistor with good performance using sol-gel derived SiO2 gate dielectric layer

    Science.gov (United States)

    Cavas, M.; Al-Ghamdi, Ahmed A.; Al-Hartomy, O. A.; El-Tantawy, F.; Yakuphanoglu, F.

    2013-02-01

    A low-voltage pentacene field-effect transistor with sol-gel derived SiO2 gate dielectric was fabricated. The mobility of the transistor was achieved as high as 1.526 cm2/V on the bared SiO2/Si substrate by a higher dielectric constant. The interface state density for the transistor was found to vary from 3.8 × 1010 to 7.5 × 1010 eV-1 cm-2 at frequency range of 100 kHz-1 MHz. It is evaluated that the SiO2 derived by low cost sol-gel is quite a promising candidate as a gate dielectric layer for low-voltage pentacene field-effect transistor.

  14. Silver nanoparticle deposition on inverse opal SiO2 films embedded in protective polypropylene micropits for SERS applications

    Science.gov (United States)

    Ammosova, Lena; Ankudze, Bright; Philip, Anish; Jiang, Yu; Pakkanen, Tuula T.; Pakkanen, Tapani A.

    2018-01-01

    Common methods to fabricate surface enhanced Raman scattering (SERS) substrates with controlled micro-nanohierarchy are often complex and expensive. In this study, we demonstrate a simple and cost effective method to fabricate SERS substrates with complex geometries. Microworking robot structuration is used to pattern a polypropylene (PP) substrate with micropits, facilitating protective microenvironment for brittle SiO2 inverse opal (IO) structure. Hierarchical SiO2 IO patterns were obtained using polystyrene (PS) spheres as a sacrificial template, and were selectively embedded into the hydrophilized PP micropits. The same microworking robot technique was subsequently used to deposit silver nanoparticle ink into the SiO2 IO cavities. The fabricated multi-level micro-nanohierarchy surface was studied to enhance Raman scattering of the 4-aminothiophenol (4-ATP) analyte molecule. The results show that the SERS performance of the micro-nanohierarchical substrate increases significantly the Raman scattering intensity compared to substrates with structured 2D surface geometries.

  15. Effect of a SiO2 buffer layer on the characteristics of In2O3-ZnO-SnO2 films deposited on PET substrates

    International Nuclear Information System (INIS)

    Woo, B.-J.; Hong, J.-S.; Kim, S.-T.; Kim, H.-M.; Park, S.-H.; Kim, J.-J.; Ahn, J.-S.

    2006-01-01

    Transparent and conducting In 2 O 3 -ZnO-SnO 2 (IZTO) thin films were prepared on flexible PET substrates at room temperature by using an ion-gun-assisted sputtering technique. We mainly investigated the effect of a SiO 2 buffer layer, deposited in-between the film and the PET substrate, on the electrical stability of the film under various external stresses caused by moist-heat or violent temperature variations. The insertion of the SiO 2 layer improves structural, optical and electrical properties of the films: The IZTO/SiO 2 /PET film with a buffer shows a change (∼4 %) in the sheet resistance much smaller than that of the IZTO/PET film without a buffer (∼22 %), against a severe thermal stress of the repeated processes between quenching at -25 .deg. C and annealing at 100 .deg. C for 5 min at each process. Under a moist-heat stress at 90 % relative humidity at 80 .deg. C, the IZTO/SiO 2 /PET film responds with only a slight change (∼8.5 %) in the sheet resistance from 30.2 to 33.0 Ω/□ after being exposed for 240 h. The enhanced stability is understood to be the result of the buffer layers acting as a blocking barrier to water vapor or organic solvents diffusing from the PET substrate during deposition or annealing.

  16. In situ coating of flame-made TiO2 particles with nanothin SiO2 films.

    Science.gov (United States)

    Teleki, Alexandra; Heine, Martin C; Krumeich, Frank; Akhtar, M Kamal; Pratsinis, Sotiris E

    2008-11-04

    Rutile TiO2 particles made by flame spray pyrolysis (FSP) were coated in a single step with SiO2 layers in an enclosed flame reactor. This in situ particle coating was accomplished by a hollow ring delivering hexamethyldisiloxane (HMDSO) vapor (precursor to SiO2) through multiple jets in swirl cross-flow to Al-doped nanostructured rutile TiO2 aerosol freshly made by FSP of a solution of titanium tetraisopropoxide and aluminum sec-butoxide in xylene. The as-prepared powders were characterized by (scanning) transmission electron microscopy (STEM and TEM), energy dispersive X-ray analysis, X-ray diffraction, nitrogen adsorption, electrophoretic mobility, DC plasma optical emission (DCP-OES), and Fourier transform infrared (FT-IR) spectroscopy. The coating quality was assessed further by the photocatalytic oxidation of isopropyl alcohol to acetone. The effect of HMDSO injection point and vapor concentration on product particle morphology was investigated. The titania particles were uniformly SiO2-coated with controlled and uniform thickness at a production rate of about 30 g h(-1) and exhibited limited, if any, photoactivity. In contrast, spraying and combusting equivalent mixtures of the above Si/Al/Ti precursors in the above reactor (without delivering HMDSO through the hollow ring) resulted in particles segregated in amorphous (SiO2) and crystalline (TiO2) domains which exhibited high photocatalytic activity.

  17. Simultaneous ultra-long data retention and low power based on Ge10Sb90/SiO2 multilayer thin films

    Science.gov (United States)

    You, Haipeng; Hu, Yifeng; Zhu, Xiaoqin; Zou, Hua; Song, Sannian; Song, Zhitang

    2018-02-01

    In this article, Ge10Sb90/SiO2 multilayer thin films were prepared to improve thermal stability and data retention for phase change memory. Compared with Ge10Sb90 monolayer thin film, Ge10Sb90 (1 nm)/SiO2 (9 nm) multilayer thin film had higher crystallization temperature and resistance contrast between amorphous and crystalline states. Annealed Ge10Sb90 (1 nm)/SiO2 (9 nm) had uniform grain with the size of 15.71 nm. After annealing, the root-mean-square surface roughness for Ge10Sb90 (1 nm)/SiO2 (9 nm) thin film increased slightly from 0.45 to 0.53 nm. The amorphization time for Ge10Sb90 (1 nm)/SiO2 (9 nm) thin film (2.29 ns) is shorter than Ge2Sb2Te5 (3.56 ns). The threshold voltage of a cell based on Ge10Sb90 (1 nm)/SiO2 (9 nm) (3.57 V) was smaller than GST (4.18 V). The results indicated that Ge10Sb90/SiO2 was a promising phase change thin film with high thermal ability and low power consumption for phase change memory application.

  18. Microporous SiO2-based solid electrolyte with improved polarization response for 0.8 V transparent thin-film transistors

    International Nuclear Information System (INIS)

    Sun Jia; Jiang Jie; Lu Aixia; Wan Qing

    2010-01-01

    The polarization mechanism of a microporous SiO 2 -based solid electrolyte is developed and three polarizations (electric double layer formation, ionic relaxation and dipole relaxation) are identified. The polarization response of the microporous SiO 2 -based solid electrolyte is optimized by tuning the deposition temperature and the improved specific capacitance is 1 μF cm -2 at 1 kHz and remains above 0.6 μF cm -2 even at 10 kHz. Ultralow-voltage transparent In-Zn-O thin-film transistors (TFTs) gated by such dielectrics are fabricated at low temperatures. The field-effect mobility, current on/off ratio and subthreshold swing are estimated to be 46.2 cm 2 V -1 s -1 , ∼10 6 and 69 mV/decade, respectively. Such TFTs hold promise for portable electronic applications.

  19. Purely electronic switching with high uniformity, resistance tunability, and good retention in Pt-dispersed SiO2 thin films for ReRAM.

    Science.gov (United States)

    Choi, Byung Joon; Chen, Albert B K; Yang, Xiang; Chen, I-Wei

    2011-09-01

    Resistance switching memory operating by a purely electronic switching mechanism, which was first realized in Pt-dispersed SiO2 thin films, satisfies criteria including high uniformity, fast switching speed, and long retention for non-volatile memory application. This resistive element obeys Ohm's law for the area dependence, but its resistance exponentially increases with the film thickness, which provides new freedom to tailor the device characteristics. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  20. Photoprocesses in 7-hydroxy coumarins molecules in solutions and SiO2 sol–gel films – Materials for optical chemical sensorics

    International Nuclear Information System (INIS)

    Selivanov, N.I.; Samsonova, L.G.; Kopylova, T.N.

    2016-01-01

    The paper investigates the spectral properties of protolytic forms of three substituted 7-hydroxy coumarin molecules in aqueous ethanol solutions and SiO 2 films. It explains spectral-and-luminescent properties of coumarins in the produced films. It is found that in aqueous ethanol solutions and sol–gel films, upon excitation in the S 1 state, there is a reaction of proton phototransfer from the O–H group of neutral coumarins molecules to the water molecule with development of anionic forms solvated by hydroxonium ions. We studied sensory properties of compounds in the films to the ammonia gas in terms of changes in their fluorescent properties and revealed the reasons causing such changes. We demonstrated the prospects of using films with one of the investigated coumarins as the ammonia gas sensitive material of an optical chemical sensor.

  1. The effects of irradiation and proton implantation on the density of mobile protons in SiO2 films

    International Nuclear Information System (INIS)

    Vanheusden, K.

    1998-04-01

    Proton implantation into the buried oxide of Si/SiO 2 /Si structures does not introduce mobile protons. The cross section for capture of radiation-induced electrons by mobile protons is two orders of magnitude smaller than for electron capture by trapped holes. The data provide new insights into the atomic mechanisms governing the generation and radiation tolerance of mobile protons in SiO 2 . This can lead to improved techniques for production and radiation hardening of radiation tolerant memory devices

  2. Water adsorption, solvation and deliquescence of alkali halide thin films on SiO2 studied by ambient pressure X-ray photoelectron spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Arima, Kenta; Jiang, Peng; Deng, Xingyi; Bluhm, Henrik; Salmeron, Miquel

    2010-03-31

    The adsorption of water on KBr thin films evaporated onto SiO2 was investigated as a function of relative humidity (RH) by ambient pressure X-ray photoelectron spectroscopy. At 30percent RH adsorbed water reaches a coverage of approximately one monolayer. As the humidity continues to increase, the coverage of water remains constant or increases very slowly until 60percent RH, followed by a rapid increase up to 100percent RH. At low RH a significant number of the Br atoms are lost due to irradiation damage. With increasing humidity solvation increases ion mobility and gives rise to a partial recovery of the Br/K ratio. Above 60percent RH the increase of the Br/K ratio accelerates. Above the deliquescence point (85percent RH), the thickness of the water layer continues to increase and reaches more than three layers near saturation. The enhancement of the Br/K ratio at this stage is roughly a factor 2.3 on a 0.5 nm KBr film, indicating a strong preferential segregation of Br ions to the surface of the thin saline solution on SiO2.

  3. Room-Temperature Voltage Stressing Effects on Resistive Switching of Conductive-Bridging RAM Cells with Cu-Doped SiO2 Films

    Directory of Open Access Journals (Sweden)

    Jian-Yang Lin

    2014-01-01

    Full Text Available SiO2 or Cu-doped SiO2 (Cu:SiO2 insulating films combined with Cu or W upper electrodes were constructed on the W/Si substrates to form the conductive-bridging RAM (CB-RAM cells. The CB-RAMs were then subjected to a constant-voltage stressing (CVS at room temperature. The experimental results show that the room-temperature CVS treatment can effectively affect the current conduction behavior and stabilize the resistive switching of the memory cells. After the CVS, the current conduction mechanisms in the high resistance state during the set process of the Cu/Cu:SiO2/W cell can be changed from Ohm’s law and the space charge limited conduction to Ohm’s law, the Schottky emission, and the space charge limited conduction. Presumably, it is due to the breakage of the conduction filaments during the CVS treatment that the conduction electrons cannot go back to the back electrode smoothly.

  4. Design of laser-driven SiO2-YAG:Ce composite thick film: Facile synthesis, robust thermal performance, and application in solid-state laser lighting

    Science.gov (United States)

    Xu, Jian; Liu, Bingguo; Liu, Zhiwen; Gong, Yuxuan; Hu, Baofu; Wang, Jian; Li, Hui; Wang, Xinliang; Du, Baoli

    2018-01-01

    In recent times, there have been rapid advances in the solid-state laser lighting technology. Due to the large amounts of heat accumulated from the high flux laser radiation, color conversion materials used in solid-state laser lighting devices should possess high durability, high thermal conductivity, and low thermal quenching. The aim of this study is to develop a thermally robust SiO2-YAG:Ce composite thick film (CTF) for high-power solid-state laser lighting applications. Commercial colloidal silica which was used as the source of SiO2, played the roles of an adhesive, a filler, and a protecting agent. Compared to the YAG:Ce powder, the CTF exhibits remarkable thermal stability (11.3% intensity drop at 200 °C) and durability (4.5% intensity drop after 1000 h, at 85 °C and 85% humidity). Furthermore, the effects of the substrate material and the thickness of the CTF on the laser lighting performance were investigated in terms of their thermal quenching and luminescence saturation behaviors, respectively. The CTF with a thickness of 50 μm on a sapphire substrate does not show luminescence saturation, despite a high-power density of incident radiation i.e. 20 W/mm2. These results demonstrate the potential applicability of the CTF in solid-state laser lighting devices.

  5. High-resolution ellipsometric study of an n-alkane film, dotriacontane, adsorbed on a SiO2 surface

    DEFF Research Database (Denmark)

    Volkmann, U.G.; Pino, M.; Altamirano, L.A.

    2002-01-01

    to the interface. At still higher coverages and at temperatures below the bulk melting point at T-b=341 K, solid bulk particles coexist on top of the "perpendicular film." For higher temperatures in the range T-bT-s, a uniformly thick fluid film wets to the parallel film phase. This structure of the alkane/SiO2...

  6. Ti-catalyzed HfSiO4 formation in HfTiO4 films on SiO2 studied by Z-contrast scanning electron microscopy

    Directory of Open Access Journals (Sweden)

    Elizabeth Ellen Hoppe

    2013-08-01

    Full Text Available Hafnon (HfSiO4 as it is initially formed in a partially demixed film of hafnium titanate (HfTiO4 on fused SiO2 is studied by atomic number (Z contrast high resolution scanning electron microscopy, x-ray diffraction, and Raman spectroscopy and microscopy. The results show exsoluted Ti is the catalyst for hafnon formation by a two-step reaction. Ti first reacts with SiO2 to produce a glassy Ti-silicate. Ti is then replaced by Hf in the silicate to produce HfSiO4. The results suggest this behavior is prototypical of other Ti-bearing ternary or higher order oxide films on SiO2 when film thermal instability involves Ti exsolution.

  7. Optical and Electrical Characterization of SiO2 films deposited at low temperature by means of remote ICPECVD

    NARCIS (Netherlands)

    Boogaard, A.; Kovalgin, Alexeij Y.; Brunets, I.; Holleman, J.; Schmitz, Jurriaan

    2007-01-01

    Silicon dioxide films were deposited by means of remote inductively coupled plasma enhanced chemical vapor deposition (ICPECVD) in Ar-N2O-SiH4 plasma at 150 °C and pressures between 1 and 6 Pa. We found that the films contained a high amount of positive oxide charge and exhibited large leakage

  8. Surface viscoelasticity studies of Gd2O3, SiO2 optical thin films and multilayers using force modulation and force-distance scanning probe microscopy

    International Nuclear Information System (INIS)

    Sahoo, N.K.; Thakur, S.; Senthilkumar, M.; Das, N.C.

    2003-01-01

    The single and multilayer of Gd 2 O 3 and SiO 2 thin films deposited through reactive electron beam evaporation have been studied for their viscoelasticity properties and optical spectral stability using multimode scanning probe microscope and spectrophotometric techniques. A conspicuous changes in viscoelasticity properties and surface topographies have been observed with the Gd 2 O 3 films deposited under various oxygen pressures. The scanning probe measurements on the multilayer filters fabricated using these film materials for laser wavelengths of 248 nm (KrF) and 355 nm (Nd:Yag-III) have shown superior viscoelasticity property, which is not the case with the most conventional multilayers. The results were correlated with the long-term spectral stability that has been studied by recording transmittance spectra of these filters at a time interval of 10 months. Both the multilayer filters have shown excellent temporal spectral stabilities with a relatively better result for the 248 nm reflection filter. Further analysis has shown a very good co-relationship in the spectral stability and viscoelasticity properties in these multilayers

  9. Room temperature ferromagnetism and ferroelectricity in strained multiferroic BiFeO3 thin films on La0.7Sr0.3MnO3/SiO2/Si substrates

    International Nuclear Information System (INIS)

    Ramírez-Camacho, M.C.; Sánchez-Valdés, C.F.; Gervacio-Arciniega, J.J.; Font, R.; Ostos, C.; Bueno-Baques, D.; Curiel, M.; Sánchez-Llamazares, J.L.

    2017-01-01

    A novel ferromagnetic state coexisting with ferroelectric ordering at room temperature in strained BiFeO 3 (BFO) thin films grown using a sputtering technique on La 0.7 Sr 0.3 MnO 3 /SiO 2 /Si(100) (LSMO/SOS) substrates is reported. The properties of BFO films with different thicknesses (t BFO  = 15, 50, 70, 120, and 140 nm) on 40 nm LSMO layers are explored. [012] out-of-plane highly textured BFO/LSMO stacks grew with rhombohedral structures. LSMO layers are nanostructured in nature, constituted by ferromagnetic single-domain nanoregions induced by the constrain of the SiO 2 surface, with T C ∼200 K and high coercive field (H C ) of ∼1100 Oe at 2.5 K. BFO films grew epitaxially nanostructured on LSMO, exhibiting ∼4 nm spherical nanoregions. The BFO layers show typical antiferromagnetic behavior (in a greater volume fraction) when made thicker (t BFO  > 70 nm). The thinner films (t BFO  < 50 nm) display ferromagnetic behavior with T C  > 400 K, H C  ∼ 1600 Oe for 15 nm and ∼1830 Oe for 50 nm. We propose that such ferromagnetic behavior is originated by the establishment of a new magnetic configuration in the Fe 3+ −O−Fe 3+ sublattice of the BFO structure, induced by strong hybridization at the interface as consequence of superexchange coupling interactions with the ferromagnetic Mn 3+ −O−Mn 3+ /Mn 4+ sublattice of LSMO. All BFO layers show excellent ferroelectric and piezoelectric properties (coercive field ∼ 740 kV/cm, and d 33  = 23 p.m./V for 50 nm; ∼200 kV/cm and 55 p.m./V for 140 nm), exhibiting 180° and 109° DWs structures depending on the thickness. Such multiferroic properties predict the potential realization of new magneto-electronic devices integrated with Si technology.

  10. Deposition of High-Quality SiO2 Insulating Films at Low Temperatures by means of Remote PECVD

    NARCIS (Netherlands)

    Boogaard, A.; Roesthuis, R.; Brunets, I.; Aarnink, Antonius A.I.; Kovalgin, Alexeij Y.; Holleman, J.; Wolters, Robertus A.M.; Schmitz, Jurriaan

    2008-01-01

    Silicon dioxide films were deposited by means of remote inductively coupled plasma enhanced chemical vapor deposition (ICPECVD) in Ar-N2O-SiH4 plasma at 150 °C and pressures between 1 and 6 Pa. The gas phase contained 0.08% of SiH4 and 18% of N2O. We observed that, at a total pressure of 1 Pa, the

  11. Preparation and Faraday rotation of Nd2O3 doped Fe2O3-SiO2 nano-composite films

    Science.gov (United States)

    Fang, Xueling; Yao, Lanfang; Li, Lin; Tian, Lin-lin; Xu, Ruiqing; Wang, Shuo

    2011-02-01

    Magneto-optic properties of magnetic materials have much influence on the performance of these current sensors. For practical using, it is generally demanded that the sensing materials had the good magneto-optic properties of large Faraday rotation. Among the most attractive properties of the transparent materials containing Fe2O3 are those related to the magneto-optical effects. The Sol-gel processes are extensively used for the preparation of optical or magneto-optical nano-composite materials though the incorporation of metal ions in the silica matrix. In this study, the Nd2O3 doped Fe2O3-SiO2 nano-composite films with different concentrations of Nd2O3, heated temperature and the number of layers were prepared by sol-gel method. The dependence of Faraday rotation angle of films is studied at room temperature. We find that appropriate concentrations of Nd2O3 (Nd/Si=0.011) doped has improved magneto-optic properties of higher Faraday rotation angle, the θF value increases with the decrease of the temperature below 500°C, the absolute value of Faraday rotation angle increases as the number of layers increases.

  12. Fabrication and characterization of Er+3 doped SiO2/SnO2 glass-ceramic thin films for planar waveguide applications

    Science.gov (United States)

    Guddala, S.; Chiappini, A.; Armellini, C.; Turell, S.; Righini, G. C.; Ferrari, M.; Narayana Rao, D.

    2015-02-01

    Glass-ceramics are a kind of two-phase materials constituted by nanocrystals embedded in a glass matrix and the respective volume fractions of crystalline and amorphous phase determine the properties of the glass-ceramics. Among these properties transparency is crucial in particular when confined structures, such as, dielectric optical waveguides, are considered. Moreover, the segregation of dopant rare-earth ions, like erbium, in low phonon energy crystalline medium makes these structures more promising in the development of waveguide amplifiers. Here we are proposing a new class of low phonon energy tin oxide semiconductor medium doped silicate based planar waveguides. Er3+ doped (100-x) SiO2-xSnO2 (x= 10, 20, 25 and 30mol%), glass-ceramic planar waveguide thin films were fabricated by a simple sol-gel processing and dip coating technique. XRD and HRTEM studies indicates the glass-ceramic phase of the film and the dispersion of ~4nm diameter of tin oxide nanocrystals in the amorphous phase of silica. The spectroscopic assessment indicates the distribution of the dopant erbium ions in the crystalline medium of tin oxide. The observed low losses, 0.5±0.2 dB/cm, at 1.54 μm communication wavelength makes them a quite promising material for the development of high gain integrated optical amplifiers.

  13. Rational Design and Construction of Well-Organized Macro-Mesoporous SiO2/TiO2Nanostructure toward Robust High-Performance Self-Cleaning Antireflective Thin Films.

    Science.gov (United States)

    Jin, Binbin; He, Junhui; Yao, Lin; Zhang, Yue; Li, Jing

    2017-05-24

    Antireflection (AR) thin films on optical substrates are of great significance in high-performance optoelectronic devices. Here, we present a rational design and construction of well-organized macro-mesoporous nanostructure toward robust high-performance self-cleaning antireflective thin films on the basis of effective medium theory and finite difference time domain (FDTD) simulations that combine the optical design principle. A hierarchical macro-mesoporous SiO 2 thin film with very high porosity and gradient refractive indexes works as a λ/4-wavelength AR layer and significantly suppresses the reflection in the range from 350 to 1200 nm. Even after dip-coating a layer of high refractive index TiO 2 nanocrystals, the nanostructured thin film still exhibits broadband AR properties which are much superior to conventional flat SiO 2 /TiO 2 thin films, especially in the range of 350-500 nm. In addition, the obtained thin film exhibits photocatalytic self-cleaning and durable superhydrophilicity. The advantages brought by the well-organized macro-mesoporous structure are also testified through comparing to the solely mesoporous SiO 2 /TiO 2 film counterpart. Moreover, the pencil hardness test and sandpaper abrasion test show favorable robustness and functional durability of the thin film, which make it extremely attractive for practical applications in optical devices, display devices, and photovoltaic cells.

  14. Stress relaxation in dual ion beam sputtered Nb2O5 and SiO2 thin films: application in a Fabry–Pérot filter array with 3D nanoimprinted cavities

    International Nuclear Information System (INIS)

    Ullah, Anayat; Wilke, Hans; Memon, Imran; Shen, Yannan; Nguyen, Duc Toan; Woidt, Carsten; Hillmer, Hartmut

    2015-01-01

    Miniaturized spectrometers can be implemented using Fabry–Pérot (FP) filter arrays. Such filters are defined by two parallel mirrors with a resonance cavity in between. For high optical quality, ion beam sputtered distributed Bragg reflectors (DBRs), with alternating high and low refractive index material pairs, can be used as the FP mirrors; while 3D nanoimprint technology provides an efficient way of implementing multiple organic FP cavities of different heights in a single step. However, the high residual stress in ion beam sputtered films results in poor adhesion between the DBR films and the organic polymer cavities, causing debonding of the DBR. Therefore, the residual stress of the ion beam sputtered films forming the DBRs must be reduced. Niobium pentoxide (Nb 2 O 5 ) and silicon dioxide (SiO 2 ) are used as the DBR materials in this work due to their high index contrast, resulting in high reflectivity for only a few alternating pairs. Stress relaxation in ion beam sputtered Nb 2 O 5 and SiO 2 films is achieved in this work by deposition under simultaneous high energy ion bombardment (oxygen and argon gas mixture) from a second ion source. Using this technique, the film density and hence compressive film stress for both Nb 2 O 5 and SiO 2 films is reduced without introducing any additional optical absorption in the films. FP filter arrays fabricated with stress reduced Nb 2 O 5 and SiO 2 as DBR films exhibit high optical and mechanical performance, with good adhesion between the films and the polymer cavity. (paper)

  15. Fe/Ni thin films temperature investigation with MgO and SiO2 interfaces by ferromagnetic resonance

    International Nuclear Information System (INIS)

    Zyubin, A; Orlova, A; Astashonok, A; Kupriyanova, G; Nevolin, V

    2011-01-01

    In this work the temperature study of magnetic – resonance properties of the structures such as Fe/MgO/Ni, Fe/SiO2/Ni differing thickness of spacer and of method of preparation was carried out by FMR. These systems are investigated to estimate their applicability in model creation experiments for a spintronics devices research [1–4]. The special attention was given to the temperature dependence research of three layer films linewidths. The out-of-plane temperature dependences of FMR signal position and line widths have been measured for Fe/Ni samples with MgO and Si/SiO2 interfaces in static position of 0 and 90 degrees rotation angle to the external static magnetic field. The extracted magnetic parameters such as linewidths and resonance field position were studied.

  16. Degradation of TiO2 and/or SiO2 hybrid films doped with different cationic dyes

    International Nuclear Information System (INIS)

    Purcar, Violeta; Caprarescu, Simona; Donescu, Dan; Petcu, Cristian; Stamatin, Ioan; Ianchis, Raluca; Stroescu, Hermine

    2013-01-01

    Hybrid thin films, silica–titanium oxides and silica–aluminum oxides, designed based on the sol–gel process are evaluated as catalysts in the photo-degradation of the cationic dyes. Silica matrices from different precursors with various organic functional groups and cross-linked with titanium or aluminum agents (tetraisopropyl orthotitanate and aluminum sec-butoxide) allow the surface property tailoring related to the high capacity of the dye adsorption respective, high photo-degradation activity. The cationic dyes (methylene blue, rhodamine B, crystal violet, malachite green) embedded on the hybrid silica matrix, under ultraviolet light, have a first order kinetics of photodegradation. The cross-linking agents play a key role in the photocatalytic degradation and silica matrix as dye absorbent. The photo-degradation rate for the binary system derived from methyltriethoxysilane/vinyltriethoxysilane precursors with both cross linkers showed a significant improvement by comparison with other hybrid materials. The significant increasing in the photodecomposition rate is related to the capacity to generate additional oxidizing species by each silica hybrid compounds. - Highlights: ► Dyes display different electrostatic interactions to the silica matrix. ► Cross-linking agent influences the photocatalytic degradation of dyes. ► Photodegradation reaction obeyed the rules of a pseudo-first-order kinetic reaction. ► UV radiation can be the origin of the photodegradation

  17. Determinação da espessura de filme bioativo SiO2-CaO-P2O5 obtido via sol-gel Evaluation of the thickness of SiO2-CaO-P2O5 bioactive film obtained via sol-gel

    Directory of Open Access Journals (Sweden)

    S. R. Federman

    2009-06-01

    Full Text Available Foi preparado um filme bioativo do sistema SiO2-CaO-P2O5 via sol-gel pela hidrólise e condensação de TEOS, TEP, álcool e nitrato de cálcio em meio ácido. Após a mistura, a solução sintetizada serviu para revestir substrato de aço inoxidável pelo método de imersão utilizando baixa velocidade de emersão. Após o revestimento, o compósito foi tratado termicamente em diferentes temperaturas durante 1 h, com o propósito de avaliar a influência do tratamento térmico especificamente na espessura do filme revestindo o substrato metálico. A influência da variação da temperatura foi acessada através das técnicas de microscopia eletrônica de varredura (MEV e espectroscopia de centelhamento (GDS. Os resultados comprovaram a influência da temperatura na espessura do filme obtido. A reduzida espessura do filme bioativo foi determinada por MEV e GDS.A sol-gel bioactive film of the SiO2-CaO-P2O5 system was prepared, via a sol-gel method, by hydrolysis and condensation of tetraethylortosilicate [TEOS], triethylphosphate [TEP] and hydrated calcium nitrate under acidic conditions. After mixing, the as-obtained solution was used to coat stainless steel substrates by dip-coating in a low withdraw speed. After deposition, the composite was heat treated at different temperatures for 1 h to evaluate the temperature influence on the thickness of the coating over the stainless steel substrate. The development of the coating thickness was accessed through the techniques of scanning electronic microscopy (SEM and glow discharge spectroscopy (GDS. Results indicated the heat treatment effect on the film thickness. Also, the SEM and the GDS techniques were used to determine the thin bioactive coating thickness.

  18. DEPENDENCE OF THE SURFACE-ENHANCED RAMAN SCATTERING SIGNAL ON THE SHAPE OF SILVER NANOSTRUCTURES GROWN IN THE SiO2 /n-Si POROUS TEMPLATE

    Directory of Open Access Journals (Sweden)

    D. V. Yakimchuk

    2017-01-01

    Full Text Available Surface-enhanced Raman scattering is a powerful method used in chemoand biosensorics. The aim of this work was to determine the relationship between the signal of Surface-enhanced Raman scattering and the shape of silver nanostructures under the influence of laser radiation with different power.Plasmonic nanostructures were synthesized in silicon dioxide pores on monocrystalline silicon n-type substrate. The pores were formed using ion-track technology and selective chemical etching. Silver deposition was carried out by galvanic displacement method. Synthesis time was chosen as a parameter that allows controlling the shape of a silver deposit in the pores of silicon dioxide on the surface of single-crystal n-silicon during electrodeless deposition. Deposition time directly effects on the shape of metal nanostructures.Analysis of the dynamics of changing the morphology of the metal deposit showed that as the deposition time increases, the metal evolves from individual metallic crystallites within the pores at a short deposition time to dendritic-like nanostructures at a long time. The dependence of the intensity of Surface-enhanced Raman scattering spectra on the shape of the silver deposit is studied at the powers of a green laser (λ = 532 nm from 2.5 μW to 150 μW on the model dye analyte Rodamin 6G. The optimum shape of the silver deposit and laser power is analyzed from this point of view design of active surfaces for Surface-enhanced Raman scattering with nondestructive control of small concentrations of substances.The silver nanostructures obtained in porous template SiO2 on n-type silicon substrate could be used as plasmon-active surfaces for nondestructive investigations of substances with low concentrations at low laser powers. 

  19. Structural and interfacial characteristics of thin (2 films grown by electron cyclotron resonance plasma oxidation on [100] Si substrates

    International Nuclear Information System (INIS)

    Nguyen, T.D.; Carl, D.A.; Hess, D.W.; Lieberman, M.A.; Gronsky, R.

    1991-04-01

    The feasibility of fabricating ultra-thin SiO 2 films on the order of a few nanometer thickness has been demonstrated. SiO 2 thin films of approximately 7 nm thickness have been produced by ion flux-controlled Electron Cyclotron Resonance plasma oxidation at low temperature on [100] Si substrates, in reproducible fashion. Electrical measurements of these films indicate that they have characteristics comparable to those of thermally grown oxides. The thickness of the films was determined by ellipsometry, and further confirmed by cross-sectional High-Resolution Transmission Electron Microscopy. Comparison between the ECR and the thermal oxide films shows that the ECR films are uniform and continuous over at least a few microns in lateral direction, similar to the thermal oxide films grown at comparable thickness. In addition, HRTEM images reveal a thin (1--1.5 nm) crystalline interfacial layer between the ECR film and the [100] substrate. Thinner oxide films of approximately 5 nm thickness have also been attempted, but so far have resulted in nonuniform coverage. Reproducibility at this thickness is difficult to achieve

  20. Avaliação da biocompatibilidade do compósito aço/filme bioativo SiO2-CaO para aplicação biomédica Biocompatibility evaluation of SiO2-CaO/stainless steel composite bioactive film for biomedical application

    Directory of Open Access Journals (Sweden)

    S. R. Federman

    2009-09-01

    Full Text Available Foi obtido um filme bioativo sol-gel do sistema SiO2-CaO através da mistura de precursor de silício (TEOS - tetraetil ortosilicato, precursor de cálcio (nitrato de cálcio tetrahidratado e álcool em meio ácido. Após a mistura, a solução serviu para revestir o aço inoxidável através do método de imersão empregando baixa velocidade de emersão. O compósito obtido foi então submetido a tratamento térmico para densificação do filme a 400 ºC durante 1 h. A biocompatibilidade do compósito foi avaliada através de dois métodos no sistema in vitro: a solução concentrada similar ao fluido fisiológico - SFC 1,5 - e b cultura de células. Imagens de microscopia eletrônica de varredura e espectroscopia de energia dispersiva comprovaram a precipitação de precursor da hidroxiapatita na superfície do filme bioativo após exposição à solução SFC durante 3 semanas. Imagens de microscopia eletrônica de varredura confirmaram aderência, crescimento e espalhamento celular na superfície do filme bioativo sol-gel após 24 h de cultivo celular, empregando células VERO (ATCC CCL-81, sugerindo que o compósito é um material potencialmente aplicável nas áreas de medicina e odontologia. Resultados obtidos com o ensaio de viabilidade celular através de MTT [brometo de 3-(4,5-dimetiltiazol-2-YL-2,5-difeniltetrazolio] indicaram total ausência de toxicidade na interface filme sol-gel/células VERO.Sol-gel film in the SiO2-CaO system was prepared via reacting silicate precursor (TEOS - tetraethyl orthosilicate, calcium precursor (tetrahydrated calcium nitrate, alcohol in an acidic medium. After mixing, the coating was deposited on stainless steel by dip-coating technique at a low withdraw speed. After deposition, the composite was submitted to heat treatment, in air, at 400 ºC for 1 h. The composite biocompatibility has been analyzed by in vitro studies using two methods: a concentrated simulated body fluid - SBF 1.5 - and b cell

  1. In vacuo growth studies of Ru thin films on Si, SiN, and SiO2 by high-sensitivity low energy ion scattering

    NARCIS (Netherlands)

    Coloma Ribera, R.; van de Kruijs, Robbert Wilhelmus Elisabeth; Sturm, Jacobus Marinus; Yakshin, Andrey; Bijkerk, Frederik

    2016-01-01

    In vacuo high-sensitivity low energy ion scattering (HS-LEIS) has been used to investigate the initial growth stages of DC sputtered Ru on top of Si, SiN, and SiO2. The high surface sensitivity of this technique allowed an accurate determination of surface coverages and thicknesses required for

  2. Manufacturing and investigation of surface morphology and optical properties of composite thin films reinforced by TiO2, Bi2O3 and SiO2 nanoparticles

    Science.gov (United States)

    Jarka, Paweł; Tański, Tomasz; Matysiak, Wiktor; Krzemiński, Łukasz; Hajduk, Barbara; Bilewicz, Marcin

    2017-12-01

    The aim of submitted paper is to present influence of manufacturing parameters on optical properties and surface morphology of composite materials with a polymer matrix reinforced by TiO2 and SiO2 and Bi2O3 nanoparticles. The novelty proposed by the authors is the use of TiO2 and SiO2 and Bi2O3 nanoparticles simultaneously in polymeric matrix. This allows using the combined effect of nanoparticles to a result composite material. The thin films of composite material were prepared by using spin-coating method with various spinning rates from solutions of different concentration of nanoparticles. In order to prepare the spinning solution polymer, Poly(methyl methacrylate) (PMMA) was used as a matrix. The reinforcing phase was the mixture of the nanoparticles of SiO2, TiO2 and B2O3. In order to identify the surface morphology of using thin films and arrangement of the reinforcing phase Atomic Force Microscope (AFM) and Scanning Electron Microscope (SEM) were used. In order to study the optical properties of the obtained thin films, the thin films of composites was subjected to an ellipsometry analysis. The measurements of absorbance of the obtained materials, from which the value of the band gap width was specified, were carried out using the UV/VIS spectroscopy. The optical properties of obtain composite thin films depend not only on the individual components used, but also on the morphology and the interfacial characteristics. Controlling the participation of three kinds of nanoparticles of different sizes and optical parameters allows to obtaining the most optimal optical properties of nanocomposites and also controlling the deposition parameters allows to obtaining the most optimal surface morphology of nanocomposites.

  3. Characterization, modeling and physical mechanisms of different surface treatment methods at room temperature on the oxide and interfacial quality of the SiO2 film using the spectroscopic scanning capacitance microscopy

    Directory of Open Access Journals (Sweden)

    Kin Mun Wong

    Full Text Available In this article, a simple, low cost and combined surface treatment method [pre-oxidation immersion of the p-type silicon (Si substrate in hydrogen peroxide (H2O2 and post oxidation ultra-violet (UV irradiation of the silicon-dioxide (SiO2 film] at room temperature is investigated. The interface trap density at midgap [Dit(mg] of the resulting SiO2 film (denoted as sample 1A is quantified from the full width at half-maximum of the scanning capacitance microscopy (SCM differential capacitance (dC/dV characteristics by utilizing a previously validated theoretical model. The Dit(mg of sample 1A is significantly lower than the sample without any surface treatments which indicates that it is a viable technique for improving the interfacial quality of the thicker SiO2 films prepared by wet oxidation. Moreover, the proposed combined surface treatment method may possibly complement the commonly used forming gas anneal process to further improve the interfacial quality of the SiO2 films. The positive shift of the flatband voltage due to the overall oxide charges (estimated from the probe tip dc bias at the peak dC/dV spectra of sample 1A suggests the presence of negative oxide fixed charge density (Nf in the oxide. In addition, an analytical formula is derived to approximate the difference of the Nf values between the oxide samples that are immersed in H2O2 and UV irradiated from their measured SCM dC/dV spectra. Conversely, some physical mechanisms are proposed that result in the ionization of the SiO− species (which are converted from the neutral SiOH groups that originate from the pre-oxidation immersion in H2O2 and ensuing wet oxidation during the UV irradiation as well as the UV photo-injected electrons from the Si substrate (which did not interact with the SiOH groups. They constitute the source of mobile electrons which partially passivate the positively charged empty donor-like interface traps at the Si-SiO2 interface. Keywords: Dielectrics

  4. Preparation and Characterization of PbO-SrO-Na2O-Nb2O5-SiO2 Glass Ceramics Thin Film for High-Energy Storage Application

    Science.gov (United States)

    Tan, Feihu; Zhang, Qingmeng; Zhao, Hongbin; Wei, Feng; Du, Jun

    2018-03-01

    PbO-SrO-Na2O-Nb2O5-SiO2 (PSNNS) glass ceramic thin films were prepared by pulsed laser deposition technology on heavily doped silicon substrates. The influence of annealing temperatures on microstructures, dielectric properties and energy storage performances of the as-prepared films were investigated in detail. X-ray diffraction studies indicate that Pb2Nb2O7 crystallizes at 800°C and disappears at 900°C, while NaNbO3 and PbNb2O6 are formed at the higher temperature of 900°C. The dielectric properties of the glass ceramics thin films have a strong dependence on the phase assemblages that are developed during heat treatment. The maximum dielectric constant value of 171 was obtained for the film annealed at 800°C, owing to the high electric breakdown field strength, The energy storage densities of the PSNNS films annealed at 800°C were as large as 36.9 J/cm3, These results suggest that PSNNS thin films are promising for energy storage applications.

  5. Development of Microwave-Excited Plasma-Enhanced Metal-Organic Chemical Vapor Deposition System for Forming Ferroelectric Sr2(Ta1-x,Nbx)2O7 Thin Film on Amorphous SiO2

    Science.gov (United States)

    Takahashi, Ichirou; Funaiwa, Kiyoshi; Azumi, Keita; Yamashita, Satoru; Shirai, Yasuyuki; Hirayama, Masaki; Teramoto, Akinobu; Sugawa, Shigetoshi; Ohmi, Tadahiro

    2007-04-01

    Sr2(Ta1-x,Nbx)2O7 (STN; x = 0.3) is suitable for use as ferroelectric gate field-effect transistors (FETs) for one-transistor-type ferroelectric memory devices, because it has a low dielectric constant. For applications using metal-ferroelectric-insulator-semiconductor (MFIS) FETs, crystallization of ferroelectric film on insulator is necessary. Perovskite STN can be successfully obtained on amorphous SiO2 by ferroelectric-multilayer-stack (FMLS) deposition, which uses alternating steps of STN sputtering deposition and oxygen radical treatment. In this study, we report on a newly developed microwave-excited plasma-enhanced metal-organic chemical vapor deposition (MOCVD) system, in which STN can be deposited in radical oxygen atmosphere. We succeeded in the fabrication of STN on amorphous SiO2 in a single process. The IrO2/STN (200 nm)/SiO2 (10 nm)/p-type Si device shows capacitance-voltage (C-V) hysteresis curves and a memory window of 1.2 V with a 5 V writing operation.

  6. Sol-Gel Synthesis and Characterization of Ba1-xGdxTiO3+δ Thin Films on SiO2/Si Substrates Using Spin-Coating Technique

    Directory of Open Access Journals (Sweden)

    Yen Chin TEH

    2017-02-01

    Full Text Available Ba1-xGdxTiO3+δ, at x = 0, 0.05, 0.1, 0.15, 0.2, (BGT thin films have been fabricated on SiO2/Si substrate using Sol-Gel method. The microstructure and surface morphology of the fabricated films have been investigated using X-ray diffraction (XRD and atomic force microscopy (AFM. The XRD results show that the fabricated films are crystalline with perovskite structure. There is a shifting of the preferred peak at 31.5o to a higher angle as the doping ratio increases suggesting a distortion lattice exists in the films, which could be due to the substitution of Gd3+ ions into Ba-site. The decreasing of lattice constants confirms the substitution of Gd3+ in BaTiO3 lattice structure. The microstrain and dislocation density are found to be increased with the increase of Gd3+ doping, which attributed to the reduction of lattice volume that due to the ionic size mismatch effect. The AFM results show decreasing trend in both average grain size and roughness parameters. Therefore, the microstructure and surface morphology of BGT samples is strongly dependent on the Gd3+ doping concentration that mainly due to the difference ionic radius substitution.DOI: http://dx.doi.org/10.5755/j01.ms.23.1.13954

  7. Cellulose acetate-based SiO2/TiO2 hybrid microsphere composite aerogel films for water-in-oil emulsion separation

    Science.gov (United States)

    Yang, Xue; Ma, Jianjun; Ling, Jing; Li, Na; Wang, Di; Yue, Fan; Xu, Shimei

    2018-03-01

    The cellulose acetate (CA)/SiO2-TiO2 hybrid microsphere composite aerogel films were successfully fabricated via water vapor-induced phase inversion of CA solution and simultaneous hydrolysis/condensation of 3-aminopropyltrimethoxysilane (APTMS) and tetrabutyl titanate (TBT) at room temperature. Micro-nano hierarchical structure was constructed on the surface of the film. The film could separate nano-sized surfactant-stabilized water-in-oil emulsions only under gravity. The flux of the film for the emulsion separation was up to 667 L m-2 h-1, while the separation efficiency was up to 99.99 wt%. Meanwhile, the film exhibited excellent stability during multiple cycles. Moreover, the film performed excellent photo-degradation performance under UV light due to the photocatalytic ability of TiO2. Facile preparation, good separation and potential biodegradation maked the CA/SiO2-TiO2 hybrid microsphere composite aerogel films a candidate in oil/water separation application.

  8. Study of catalytic properties of sol-gel-derived CoO x -SiO2 film systems by the example of the growth of carbon nanomaterials

    Science.gov (United States)

    Levitskii, V. S.; Maksimov, A. I.; Moshnikov, V. A.; Terukov, E. I.

    2014-07-01

    Film catalytic samples in the Si-Co-O system in the composition range from 15 to 90 mol % Co have been prepared using the sol-gel technology. Carbon nanomaterials have been fabricated by pyrolytic synthesis using these films as catalysts. Raman spectroscopy of materials has shown that multiwalled carbon nanotubes are formed by pyrolysis on catalytic films containing Co3O4. The dependence of the carbon material length on the synthesis time has been considered. It has been shown that the average growth rate of tubes and fibers is ˜3 μm/min.

  9. TEM and STEM Studies on the Cross-sectional Morphologies of Dual-/Tri-layer Broadband SiO2Antireflective Films.

    Science.gov (United States)

    Wang, Shuangyue; Yan, Hongwei; Li, Dengji; Qiao, Liang; Han, Shaobo; Yuan, Xiaodong; Liu, Wei; Xiang, Xia; Zu, Xiaotao

    2018-02-12

    Dual-layer and tri-layer broadband antireflective (AR) films with excellent transmittance were successfully fabricated using base-/acid-catalyzed mixed sols and propylene oxide (PO) modified silica sols. The sols and films were characterized by scanning electron microscope (SEM), Fourier transform infrared spectroscopy (FTIR), nuclear magnetic resonance (NMR), transmission electron microscope (TEM), and scanning transmission electron microscope (STEM). FTIR and TEM results suggest that the PO molecules were covalently bonded to the silica particles and the bridge structure existing in PO modified silica sol is responsible for the low density of the top layer. The density ratio between different layers was measured by cross-sectional STEM, and the results are 1.69:1 and 2.1:1.7:1 from bottom-layer to top-layer for dual-layer and tri-layer films, respectively. The dual-layer film demonstrates good stability with 99.8% at the central wavelength of 351 nm and nearly 99.5% at the central wavelength of 1053 nm in laser system, and for the tri-layer AR film, the maximum transmittance reached nearly 100% at both the central wavelengths of 527 and 1053 nm.

  10. Growth and structure of water on SiO2 films on Si investigated byKelvin probe microscopy and in situ X-ray Spectroscopies

    Energy Technology Data Exchange (ETDEWEB)

    Verdaguer, A.; Weis, C.; Oncins, G.; Ketteler, G.; Bluhm, H.; Salmeron, M.

    2007-06-14

    The growth of water on thin SiO{sub 2} films on Si wafers at vapor pressures between 1.5 and 4 torr and temperatures between -10 and 21 C has been studied in situ using Kelvin Probe Microscopy and X-ray photoemission and absorption spectroscopies. From 0 to 75% relative humidity (RH) water adsorbs forming a uniform film 4-5 layers thick. The surface potential increases in that RH range by about 400 mV and remains constant upon further increase of the RH. Above 75% RH the water film grows rapidly, reaching 6-7 monolayers at around 90% RH and forming a macroscopic drop near 100%. The O K-edge near-edge X-ray absorption spectrum around 75% RH is similar to that of liquid water (imperfect H-bonding coordination) at temperatures above 0 C and ice-like below 0 C.

  11. Statistical Design of Ultra-Thin SiO2 for Nano devices

    International Nuclear Information System (INIS)

    Hashim, U.; Abdul-Fatah, M.F.A.; Ahmad, I.; Majlis, B.Y.

    2009-01-01

    A study was performed on a series of ultra thin SiO 2 films in order to determine the factors affecting the oxide growth and also the effect of temperature to the film surface roughness. The samples of ultra thin SiO 2 were prepared through a dry oxidation method using a high temperature furnace. There are three levels of temperature used, that is 900, 950 and 1000 degree Celsius and the samples were grown at 0.333 litre/ min, 0.667 liter/ min and 1 liter/ min oxygen flow rate and different oxidation times of 1, 2 and 3 minutes. The thickness was determined using an ellipsometers and the micro morphology of the oxide surface was obtained by using an atomic force microscope (AFM). The thickness of the oxide ranged from 1 to 5 nm. All the data has been interpreted using Taguchi's method to analyze the most affecting factors in producing an ultra thin silicon dioxide. The optimum parameters are 900 degree Celsius, 0.333 litre/ min and at 1 minute time. The most influential parameter is temperature. The temperature also affects the surface roughness. The AFM result of 950 degree Celsius with RMS value of 0.1088 nm is better than the 900 degree Celsius oxide with RMS value 0.4553 nm. This shows that oxides need to be grown at a higher temperature to provide better surface roughness which is also important in ultra thin gate oxide characteristics. (author)

  12. Effect of ion implantation energy for the synthesis of Ge nanocrystals in SiN films with HfO2/SiO2 stack tunnel dielectrics for memory application

    Directory of Open Access Journals (Sweden)

    Gloux Florence

    2011-01-01

    Full Text Available Abstract Ge nanocrystals (Ge-NCs embedded in SiN dielectrics with HfO2/SiO2 stack tunnel dielectrics were synthesized by utilizing low-energy (≤5 keV ion implantation method followed by conventional thermal annealing at 800°C, the key variable being Ge+ ion implantation energy. Two different energies (3 and 5 keV have been chosen for the evolution of Ge-NCs, which have been found to possess significant changes in structural and chemical properties of the Ge+-implanted dielectric films, and well reflected in the charge storage properties of the Al/SiN/Ge-NC + SiN/HfO2/SiO2/Si metal-insulator-semiconductor (MIS memory structures. No Ge-NC was detected with a lower implantation energy of 3 keV at a dose of 1.5 × 1016 cm-2, whereas a well-defined 2D-array of nearly spherical and well-separated Ge-NCs within the SiN matrix was observed for the higher-energy-implanted (5 keV sample for the same implanted dose. The MIS memory structures implanted with 5 keV exhibits better charge storage and retention characteristics compared to the low-energy-implanted sample, indicating that the charge storage is predominantly in Ge-NCs in the memory capacitor. A significant memory window of 3.95 V has been observed under the low operating voltage of ± 6 V with good retention properties, indicating the feasibility of these stack structures for low operating voltage, non-volatile memory devices.

  13. A fibre optic humidity sensor based on a long-period fibre grating coated with a thin film of SiO2 nanospheres

    Science.gov (United States)

    Viegas, D.; Goicoechea, J.; Corres, J. M.; Santos, J. L.; Ferreira, L. A.; Araújo, F. M.; Matias, I. R.

    2009-03-01

    A novel sensing configuration for measuring humidity based on a long-period fibre grating coated with a thin film of silica nanospheres is proposed. The polymeric overlay is deposited on the grating using the electrostatic self-assembly technique. This thin film changes its optical properties when exposed to different humidity levels that translate into a shift of the resonance wavelength of the fibre grating. Wavelength shifts up to 12 nm in a relative humidity range from 20% to 80% are reported, and it is further demonstrated that such humidity sensitivity has negligible thermal dependence.

  14. Composite SiOx/fluorocarbon plasma polymer films prepared by r.f. magnetron sputtering of SiO2 and PTFE

    Czech Academy of Sciences Publication Activity Database

    Pihosh, Y.; Biederman, H.; Slavínská, D.; Kousal, J.; Choukourov, A.; Trchová, Miroslava; Macková, Anna; Boldyryeva, Hanna

    2006-01-01

    Roč. 81, 1-4 (2006), s. 38-44 ISSN 0042-207X R&D Projects: GA MŠk OC 527.10; GA MŠk ME 553 Institutional research plan: CEZ:AV0Z40500505; CEZ:AV0Z10480505 Keywords : composite films * magnetron * sputtering Subject RIV: BL - Plasma and Gas Discharge Physics Impact factor: 0.834, year: 2006

  15. In situ observation of electron-beam-induced dewetting of CdSe thin film embedded in SiO2

    DEFF Research Database (Denmark)

    Fabrim, Zacarias Eduardo; Kjelstrup-Hansen, Jakob; Fichtner, Paulo F. P.

    .33 A.cm2 and 1.0 A.cm2 and at 80 kV with 0.37 A.cm2. The dewetting of the CdSe film is inferred by a number of micrographs taken during the irradiation. The microstructural changes were analyzed under the assumption of being induced by ballistic collision effects in the absence of sample heating....

  16. Growth of ZnO thin films on GaAs by pulsed laser deposition

    NARCIS (Netherlands)

    Craciun, V.; Elders, J.; Gardeniers, Johannes G.E.; Geretovsky, J.; Boyd, Ian W.

    1995-01-01

    ZnO thin films have been grown on GaAs substrates using the pulsed laser deposition technique with or without a photodeposited SiO2 buffer layer. The presence of the SiO2 layer has a beneficial effect on the crystalline quality of the grown ZnO films. Highly c-axis oriented ZnO films having a full

  17. Single layer porous gold films grown at different temperatures

    International Nuclear Information System (INIS)

    Zhang Renyun; Hummelgard, Magnus; Olin, Hakan

    2010-01-01

    Large area porous gold films can be used in several areas including electrochemical electrodes, as an essential component in sensors, or as a conducting material in electronics. Here, we report on evaporation induced crystal growth of large area porous gold films at 20, 40 and 60 deg. C. The gold films were grown on liquid surface at 20 deg. C, while the films were grown on the wall of beakers when temperature increased to 40 and 60 deg. C. The porous gold films consisted of a dense network of gold nanowires as characterized by TEM and SEM. TEM diffraction results indicated that higher temperature formed larger crystallites of gold wires. An in situ TEM imaging of the coalescence of gold nanoparticles mimicked the process of the growth of these porous films, and a plotting of the coalescence time and the neck radius showed a diffusion process. The densities of these gold films were also characterized by transmittance, and the results showed film grown at 20 deg. C had the highest density, while the film grown at 60 deg. C had the lowest consistent with SEM and TEM characterization. Electrical measurements of these gold films showed that the most conductive films were the ones grown at 40 deg. C. The conductivities of the gold films were related to the amount of contamination, density and the diameter of the gold nanowires in the films. In addition, a gold film/gold nanoparticle hybrid was made, which showed a 10% decrease in transmittance during hybridization, pointing to applications as chemical and biological sensors.

  18. Sol-gel preparation of self-cleaning SiO2-TiO2/SiO2-TiO2 double-layer antireflective coating for solar glass

    Science.gov (United States)

    Lin, Wensheng; Zheng, Jiaxian; Yan, Lianghong; Zhang, Xinxiang

    2018-03-01

    Self-cleaning SiO2-TiO2/SiO2-TiO2 double-layer antireflective (AR) coating is prepared by sol-gel process. SiO2 sol is prepared by using tetraethyl orthosilicate (TEOS) as precursor and ammonia as catalyst, while TiO2 sol was prepared by using tetrabutyl orthotitanate (TBOT) as precursor and hydrochloric acid as catalyst. The effect of TiO2 content on refractive index, abrasion-resistance and photo-catalytic activity of SiO2-TiO2 hybrid thin films or powders is systematically investigated. It is found that the refractive index of SiO2-TiO2 hybrid thin films increases gradually from 1.18 to 1.53 as the weight ratio of TiO2 to SiO2 increased from 0 to 1.0. The SiO2-TiO2 hybrid thin film and powder possesses good abrasion-resistance and photo-catalytic activity, respectively, as the weight ratio of TiO2 to SiO2 is 0.4. The degradation degree of Rhodamine B by SiO2-TiO2 hybrid powder is 88.3%. Finally, SiO2-TiO2/SiO2-TiO2 double-layer AR coating with high transmittance, abrasion-resistance and self-cleaning property is realized.

  19. Cuprous oxide thin films grown by hydrothermal electrochemical deposition technique

    International Nuclear Information System (INIS)

    Majumder, M.; Biswas, I.; Pujaru, S.; Chakraborty, A.K.

    2015-01-01

    Semiconducting cuprous oxide films were grown by a hydrothermal electro-deposition technique on metal (Cu) and glass (ITO) substrates between 60 °C and 100 °C. X-ray diffraction studies reveal the formation of cubic cuprous oxide films in different preferred orientations depending upon the deposition technique used. Film growth, uniformity, grain size, optical band gap and photoelectrochemical response were found to improve in the hydrothermal electrochemical deposition technique. - Highlights: • Cu 2 O thin films were grown on Cu and glass substrates. • Conventional and hydrothermal electrochemical deposition techniques were used. • Hydrothermal electrochemical growth showed improved morphology, thickness and optical band gap

  20. Preparation and optical and electrical evaluation of bulk SiO2 sonogel hybrid composites and vacuum thermal evaporated thin films prepared from molecular materials derived from (Fe, Co) metallic phthalocyanines and 1,8 dihydroxiantraquinone compounds

    International Nuclear Information System (INIS)

    Sanchez Vergara, Maria Elena; Morales-Saavedra, Omar G.; Ontiveros-Barrera, Fernando G.; Torres-Zuniga, Vicente; Ortega-Martinez, Roberto; Ortiz Rebollo, Armando

    2009-01-01

    Semiconducting molecular material of PcFe(CN)L1 and PcCo(CN)L1 (L1 = 1,8 dihydroxianthraquinone), PcFe(CN)L2 and PcCo(CN)L2 (L2 = double potassium salt of 1,8 dihydroxianthraquinone) have been successfully used to prepare thin film and bulk sol-gel hybrid optical materials. These samples were developed according to the vacuum thermal evaporation technique and the catalyst-free sonogel route, respectively. Thin films samples were deposited on Corning glass substrates and crystalline silicon wafers and were characterized by infrared (FTIR), Raman and ultraviolet-visible (UV-vis) spectroscopies. IR-spectroscopy and Raman studies unambiguously confirmed that the molecular material thin films exhibit the same intra-molecular bonds, which suggests that the thermal evaporation process does not alter these bonds significantly. These results show that it is possible to deposit molecular materials of PcFe(CN)L2 and PcCo(CN)L2 on Corning glass substrates and silicon wafers. From the UV-vis studies the optical band gap (E g ) was evaluated. The effect of temperature on conductivity was also evaluated in these samples. Finally, the studied molecular systems dissolved at different concentrations in tetrahydrofuran (THF) were successfully embedded into a highly pure SiO 2 sonogel network generated via sonochemical reactions to form several solid state, optically active sol-gel hybrid glasses. By this method, homogeneous and stable hybrid monoliths suitable for optical characterization can be produced. The linear optical properties of these amorphous bulk structures were determined by the Brewster angle method and by absorption-, Raman- and photoluminescent (PL)-spectroscopies, respectively

  1. Simultaneous electroanalytical determination of hydroquinone and catechol in the presence of resorcinol at an SiO2/C electrode spin-coated with a thin film of Nb2O5.

    Science.gov (United States)

    Canevari, Thiago C; Arenas, Leliz T; Landers, Richard; Custodio, Rogério; Gushikem, Yoshitaka

    2013-01-07

    This paper describes the development, characterization and application of an Nb(2)O(5) film formed on the surface of a carbon ceramic material, SiO(2)/C, obtained by a sol-gel method, using the spin-coating technique. The working electrode using this material will be designated as SiCNb. Hydroquinone and catechol can be oxidized at this electrode in the presence of resorcinol, allowing their simultaneous detection. The electrochemical properties of the resulting electrode were investigated using cyclic and differential pulse voltammetry techniques. Well-defined and separated oxidation peaks were observed by differential pulse voltammetry in Tris-HCl buffer solution at pH 7 containing 1 mol L(-1) KCl in the supporting electrolyte solution. The SiCNb electrode exhibited high sensitivity in the simultaneous determination of hydroquinone and catechol in the presence of resorcinol, with the limits of detection for hydroquinone and catechol being 1.6 μmol L(-1) and 0.8 μmol L(-1), respectively. Theoretical calculations were performed to determine the ionization energies of hydroquinone, catechol and resorcinol; the results were used to explain the simultaneous determination of species by differential pulse voltammetry. The presence of resorcinol did not produce any interference in the simultaneous detection of hydroquinone and catechol on the surface of the modified electrode.

  2. Photosensitivity of nanocrystalline ZnO films grown by PLD

    International Nuclear Information System (INIS)

    Ayouchi, R.; Bentes, L.; Casteleiro, C.; Conde, O.; Marques, C.P.; Alves, E.; Moutinho, A.M.C.; Marques, H.P.; Teodoro, O.; Schwarz, R.

    2009-01-01

    We have studied the properties of ZnO thin films grown by laser ablation of ZnO targets on (0 0 0 1) sapphire (Al 2 O 3 ), under substrate temperatures around 400 deg. C. The films were characterized by different methods including X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) and atomic force microscopy (AFM). XPS analysis revealed that the films are oxygen deficient, and XRD analysis with θ-2θ scans and rocking curves indicate that the ZnO thin films are highly c-axis oriented. All the films are ultraviolet (UV) sensitive. Sensitivity is maximum for the films deposited at lower temperature. The films deposited at higher temperatures show crystallite sizes of typically 500 nm, a high dark current and minimum photoresponse. In all films we observe persistent photoconductivity decay. More densely packed crystallites and a faster decay in photocurrent is observed for films deposited at lower temperature

  3. Silicon nanocrystals embedded in oxide films grown by magnetron sputtering

    Directory of Open Access Journals (Sweden)

    Caroline Bonafos

    2016-05-01

    Full Text Available This paper presents a comparison of the results that we obtained and reported over the last few years on the structural, optical and light emitting properties of Si-SiO2 and Si-Al2O3 films that were fabricated using a specific configuration of RF magnetron sputtering. In these films the Si volume fraction, x, varies along the film (which is typically 14 cm long from a value of ~0.1 at one end to ~0.9 at the other end. For the films with x > 0.3, the formation of amorphous Si clusters was observed in as-deposited Si-SiO2 and Si-Al2O3 films. Si nanocrystals (Si-ncs were generated by high-temperature annealing of the films in nitrogen atmosphere. We found that two processes can contribute to the Si-ncs formation: (i the crystallization of the existing amorphous Si inclusions in the as-deposited films, and (ii the thermally stimulated phase separation. Process (i can be responsible for the independence of Si-ncs mean sizes on x in annealed films with x > 0.5. At the same time, difference in the structural and the light emitting properties of the two types of films was observed. For the samples of the same x, the Si-ncs embedded in the Al2O3 host were found to be larger than the Si-ncs in the SiO2 host. This phenomenon can be explained by the lower temperature required for phase separation in Si-Al2O3 or by the lower temperature of the crystallization of Si-ncs in alumina. The latter suggestion is supported by Raman scattering and electron paramagnetic resonance spectra. In contrast with the Si-SiO2, the Si-ncs embedded in Si-Al2O3 films were found to be under tensile stress. This effect was explained by the strains at the interfaces between the film and silica substrate as well as between the Si inclusions and the Al2O3 host. It was also shown that exciton recombination in Si-ncs is the dominant radiative channel in Si-SiO2 films, while the emission from the oxide defects dominates in Si-Al2O3 films. This can be due to the high number of non

  4. Conductivity and scaling properties of chemically grown granular silver films

    Science.gov (United States)

    Peterson, M. S. M.; Deutsch, M.

    2009-09-01

    We address room-temperature conductivities of chemically grown silver films. Disordered, granular silver films are grown using a modified Tollens reaction. Thick, polycrystalline films are transparent at visible wavelengths, with crystallinity similar to that of silver powders. The measured conductivities are close to those measured by I. V. Antonets, L. N. Kotov, S. V. Nekipelov, and Ye. A. Golubev, Tech. Phys. 49, 306 (2004) in amorphous silver films, however the thickness where bulk conductivity is reached is anomalously high. While measured resistance values do not obey a scaling relation in thickness, accounting for the films' structural porosity through geometrical rescaling of the thickness leads to emergence of the well-known percolation power-law scaling, albeit that of two-dimensional percolating films.

  5. Study of Al2O3 nanolayers synthesized onto porous SiO2 using X-ray reflection spectroscopy

    International Nuclear Information System (INIS)

    Konashuk, A.S.; Sokolov, A.A.; Drozd, V.E.; Schaefers, F.; Filatova, E.O.

    2013-01-01

    The structure of alumina (Al 2 O 3 ) films with different thickness grown by the atomic layer deposition method on porous silica substrates has been studied using soft X-ray reflection spectroscopy. It was established that synthesized films were amorphous and the proportion of Al coordination (tetrahedral: octahedral) depends on the film thickness. The film growth starts from excess of tetrahedral (AlO 4 ) coordination and thickening of the film leads to increasing of number of octahedral (AlO 6 ) coordination in the structure. A critical thickness of amorphous Al 2 O 3 film exists (in the range of studied films, this is a thickness of 13 nm). For thicker films, the structure of amorphous Al 2 O 3 film corresponds to massive film with the typical proportion of tetrahedrally and octahedrally coordinated sites in the structure. - Highlights: • Growth of Al 2 O 3 film on porous SiO 2 begins with excess of AlO 4 coordinations. • On the contrary, film growth on nonporous substrates starts with excess of AlO 6 . • When thickness reaches 13 nm, the film achieves structure of massive amorphous Al 2 O 3 . • Substrate material doesn't affect structure for thicknesses more than 13 nm

  6. Field emission properties of SiO2-wrapped CNT field emitter

    Science.gov (United States)

    Lim, Yu Dian; Hu, Liangxing; Xia, Xin; Ali, Zishan; Wang, Shaomeng; Tay, Beng Kang; Aditya, Sheel; Miao, Jianmin

    2018-01-01

    Carbon nanotubes (CNTs) exhibit unstable field emission (FE) behavior with low reliability due to uneven heights of as-grown CNTs. It has been reported that a mechanically polished SiO2-wrapped CNT field emitter gives consistent FE performance due to its uniform CNT heights. However, there are still a lack of studies on the comparison between the FE properties of freestanding and SiO2-wrapped CNTs. In this study, we have performed a comparative study on the FE properties of freestanding and SiO2-wrapped CNT field emitters. From the FE measurements, freestanding CNT field emitter requires lower applied voltage of 5.5 V μm‑1 to achieve FE current density of 22 mA cm‑2 whereas SiO2-wrapped field emitter requires 8.5 V μm‑1 to achieve the same current density. This can be attributed to the lower CNT tip electric field of CNTs embedded in SiO2, as obtained from the electric field simulation. Nevertheless, SiO2-wrapped CNTs show higher consistency in FE current than freestanding CNTs. Under repeated FE measurement, SiO2-wrapped CNT field emitter achieves consistent FE behavior from the 1st voltage sweep, whereas freestanding field emitter only achieved consistent FE performance after 3rd voltage sweep. At the same time, SiO2-wrapped CNTs exhibit better emission stability than freestanding CNTs over 4000 s continuous emission.

  7. H2O and O2 molecules in amorphous SiO2: Defect formation and annihilation mechanisms

    International Nuclear Information System (INIS)

    Bakos, T.; Rashkeev, S.N.; Pantelides, S.T.

    2004-01-01

    Interstitial water and oxygen molecules are ubiquitous impurities and participate in various defect formation processes in thermally grown SiO 2 films and synthetic silica glass. Using results of first-principles calculations we report the types of defects (including different possible charge states) that H 2 O and O 2 molecules may form in bulk amorphous SiO 2 . We calculate their formation energies and, in the most interesting cases, the energy barriers in order to map out the most likely defect formation scenarios. In particular, we show that water molecules may form double silanol groups (Si-OH) as well as H 3 O + and OH - ions at a low energy cost with a barrier of about 1.5 eV. The formation energies of other defects emanating from H 2 O interstitials are, however, too high to be thermally activated. We found that O 2 molecules may form ozonyl (Si-O-O-O-Si) linkages with an energy barrier of ∼2.4 eV. An explanation for the oxygen isotope exchange observed in thin SiO 2 films near the Si-SiO 2 and SiO 2 -vacuum interfaces is suggested based on the energy barrier for ozonyl formation being commensurate with the O 2 diffusion barrier close to the Si/SiO 2 interface and the O 2 incorporation energy from vacuum. We also explain the different creation rates of E ' centers in wet and dry oxides by studying the annihilation mechanism of neutral and charged oxygen vacancies

  8. Hierarchical Cd4SiS6/SiO2 Heterostructure Nanowire Arrays.

    Science.gov (United States)

    Liu, Jian; Wang, Chunrui; Xie, Qingqing; Cai, Junsheng; Zhang, Jing

    2009-10-29

    Novel hierarchical Cd4SiS6/SiO2 based heterostructure nanowire arrays were fabricated on silicon substrates by a one-step thermal evaporation of CdS powder. The as-grown products were characterized using scanning electron microscopy, X-ray diffraction, and transmission electron microscopy. Studies reveal that a typical hierarchical Cd4SiS6/SiO2 heterostructure nanowire is composed of a single crystalline Cd4SiS6 nanowire core sheathed with amorphous SiO2 sheath. Furthermore, secondary nanostructures of SiO2 nanowires are highly dense grown on the primary Cd4SiS6 core-SiO2 sheath nanowires and formed hierarchical Cd4SiS6/SiO2 based heterostructure nanowire arrays which stand vertically on silicon substrates. The possible growth mechanism of hierarchical Cd4SiS6/SiO2 heterostructure nanowire arrays is proposed. The optical properties of hierarchical Cd4SiS6/SiO2 heterostructure nanowire arrays are investigated using Raman and Photoluminescence spectroscopy.

  9. Hierarchical Cd4SiS6/SiO2 Heterostructure Nanowire Arrays

    Directory of Open Access Journals (Sweden)

    Liu Jian

    2009-01-01

    Full Text Available Abstract Novel hierarchical Cd4SiS6/SiO2 based heterostructure nanowire arrays were fabricated on silicon substrates by a one-step thermal evaporation of CdS powder. The as-grown products were characterized using scanning electron microscopy, X-ray diffraction, and transmission electron microscopy. Studies reveal that a typical hierarchical Cd4SiS6/SiO2 heterostructure nanowire is composed of a single crystalline Cd4SiS6 nanowire core sheathed with amorphous SiO2 sheath. Furthermore, secondary nanostructures of SiO2 nanowires are highly dense grown on the primary Cd4SiS6 core-SiO2 sheath nanowires and formed hierarchical Cd4SiS6/SiO2 based heterostructure nanowire arrays which stand vertically on silicon substrates. The possible growth mechanism of hierarchical Cd4SiS6/SiO2 heterostructure nanowire arrays is proposed. The optical properties of hierarchical Cd4SiS6/SiO2 heterostructure nanowire arrays are investigated using Raman and Photoluminescence spectroscopy.

  10. Hierarchical Cd4SiS6/SiO2 Heterostructure Nanowire Arrays

    OpenAIRE

    Liu, Jian; Wang, Chunrui; Xie, Qingqing; Cai, Junsheng; Zhang, Jing

    2009-01-01

    Abstract Novel hierarchical Cd4SiS6/SiO2 based heterostructure nanowire arrays were fabricated on silicon substrates by a one-step thermal evaporation of CdS powder. The as-grown products were characterized using scanning electron microscopy, X-ray diffraction, and transmission electron microscopy. Studies reveal that a typical hierarchical Cd4SiS6/SiO2 heterostructure nanowire is composed of a single crystalline Cd4SiS6 nanowire core sheathed with amorphous SiO2 sheath. Furthermore, secondar...

  11. Nanocomposite oxide thin films grown by pulsed energy beam deposition

    International Nuclear Information System (INIS)

    Nistor, M.; Petitmangin, A.; Hebert, C.; Seiler, W.

    2011-01-01

    Highly non-stoichiometric indium tin oxide (ITO) thin films were grown by pulsed energy beam deposition (pulsed laser deposition-PLD and pulsed electron beam deposition-PED) under low oxygen pressure. The analysis of the structure and electrical transport properties showed that ITO films with a large oxygen deficiency (more than 20%) are nanocomposite films with metallic (In, Sn) clusters embedded in a stoichiometric and crystalline oxide matrix. The presence of the metallic clusters induces specific transport properties, i.e. a metallic conductivity via percolation with a superconducting transition at low temperature (about 6 K) and the melting and freezing of the In-Sn clusters in the room temperature to 450 K range evidenced by large changes in resistivity and a hysteresis cycle. By controlling the oxygen deficiency and temperature during the growth, the transport and optical properties of the nanocomposite oxide films could be tuned from metallic-like to insulating and from transparent to absorbing films.

  12. Simulation, fabrication and characterization of ZnO based thin film transistors grown by radio frequency magnetron sputtering.

    Science.gov (United States)

    Singh, Shaivalini; Chakrabarti, P

    2012-03-01

    We report the performance of the thin film transistors (TFTs) using ZnO as an active channel layer grown by radio frequency (RF) magnetron sputtering technique. The bottom gate type TFT, consists of a conventional thermally grown SiO2 as gate insulator onto p-type Si substrates. The X-ray diffraction patterns reveal that the ZnO films are preferentially orientated in the (002) plane, with the c-axis perpendicular to the substrate. A typical ZnO TFT fabricated by this method exhibits saturation field effect mobility of about 0.6134 cm2/V s, an on to off ratio of 102, an off current of 2.0 x 10(-7) A, and a threshold voltage of 3.1 V at room temperature. Simulation of this TFT is also carried out by using the commercial software modeling tool ATLAS from Silvaco-International. The simulated global characteristics of the device were compared and contrasted with those measured experimentally. The experimental results are in fairly good agreement with those obtained from simulation.

  13. Alkaline-doped manganese perovskite thin films grown by MOCVD

    International Nuclear Information System (INIS)

    Bibes, M.; Gorbenko, O.; Martinez, B.; Kaul, A.; Fontcuberta, J.

    2000-01-01

    We report on the preparation and characterization of La 1-x Na x MnO 3 thin films grown by MOCVD on various single-crystalline substrates. Under appropriate conditions epitaxial thin films have been obtained. The Curie temperatures of the films, which are very similar to those of bulk samples of similar composition, reflect the residual strain caused by the substrate. The anisotropic magnetoresistance AMR of the films has been analyzed in some detail, and it has been found that it has a two-fold symmetry at any temperature. Its temperature dependence mimics that of the electrical resistivity and magnetoresistance measured at similar fields, thus suggesting that the real structure of the material contributes to the measured AMR besides the intrinsic component

  14. Surface characterisation of GaSb-films grown by MOCVD

    Energy Technology Data Exchange (ETDEWEB)

    Seemayer, Andreas; Hommes, Alexander; Wandelt, Klaus [Institute for Physical Cchemistry, University of Bonn (Germany); Huemann, Sascha; Vogel, Dirk [Max Planck Institut fuer Eisenforschung, Duesseldorf (Germany); Schulz, Stephan [Department of Chemistry, University of Essen (Germany)

    2009-07-01

    III-V semiconductor films used for opto- and microelectronic devices have traditionally been grown by (MO)MBE and LPE processes. An alternative metal-organic CVD-process, which has been established in the last two decades for high-throughput and low-cost fabrication works for nitrides, phosphides and arsenides, but is problematic for antimonides. In particular, for GaSb films an alternative route is a CVD-process using the heterocyclic single source precursor [{sup t}Bu{sub 2}GaSbEt{sub 2}]{sub 2}. Subject of the present work is the gas phase behaviour of the used precursor under UHV conditions and the surface characterisation of thin GaSb-films, which were grown in a self-made HV-MOCVD reactor on Si(001), by AES, S-XPS and AFM. The results are discussed in terms of a correlation of the electronic properties with the composition and structure of the films.

  15. Nitric acid oxidation of Si (NAOS) method for low temperature fabrication of SiO2/Si and SiO2/SiC structures

    International Nuclear Information System (INIS)

    Kobayashi, H.; Imamura, K.; Kim, W.-B.; Im, S.-S.; Asuha

    2010-01-01

    We have developed low temperature formation methods of SiO 2 /Si and SiO 2 /SiC structures by use of nitric acid, i.e., nitric acid oxidation of Si (or SiC) (NAOS) methods. By use of the azeotropic NAOS method (i.e., immersion in 68 wt% HNO 3 aqueous solutions at 120 deg. C), an ultrathin (i.e., 1.3-1.4 nm) SiO 2 layer with a low leakage current density can be formed on Si. The leakage current density can be further decreased by post-metallization anneal (PMA) at 200 deg. C in hydrogen atmosphere, and consequently the leakage current density at the gate bias voltage of 1 V becomes 1/4-1/20 of that of an ultrathin (i.e., 1.5 nm) thermal oxide layer usually formed at temperatures between 800 and 900 deg. C. The low leakage current density is attributable to (i) low interface state density, (ii) low SiO 2 gap-state density, and (iii) high band discontinuity energy at the SiO 2 /Si interface arising from the high atomic density of the NAOS SiO 2 layer. For the formation of a relatively thick (i.e., ≥10 nm) SiO 2 layer, we have developed the two-step NAOS method in which the initial and subsequent oxidation is performed by immersion in ∼40 wt% HNO 3 and azeotropic HNO 3 aqueous solutions, respectively. In this case, the SiO 2 formation rate does not depend on the Si surface orientation. Using the two-step NAOS method, a uniform thickness SiO 2 layer can be formed even on the rough surface of poly-crystalline Si thin films. The atomic density of the two-step NAOS SiO 2 layer is slightly higher than that for thermal oxide. When PMA at 250 deg. C in hydrogen is performed on the two-step NAOS SiO 2 layer, the current-voltage and capacitance-voltage characteristics become as good as those for thermal oxide formed at 900 deg. C. A relatively thick (i.e., ≥10 nm) SiO 2 layer can also be formed on SiC at 120 deg. C by use of the two-step NAOS method. With no treatment before the NAOS method, the leakage current density is very high, but by heat treatment at 400 deg. C in

  16. Screen-Printed Photochromic Textiles through New Inks Based on SiO2@naphthopyran Nanoparticles.

    Science.gov (United States)

    Pinto, Tânia V; Costa, Paula; Sousa, Céu M; Sousa, Carlos A D; Pereira, Clara; Silva, Carla J S M; Pereira, Manuel Fernando R; Coelho, Paulo J; Freire, Cristina

    2016-10-26

    Photochromic silica nanoparticles (SiO 2 @NPT), fabricated through the covalent immobilization of silylated naphthopyrans (NPTs) based on 2H-naphtho[1,2-b]pyran (S1, S2) and 3H-naphtho[2,1-b]pyran (S3, S4) or through the direct adsorption of the parent naphthopyrans (1, 3) onto silica nanoparticles (SiO 2 NPs), were successfully incorporated onto cotton fabrics by a screen-printing process. Two aqueous acrylic- (AC-) and polyurethane- (PU-) based inks were used as dispersing media. All textiles exhibited reversible photochromism under UV and solar irradiation, developing fast responses and intense coloration. The fabrics coated with SiO 2 @S1 and SiO 2 @S2 showed rapid color changes and high contrasts (ΔE* ab = 39-52), despite presenting slower bleaching kinetics (2-3 h to fade to the original color), whereas the textiles coated with SiO 2 @S3 and SiO 2 @S4 exhibited excellent engagement between coloration and decoloration rates (coloration and fading times of 1 and 2 min, respectively; ΔE* ab = 27-53). The PU-based fabrics showed excellent results during the washing fastness tests, whereas the AC-based textiles evidenced good results only when a protective transfer film was applied over the printed design.

  17. Characterization of Si nanocrystals into SiO2 matrix

    International Nuclear Information System (INIS)

    Gravalidis, C.; Logothetidis, S.; Hatziaras, N.; Laskarakis, A.; Tsiaoussis, I.; Frangis, N.

    2006-01-01

    Silicon nanocrystals (nc-Si) have gained great interest due to their excellent optical and electronic properties and their applications in optoelectronics. The aim of this work is the study of growth mechanism of nc-Si into a-SiO 2 matrix from SiO/SiO 2 multilayer annealing, using non-destructive and destructive techniques. The multilayer were grown by e-beam evaporation from SiO and SiO 2 materials and annealing at temperatures up to 1100 deg. C in N 2 atmosphere. X-rays reflectivity (XRR) and high resolution transmission electron microscopy (HRTEM) were used for the structural characterization and spectroscopic ellipsometry in IR (FTIRSE) energy region for the study of the bonding structure. The ellipsometric results gave a clear evidence of the formation of an a-SiO 2 matrix after the annealing process. The XRR data showed that the density is being increased in the range from 25 to 1100 deg. C. Finally, the HRTEM characterization proved the formation of nc-Si. Using the above results, we describe the growth mechanism of nc-Si into SiO 2 matrix under N 2 atmosphere

  18. Optical properties of large-area MoS2 thin films grown via magnetron sputtering: Thickness and substrate dependence

    Science.gov (United States)

    Alkabsh, Asma; Samassekou, Hassana; Mazumdar, Dipanjan

    Transition metal dichalcogenides (TMDS) have gained exceptional attention because of their thickness dependent electronic structure which makes them suitable for electronic and optoelectronic applications. MoS2 is among the most promising material in this family. Recently we have successfully developed growth of large-area MoS2 using magnetron sputtering. In this work, we investigated the large-area optical properties of few and bilayer MoS2 grown on different amorphous underlayers (BN and SiO2) using spectroscopic ellipsometry (SE), UV-VIS and Raman spectroscopy. SE spectra provided thickness and optical constants within 1.0-3.0 eV range, whereas broadband (0.5-6.5 eV) transmission and reflectance measurements provided direct measurements of optical constants through Glover-Tinkham analysis. A comprehensive analysis of thickness and substance dependence of optical properties of our large-area films will be presented and compared with existing literature reports and first-principles electronic structure. Also, Raman measurements reveal interesting disorder related effects on our MoS2 films.

  19. Photoemission electronic states of epitaxially grown magnetite films

    International Nuclear Information System (INIS)

    Zalecki, R.; Kolodziejczyk, A.; Korecki, J.; Spiridis, N.; Zajac, M.; Kozlowski, A.; Kakol, Z.; Antolak, D.

    2007-01-01

    The valence band photoemission spectra of epitaxially grown 300 A single crystalline magnetite films were measured by the angle-resolved ultraviolet photoemission spectroscopy (ARUPS) at 300 K. The samples were grown either on MgO(0 0 1) (B termination) or on (0 0 1) Fe (iron-rich A termination), thus intentionally presenting different surface stoichiometry, i.e. also different surface electronic states. Four main features of the electron photoemission at about -1.0, -3.0, -5.5 and -10.0 eV below a chemical potential show systematic differences for two terminations; this difference depends on the electron outgoing angle. Our studies confirm sensitivity of angle resolved PES technique on subtleties of surface states

  20. Dry etched SiO2 Mask for HgCdTe Etching Process

    Science.gov (United States)

    Chen, Y. Y.; Ye, Z. H.; Sun, C. H.; Deng, L. G.; Zhang, S.; Xing, W.; Hu, X. N.; Ding, R. J.; He, L.

    2016-09-01

    A highly anisotropic etching process with low etch-induced damage is indispensable for advanced HgCdTe (MCT) infrared focal plane array (IRFPA) detectors. The inductively coupled plasma (ICP) enhanced reactive ion etching technique has been widely adopted in manufacturing HgCdTe IRFPA devices. An accurately patterned mask with sharp edges is decisive to accomplish pattern duplication. It has been reported by our group that the SiO2 mask functions well in etching HgCdTe with high selectivity. However, the wet process in defining the SiO2 mask is limited by ambiguous edges and nonuniform patterns. In this report, we patterned SiO2 with a mature ICP etching technique, prior to which a thin ZnS film was deposited by thermal evaporation. The SiO2 film etching can be terminated at the auto-stopping point of the ZnS layer thanks to the high selectivity of SiO2/ZnS in SF6 based etchant. Consequently, MCT etching was directly performed without any other treatment. This mask showed acceptable profile due to the maturity of the SiO2 etching process. The well-defined SiO2 pattern and the etched smooth surfaces were investigated with scanning electron microscopy and atomic force microscope. This new mask process could transfer the patterns exactly with very small etch-bias. A cavity with aspect-ratio (AR) of 1.2 and root mean square roughness of 1.77 nm was achieved first, slightly higher AR of 1.67 was also get with better mask profile. This masking process ensures good uniformity and surely benefits the delineation of shrinking pixels with its high resolution.

  1. Growth stress evolution in HfO2/SiO2 multilayers

    International Nuclear Information System (INIS)

    Li, Jingping; Fang, Ming; He, Hongbo; Shao, Jianda; Fan, Zhengxiu; Li, Zhaoyang

    2012-01-01

    Growth stress in hafnium oxide/silicon dioxide (HfO 2 /SiO 2 ) multilayers was measured in situ to understand the role of the sublayers and the influence of the underlayers' structural features. Experiments using three- and six-layer films were performed by electron-beam evaporation. During deposition, the developing trend of the force per unit width was controlled by changing the thickness ratio of the HfO 2 and SiO 2 layers. The substrate material affected the initial stress evolution of HfO 2 film. The structural feature of the HfO 2 layer onto which SiO 2 was deposited and the whole film thickness have a combined effect on the stress evolution of the SiO 2 layer. - Highlights: ► Film radius stress relates to thickness ratio of sublayers. ► The initial stress evolutions of HfO 2 depended on the substrate material. ► The structural feature of H layer affects the stress evolution of L layer.

  2. Growth Mode Study of MgCl2 on Ti (0001 and SiO2 under Ultra High Vacuum by XPS

    Directory of Open Access Journals (Sweden)

    S. Karakalos

    2012-12-01

    Full Text Available The growth mode of MgCl2 on Ti (0001 and on SiO2 grown on Si (100 was investigated by X-ray Photoelectron Spectroscopy (XPS under UHV conditions. Magnesium chloride grows on both Ti (0001 single crystal and SiO2 following the Frank-van der Merve, (FM growth mode.

  3. Thermoluminescence of ion-implanted SiO2

    International Nuclear Information System (INIS)

    Arnold, G.W.

    1976-01-01

    Thermoluminescence (TL) has been measured from room temperature to 500 0 C for ion-implanted fused silica glasses, crystalline synthetic quartz and rf-sputtered SiO 2 films. Measurements of the TL spectra for widely varying values of electronic and atomic energy depositions, along with the known impurity concentrations of the various systems, has allowed some of the TL features to be identified. In particular, (1) a TL peak at 150 0 C in fused silica has been identified with defects formed by structural modification, (2) a 330 0 C peak in crystalline quartz and relatively impure fused silica is tentatively assigned to a center involving Al, (3) a 100 0 C peak, common to all silicas may be related to oxygen vacancies, and (4) an approximately 200 0 C peak may be the analog of the 245 nm impurity absorption band seen in some fused silica glasses

  4. SiO2 coating of silver nanoparticles by photoinduced chemical vapor deposition.

    Science.gov (United States)

    Boies, Adam M; Roberts, Jeffrey T; Girshick, Steven L; Zhang, Bin; Nakamura, Toshitaka; Mochizuki, Amane

    2009-07-22

    Gas-phase silver nanoparticles were coated with silicon dioxide (SiO2) by photoinduced chemical vapor deposition (photo-CVD). Silver nanoparticles, produced by inert gas condensation, and a SiO2 precursor, tetraethylorthosilicate (TEOS), were exposed to vacuum ultraviolet (VUV) radiation at atmospheric pressure and varying temperatures. The VUV photons dissociate the TEOS precursor, initiating a chemical reaction that forms SiO2 coatings on the particle surfaces. Coating thicknesses were measured for a variety of operation parameters using tandem differential mobility analysis and transmission electron microscopy. The chemical composition of the particle coatings was analyzed using energy dispersive x-ray spectrometry and Fourier transform infrared spectroscopy. The highest purity films were produced at 300-400 degrees C with low flow rates of additional oxygen. The photo-CVD coating technique was shown to effectively coat nanoparticles and limit core particle agglomeration at concentrations up to 10(7) particles cm(-3).

  5. SiO2 coating of silver nanoparticles by photoinduced chemical vapor deposition

    International Nuclear Information System (INIS)

    Boies, Adam M; Girshick, Steven L; Roberts, Jeffrey T; Zhang Bin; Nakamura, Toshitaka; Mochizuki, Amane

    2009-01-01

    Gas-phase silver nanoparticles were coated with silicon dioxide (SiO 2 ) by photoinduced chemical vapor deposition (photo-CVD). Silver nanoparticles, produced by inert gas condensation, and a SiO 2 precursor, tetraethylorthosilicate (TEOS), were exposed to vacuum ultraviolet (VUV) radiation at atmospheric pressure and varying temperatures. The VUV photons dissociate the TEOS precursor, initiating a chemical reaction that forms SiO 2 coatings on the particle surfaces. Coating thicknesses were measured for a variety of operation parameters using tandem differential mobility analysis and transmission electron microscopy. The chemical composition of the particle coatings was analyzed using energy dispersive x-ray spectrometry and Fourier transform infrared spectroscopy. The highest purity films were produced at 300-400 0 C with low flow rates of additional oxygen. The photo-CVD coating technique was shown to effectively coat nanoparticles and limit core particle agglomeration at concentrations up to 10 7 particles cm -3 .

  6. Coulombic and neutral electron trapping centers in SiO 2

    Science.gov (United States)

    Buchanan, D. A.; Fischetti, M. V.; Dimaria, D. J.

    1989-10-01

    Metal-oxide-semiconductor (MOS) structures incorporating thermally grown silicon dioxide (SiO 2) films were implanted with arsenic ions (As +) and then annealed at high temperatures. Coulombic-attractive traps (for electrons) were produced with the avalanche injection of holes from the silicon substrate and their subsequent capture on some of these arsenic-related sites. During internal photo-emission of electrons from a thin aluminum gate, the voltage shifts due to hole annihilation by electrons were recorded and the macroscopic capture cross-section, σ, was determined. We found that σ varies from ˜10 -12 to 3 × 10 -15 cm 2 for average electric fields ranging from 2 × 10 5 to 3 × 10 6 V/cm. Below an average field threshold of Fth ≈ 1.2 × 10 6 V/cm, the capture cross-section versus average field (σ versus Fave) dependence follows a power law with the exponent n ≈ -1.5. Above the average field threshold, the power law exponent was found to be n ≈ -3.0. Also when the amphoteric arsenic-related sites are empty, they form neutral trapping sites for electrons. For average fields ranging from 5 × 10 5 to 6 × 10 6 V/cm, the neutral cross-section is found to be approximately constant at σ ≈ (1-2) × 10 -15 cm 2.

  7. Effect of SiO2 Overlayer on WO3 Sensitivity to Ammonia

    Directory of Open Access Journals (Sweden)

    Vibha Srivastava

    2010-06-01

    Full Text Available Ammonia gas sensing properties of tungsten trioxide thick film sensor was investigated. The doping of noble catalysts such as Pt, Pd, Au enhanced the gas sensitivity. Platinum doping was found to result in highest sensitivity. Remarkable sensitivity enhancement was realized by coating WO3 thick film sensors with SiO2 overlayer. Sol gel process derived silica overlayer increased ammonia gas sensitivity for doped as well as undoped sensor.

  8. Photoluminescence properties of powder and pulsed laser-deposited PbS nanoparticles in SiO2

    International Nuclear Information System (INIS)

    Dhlamini, M.S.; Terblans, J.J.; Ntwaeaborwa, O.M.; Ngaruiya, J.M.; Hillie, K.T.; Botha, J.R.; Swart, H.C.

    2008-01-01

    Thin films of lead sulfide (PbS) nanoparticles embedded in an amorphous silica (SiO 2 ) host were grown on Si(1 0 0) substrates at different temperatures by the pulsed laser deposition (PLD) technique. Surface morphology and photoluminescence (PL) properties of samples were analyzed with scanning electron microscopy (SEM) and a 458 nm Ar + laser, respectively. The PL data show a blue-shift from the normal emission at ∼3200 nm in PbS bulk to ∼560-700 nm in nanoparticulate PbS powders and thin films. Furthermore, the PL emission of the films was red-shifted from that of the powders at ∼560 to ∼660 nm. The blue-shifting of the emission wavelengths from 3200 to ∼560-700 nm is attributed to quantum confinement of charge carriers in the restricted volume of nanoparticles, while the red-shift between powders and thin-film PbS nanoparticles is speculated to be due to an increase in the defect concentration. The red-shift increased slightly with an increase in deposition temperature, which suggests that there has been a relative growth in particle sizes during the PLD of the films at higher temperatures. Generally, the PL emission of the powders was more intense than that of the films, although the intensity of some of the films was improved marginally by post-deposition annealing at 400 deg. C. This paper compares the PL properties of powder and pulsed laser-deposited thin films of PbS nanoparticles and the effects of deposition temperatures

  9. Enhanced formation of Ge nanocrystals in Ge : SiO2 layers by swift heavy ions

    International Nuclear Information System (INIS)

    Antonova, I V; Volodin, V A; Marin, D M; Skuratov, V A; Smagulova, S A; Janse van Vuuren, A; Neethling, J; Jedrzejewski, J; Balberg, I

    2012-01-01

    In this paper we report the ability of swift heavy Xe ions with an energy of 480 MeV and a fluence of 10 12 cm -2 to enhance the formation of Ge nanocrystals within SiO 2 layers with variable Ge contents. These Ge-SiO 2 films were fabricated by the co-sputtering of Ge and quartz sources which followed various annealing procedures. In particular, we found that the irradiation of the Ge : SiO 2 films with subsequent annealing at 500 °C leads to the formation of a high concentration of nanocrystals (NCs) with a size of 2-5 nm, whereas without irradiation only amorphous inclusions were observed. This effect, as evidenced by Raman spectra, is enhanced by pre-irradiation at 550 °C and post-irradiation annealing at 600 °C, which also leads to the observation of room temperature visible photoluminescence. (paper)

  10. Textured YBCO films grown on wires: application to superconducting cables

    International Nuclear Information System (INIS)

    Dechoux, N; Jiménez, C; Chaudouët, P; Rapenne, L; Sarigiannidou, E; Robaut, F; Petit, S; Garaudée, S; Porcar, L; Soubeyroux, J L; Odier, P; Bruzek, C E; Decroux, M

    2012-01-01

    Efforts to fabricate superconducting wires made of YBa 2 Cu 3 O 7 (YBCO) on La 2 Zr 2 O 7 (LZO) buffered and biaxially textured Ni-5 at.%W (NiW) are described. Wires were manually shaped from LZO buffered NiW tapes. Different diameters were produced: 1.5, 2 and 3 mm. The wires were further covered with YBCO grown by metal organic chemical vapor deposition (MOCVD). We developed an original device in which the round substrate undergoes an alternated rotation of 180° around its axis in addition to a reel-to-reel translation. This new approach allows covering the whole circumference of the wire with a YBCO layer. This was confirmed by energy dispersive x-ray spectroscopy (EDX) analysis coupled to a scanning electron microscope (SEM). For all wire diameters, the YBCO layer thickness varied from 300 to 450 nm, and the cationic composition was respected. Electron backscattering diffraction (EBSD) measurements were performed directly on an as-deposited wire without surface preparation allowing the investigation of the crystalline quality of the film surface. Combining EBSD with XRD results we show that YBCO grows epitaxially on the LZO buffered NiW wires. For the first time, superconductive behaviors have been detected on round substrates in both the rolling and circular direction. J c reached 0.3 MA cm −2 as measured at 77 K by transport and third-harmonic detection. Those preliminary results confirm the effectiveness of the MOCVD for complex geometries, especially for YBCO deposition on small diameter wires. This approach opens huge perspectives for the elaboration of a new generation of YBCO-based round conductors. (paper)

  11. Vapor Phase Sensing Using Metal Nanorod Thin Films Grown by Cryogenic Oblique Angle Deposition

    Directory of Open Access Journals (Sweden)

    Piyush Shah

    2013-01-01

    Full Text Available We demonstrate the chemical sensing capability of silver nanostructured films grown by cryogenic oblique angle deposition (OAD. For comparison, the films are grown side by side at cryogenic (~100 K and at room temperature (~300 K by e-beam evaporation. Based on the observed structural differences, it was hypothesized that the cryogenic OAD silver films should show an increased surface enhanced Raman scattering (SERS sensitivity. COMSOL simulation results are presented to validate this hypothesis. Experimental SERS results of 4-aminobenzenethiol (4-ABT Raman test probe molecules in vapor phase show good agreement with the simulation and indicate promising SERS applications for these nanostructured thin films.

  12. Systematic investigation of the reactive ion beam sputter deposition process of SiO2

    Science.gov (United States)

    Mateev, Maria; Lautenschläger, Thomas; Spemann, Daniel; Finzel, Annemarie; Gerlach, Jürgen W.; Frost, Frank; Bundesmann, Carsten

    2018-02-01

    Ion beam sputter deposition (IBSD) is an established physical vapour deposition technique that offers the opportunity to tailor the properties of film-forming particles and, consequently, film properties. This is because of two reasons: (i) ion generation and acceleration (ion source), sputtering (target) and film deposition (substrate) are locally separated. (ii) The angular and energy distribution of sputtered target atoms and scattered primary particles depend on ion incidence angle, ion energy, and ion species. Ion beam sputtering of a Si target in a reactive oxygen atmosphere was used to grow SiO2 films on silicon substrates. The sputtering geometry, ion energy and ion species were varied systematically and their influence on film properties was investigated. The SiO2 films are amorphous. The growth rate increases with increasing ion energy and ion incidence angle. Thickness, index of refraction, stoichiometry, mass density and surface roughness show a strong correlation with the sputtering geometry. A considerable amount of primary inert gas particles is found in the deposited films. The primary ion species also has an impact on the film properties, whereas the influence of the ion energy is rather small.

  13. 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

  14. Electrical Characterization of Ti-Silicate Films Grown by Atomic Layer Chemical Vapor Deposition

    Science.gov (United States)

    Lee, Seungjae; Yong, Kijung

    2007-08-01

    Electrical characterization was performed for Ti-silicate films, which were deposited by atomic layer chemical vapor deposition (ALCVD). Before the deposition of Ti-silicate films, the silicon substrates were pretreated differently using hydrofluoric acid (HF)-etching, chemical oxidation, and thermal oxidation. Regardless of the pretreatment methods, the grown films showed a highly smooth surface with rms below 0.52 nm. The electrical properties of the grown Ti-silicate films showed a strong dependence on the substrate pretreatments. The 5-nm-thick Ti-silicate films grown on hydrogen-passivated Si and chemically oxidized Si showed rather high leakage currents, whereas the films grown on thermally oxidized Si showed low leakage currents below 1× 10-7 A/cm2 at a bias of -1 V. All of the films showed a positive shift in the flatband voltage (VFB) upon annealing. Also, each film showed low a hysteresis below 180 mV and the hysteresis decreased upon annealing.

  15. Investigation of the SiO2/Si(1 0 0) interface structure by means of angle-scanned photoelectron spectroscopy and diffraction

    International Nuclear Information System (INIS)

    Dreiner, S.; Schuermann, M.; Westphal, C.

    2004-01-01

    The local environment of Si at the interface between a thermally grown SiO 2 film and Si(1 0 0) was studied by angle-scanned photoelectron spectroscopy and diffraction. Si 2p core-level spectra containing chemically shifted components were recorded. These components were deconvoluted by least squares fitting and assigned to different Si oxidation states. The angular dependence of the photoelectron intensity was obtained from the least squares fit results. A simple statistical model was developed to describe the population and depth distribution of the different suboxide species. Using a simple electron attenuation scheme we can simulate the photoemission polar angle dependence of the various Si oxidation states within the model. The fitting of these model curves to the experimental data results in parameters which indicate a Si-O-Si bridge-bonded interface structure

  16. Electrical properties of ZnO thin films grown by MOCVD

    International Nuclear Information System (INIS)

    Pagni, O.; Somhlahlo, N.N.; Weichsel, C.; Leitch, A.W.R.

    2006-01-01

    We report on the electrical characterization of ZnO films grown by MOCVD on glass and sapphire substrates. After correcting our temperature variable Hall measurements by applying the standard two-layer model, which takes into account an interfacial layer, scattering mechanisms in the ZnO films were studied as well as donor activation energies determined. ZnO films grown at different oxygen partial pressures indicated the importance of growth conditions on the defect structure by means of their conductivities and conductivity activation energies

  17. Electrical properties of ZnO thin films grown by MOCVD

    Energy Technology Data Exchange (ETDEWEB)

    Pagni, O. [Department of Physics, Nelson Mandela Metropolitan University, P.O. Box 77000, Port Elizabeth 6031 (South Africa); Somhlahlo, N.N. [Department of Physics, Nelson Mandela Metropolitan University, P.O. Box 77000, Port Elizabeth 6031 (South Africa); Weichsel, C. [Department of Physics, Nelson Mandela Metropolitan University, P.O. Box 77000, Port Elizabeth 6031 (South Africa); Leitch, A.W.R. [Department of Physics, Nelson Mandela Metropolitan University, P.O. Box 77000, Port Elizabeth 6031 (South Africa)]. E-mail: andrew.leitch@nmmu.ac.za

    2006-04-01

    We report on the electrical characterization of ZnO films grown by MOCVD on glass and sapphire substrates. After correcting our temperature variable Hall measurements by applying the standard two-layer model, which takes into account an interfacial layer, scattering mechanisms in the ZnO films were studied as well as donor activation energies determined. ZnO films grown at different oxygen partial pressures indicated the importance of growth conditions on the defect structure by means of their conductivities and conductivity activation energies.

  18. Oxide Ceramic Films Grown on 60 Nitinol for NASA and Department of Defense Applications

    Science.gov (United States)

    Miyoshi, Kazuhisa; Street, Kenneth W.; Lukco, Dorothy; Cytron, Sheldon J.

    2005-01-01

    Both the NASA Glenn Research Center and the U.S. Army Research Laboratory, Development and Engineering Center (ARDEC) have worked to develop oxide ceramic films grown on 60 nitinol (60-wt% nickel and 40-wt% titanium) to decrease friction and increase wear resistance under unlubricated conditions. In general, oxide and nonoxide ceramic films have unique capabilities as mechanical-, chemical-, and thermal-barrier materials in diverse applications, including high-temperature bearings and gas bearings requiring low friction, wear resistance, and chemical stability. All oxide ceramic films grown on 60 nitinol were furnished by ARDEC, and materials and surface characterization and tribological experiments were conducted at Glenn.

  19. Sub-wavelength antireflection coatings from nanostructure sculptured thin films

    International Nuclear Information System (INIS)

    Schubert, E.

    2007-01-01

    Nanostructure sculptured thin films from SiO 2 are grown on quartz substrates by ion beam sputter deposition using rotating substrate motion accommodated to an oblique angle of incidence for the particle flux. Structural peculiarities of sculptured thin films have an intriguing impact on the optical response upon reflection of light with different wavelengths. The reflectivity of quartz substrates coated with SiO 2 sub-wavelength nanostructures is simulated by means of effective medium theory and antireflection is predicted for the deep ultraviolet spectral region. Spectroscopic ellipsometry and reflectivity measurements are performed on SiO 2 sculptured thin films and antireflection near λ = 193 nm is found. (copyright 2007 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  20. Thermal stability of amorphous carbon films grown by pulsed laser deposition

    Science.gov (United States)

    Friedmann, T. A.; McCarty, K. F.; Barbour, J. C.; Siegal, M. P.; Dibble, Dean C.

    1996-03-01

    The thermal stability in vacuum of amorphous tetrahedrally coordinated carbon (a-tC) films grown on Si has been assessed by in situ Raman spectroscopy. Films were grown in vacuum on room-temperature substrates using laser fluences of 12, 22, and 45 J/cm2 and in a background gas of either hydrogen or nitrogen using a laser fluence of 45 J/cm2. The films grown in vacuum at high fluence (≳20J/cm2) show little change in the a-tC Raman spectra with temperature up to 800 °C. Above this temperature the films convert to glassy carbon (nanocrystalline graphite). Samples grown in vacuum at lower fluence or in a background gas (H2 or N2) at high fluence are not nearly as stable. For all samples, the Raman signal from the Si substrate (observed through the a-tC film) decreases in intensity with annealing temperature indicating that the transparency of the a-tC films is decreasing with temperature. These changes in transparency begin at much lower temperatures (˜200 °C) than the changes in the a-tC Raman band shape and indicate that subtle changes are occurring in the a-tC films at lower temperatures.

  1. Fabrication of Nb2O5/SiO2 mixed oxides by reactive magnetron co-sputtering

    International Nuclear Information System (INIS)

    Juškevičius, Kęstutis; Audronis, Martynas; Subačius, Andrius; Kičas, Simonas; Tolenis, Tomas; Buzelis, Rytis; Drazdys, Ramutis; Gaspariūnas, Mindaugas; Kovalevskij, Vitalij; Matthews, Allan; Leyland, Adrian

    2015-01-01

    This paper investigates niobia/silica mixed oxide thin films deposited by reactive pulse-DC/RF magnetron co-sputtering of Nb and Si metal targets at room temperature. The reactive gas flow during the sputtering processes was either controlled by direct mass flow rate (i.e. constant reactive gas flow) or by an active feedback process control system. 61% and 137% higher deposition rates of Nb 2 O 5 and SiO 2 layers, respectively, were obtained using the latter technique as compared to constant reactive gas flow. Films exhibited bulk or near-bulk density. All mixture films produced in this study had an amorphous structure. A volume law of mixtures was used to determine the coating composition. It is shown that the fraction of SiO 2 or/and Nb 2 O 5 has a linear dependency on sputter target power density. On this basis, rugate filter coating designs can be easily deposited, where refractive index gradually varies between that of pure Nb 2 O 5 and pure SiO 2 . Substantially less inhomogeneity of coating mixtures was found in films produced using a reactive sputtering process with feedback-control. - Highlights: • 61% and 137% increase in deposition rates of Nb 2 O 5 and SiO 2 • Rugate coating designs can be readily deposited. • Nb 2 O 5 /SiO 2 mixture films exhibited bulk or near-bulk density. • Optimized process leads to stoichiometric and homogenous mixtures. • Films are amorphous and suitable for low loss optical coatings

  2. Electrical properties of epitaxially grown VOx thin films

    NARCIS (Netherlands)

    Rata, A.D.; Chezan, A.R; Presura, C.N.; Hibma, T

    2003-01-01

    High quality VOx thin films on MgO(100) substrates were prepared and studied from the structural and electronic point of view. Epitaxial growth was confirmed by RHEED and XRD techniques. The oxygen content of VOx thin films as a function of oxygen flux was determined using RBS. The upper and lower

  3. Doped nanostructured zinc oxide films grown by electrodeposition.

    Science.gov (United States)

    Donderis, V; Orozco, J; Cembrero, J; Curiel-Esparza, J; Damonte, L C; Hernández-Fenollosa, M A

    2010-02-01

    ZnO thin films doped with either In or Al are n-type oxide materials of interest for application in electronic devices and thin-film solar cells. In this work, the doped ZnO films were electrodeposited at 80 degrees C from an aqueous solution on polycrystalline conductive Indium Tin Oxide covered glass substrates. The incorporation of the dopants into the ZnO film has been verified by energy dispersive X-ray spectrum, X-Ray diffraction and optical transmission analysis. The optical and surface structure properties of the ZnO doped films are strongly affected by the In and Al concentrations in the electrodeposition solution as evidenced by optical transmission and reflection measurements, and scanning electron microscopy.

  4. Surface Property and Stability of Transparent Superhydrophobic Coating Based on SiO2-Polyelectrolyte Multilayer

    Directory of Open Access Journals (Sweden)

    Sunisa JINDASUWAN

    2016-05-01

    Full Text Available Artificial superhydrophobic films were deposited onto a glass slide by performing layer-by-layer deposition of 3.5 bilayers of poly(allylamine hydrochloride/ poly(acrylic acid polyelectrolyte, followed by a layer of SiO2 nanoparticles of various amounts to enhance the surface roughness and a fluorosilane to reduce the surface free energy. Higher SiO2 content incorporated into the films resulted in rougher surface and higher water contact angle. The total surface free energy determined by using the Owens-Wendt equation dramatically decreased from 31.46 mJ·m-2 for the film having the relatively flat surface to only 1.16 mJ·m-2 for the film having the highest surface roughness of 60.2 ± 1.1 nm. All the films were optically transparent and had excellent adhesion based on the peel test. Indoor and accelerated weathering tests revealed good weathering stability.DOI: http://dx.doi.org/10.5755/j01.ms.22.2.12952

  5. 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

  6. Phase transition of bismuth telluride thin films grown by MBE

    DEFF Research Database (Denmark)

    Fülöp, Attila; Song, Yuxin; Charpentier, Sophie

    2014-01-01

    A previously unreported phase transition between Bi2Te3 and Bi4Te3 in bismuth telluride grown by molecular beam epitaxy is recorded via XRD, AFM, and SIMS observations. This transition is found to be related to the Te/Bi beam equivalent pressure (BEP) ratio. BEP ratios below 17 favor the formation...

  7. Hydroxyapatite-TiO2-SiO2-Coated 316L Stainless Steel for Biomedical Application

    Science.gov (United States)

    Sidane, Djahida; Khireddine, Hafit; Bir, Fatima; Yala, Sabeha; Montagne, Alex; Chicot, Didier

    2017-07-01

    This study investigated the effectiveness of titania (TiO2) as a reinforcing phase in the hydroxyapatite (HAP) coating and silica (SiO2) single layer as a bond coat between the TiO2-reinforced hydroxyapatite (TiO2/HAP) top layer and 316L stainless steel (316L SS) substrate on the corrosion resistance and mechanical properties of the underlying 316L SS metallic implant. Single layer of SiO2 film was first deposited on 316L SS substrate and studied separately. Water contact angle measurements, X-ray photoelectron spectroscopy, and Fourier transform infrared spectrophotometer analysis were used to evaluate the hydroxyl group reactivity at the SiO2 outer surface. The microstructural and morphological results showed that the reinforcement of HAP coating with TiO2 and SiO2 reduced the crystallite size and the roughness surface. Indeed, the deposition of 50 vol pct TiO2-reinforced hydroxyapatite layer enhanced the hardness and the elastic modulus of the HAP coating, and the introduction of SiO2 inner layer on the surface of the 316L SS allowed the improvement of the bonding strength and the corrosion resistance as confirmed by scratch studies, nanoindentation, and cyclic voltammetry tests.

  8. Microhardness studies on thin carbon films grown on P-type, (100) silicon

    Science.gov (United States)

    Kolecki, J. C.

    1982-01-01

    A program to grow thin carbon films and investigate their physical and electrical properties is described. Characteristics of films grown by rf sputtering and vacuum arc deposition on p type, (100) silicon wafers are presented. Microhardness data were obtained from both the films and the silicon via the Vickers diamond indentation technique. These data show that the films are always harder than the silicon, even when the films are thin (of the order of 1000 A). Vacuum arc films were found to contain black carbon inclusions of the order of a few microns in size, and clusters of inclusions of the order of tens of microns. Transmission electron diffraction showed that the films being studied were amorphous in structure.

  9. Optical properties of Al2O3 thin films grown by atomic layer deposition.

    Science.gov (United States)

    Kumar, Pradeep; Wiedmann, Monika K; Winter, Charles H; Avrutsky, Ivan

    2009-10-01

    We employed the atomic layer deposition technique to grow Al(2)O(3) films with nominal thicknesses of 400, 300, and 200 nm on silicon and soda lime glass substrates. The optical properties of the films were investigated by measuring reflection spectra in the 400-1800 nm wavelength range, followed by numerical fitting assuming the Sellmeier formula for the refractive index of Al(2)O(3). The films grown on glass substrates possess higher refractive indices as compared to the films on silicon. Optical waveguiding is demonstrated, confirming the feasibility of high-index contrast planar waveguides fabricated by atomic layer deposition.

  10. Disordered electrical potential observed on the surface of SiO2 by electric field microscopy

    International Nuclear Information System (INIS)

    GarcIa, N; Yan Zang; Ballestar, A; Barzola-Quiquia, J; Bern, F; Esquinazi, P

    2010-01-01

    The electrical potential on the surface of ∼300 nm thick SiO 2 grown on single-crystalline Si substrates has been characterized at ambient conditions using electric field microscopy. Our results show an inhomogeneous potential distribution with fluctuations up to ∼0.4 V within regions of 1 μm. The potential fluctuations observed at the surface of these usual dielectric holders of graphene sheets should induce strong variations in the graphene charge densities and provide a simple explanation for some of the anomalous behaviors of the transport properties of graphene.

  11. SiO2-supported Pt particles studied by electron microscopy

    International Nuclear Information System (INIS)

    Wang, D.; Penner, S.; Su, D.S.; Rupprechter, G.; Hayek, K.; Schloegl, R.

    2003-01-01

    Regularly grown Pt particles supported by amorphous SiO 2 were heated in hydrogen at 873 K after an oxidising treatment. The morphological and structural changes were studied by electron microscopy. Platinum silicides Pt 3 Si with L1 2 (Cu 3 Au) structure, monoclinic Pt 3 Si and tetragonal Pt 12 Si 5 were identified after the treatment. The mechanisms of coalescence of the particles and the formation of irregular large particles are suggested. A topotactic structural transformation accompanied with the migration of Si from the substrate to the particles are suggested to take place during Pt 3 Si formation

  12. Nonequilibrium Water Permeation in SiO2 Thin Films

    Science.gov (United States)

    1982-06-01

    treatments was negligible. related by the law of detailed balance The concentrations of hydrogen carried in by absorbed wa- ter were then profiled with...2 allow some inferences to be drawn. Our evidence for a multi- used for reaction-rate law determination. Note that a break component reaction is...consistent with the results of Walra - clearly occurs in the curve of [H] vs t for either treatment fen and Samanta,Ř who showed that the 3690-cm -’ OH

  13. Morphology and photoresponse of crystalline antimony film grown on mica by physical vapor deposition

    Directory of Open Access Journals (Sweden)

    Shafa Muhammad

    2016-09-01

    Full Text Available Antimony is a promising material for the fabrication of photodetectors. This study deals with the growth of a photosensitive thin film by the physical vapor deposition (PVD of antimony onto mica surface in a furnace tube. The geometry of the grown structures was studied via scanning electron microscopy (SEM, X-ray diffraction (XRD, energy-dispersive X-ray spectroscopy (EDX and elemental diffraction analysis. XRD peaks of the antimony film grown on mica mostly matched with JCPDF Card. The formation of rhombohedral crystal structures in the film was further confirmed by SEM micrographs and chemical composition analysis. The Hall measurements revealed good electrical conductivity of the film with bulk carrier concentration of the order of 1022 Ω·cm-3 and mobility of 9.034 cm2/Vs. The grown film was successfully tested for radiation detection. The photoresponse of the film was evaluated using its current-voltage characteristics. These investigations revealed that the photosensitivity of the antimony film was 20 times higher than that of crystalline germanium.

  14. Nanocrystalline magnetite thin films grown by dual ion-beam sputtering

    Energy Technology Data Exchange (ETDEWEB)

    Prieto, Pilar, E-mail: pilar.prieto@uam.es [Departamento de Física Aplicada M-12, Universidad Autónoma de Madrid, Cantoblanco, 28049 Madrid (Spain); Ruiz, Patricia [Departamento de Física Aplicada M-12, Universidad Autónoma de Madrid, Cantoblanco, 28049 Madrid (Spain); Ferrer, Isabel J. [Departamento de Física de Materiales M-4, Universidad Autónoma de Madrid, Cantoblanco, 28049 Madrid (Spain); Figuera, Juan de la; Marco, José F. [Instituto de Química Física “Rocasolano”, CSIC, Serrano 119, 28006 Madrid (Spain)

    2015-07-05

    Highlights: • We have grown tensile and compressive strained nanocrystalline magnetite thin films by dual ion beam sputtering. • The magnetic and thermoelectric properties can be controlled by the deposition conditions. • The magnetic anisotropy depends on the crystalline grain size. • The thermoelectric properties depend on the type of strain induced in the films. • In plane uniaxial magnetic anisotropy develops in magnetite thin films with grain sizes ⩽20 nm. - Abstract: We have explored the influence of an ion-assisted beam in the thermoelectric and magnetic properties of nanocrystalline magnetite thin films grown by ion-beam sputtering. The microstructure has been investigated by XRD. Tensile and compressive strained thin films have been obtained as a function of the parameters of the ion-assisted beam. The evolution of the in-plane magnetic anisotropy was attributed to crystalline grain size. In some films, magneto-optical Kerr effect measurements reveal the existence of uniaxial magnetic anisotropy induced by the deposition process related with a small grain size (⩽20 nm). Isotropic magnetic properties have observed in nanocrystalline magnetite thin film having larger grain sizes. The largest power factor of all the films prepared (0.47 μW/K{sup 2} cm), obtained from a Seebeck coefficient of −80 μV/K and an electrical resistivity of 13 mΩ cm, is obtained in a nanocrystalline magnetite thin film with an expanded out-of-plane lattice and with a grain size ≈30 nm.

  15. Characterisation of molecular thin films grown by organic molecular beam deposition

    CERN Document Server

    Bayliss, S M

    2000-01-01

    This work concerns the growth and characterisation of molecular thin films in an ultra high vacuum regime by organic molecular beam deposition (OMBD). Films of three different molecular materials are grown, namely free base phthalocyanine (H sub 2 Pc), perylene 3,4,9,10-tetracarboxylic dianhydride (PTCDA) and aluminium tris-8-hydroxyquinoline (Alq sub 3). The relationship between the growth parameters such as film thickness, growth rate, and substrate temperature during and after growth, and the structural, optical and morphological properties of the film are investigated. These investigations are carried out using various ex-situ techniques. X-ray diffraction, Raman spectroscopy and electronic absorption spectroscopy are used to probe the bulk film characteristics, whilst Nomarski microscopy and atomic force microscopy are used to study the surface morphology. Three different levels of influence of the growth parameters on the film properties are observed. In the case of H sub 2 Pc, two crystal phases are fo...

  16. Crystalline thin films of transition metal hexacyanochromates grown under Langmuir monolayer

    International Nuclear Information System (INIS)

    Bagkar, Nitin; Choudhury, Sipra; Kim, Kyung-Hee; Chowdhury, Prasanta; Lee, Sung-Ik; Yakhmi, J.V.

    2006-01-01

    Crystalline films of cobalt, nickel and iron hexacyanochromates (analogues of Prussian blue) were grown at air-water interface using a surfactant monolayer as a template. These films were transferred on suitable substrates and characterized by X-ray diffraction (XRD), cyclic voltammetry and magnetization measurements. XRD patterns confirmed the formation of oriented crystals in {100} direction for all these films. Magnetization data on nickel and iron hexacyanochromate films indicated ferromagnetic behaviour below Curie temperatures of 72 and 21 K, respectively. The methodology adopted by us to grow crystalline films is useful in obtaining magnetic thin films of analogues of Prussian blue with interesting magnetic properties with respect to transition temperatures and nature of magnetic ordering

  17. Characterization of PLD grown WO3 thin films for gas sensing

    Science.gov (United States)

    Boyadjiev, Stefan I.; Georgieva, Velichka; Stefan, Nicolaie; Stan, George E.; Mihailescu, Natalia; Visan, Anita; Mihailescu, Ion N.; Besleaga, Cristina; Szilágyi, Imre M.

    2017-09-01

    Tungsten trioxide (WO3) thin films were grown by pulsed laser deposition (PLD) with the aim to be applied in gas sensors. The films were studied by atomic force microscopy (AFM), X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy and profilometry. To study the gas sensing behavior of these WO3 films, they were deposited on quartz resonators and the quartz crystal microbalance (QCM) method was applied to analyze their gas sensitivity. Synthesis of tetragonal-WO3 films starting from a target with predominantly monoclinic WO3 phase was observed. The films deposited at 300 °C presented a surface topology favorable for the sorption properties, consisting of a film matrix with protruding craters/cavities. QCM prototype sensors with such films were tested for NO2 sensing. The PLD grown WO3 thin films show good sensitivity and fast reaction at room temperature, even in as-deposited state. With the presented technology, the manufacturing of QCM gas sensors is simple, fast and cost-effective, and it is also suitable for energy-effective portable equipment for on-line monitoring of environmental changes.

  18. Effect of hydrostatic pressure on photoluminescence spectra from structures with Si nanocrystals fabricated in SiO2 matrix

    International Nuclear Information System (INIS)

    Zhuravlev, K.S.; Tyschenko, I.E.; Vandyshev, E.N.; Bulytova, N.V.; Misiuk, A.; Rebohle, L.; Skorupa, W.

    2002-01-01

    The effect of hydrostatic pressure applied at high temperature on photoluminescence of Si-implanted SiO 2 films was studied. A 'blue'-shift of PL spectrum from the SiO 2 films implanted with Si + ions to total dose of 1.2x10 17 cm -2 with increase in hydrostatic pressure was observed. For the films implanted with Si + ions to a total dose of 4.8x10 16 cm -2 high temperature annealing under high hydrostatic pressure (12 kbar) causes a 'red'-shift of photoluminescence spectrum. The 'red' photoluminescence bands are attributed to Si nanocrystals while the 'blue' ones are related to Si nanocrystals of reduced size or chains of silicon atoms or Si-Si defects. A decrease in size of Si nanocluster occurs in result of the pressure-induced decrease in the diffusion of silicon atoms. (author)

  19. Intrinsic Charge Trapping Observed as Surface Potential Variations in diF-TES-ADT Films.

    Science.gov (United States)

    Hoffman, Benjamin C; McAfee, Terry; Conrad, Brad R; Loth, Marsha A; Anthony, John E; Ade, Harald W; Dougherty, Daniel B

    2016-08-24

    Spatial variations in surface potential are measured with Kelvin probe force microscopy for thin films of 2,8-difluoro-5,11-bis(triethylsilylethynyl)anthradithiophenes (diF-TES-ADT) grown on SiO2 and silane-treated SiO2 substrates by organic molecular beam deposition. The variations are observed both between and within grains of the polycrystalline organic film and are quantitatively different than electrostatic variations on the substrate surfaces. The skewness of surface potential distributions is larger on SiO2 than on HMDS-treated substrates. This observation is attributed to the impact of substrate functionalization on minimizing intrinsic crystallographic defects in the organic film that can trap charge.

  20. Strain relaxation in thin films of Cu grown on Ni(001)

    DEFF Research Database (Denmark)

    Rasmussen, F.B.; Baker, J.; Nielsen, M.

    1998-01-01

    Surface X-ray diffraction and kinematical model calculations are used to determine the strain relaxation of embedded wedges with internal (111) facets formed in thin Cu films when grown on Ni(001). We show the wedges to be inhomogenously strained with a large lateral relaxation near the Cu...

  1. Optical characterization of a-Si:H thin films grown by Hg-Photo-CVD

    International Nuclear Information System (INIS)

    Barhdadi, A.; Karbal, S.; M'Gafad, N.; Benmakhlouf, A.; Chafik El Idrissi, M.; Aka, B.M.

    2006-08-01

    Mercury-Sensitized Photo-Assisted Chemical Vapor Deposition (Hg-Photo-CVD) technique opens new possibilities for reducing thin film growth temperature and producing novel semiconductor materials suitable for the future generation of high efficiency thin film solar cells onto low cost flexible plastic substrates. This paper provides some experimental data resulting from the optical characterization of hydrogenated amorphous silicon thin films grown by this deposition technique. Experiments have been performed on both as-deposited layers and thermal annealed ones. (author) [fr

  2. Optimized growth conditions of epitaxial SnSe films grown by pulsed laser deposition

    Science.gov (United States)

    Hara, Takamitsu; Fujishiro, Hiroyuki; Naito, Tomoyuki; Ito, Akihiko; Goto, Takashi

    2017-12-01

    We have grown epitaxial tin monoselenide (SnSe) films on MgO or SrTiO3 (STO) substrates by pulsed laser deposition (PLD) at T s = 473 or 573 K, and investigated the optimized growth condition in terms of crystal orientation, crystallinity, and electrical resistivity. For the PLD procedure, a SnSe x (x = 1.0–1.6) target containing excess Se was used to compensate for the vaporization of Se. The crystal orientation and crystallinity of the SnSe films changed depending on the growth conditions, and the magnitude of the electrical resistivity ρ of the films was closely related to the crystalline nature. The SnSe film grown on the MgO substrate at T s = 573 K using the target with x = 1.4 was the most highly a-axis-oriented and highly crystalized among all of the films investigated in this study. However, the ρ of the film in the bc-plane was about one order of magnitude larger than those of the reported single crystal and the a-axis-oriented crystalline sample fabricated by spark plasma sintering. This larger ρ was suggested to result from the lattice mismatch and/or a small amount of nonstoichiometry in the film.

  3. Ar ions irradiation effects in ZrN thin films grown by pulsed laser deposition

    Energy Technology Data Exchange (ETDEWEB)

    Craciun, D.; Socol, G.; Dorcioman, G. [Laser Department, National Institute for Laser, Plasma, and Radiation Physics, Bucharest-Magurele (Romania); Simeone, D.; Gosset, D. [CEA/DEN/DANS/DM2S/SERMA/LEPP-LRC CARMEN CEN Saclay France & CNRS/SPMS UMR8785 LRC CARMEN, Ecole Centrale de Paris, F92292 Chatenay Malabry (France); Behdad, S.; Boesl, B. [Department of Mechanical and Materials Engineering, Florida International University, Miami, FL 33174 (United States); Craciun, V., E-mail: valentin.craciun@inflpr.ro [Laser Department, National Institute for Laser, Plasma, and Radiation Physics, Bucharest-Magurele (Romania)

    2015-05-01

    Highlights: • Polycrystalline and hard ZrN films were grown by pulsed laser deposition technique. • The effect of 800 keV Ar ion irradiation on properties of ZrN films was investigated. • ZrN films irradiated with 10{sup 14} Ar ions/cm{sup 2}did not show major structural changes. • Irradiation with 10{sup 15} Ar ions/cm{sup 2} induced large structural and mechanical changes. - Abstract: Thin ZrN films (<500 nm) were grown on (1 0 0)Si substrates at a substrate temperature of 500 °C by the pulsed laser deposition (PLD) technique using a KrF excimer laser under CH{sub 4} or N{sub 2} atmosphere. Glancing incidence X-ray diffraction showed that films were nanocrystalline, while X-ray reflectivity studies indicated that the films were very dense and with a smooth surface. The films were used to study the effect of 800 keV Ar ion irradiation on their structure and properties. After irradiation with a dose of 10{sup 14} at/cm{sup 2} the lattice parameter and crystallites size did marginally change. However, after irradiation with a 10{sup 15} at/cm{sup 2} dose, a clear increase in the lattice parameter accompanied by a significant decrease in nanohardness and Young modulus were observed.

  4. Amphoteric Behavior of Impurities in GaN Film Grown on Si Substrate

    Science.gov (United States)

    Cho, Hyun-Ick; Lee, Dong-Sik; Lee, Heon-Bok; Hahm, Sung-Ho; Lee, Jung-Hee

    2007-05-01

    Hall measurement presented that an unintentionally doped uniform and crack-free GaN film grown on n-type (111)-oriented Si substrate with high temperature-grown relatively thin AlN single and multiple buffer layer shows p-type conductivity. The position of valence band maximum at the surface of the film measured by the synchrotron radiation photoemission spectroscopy is below Fermi level at 1.09 eV due to band bending at the surface, which is indicative for the p-type nature of the grown film. The n-channel metal-oxide-semiconductor field effect transistor (MOSFET) fabricated on the GaN layer exhibited normally-off mode operation. This cannot be achieved if the GaN layer is not p-type. It is believed that the spatial coordination of auto-doped Si atoms, out-diffused from the substrate, or carbon complexes from metal-organic (MO) precursor favorably occupy the substitutional nitrogen site of the GaN film when the film is under tensile strain during the growth, which clearly explains that the p-type conduction is originated from the stress dependent amphoteric nature of Si atom and/or carbon complex in GaN.

  5. Use of photoluminescence spectroscopy to characterize the crystalline quality of CdTe films grown by a modified CSVT technique

    International Nuclear Information System (INIS)

    Mendoza-Alvarez, J.G.; Sanchez-Sinencio, F.; Zelaya, O.; Gonzalez-Hernandez, Y.J.; Cardenas, M.; Chao, S.S.

    1987-01-01

    The authors have employed photoluminescence measurements at 10-300 0 K to study the effects of deposition parameters, surface preparation and heat treatment on the properties of CdTe polycrystalline thin films. The films were grown using a modified hot wall close spaced vapor transport system. The authors found strong differences in the photoluminescence spectra of samples grown under different conditions. Heat treatments in the as-grown samples increase the average particle size and reduce the native defect density

  6. Crystallinity Improvement of Zn O Thin Film on Different Buffer Layers Grown by MBE

    International Nuclear Information System (INIS)

    Shao-Ying, T.; Che-Hao, L.; Wen-Ming, Ch.; Yang, C.C.; Po-Ju, Ch.; Hsiang-Chen, W.; Ya-Ping, H.

    2012-01-01

    The material and optical properties of Zn O thin film samples grown on different buffer layers on sapphire substrates through a two-step temperature variation growth by molecular beam epitaxy were investigated. The thin buffer layer between the Zn O layer and the sapphire substrate decreased the lattice mismatch to achieve higher quality Zn O thin film growth. A Ga N buffer layer slightly increased the quality of the Zn O thin film, but the threading dislocations still stretched along the c-axis of the Ga N layer. The use of Mg O as the buffer layer decreased the surface roughness of the Zn O thin film by 58.8% due to the suppression of surface cracks through strain transfer of the sample. From deep level emission and rocking curve measurements it was found that the threading dislocations play a more important role than oxygen vacancies for high-quality Zn O thin film growth.

  7. Nanostructured Diamond-Like Carbon Films Grown by Off-Axis Pulsed Laser Deposition

    Directory of Open Access Journals (Sweden)

    Seong Shan Yap

    2015-01-01

    Full Text Available Nanostructured diamond-like carbon (DLC films instead of the ultrasmooth film were obtained by pulsed laser ablation of pyrolytic graphite. Deposition was performed at room temperature in vacuum with substrates placed at off-axis position. The configuration utilized high density plasma plume arriving at low effective angle for the formation of nanostructured DLC. Nanostructures with maximum size of 50 nm were deposited as compared to the ultrasmooth DLC films obtained in a conventional deposition. The Raman spectra of the films confirmed that the films were diamond-like/amorphous in nature. Although grown at an angle, ion energy of >35 eV was obtained at the off-axis position. This was proposed to be responsible for subplantation growth of sp3 hybridized carbon. The condensation of energetic clusters and oblique angle deposition correspondingly gave rise to the formation of nanostructured DLC in this study.

  8. High quality atomically thin PtSe2 films grown by molecular beam epitaxy

    Science.gov (United States)

    Yan, Mingzhe; Wang, Eryin; Zhou, Xue; Zhang, Guangqi; Zhang, Hongyun; Zhang, Kenan; Yao, Wei; Lu, Nianpeng; Yang, Shuzhen; Wu, Shilong; Yoshikawa, Tomoki; Miyamoto, Koji; Okuda, Taichi; Wu, Yang; Yu, Pu; Duan, Wenhui; Zhou, Shuyun

    2017-12-01

    Atomically thin PtSe2 films have attracted extensive research interests for potential applications in high-speed electronics, spintronics and photodetectors. Obtaining high quality thin films with large size and controlled thickness is critical. Here we report the first successful epitaxial growth of high quality PtSe2 films by molecular beam epitaxy. Atomically thin films from 1 ML to 22 ML have been grown and characterized by low-energy electron diffraction, Raman spectroscopy and x-ray photoemission spectroscopy. Moreover, a systematic thickness dependent study of the electronic structure is revealed by angle-resolved photoemission spectroscopy (ARPES), and helical spin texture is revealed by spin-ARPES. Our work provides new opportunities for growing large size single crystalline films to investigate the physical properties and potential applications of PtSe2.

  9. Nondestructive measurement of homoepitaxially grown GaN film thickness with Fourier transform infrared spectroscopy

    Science.gov (United States)

    Horikiri, Fumimasa; Narita, Yoshinobu; Yoshida, Takehiro

    2017-12-01

    In vertical devices containing GaN homoepitaxial layers on GaN substrates, the layer thickness is a key parameter that needs to be clarified before starting the device process. We applied Fourier transform infrared spectroscopy (FT-IR) to a homoepitaxially grown GaN film that consisted of an n--GaN layer. The estimated film thickness from the FT-IR spectrum agreed well with the results of cross-sectional scanning electron microscope cathodoluminescence images. This is the first report of nondestructive film thickness measurements for homoepitaxially grown GaN and indicates the applicability of FT-IR to the nondestructive inspection of vertical GaN power devices.

  10. Structural and nonlinear optical properties of as-grown and annealed metallophthalocyanine thin films

    Energy Technology Data Exchange (ETDEWEB)

    Zawadzka, A., E-mail: azawa@fizyka.umk.pl [Institute of Physics, Faculty of Physics, Astronomy and Informatics, Nicolaus Copernicus University, Grudziadzka 5, 87-100 Torun (Poland); Płóciennik, P.; Strzelecki, J. [Institute of Physics, Faculty of Physics, Astronomy and Informatics, Nicolaus Copernicus University, Grudziadzka 5, 87-100 Torun (Poland); Pranaitis, M.; Dabos-Seignon, S.; Sahraoui, B. [LUNAM Université, Université d' Angers, CNRS UMR 6200, Laboratoire MOLTECH-Anjou, 2 bd Lavoisier, 49045 Angers cedex (France)

    2013-10-31

    The paper presents the Third Harmonic Generation investigation of four metallophtalocyanine (MPc, M = Cu, Co, Mg and Zn) thin films. The investigated films were fabricated by Physical Vapor Deposition in high vacuum onto quartz substrates. MPc thin films were annealed after fabrication in ambient atmosphere for 12 h at the temperature equal to 150 °C or 250 °C. The Third Harmonic Generation spectra were measured to investigate the nonlinear optical properties and their dependence on the structure of the thin film after the annealing process. This approach allowed us to determine the electronic contribution of the third-order nonlinear optical susceptibility χ{sup <3>}{sub elec} of these MPc films and to investigate two theoretical models for explanation of the observed results. We find that the annealing process significantly changes the optical and structural properties of MPc thin films. - Highlights: • Metallophtalocyanine thin films were grown by Physical Vapor Deposition technique. • MPcs thin films were undergone an annealing process in ambient atmosphere. • Third Harmonic spectra were measured to investigate nonlinear optical properties. • The third order nonlinear optical susceptibility χ{sup <3>}{sub elec} was determined. • We report changing both nonlinear optical and structural properties of thin films.

  11. Magnetic properties of the SiO2(Co)/GaAs interface: Polarized neutron reflectometry and SQUID magnetometry

    Science.gov (United States)

    Ukleev, V. A.; Grigoryeva, N. A.; Dyadkina, E. A.; Vorobiev, A. A.; Lott, D.; Lutsev, L. V.; Stognij, A. I.; Novitskiy, N. N.; Mistonov, A. A.; Menzel, D.; Grigoriev, S. V.

    2012-10-01

    The effect of giant injection magnetoresistance (GIMR) was recently observed in a granular SiO2/(54-75 at. % Co) film on a semiconductor GaAs substrate in a temperature range near T=300 K. The magnetoresistance coefficient reaches a value of 105% in a magnetic field of 1.9 T and at a voltage of 90 V. A structural model of the film was proposed based on the results of the grazing-incidence small-angle scattering (GISAXS) and x-ray reflectivity, which showed a specific interface layer 70-75 Å thick separating bulk SiO2(Co) granular film from the semiconductor substrate. This layer is formed by a monolayer of flattened Co particles which are laterally spaced apart much further than the particles in the bulk film. In the present work, using polarized neutron reflectometry (PNR), we study both the structural and magnetic properties of SiO2(Co) film separately in the bulk and in the interface layer, which is possible due to the depth resolution of the method. Temperature-dependent PNR and magnetization measurements performed by Superconducting Quantum Interference Device (SQUID) revealed the occurrence of two types of magnetic nanoparticles with different blocking temperatures and magnetization. The magnetization hysteresis curve demonstrated specific two-loop structure in fields 0.5-2 T. Thus our self-consistent results of PNR, GISAXS, and SQUID measurements emphasize the role of the interface features in the SiO2(Co)/GaAs heterostructures and show a direction for further development of the GIMR theory.

  12. Luminescent properties and characterization of Gd2O3:Eu3+@SiO2 and Gd2Ti2O7:Eu3+@SiO2 core shell phosphors prepared by a sol gel process

    Science.gov (United States)

    Lin, Kuo-Min; Lin, Chih-Cheng; Li, Yuan-Yao

    2006-03-01

    Gd2O3:Eu3+ and Gd2Ti2O7:Eu3+ films 10 nm in thickness were individually coated onto silica spheres (particle size of 150-170 nm) using the sol-gel method. The synthesized materials were addressed as Gd2O3:Eu3+@SiO2 and Gd2Ti2O7:Eu3+@SiO2 phosphors. An x-ray powder diffractometer (XRD), field emission scanning electron microscope (FE-SEM), high-resolution transmission electron microscope (HR-TEM), and photoluminescence spectrophotometer (PL) were employed to characterize the core-shell phosphors. Uniform core-shell phosphor particles were observed using FE-SEM. The XRD and HR-TEM results indicated that the coated-shell layer was well crystallized after sintering at 1000 °C. The Gd2O3:Eu3+@SiO2 PL measurement showed a red emission at the main 615 nm wavelength. The Gd2Ti2O7:Eu3+@SiO2 phosphor showed an orange-red emission at the 588 and 615 nm wavelengths. In comparison with the Gd2O3:Eu3+ and Gd2Ti2O7:Eu3+ bulk material results, the core-shell phosphors maintained the same emission ability as the bulk materials and the novel core-shell phosphors possessed great potential in quantum phosphor applications.

  13. Luminescent properties and characterization of Gd2O3:Eu(3+)@SiO2 and Gd2Ti2O7:Eu(3+)@SiO2 core-shell phosphors prepared by a sol-gel process.

    Science.gov (United States)

    Lin, Kuo-Min; Lin, Chih-Cheng; Li, Yuan-Yao

    2006-03-28

    Gd2O3:Eu(3+) and Gd2Ti2O7:Eu(3+) films 10 nm in thickness were individually coated onto silica spheres (particle size of 150-170 nm) using the sol-gel method. The synthesized materials were addressed as Gd2O3:Eu(3+)@SiO2 and Gd2Ti2O7:Eu(3+)@SiO2 phosphors. An x-ray powder diffractometer (XRD), field emission scanning electron microscope (FE-SEM), high-resolution transmission electron microscope (HR-TEM), and photoluminescence spectrophotometer (PL) were employed to characterize the core-shell phosphors. Uniform core-shell phosphor particles were observed using FE-SEM. The XRD and HR-TEM results indicated that the coated-shell layer was well crystallized after sintering at 1000 °C. The Gd2O3:Eu(3+)@SiO2 PL measurement showed a red emission at the main 615 nm wavelength. The Gd2Ti2O7:Eu(3+)@SiO2 phosphor showed an orange-red emission at the 588 and 615 nm wavelengths. In comparison with the Gd2O3:Eu(3+) and Gd2Ti2O7:Eu(3+) bulk material results, the core-shell phosphors maintained the same emission ability as the bulk materials and the novel core-shell phosphors possessed great potential in quantum phosphor applications.

  14. Synthesis of metallic nanoparticles in SiO2 matrices

    International Nuclear Information System (INIS)

    Gutierrez W, C.; Mondragon G, G.; Perez H, R.; Mendoza A, D.

    2004-01-01

    Metallic nanoparticles was synthesized in SiO 2 matrices by means of a process of two stages. The first one proceeded via sol-gel, incorporating the metallic precursors to the reaction system before the solidification of the matrix. Later on, the samples underwent a thermal treatment in atmosphere of H 2 , carrying out the reduction of the metals that finally formed to the nanoparticles. Then it was detected the presence of smaller nanoparticles than 20 nm, dispersed and with the property of being liberated easily of the matrix, conserving a free surface, chemically reactive and with response to external electromagnetic radiation. The system SiO 2 -Pd showed an important thermoluminescent response. (Author)

  15. Electrochromism and photocatalysis in dendrite structured Ti:WO3 thin films grown by sputtering

    Energy Technology Data Exchange (ETDEWEB)

    Karuppasamy, A., E-mail: karuppasamy@psnacet.edu.in

    2015-12-30

    Graphical abstract: - Highlights: • Dendrite structured Ti doped WO{sub 3} (WTO) thin films are grown by co-sputtering. • Sputtering condition influences structure and surface morphology of WTO films. • Titanium doping and annealing lead to dendritic surface structures in WTO films. • Structural, optical, electrochromic and photocatalytic properties of WTO films. • Enhanced electrochromism and photocatalysis in dendrite structured WTO thin films. - Abstract: Titanium doped tungsten oxide (Ti:WO{sub 3}) thin films with dendrite surface structures were grown by co-sputtering titanium and tungsten in Ar + O{sub 2} atmosphere. Ti:WO{sub 3} thin films were deposited at oxygen flow rates corresponding to pressures in the range 1.0 × 10{sup −3}–5.0 × 10{sup −3} mbar. Argon flow rate and sputtering power densities for titanium (2 W/cm{sup 2}) and tungsten (3 W/cm{sup 2}) were kept constant. Ti:WO{sub 3} films deposited at an oxygen pressure of 5 × 10{sup −3} mbar are found to be better electrochromic and photocatalytic. They have high optical modulation (80% at λ = 550 nm), coloration efficiency (60 cm{sup 2}/C at λ = 550 nm), electron/ion storage and removal capacity (Qc: −22.01 mC/cm{sup 2}, Qa: 17.72 mC/cm{sup 2}), reversibility (80%) and methylene blue decomposition rate (−1.38 μmol/l d). The combined effects of titanium doping, dendrite surface structures and porosity leads to significant enhancement in the electrochromic and photocatalytic properties of Ti:WO{sub 3} films.

  16. Electrochromism and photocatalysis in dendrite structured Ti:WO3 thin films grown by sputtering

    International Nuclear Information System (INIS)

    Karuppasamy, A.

    2015-01-01

    Graphical abstract: - Highlights: • Dendrite structured Ti doped WO 3 (WTO) thin films are grown by co-sputtering. • Sputtering condition influences structure and surface morphology of WTO films. • Titanium doping and annealing lead to dendritic surface structures in WTO films. • Structural, optical, electrochromic and photocatalytic properties of WTO films. • Enhanced electrochromism and photocatalysis in dendrite structured WTO thin films. - Abstract: Titanium doped tungsten oxide (Ti:WO 3 ) thin films with dendrite surface structures were grown by co-sputtering titanium and tungsten in Ar + O 2 atmosphere. Ti:WO 3 thin films were deposited at oxygen flow rates corresponding to pressures in the range 1.0 × 10 −3 –5.0 × 10 −3 mbar. Argon flow rate and sputtering power densities for titanium (2 W/cm 2 ) and tungsten (3 W/cm 2 ) were kept constant. Ti:WO 3 films deposited at an oxygen pressure of 5 × 10 −3 mbar are found to be better electrochromic and photocatalytic. They have high optical modulation (80% at λ = 550 nm), coloration efficiency (60 cm 2 /C at λ = 550 nm), electron/ion storage and removal capacity (Qc: −22.01 mC/cm 2 , Qa: 17.72 mC/cm 2 ), reversibility (80%) and methylene blue decomposition rate (−1.38 μmol/l d). The combined effects of titanium doping, dendrite surface structures and porosity leads to significant enhancement in the electrochromic and photocatalytic properties of Ti:WO 3 films.

  17. High-quality AlN films grown on chemical vapor-deposited graphene films

    Directory of Open Access Journals (Sweden)

    Chen Bin-Hao

    2016-01-01

    Full Text Available We report the growth of high-quality AlN films on graphene. The graphene films were synthesized by CVD and then transferred onto silicon substrates. Epitaxial aluminum nitride films were deposited by DC magnetron sputtering on both graphene as an intermediate layer and silicon as a substrate. The structural characteristics of the AlN films and graphene were investigated. Highly c-axis-oriented AlN crystal structures are investigated based on the XRDpatterns observations.

  18. Adsorption of uranyl in SiO2 porous glass

    International Nuclear Information System (INIS)

    Benedetto, F. E.; Prado, M. O.

    2013-01-01

    Vitreous SiO 2 porous matrices can be used in many applications involving the uptake of chemical species on its solid surface. In this work, vitreous silica sponges were prepared from a sodium borosilicate glass manufactured in our laboratory. The product obtained was then separated into phases with subsequent leaching of the soluble phase rich in B and Na. The resulting porous matrices have a specific surface of 35 m2/gr. Adsorption of uranyl ions onto the SiO 2 porous surface was studied to evaluate the use of this material as a filter for treatment of uranium containing water. The effects of contact time, adsorbent mass and equilibrium concentration of solution were studied. The porous adsorbent exhibits a pseudo-second-order kinetic behavior. The sponges with adsorbed uranium were thermally sealed as a way of U immobilization. Retention of uranium was confirmed during the matrix sealing by TGA. Uranium concentration before and after adsorption tests were made by means of ICP-OES. For uranium concentration of 800 ppm, 72 hours contact time and pH of 3.5, the amount of uranium adsorbed was 21.06 ± 0.02 mg U per gram of vitreous porous SiO 2 . (author)

  19. Soft nanoimprint lithography on SiO2 sol-gel to elaborate sensitive substrates for SERS detection

    Science.gov (United States)

    Hamouda, Frédéric; Bryche, Jean-François; Aassime, Abdelhanin; Maillart, Emmanuel; Gâté, Valentin; Zanettini, Silvia; Ruscica, Jérémy; Turover, Daniel; Bartenlian, Bernard

    2017-12-01

    This paper presents a new alternative fabrication of biochemical sensor based on surface enhanced Raman scattering (SERS) by soft nanoimprint lithography (S-NIL) on SiO2 sol-gel. Stabilization of the sol-gel film is obtained by annealing which simplifies the manufacturing of these biosensors and is compatible with mass production at low cost. This detector relies on a specific pattern of gold nanodisks on a thin gold film to obtain a better sensitivity of molecules' detection. Characterizations of SERS devices were performed on a confocal Raman microspectrophotometer after a chemical functionalization. We report a lateral collapse effect on poly(diméthylsiloxane) (PDMS) stamp for specific nanostructure dimensions. This unintentional effect is used to evaluate S-NIL resolution in SiO2 sol-gel.

  20. High thermal stability of abrupt SiO2/GaN interface with low interface state density

    Science.gov (United States)

    Truyen, Nguyen Xuan; Taoka, Noriyuki; Ohta, Akio; Makihara, Katsunori; Yamada, Hisashi; Takahashi, Tokio; Ikeda, Mitsuhisa; Shimizu, Mitsuaki; Miyazaki, Seiichi

    2018-04-01

    The effects of postdeposition annealing (PDA) on the interface properties of a SiO2/GaN structure formed by remote oxygen plasma-enhanced chemical vapor deposition (RP-CVD) were systematically investigated. X-ray photoelectron spectroscopy clarified that PDA in the temperature range from 600 to 800 °C has almost no effects on the chemical bonding features at the SiO2/GaN interface, and that positive charges exist at the interface, the density of which can be reduced by PDA at 800 °C. The capacitance-voltage (C-V) and current density-SiO2 electric field characteristics of the GaN MOS capacitors also confirmed the reduction in interface state density (D it) and the improvement in the breakdown property of the SiO2 film after PDA at 800 °C. Consequently, a high thermal stability of the SiO2/GaN structure with a low fixed charge density and a low D it formed by RP-CVD was demonstrated. This is quite informative for realizing highly robust GaN power devices.

  1. Simple morphological control of ZnPc thin films grown on subpc underlayer

    International Nuclear Information System (INIS)

    Park, Da Som; Yim, Sang Gyu

    2015-01-01

    Morphological templating in molecular double-layer thin films, i.e., the phenomenon where the surface morphology of the top layer is strongly influenced by that of the underlying layer, was investigated to control the surface nanomorphology of zinc phthalocyanine (ZnPc) thin films. Three types of molecular thin films, ZnPc single-layer, chloro[subphthalocyaninato]boron(III) (SubPc) single-layer, and ZnPc on SubPc (SubPc/ZnPc) double-layer thin films were grown on glass substrates and post-annealed at 250 °C. While the changes in surface roughness and morphology of the ZnPc single layer were negligible during post-annealing, the roughness of the SubPc/ZnPc double layer significantly increased, similar to that of the SubPc single-layer film. However, the lateral size of the surface crystallites of the SubPc/ZnPc film did not change apparently. Consequently, the fabricated regular, nanopillar-like surface morphology obtained by this simple treatment is expected to provide desirable interdigitated donor–acceptor interface with large contact area for small-molecule organic photovoltaic device applications. In addition, the ZnPc and SubPc single-layer thin films showed absorption maxima in different spectral regions; hence, the double-layer film absorbed the incident light effectively in a broader spectral range

  2. N-Type Conductive Ultrananocrystalline Diamond Films Grown by Hot Filament CVD

    Directory of Open Access Journals (Sweden)

    Michael Mertens

    2015-01-01

    Full Text Available We present the synthesis of ultrananocrystalline diamond (UNCD films by application of hot filament chemical vapor deposition (HFCVD. We furthermore studied the different morphological, structural, and electrical properties. The grown films are fine grained with grain sizes between 4 and 7 nm. The UNCD films exhibit different electrical conductivities, dependent on grain boundary structure. We present different contact metallizations exhibiting ohmic contact behavior and good adhesion to the UNCD surface. The temperature dependence of the electrical conductivity is presented between −200 and 900°C. We furthermore present spectroscopic investigations of the films, supporting that the origin of the conductivity is the structure and volume of the grain boundary.

  3. Effects of aluminium doping on zinc oxide transparent thin films grown by filtered vacuum arc deposition

    Energy Technology Data Exchange (ETDEWEB)

    Gontijo, L.C., E-mail: pleooog@gmail.com [Instituto Federal do Espirito Santo, Programa de Pos-Graduacao em Engenharia Metalurgica e de Materiais, Av. Vitoria, 1729, Jucutuquara, 29040-780, Vitoria, ES (Brazil); Machado, R., E-mail: rogerio.machado.2l@gmail.com [Universidade Federal de Sergipe, Departamento de Fisica, Rod. Mal Rondon S/N, Jd Rosa Elze, CEP 49.100-000, Sao Cristovao, SE (Brazil); Nascimento, V.P., E-mail: valberpn@yahoo.com.br [Universidade Federal do Espirito Santo, Departamento de Fisica, Av. Fernando Ferrari, 514 Goiabeiras, CEP 29075-910, Vitoria, ES (Brazil)

    2012-06-25

    Highlights: Black-Right-Pointing-Pointer AZO films prepared by filtered vacuum arc deposition. Black-Right-Pointing-Pointer Systematic variation of Al concentration. Black-Right-Pointing-Pointer Structural, electrical and optical properties analyzed. Black-Right-Pointing-Pointer Optimized system for Al concentration between 4% and 6%. - Abstract: Thin n-type ZnO films doped with different atomic concentrations of aluminium were grown by filtered vacuum arc deposition (FVAD) on glass substrates. The films were deposited using an oxygen working pressure of 2.0 mTorr with an arc current running at two 100 ms pulses s{sup -1}. Structural, optical and electrical properties were investigated to understand the effect of Al doping on ZnO films. The best values were found for an ideal aluminium percentage between 4 and 6 at.%.

  4. Reordering between tetrahedral and octahedral sites in ultrathin magnetite films grown on MgO(001)

    Energy Technology Data Exchange (ETDEWEB)

    Bertram, F.; Deiter, C. [Hamburger Synchrotronstrahlungslabor am Deutschen Elektronen-Synchrotron, Notkestr. 85, 22607 Hamburg (Germany); Schemme, T.; Jentsch, S.; Wollschlaeger, J. [Fachbereich Physik, Universitaet Osnabrueck, Barbarastr. 7, 49069 Osnabrueck (Germany)

    2013-05-14

    Magnetite ultrathin films were grown using different deposition rates and substrate temperatures. The structure of these films was studied using (grazing incidence) x-ray diffraction, while their surface structure was characterized by low energy electron diffraction. In addition to that, we performed x-ray photoelectron spectroscopy and magneto optic Kerr effect measurements to probe the stoichiometry of the films as well as their magnetic properties. The diffraction peaks of the inverse spinel structure, which originate exclusively from Fe ions on tetrahedral sites are strongly affected by the preparation conditions, while the octahedral sites remain almost unchanged. With both decreasing deposition rate as well as decreasing substrate temperature, the integrated intensity of the diffraction peaks originating exclusively from Fe on tetrahedral sites is decreasing. We propose that the ions usually occupying tetrahedral sites in magnetite are relocated to octahedral vacancies. Ferrimagnetic behaviour is only observed for well ordered magnetite films.

  5. Structural and morphological characterizations of ZnO films grown on GaAs substrates by MOCVD

    Energy Technology Data Exchange (ETDEWEB)

    Agouram, S.; Zuniga Perez, J.; Munoz-Sanjose, V. [Universitat de Valencia, Departamento de Fisica Aplicada y Electromagnetismo, Burjassot (Spain)

    2007-07-15

    ZnO films were grown on GaAs(100), GaAs(111)A and GaAs(111)B substrates by metal organic chemical vapour deposition (MOCVD). Diethylzinc (DEZn) and tertiarybutanol (t-butanol) were used as Zn and O precursors, respectively. The influence of the growth temperature and GaAs substrate orientation on the crystalline orientation and morphology of the ZnO grown films has been analysed. Crystallinity of grown films was studied by X-ray diffraction (XRD); thickness and morphology of ZnO films were investigated by scanning electron microscopy (SEM). SEM results reveal significant differences between morphologies depending on growth temperature but not significant differences were detected on the texture of grown films. (orig.)

  6. In situ synthesis and hydrothermal crystallization of nanoanatase TiO2 -SiO2 coating on aramid fabric (HTiSiAF) for UV protection.

    Science.gov (United States)

    Deng, Hui; Zhang, Hongda

    2015-10-01

    TiO2 -SiO2 thin film was prepared by sol-gel method and coated on the aramid fabric to prepare functional textiles. The aramid fabric was dipped and withdrawn in TiO2 -SiO2 gel and hydrothermal crystallization at 80(°) C, then its UV protection functionality was evaluated. The crystalline phase and the surface morphology of TiO2 -SiO2 thin film were characterized using SEM, XRD, and AFM respectively. SEM showed hydrothermal crystallization led to a homogeneous dispersion of anatase nonocrystal in TiO2 -SiO2 film, and XRD suggested the mean particle size of the formed anatase TiO2 was less than 30 nm. AFM indicated that hydrothermal treatment enhanced the crystallization of TiO2 . UV protection analysis suggested that the hydrothermally treated coated textile had a better screening property in comparison with TiO2 -SiO2 gel and native aramid fabric. © 2015 Wiley Periodicals, Inc.

  7. Solution-Grown Monocrystalline Hybrid Perovskite Films for Hole-Transporter-Free Solar Cells

    KAUST Repository

    Peng, Wei

    2016-03-02

    High-quality perovskite monocrystalline films are successfully grown through cavitation-triggered asymmetric crystallization. These films enable a simple cell structure, ITO/CH3NH3PbBr3/Au, with near 100% internal quantum efficiency, promising power conversion efficiencies (PCEs) >5%, and superior stability for prototype cells. Furthermore, the monocrystalline devices using a hole-transporter-free structure yield PCEs ≈6.5%, the highest among other similar-structured CH3NH3PbBr3 solar cells to date.

  8. Irradiation induced improvement in crystallinity of epitaxially grown Ag thin films on Si substrates

    Energy Technology Data Exchange (ETDEWEB)

    Takahiro, Katsumi; Nagata, Shinji; Yamaguchi, Sadae [Tohoku Univ., Sendai (Japan). Inst. for Materials Research

    1997-03-01

    We report the improvement in crystallinity of epitaxially grown Ag films on Si(100) substrates with ion irradiation. The irradiation of 0.5 MeV Si ions to 2x10{sup 16}/cm{sup 2} at 200degC, for example, reduces the channeling minimum yield from 60% to 6% at Ag surface. The improvement originates from the decrease of mosaic spread in the Ag thin film. In our experiments, ion energy, ion species and irradiation temperature have been varied. The better crystallinity is obtained as the higher concentration of defect is generated. The mechanism involved in the irradiation induced improvement is discussed. (author)

  9. One-dimensional edge state of Bi thin film grown on Si(111)

    Energy Technology Data Exchange (ETDEWEB)

    Kawakami, Naoya; Lin, Chun-Liang; Kawai, Maki; Takagi, Noriaki [Department of Advanced Materials Science, Graduate School of Frontier Science, The University of Tokyo, Kashiwa 5-1-5, Chiba 277-8561 (Japan); Arafune, Ryuichi [International Center for Materials Nanoarchitectonics (WPI-MANA), National Institute for Materials Science, 1-1 Namiki, Ibaraki 305-0044 (Japan)

    2015-07-20

    The geometric and electronic structures of the Bi thin film grown on Si(111) were investigated by using scanning tunneling microscopy and spectroscopy. We have found two types of edges, one of which hosts an electronic state localized one-dimensionally. We also revealed the energy dispersion of the localized edge state from the evolution of quasiparticle interference patterns as a function of energy. These spectroscopic findings well reproduce those acquired for the cleaved surface of the bulk Bi crystal [I. K. Drozdov et al., Nat. Phys. 10, 664 (2014)]. The present results indicate that the deposited Bi film provides a tractable stage for further scrutiny of the one-dimensional edge state.

  10. Effect of BST film thickness on the performance of tunable interdigital capacitors grown by MBE

    Science.gov (United States)

    Meyers, Cedric J. G.; Freeze, Christopher R.; Stemmer, Susanne; York, Robert A.

    2017-12-01

    Voltage-tunable, interdigital capacitors (IDCs) were fabricated on Ba0.29Sr0.71TiO3 grown by hybrid molecular beam epitaxy (MBE). In this growth technique, we utilize the metal-organic precursor titanium tetraisopropoxide rather than solid-source Ti as with conventional MBE. Two samples of varying BaxSr(1-x)TiO3 (BST) thicknesses were fabricated and analyzed. High-quality, epitaxial Pt electrodes were deposited by sputtering from a high-purity Pt target at 825 °C. The Pt electrodes were patterned and etched by argon ion milling, passivated with reactively sputtered SiO2, and then metallized with lift-off Ti/Au. The fabricated devices consisted of two-port IDCs embedded in ground-signal-ground, coplanar waveguide (CPW) transmission lines to enable radio-frequency (RF) probing. The sample included open and thru de-embedding structures to remove pad and CPW parasitic impedances. Two-port RF scattering (S) parameters were measured from 100 MHz to 40 GHz while DC bias was stepped from 0 V to 100 V. The IDCs exhibit a high zero-bias radio-frequency (RF) quality factor (Q) approaching 200 at 1 GHz and better than 2.3:1 capacitance tuning for the 300-nm-thick sample. Differences in the Q(V) and C(V) response with varying thicknesses indicate that unknown higher order material phenomena are contributing to the loss and tuning characteristics of the material.

  11. Extremely smooth YBa 2Cu 3O 7- δ "thin" film grown by liquid phase epitaxy

    Science.gov (United States)

    Hao, Z.; Wu, Y.; Enomoto, Y.; Tanabe, K.; Koshizuka, N.

    2002-02-01

    Extremely smooth single crystal YBa 2Cu 3O 7- δ "thin" films, 1-3 μm thick, have been successfully grown on YBCO-seeded MgO substrates by liquid phase epitaxy. The morphology study on the as-grown samples has revealed a step-flow growth mechanism, with each step height of about 1.1 nm, i.e. the c-axis lattice constant of YBCO. The mean surface roughness in a large 25 μm×25 μm area is ˜0.76 nm, determined by an atomic force microscope. After annealing in pure oxygen, the ˜2 μm thick films exhibit high-quality high- Tc superconductivity with zero resistance transition temperature TC0≈91 K and critical current density JC=4.74×10 4 A/cm 2 (transport measurement with 1 μV/cm criterion) at 77 K.

  12. Photoluminescence properties of ZnO thin films grown by using the hydrothermal technique

    International Nuclear Information System (INIS)

    Sahoo, Trilochan; Jang, Leewoon; Jeon, Juwon; Kim, Myoung; Kim, Jinsoo; Lee, Inhwan; Kwak, Joonseop; Lee, Jaejin

    2010-01-01

    The photoluminescence properties of zinc-oxide thin films grown by using the hydrothermal technique have been investigated. Zinc-oxide thin films with a wurtzite symmetry and c-axis orientation were grown in aqueous solution at 90 .deg. C on sapphire substrates with a p-GaN buffer layer by using the hydrothermal technique. The low-temperature photoluminescence analysis revealed a sharp bound-exciton-related luminescence peak at 3.366 eV with a very narrow peak width. The temperature-dependent variations of the emission energy and of the integrated intensity were studied. The activation energy of the bound exciton complex was calculated to be 7.35 ± 0.5 meV from the temperature dependent quenching of the integral intensities.

  13. Low-Temperature, Chemically Grown Titanium Oxide Thin Films with a High Hole Tunneling Rate for Si Solar Cells

    Directory of Open Access Journals (Sweden)

    Yu-Tsu Lee

    2016-05-01

    Full Text Available In this paper, we propose a chemically grown titanium oxide (TiO2 on Si to form a heterojunction for photovoltaic devices. The chemically grown TiO2 does not block hole transport. Ultraviolet photoemission spectroscopy was used to study the band alignment. A substantial band offset at the TiO2/Si interface was observed. X-ray photoemission spectroscopy (XPS revealed that the chemically grown TiO2 is oxygen-deficient and contains numerous gap states. A multiple-trap-assisted tunneling (TAT model was used to explain the high hole injection rate. According to this model, the tunneling rate can be 105 orders of magnitude higher for holes passing through TiO2 than for flow through SiO2. With 24-nm-thick TiO2, a Si solar cell achieves a 33.2 mA/cm2 photocurrent on a planar substrate, with a 9.4% power conversion efficiency. Plan-view scanning electron microscopy images indicate that a moth-eye-like structure formed during TiO2 deposition. This structure enables light harvesting for a high photocurrent. The high photocurrent and ease of production of chemically grown TiO2 imply that it is a suitable candidate for future low-cost, high-efficiency solar cell applications.

  14. Effect of the niobium additions in the passive films potentiostatically grown in a sulphate medium

    International Nuclear Information System (INIS)

    Kuri, S.E.; Martins, M.; D'Alkaine, C.V.

    1984-01-01

    The stability of passive films potentiostatically grown on stainless steel electrodes was studied in a 2 N sulfuric acid. The effect of Niobium contents in the base metal was considered. The reactivation time was measured using the method of Potential Decay Measurements under Open-Circuit Conditions after electrochemical aging in the passivity region, and its influence on the surface oxidation states, was discussed. (Author) [pt

  15. Characterization of interference thin films grown on stainless steel surface by alternate pulse current in a sulphochromic solution

    Directory of Open Access Journals (Sweden)

    Rosa Maria Rabelo Junqueira

    2008-12-01

    Full Text Available The aim of this work was to characterize thin interference films grown on the surface of AISI 304 stainless steel for decorative purposes. Films were grown in a sulphochromic solution at room temperature by an alternating pulse current method. The morphology and chemical state of the elements in the films were investigated by field emission scanning electron microscopy (FESEM, atomic force microscopy (AFM, glow discharge optical emission spectrometry (GDOES, and infrared Fourier transform spectroscopy (FTIR. Depth-sensing indentation (DSI experiments and wear abrasion tests were employed to assess the mechanical resistance of the films. The coloration process resulted in porous thin films which increased the surface roughness of the substrate. The interference films mainly consisted of hydrated chromium oxide containing iron. Increasing film thickness produced different colors and affected the mechanical properties of the coating-substrate system. Thicker films, such as those producing gold and green colors, were softer but more abrasion resistant.

  16. 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.

  17. Triboelectric charge generation by semiconducting SnO2 film grown by atomic layer deposition

    Science.gov (United States)

    Lee, No Ho; Yoon, Seong Yu; Kim, Dong Ha; Kim, Seong Keun; Choi, Byung Joon

    2017-07-01

    Improving the energy harvesting efficiency of triboelectric generators (TEGs) requires exploring new types of materials that can be used, and understanding their properties. In this study, we have investigated semiconducting SnO2 thin films as friction layers in TEGs, which has not been explored thus far. Thin films of SnO2 with various thicknesses were grown by atomic layer deposition on Si substrates. Either polymer or glass was used as counter friction layers. Vertical contact/separation mode was utilized to evaluate the TEG efficiency. The results indicate that an increase in the SnO2 film thickness from 5 to 25 nm enhances the triboelectric output voltage of the TEG. Insertion of a 400-nm-thick Pt sub-layer between the SnO2 film and Si substrate further increased the output voltage up to 120 V in a 2 cm × 2 cm contact area, while the enhancement was cancelled out by inserting a 10-nm-thick insulating Al2O3 film between SnO2 and Pt films. These results indicate that n-type semiconducting SnO2 films can provide triboelectric charge to counter-friction layers in TEGs.[Figure not available: see fulltext.

  18. Electrical transport and morphological study of PLD-grown nanostructured amorphous carbon thin films

    International Nuclear Information System (INIS)

    Kant, K Mohan; Reddy, N Mahipal; Rama, N; Sethupathi, K; Rao, M S Ramachandra

    2006-01-01

    Nanostructured carbon thin films have been actively investigated recently for their electroresistance (ER) properties. Furthermore, carbon films with nonlinear current-voltage (I-V) characteristics have potential application in field-emission devices. This has motivated us to study the effect of various growth parameters on the physical and morphological properties of carbon films grown by pulsed laser deposition (PLD). Carbon films have been deposited using a graphite target at different partial pressures of argon. The morphology of film surfaces deposited at various growth conditions was monitored using an atomic force microscope (AFM). AFM studies showed nanostructured grain growth with average grain size of about 80-90 nm. As the deposition time was decreased down to 1 min, the grain size was also found to decrease correspondingly. From Raman spectroscopic measurements an increase in the I(D)/I(G) ratio and a decrease in FWHM (G) clearly revealed the promotion of sp 2 hybridization as the substrate temperature increased. All the films show semiconducting behaviour with the dominant conduction process being the three-dimensional (3D) variable range hopping (VRH) mechanism. Nonlinear I-V curves were obtained for carbon films deposited on p-type Si indicating diode-like behaviour. The most significant result of this study was the observation of a large electroresistance value

  19. Thickness dependence of Hall mobility of HWE grown PbTe films

    International Nuclear Information System (INIS)

    Vaya, P.R.; Majhi, J.; Gopalam, B.S.V.; Dattatreyan, C.

    1985-01-01

    Thin epitaxial n-PbTe films of various thicknesses are grown on KCl substrates by hot wall epitaxy (HWE) technique. The X-ray, SEM and TEM studies of these films revealed their single crystalline nature. The Hall mobility (μ/sub H/) of these films is measured by Van der Pauw technique and compared with the numerically calculated values of PbTe. It is observed that μ/sub H/ very strongly depends on thickness for thin films but becomes independent of film thickness beyond 5 μm approaching its bulk value. The constant value of Hall coefficient in the temperature range 77 to 300 K show the extrinsic nature of these films. It is also noticed that the rate of increase of mobility with decreasing temperature becomes higher with film thickness. The diffused scattering mobility due to the size effect is calculated and compared with experimental data. A large discrepancy observed between these two is explained on the basis of the residual mobility contribution. The residual mobility is attributed to overall scattering due to grain boundaries, dislocations, defects, cleavage steps, and other surface effects. (author)

  20. CO gas sensing by ultrathin tin oxide films grown by atomic layer deposition using transmission FTIR spectroscopy.

    Science.gov (United States)

    Du, X; Du, Y; George, S M

    2008-10-02

    Ultrathin tin oxide films were deposited on SiO2 nanoparticles using atomic layer deposition (ALD) techniques with SnCl4 and H2O2 as the reactants. These SnO(x) films were then exposed to O2 and CO gas pressure at 300 degrees C to measure and understand their ability to serve as CO gas sensors. In situ transmission Fourier transform infrared (FTIR) spectroscopy was used to monitor both the charge conduction in the SnO(x) films and the gas-phase species. The background infrared absorbance measured the electrical conductivity of the SnO(x) films based on Drude-Zener theory. O2 pressure was observed to decrease the SnO(x) film conductivity. Addition of CO pressure then increased the SnO(x) film conductivity. Static experiments also monitored the buildup of gas-phase CO2 reaction products as the CO reacted with oxygen species. These results were consistent with both ionosorption and oxygen-vacancy models for chemiresistant semiconductor gas sensors. Additional experiments demonstrated that O2 pressure was not necessary for the SnO(x) films to detect CO pressure. The background infrared absorbance increased with CO pressure in the absence of O2 pressure. These results indicate that CO can produce oxygen vacancies on the SnO(x) surface that ionize and release electrons that increase the SnO(x) film conductivity, as suggested by the oxygen-vacancy model. The time scale of the response of the SnO(x) films to O2 and CO pressure was also measured by using transient experiments. The ultrathin SnO(x) ALD films with a thickness of approximately 10 A were able to respond to O2 within approximately 100 s and to CO within approximately 10 s. These in situ transmission FTIR spectroscopy help confirm the mechanisms for chemiresistant semiconductor gas sensors.

  1. Structural and chemical characterization of terbia thin films grown on hexagonally close packed metal substrates

    Science.gov (United States)

    Cartas, William

    Rare earth oxides (REOs) exhibit favorable catalytic performance for a diverse set of chemical transformations, including both partial and complete oxidation reactions. I will discuss our efforts to develop thin film systems of terbia for model surface science investigations of a REO that is effectively reducible, and which is thus expected to promote complete oxidation chemistry of adsorbed species. The growth of terbia on Cu(111) is shown to produce a complex surface that exhibits multiple phases of the oxide as well as exposed substrate. Growing the film on Pt(111) results in more uniform, single phase, and closed film. We used low energy electron diffraction (LEED) and scanning tunneling microscopy (STM) to characterize the structural properties of terbia thin films grown on Pt(111) in ultrahigh vacuum (UHV) using physical vapor deposition. We find that the REO grows as a high quality Tb2O 3(111) film, and adopts oxygen-deficient fluorite structures wherein the metal cations form a hexagonal lattice in registry with the Pt(111) substrate, while oxygen vacancies are randomly distributed within the film. The Tb 2O3(111) films are thermally stable when heated to 1000 K in UHV. LEED and STM show that a fraction of the Tb2O3 forms hexagonal islands when first deposited, and further depositions typically result in three dimensional growth of the film. The Tb2O3 (111) / Pt(111) system produces a coincidence structure, seen very clearly in LEED images. We have also found that Tb2O3(111) films can be oxidized in UHV by exposure to plasma-generated atomic oxygen beams. The oxidized films have an estimated TbO2 stoichiometry and decompose to Tb2O3 during heating, with O2 desorption starting at about 500 K. Terbia films oxidized at 90 K show a weakly bound state of oxygen that is likely chemisorbed. Temperature programmed reaction spectroscopy (TPRS) studies using methanol show that increased oxygen in the film does not modify the chemical selectivity of the film; however

  2. Fabrication and characterization of TiO2/SiO2 based Bragg reflectors for light trapping applications

    Directory of Open Access Journals (Sweden)

    R.S. Dubey

    Full Text Available Distributed Bragg reflectors (DBRs have received an intensive attention due to their increasing demand in optoelectronic and photonic devices. Such reflectors are capable to prohibit the light propagation within the specified wavelength range of interest. In this paper, we present the fabrication of TiO2/SiO2 stacks based Bragg reflectors by using a simple and in-expensive sol-gel spin coating technique. The prepared single-layer thin films of TiO2 and SiO2 onto glass substrates were characterized for their optical constants. By tuning the process parameters, one-seven DBR stacks of TiO2/SiO2 were prepared. The corresponding shift of the Bragg reflection peak was observed with the increased number of DBR stacks and as much as about 90% reflectance is observed from the 7DBR stacks. The experimentally measured reflectance was compared with the simulated one, which showed good in agreement. FESEM measurement has confirmed the formation of bright and dark strips of TiO2 and SiO2 films with their thicknesses 80 and 115 nm respectively. The simulation study was explored to a design of thin film silicon solar cell using 7DBR stacks. An enhancement in light absorption in the visible wavelength range is observed which coincides with the experimental result of the reflectance. The use of DBR at the bottom of the solar cell could felicitate the better light harvesting with the occurrence of Fabry-Perot resonances in the absorbing layer. Keywords: Bragg reflector, Photonic bandgap, Sol-gel coating, Reflection, Absorption

  3. Fabrication and characterization of TiO2/SiO2 based Bragg reflectors for light trapping applications

    Science.gov (United States)

    Dubey, R. S.; Ganesan, V.

    Distributed Bragg reflectors (DBRs) have received an intensive attention due to their increasing demand in optoelectronic and photonic devices. Such reflectors are capable to prohibit the light propagation within the specified wavelength range of interest. In this paper, we present the fabrication of TiO2/SiO2 stacks based Bragg reflectors by using a simple and in-expensive sol-gel spin coating technique. The prepared single-layer thin films of TiO2 and SiO2 onto glass substrates were characterized for their optical constants. By tuning the process parameters, one-seven DBR stacks of TiO2/SiO2 were prepared. The corresponding shift of the Bragg reflection peak was observed with the increased number of DBR stacks and as much as about 90% reflectance is observed from the 7DBR stacks. The experimentally measured reflectance was compared with the simulated one, which showed good in agreement. FESEM measurement has confirmed the formation of bright and dark strips of TiO2 and SiO2 films with their thicknesses 80 and 115 nm respectively. The simulation study was explored to a design of thin film silicon solar cell using 7DBR stacks. An enhancement in light absorption in the visible wavelength range is observed which coincides with the experimental result of the reflectance. The use of DBR at the bottom of the solar cell could felicitate the better light harvesting with the occurrence of Fabry-Perot resonances in the absorbing layer.

  4. High efficiency thin film solar cells grown by molecular beam epitaxy (HEFTY)

    Energy Technology Data Exchange (ETDEWEB)

    Mason, N.B.; Barnham, K.W.J.; Ballard, I.M.; Zhang, J. [Imperial College, London (United Kingdom)

    2006-05-04

    The project sought to show the UK as a world leader in the field of thin film crystalline solar cells. A premise was that the cell design be suitable for large-scale manufacturing and provide a basis for industrial exploitation. The study demonstrated (1) that silicon films grown at temperatures suitable for deposition on glass by Gas Phase Molecular Beam Epitaxy gives better PV cells than does Ultra Low Pressure Chemical Vapor Deposition; (2) a conversion energy of 15 per cent was achieved - the project target was 18 per cent and (3) one of the highest reported conversion efficiencies for a 15 micrometre silicon film was achieved. The study was carried out by BP Solar Limited under contract to the DTI.

  5. Preparation and chemical characterization of neodymium-doped molybdenum oxide films grown using spray pyrolysis

    Energy Technology Data Exchange (ETDEWEB)

    Alfonso, J. E. [Universidad Nacional de Colombia, Departamento de Fisica, Grupo de Ciencia Materiales y Superficies, AA 5997 Bogota DC (Colombia); Moreno, L. C., E-mail: jealfonsoo@unal.edu.co [Universidad Nacional de Colombia, Departamento de Quimica, AA 5997 Bogota DC (Colombia)

    2014-07-01

    We studied the crystalline, morphology, and surface composition of Nd-doped molybdenum oxide films grown on glass slides through spray pyrolysis. After fabrication, the films were subjected to thermal treatment in oxygen for periods ranging from 2 to 20 hours. The films were structurally characterized though X-ray diffraction (XRD), their bulk chemical composition was determined using Energy-Dispersive X-ray analysis (EDX), and their surface composition was determined using X-ray Photoelectron Spectroscopy (XP S). The XRD results show that the films obtained from different dissolution volumes and at substrate temperature of 300 grades C exhibit the characteristics of the oxygen-deficient molybdenum trioxide Mo{sub 9}O{sub 26} phase. The films subjected to different thermal treatments exhibit a mixture of Mo{sub 9}O{sub 26} and Mo{sub 17}O{sub 47} phases. EDX study shows the energy belonging to the L line of Nd. Finally, films doped with Nd and subjected to a thermal treatment of 20 h were analyzed through XP S, showing the binding energies at the crystalline lattice correspond to Nd{sub 2} (MoO{sub 4}){sub 3} and Nd{sub 2}Mo{sub 2}O{sub 7}. (Author)

  6. Characterization of Co:TiO2 Thin Film Grown by MOCVD Technique

    Science.gov (United States)

    Saripudin, A.; Purnama, W.

    2018-02-01

    The Co:TiO2 thin film was grown on n-type Si(100) by metal organic chemical vapor deposition (MOCVD) technique. The film’s growth parameters are as follow: substrate temperature of 450°C, bubbler temperature of 70°C, reactor chamber pressure of 2 militorr, and growth time of 2 hours. We characterized the structure of film by X-ray Difractometer (XRD), the morphology was characterized by Scanning Electron Microscope (SEM), and the fraction of Co atoms in TiO2 was characterized by Energy Dispersive x-ray Spectroscopy (EDS). The XRD result shows that the Co:TiO2 thin film is an anatase phase crystal dominated by A(213) orientation. Using Warren-Scherrer’s formula, the average grain size of Co:TiO2 is 169 nm. The SEM result shows that the Co:TiO2 film surface is quite coarse with relatively homogeneous grain shape. the average growth rate of Co:TiO2 film is 0.78 μm/h. In addition, the EDS result shows that Co atoms have been incorporated into the film replacing a portion of the Ti atoms by 0.085%.

  7. Infrared reflectance of GaN films grown on Si(001) substrates

    International Nuclear Information System (INIS)

    Zhang, Xiong; Hou, Yong-Tian; Feng, Zhe-Chuan; Chen, Jin-Li

    2001-01-01

    GaN thin films on Si(001) substrates are studied by infrared reflectance (IRR) spectroscopy at room temperature (RT). Variations in the IRR spectral line shape with the microstructure of GaN/Si(011) film are quantitatively explained in terms of a three-component effective medium model. In this model, the nominally undoped GaN film is considered to consist of three elementary components, i.e., single crystalline GaN grains, pores (voids), and inter-granulated materials (amorphous GaN clusters). Such a polycrystalline nature of the GaN/Si(001) films was confirmed by scanning electron microscopy measurements. It was demonstrated that based on the proposed three-component effective medium model, excellent overall simulation of the RT-IRR spectra can be achieved, and the fine structures of the GaN reststrahlen band in the measured RT-IRR spectra can also be interpreted very well. Furthermore, the volume fraction for each component in the GaN/Si(001) film was accurately determined by fitting the experimental RT-IRR spectra with the theoretical simulation. These results indicate that IRR spectroscopy can offer a sensitive and convenient tool to probe the microstructure of GaN films grown on silicon. [copyright] 2001 American Institute of Physics

  8. Large-Area WS2 Film with Big Single Domains Grown by Chemical Vapor Deposition

    Science.gov (United States)

    Liu, Pengyu; Luo, Tao; Xing, Jie; Xu, Hong; Hao, Huiying; Liu, Hao; Dong, Jingjing

    2017-10-01

    High-quality WS2 film with the single domain size up to 400 μm was grown on Si/SiO2 wafer by atmospheric pressure chemical vapor deposition. The effects of some important fabrication parameters on the controlled growth of WS2 film have been investigated in detail, including the choice of precursors, tube pressure, growing temperature, holding time, the amount of sulfur powder, and gas flow rate. By optimizing the growth conditions at one atmospheric pressure, we obtained tungsten disulfide single domains with an average size over 100 μm. Raman spectra, atomic force microscopy, and transmission electron microscopy provided direct evidence that the WS2 film had an atomic layer thickness and a single-domain hexagonal structure with a high crystal quality. And the photoluminescence spectra indicated that the tungsten disulfide films showed an evident layer-number-dependent fluorescence efficiency, depending on their energy band structure. Our study provides an important experimental basis for large-area, controllable preparation of atom-thick tungsten disulfide thin film and can also expedite the development of scalable high-performance optoelectronic devices based on WS2 film.

  9. Comparative study of Laser induce damage of HfO2/SiO2 and TiO2/SiO2 mirrors at 1064 nm.

    Science.gov (United States)

    Jiao, Hongfei; Ding, Tao; Zhang, Qian

    2011-02-28

    A comparative study of laser induced damage of HfO2/SiO2 and TiO2/SiO2 mirrors at 1064 nm has been carried out. One TiO2/SiO2 mirror with absorption of 300 ppm and two HfO2/SiO2 mirrors with absorption of 40 and 4.5 ppm were fabricated using electron beam evaporation method. For r-on-1 test, all HfO2/SiO2 mirrors with low average absorption are above 150 J/cm2 at 10 ns. However, the TiO2/SiO2 mirrors with high average absorption are just 9.5 J/cm2, which are probably due to the rather high absorption and rather low band gap energy. Meanwhile, all the samples were irradiated from front and back side respectively using the raster scan test mode. In case of front side irradiation, it is found that: for TiO2/SiO2 high reflectors, the representative damage morphologies are shallow pits that were probably caused by absorbing centers. However, for HfO2/SiO2 high reflectors, the dominant damage morphologies are micrometer-sized nodules ejected pits and the delamination initiating from the pits. The absorption of HfO2/SiO2 coatings is low enough to have minor influence on the laser damage resistance. In case of backside irradiation, the morphology of TiO2/SiO2 mirrors is mainly center melted pits that are thermal melting induced damage. Meanwhile, HfO2/SiO2 mirrors with isometrical fracture rings damage morphology are thermal induced stress damage.

  10. Suppressing Structural Colors of Photocatalytic Optical Coatings on Glass: The Critical Role of SiO2.

    Science.gov (United States)

    Li, Ronghua; Boudot, Mickael; Boissière, Cédric; Grosso, David; Faustini, Marco

    2017-04-26

    The appearance of structural colors on coated-glass is a critical esthetical drawback toward industrialization of photocatalytic coatings on windows for architecture or automobile. Herein we describe a rational approach to suppress the structural color of mesoporous TiO 2 -based coatings preserving photoactivity and mechanical stiffness. Addition of SiO 2 as third component is discussed. Ti x Si (1-x) O 2 mesoporous coatings were fabricated by one-step liquid deposition process through the evaporation induced self-assembling and characterized by GI-SAXS, GI-WAXS, electron microscopies, and in situ Environmental Ellipsometry Porosimetry. Guided by optical simulation, we investigated the critical role of SiO 2 on the optical responses of the films but also on the structural, mechanical, and photocatalytic properties, important requirements to go toward real applications. We demonstrate that adding SiO 2 to porous TiO 2 allows tuning and suppression of structural colors through refractive index matching and up to 160% increase in mechanical stiffening of the films. This study leads us to demonstrate an example of "invisible" coating, in which the light reflection is angle- and thickness-independent, and exhibiting high porosity, mechanical stiffness, and photoactivity.

  11. Bacterial adherence to SiO2-based multifunctional bioceramics.

    Science.gov (United States)

    Kinnari, Teemu J; Esteban, Jaime; Gomez-Barrena, Enrique; Zamora, Nieves; Fernandez-Roblas, Ricardo; Nieto, Alejandra; Doadrio, Juan C; López-Noriega, Adolfo; Ruiz-Hernández, Eduardo; Arcos, Daniel; Vallet-Regí, María

    2009-04-01

    The bacterial adherence onto different multifunctional silica-based bioceramics has been evaluated. Staphylococcus aureus and Staphylococcus epidermidis were chosen, as they cause the majority of the implant-related infections in this field. Two SiO2 mesoporous materials (MCM-41, SBA-15), an ordered SiO2-CaO-P2O5 mesoporous glass (OMG), and a biphasic magnetic bioceramic (BMB), were incubated with S. aureus and S. epidermidis for 90 min, and subsequently sonicated to quantify the number of adhered bacteria on each material. It was found that S. aureus and S. epidermidis (10(8) CFU/mL) adhered significantly less to BMB samples when compared to MCM-41, SBA-15, or OMG. However, when the material pores accessible for bacteria in each material were taken into account, the lowest bacterial adherence was found in MCM-41, and the highest in SBA-15. The results show that bacterial adherence is higher on mesoporous bioceramics, although this higher microbial attachment is mainly due to the intergranular porosity and grain size morphology rather than to the mesoporous structure. Copyright 2008 Wiley Periodicals, Inc.

  12. Interactions of atomic hydrogen with amorphous SiO2

    Science.gov (United States)

    Yue, Yunliang; Wang, Jianwei; Zhang, Yuqi; Song, Yu; Zuo, Xu

    2018-03-01

    Dozens of models are investigated by the first-principles calculations to simulate the interactions of an atomic hydrogen with a defect-free random network of amorphous SiO2 (a-SiO2) and oxygen vacancies. A wide variety of stable configurations are discovered due to the disorder of a-SiO2, and their structures, charges, magnetic moments, spin densities, and density of states are calculated. The atomic hydrogen interacts with the defect-free a-SiO2 in positively or negatively charged state, and produces the structures absent in crystalline SiO2. It passivates the neutral oxygen vacancies and generates two neutral hydrogenated E‧ centers with different Si dangling bond projections. Electron spin resonance parameters, including Fermi contacts, and g-tensors, are calculated for these centers. The atomic hydrogen interacts with the positive oxygen vacancies in dimer configuration, and generate four different positive hydrogenated defects, two of which are puckered like the Eγ‧ centers. This research helps to understand the interactions between an atomic hydrogen, and defect-free a-SiO2 and oxygen vacancies, which may generate the hydrogen-complexed defects that play a key role in the degeneration of silicon/silica-based microelectronic devices.

  13. Concentration effect of Tm3+ on cathodoluminescence properties of SiO2: Tm3+ and SiO2:Ho3+, Tm3+ systems

    CSIR Research Space (South Africa)

    Dhlamini, MS

    2012-05-01

    Full Text Available .physb.2011.09.091 Concentration effect of Tm3+ on cathodoluminescence properties of SiO2: Tm 3+ and SiO2:Ho 3+, Tm3+ systems M.S. Dhlamini, G.H. Mhlongo, H.C. Swart, O.M. Ntwaeaborwa, K.T. Hillie ABSTRACT: Cathodoluminescence (CL) properties of SiO...

  14. Effect of Commercial SiO2 and SiO2 from rice husk ash loading on biodegradation of Poly (lactic acid) and crosslinked Poly (lactic acid)

    Science.gov (United States)

    Prapruddivongs, C.; Apichartsitporn, M.; Wongpreedee, T.

    2017-09-01

    In this work, biodegradation behavior of poly (lactic acid) (PLA) and crosslinked PLA filled with two types of SiO2, precipitated SiO2 (commercial SiO2) and SiO2 from rice husk ash, were studied. Rice husks were first treated with 2 molar hydrochloric acid (HCl) to produce high purity SiO2, before burnt in a furnace at 800°C for 6 hours. All components were melted bending by an internal mixer then hot pressed using compression molder to form tested specimens. FTIR spectra of SiO2 and PLA samples were investigated. The results showed the lack of silanol group (Si-OH) of rice husk ash after steric acid surface modification, while the addition of particles can affect the crosslinking of the PLA. For biodegradation test by evaluating total amount of carbon dioxide (CO2) evolved during 60 days incubation at a controlled temperature of 58±2°C, the results showed that the biodegradation of crosslinked PLA occurred slower than the neat PLA. However, SiO2 incorporation enhanced the degree of biodegradation In particular, introducing commercial SiO2 in PLA and crosslinked PLA tended to clearly increase the degree of biodegradation as a consequence of the more accelerated hydrolysis degradation.

  15. Neutron irradiation effects in amorphous SiO2: optical absorption and electron paramagnetic resonance

    International Nuclear Information System (INIS)

    Guzzi, M.; Martini, M.; Paleari, A.; Pio, F.; Vedda, A.; Azzoni, C.B.

    1993-01-01

    Optical absorption spectra of as-grown and neutron-irradiated amorphous SiO 2 , both fused natural quartz and synthetic silica, have been analysed in the ultraviolet region below the fundamental edge. The description of the optical spectrum has been further clarified by a detailed study of the spectral components as a function of the neutron irradiation in different types of silica; we have verified known correlations between optical bands and between bands and paramagnetic centres. In 'as-grown' fused quartz samples, a previously unreported band at 6.2 eV has been detected. 'As-grown' synthetic silicas do not show any band, up to the intrinsic absorption edge. In the irradiated samples, the experimental results suggest a correlation between two bands at 5.8 and 7.1 eV, while previous attribution of the bands at 5.0 eV (B 2 band) and 7.6 eV (E band) to the same defect is discussed. The role of impurities in the optical absorption and in the radiation hardness is also considered. (author)

  16. Crystallinity Improvement of ZnO Thin Film on Different Buffer Layers Grown by MBE

    Directory of Open Access Journals (Sweden)

    Shao-Ying Ting

    2012-01-01

    Full Text Available The material and optical properties of ZnO thin film samples grown on different buffer layers on sapphire substrates through a two-step temperature variation growth by molecular beam epitaxy were investigated. The thin buffer layer between the ZnO layer and the sapphire substrate decreased the lattice mismatch to achieve higher quality ZnO thin film growth. A GaN buffer layer slightly increased the quality of the ZnO thin film, but the threading dislocations still stretched along the c-axis of the GaN layer. The use of MgO as the buffer layer decreased the surface roughness of the ZnO thin film by 58.8% due to the suppression of surface cracks through strain transfer of the sample. From deep level emission and rocking curve measurements it was found that the threading dislocations play a more important role than oxygen vacancies for high-quality ZnO thin film growth.

  17. Epitaxially-Grown Europium-Doped Barium Titanate Films on Various Substrates for Red Emission.

    Science.gov (United States)

    Hwang, Kyu-Seog; Jeon, Young-Sun; Lee, Young-Hwan; Hwangbo, Seung; Kim, Jin-Tae

    2015-10-01

    Intense red photoluminescence under ultraviolet excitation was observed in epitaxially-grown europium-doped perovskite BaTiO3 thin films deposited on the SrTiO3 (100), MgO (100) and sapphire (0001) substrates using metal carboxylate complexes. Precursor films prepared by spin coating were pyrolyzed at 250 °C for 120 min in argon, followed by final annealing at 850 °C for 60 min in argon. Crystallinity and epitaxy of the films were analyzed by X-ray diffraction θ-2θ scan and pole-figure analysis. Photoluminescence of the thin films at room temperature under 254 nm was confirmed by a fluorescent spectrophotometer. The obtained epitaxial BaTiO3 thin films on the SrTiO3 (100) and MgO (100) substrates show an intense red-emission lines at 615 nm corresponding to the (5)D0 --> (7)F2 transitions on Eu(3+) with broad bands at 595 and 650 nm.

  18. Surface characterisation of MOCVD single source precursor grown GaSb-films

    Energy Technology Data Exchange (ETDEWEB)

    Seemayer, Andreas; Hommes, Alexander; Huemann, Sascha; Wandelt, Klaus [University of Bonn (Germany). Institute for Physical Chemistry; Hunger, Ralf [Hahn-Meitner-Institute Berlin GmbH, Berlin (Germany); Schulz, Stephan [University of Paderborn (Germany). Department Chemie

    2008-07-01

    III-V semiconductor films used for opto- and microelectronic devices have traditionally been grown by (MO)MBE and LPE processes. An alternative metal-organic CVD-process, which has been established in the last two decades for high-throughput and low-cost fabrication works for nitrides, phosphides and arsenides, but is problematic for antimonides. In particular, for GaSb films an alternative route is a CVD-process using the heterocyclic single source precursor [tBu{sub 2}GaSbEt{sub 2}]{sub 2}. Subject of the present work is the investigation of the surface physical properties of the produced films as well as the gas phase behaviour of the used precursor. Therefore films were produced on a Si(100) substrate in a HV-MOCVD reactor and investigated using AES, S-XPS and AFM. In addition, growth experiments under UHV conditions were performed. The results are discussed in terms of a correlation of the electronic properties with the composition and structure of the films.

  19. Photoluminescence properties of ZnO films grown on InP by thermally oxidizing metallic Zn films

    CERN Document Server

    Chen, S J; Zhang, J Y; Lu, Y M; Shen, D Z; Fan, X W

    2003-01-01

    Photoluminescence (PL) properties of ZnO films grown on (001) InP substrates by thermal oxidization of metallic Zn films, in which oxygen vacancies and interstitial Zn ions are compensated by P ions diffusing from (001) InP substrates, are investigated. X-ray diffraction spectra indicate that P ions have diffused into the Zn films and chemically combined with Zn ions to form Zn sub 3 P sub 2. Intense free exciton emission dominates the PL spectra of ZnO films with very weak deep-level emission. Low-temperature PL spectra at 79 K are dominated by neutral-donor bound exciton emission at 3.299 eV (I sub 4) with a linewidth of 17.3 meV and neutral-acceptor bound exciton emission at 3.264 eV. The free exciton emission increases with increasing temperature and eventually dominates the emission spectrum for temperature higher than 170 K. Furthermore, the visible emission around 2.3 eV correlated with oxygen deficiencies and interstitial Zn defects was quenched to a remarkable degree by P diffusing from InP substrate...

  20. Electrical properties of SiO2-based graphene under monochromatic visible light irradiation

    Science.gov (United States)

    Li, Xiangdi; Liu, Xianming; Cao, Xueying; Zhang, Peng; Lei, Xiaohua; Chen, Weimin

    2017-08-01

    The purpose of this study is to investigate the electrical properties of graphene transparent conductive film under visible light irradiation. Sample in the study is chemical vapor deposition (CVD) growth graphene on the surface of copper foils and then transferred to the SiO2 substrate. Three monochromatic visible lights with wavelength of 635nm, 520nm and 450nm representing red (R), green (G) and blue (B) lights are used as irradiation sources. Results show that the graphene resistances increase slowly under light irradiation with all the three different wavelengths, while decrease slowly after the light is switched off. Light irradiation with higher power density will induce larger relative resistance change. When graphene is irradiated at the same density, blue light irradiation may result in the largest resistance change.

  1. ZnS:Co film grown by pulsed laser deposition and optical properties analysis

    Science.gov (United States)

    Gao, Dongwen; Wang, Li; Li, Shufeng

    2017-02-01

    The modification of ZnS by doping method is one of the important directions in the research of ZnS nano materials. Doping of transition metal ions in the ZnS matrix has attracted much attention in recent years. Doping transition metal ions can modulate the emission region of ZnS, and improve the efficiency of fluorescence. The doping concentration in ZnS has determined the distribution, absorption, excitation, emission, and structural properties of particles. Due to ZnS:Co crystal materials have the best characteristics: the stability of the mechanical properties, high emission cross section and wide bandgap tuning at room temperature. So the ZnS:Co film is grown by pulsed laser deposition and the near infrared spectrum properties have analyzed that have researched in theory and experiment. We change the pressure in the vacuum chamber by controlling the pressure of the argon gas to fabricated the ZnS:Co film by PLD, at the same time, we chose three kinds of materials as the substrate of the thin film, and compared the characteristics of the thin films. This method has the advantages of short fabrication time and material saving, so it is good for to detect and research the optical properties of the films of ZnS:Co. A variety of film detection of X-ray diffraction, laser particle size analyzer, UV-Vis spectrophotometer, fluorescence spectrophotometer, morphology, the particle size and optical properties of the samples have tested. From the results, the infrared transmittance of the Co doped ZnS is almost above 90%, and the transmission capacity increases with the increase of pressure. The film thickness decreases with the increase of pressure and there is a sharp peak in absorption spectrum, this point has important significance for studying photoluminescence of the near infrared spectrum.

  2. SEM, EDS, PL and absorbance study of CdTe thin films grown by CSS method

    Energy Technology Data Exchange (ETDEWEB)

    Hernandez-Torres, M.E.; Silva-Gonzalez, R.; Gracia-Jimenez, J.M. [Instituto de Fisica, BUAP, Apdo. Postal J-48, San Manuel, 72570 Puebla, Pue. (Mexico); Casarrubias-Segura, G. [CIE- UNAM, 62580 Temixco, Morelos (Mexico)

    2006-09-22

    Oxygen-doped CdTe films were grown on conducting glass substrates by the close spaced sublimation (CSS) method and characterized using SEM, EDS, photoluminescence (PL) and absorbance. A significant change in the polycrystalline morphology is observed when the oxygen proportion is increased in the deposition atmosphere. The EDS analysis showed that all samples are nonstoichiometric with excess Te. The PL spectra show emission bands associated with Te vacancies (V{sub Te}), whose intensities decrease as the oxygen proportion in the CSS chamber is increased. The oxygen impurities occupy Te vacancies and modify the surfaces states, improving the nonradiative process. (author)

  3. Interface termination and band alignment of epitaxially grown alumina films on Cu-Al alloy

    Science.gov (United States)

    Yoshitake, Michiko; Song, Weijie; Libra, Jiří; Mašek, Karel; Šutara, František; Matolín, Vladimír; Prince, Kevin C.

    2008-02-01

    Epitaxial ultrathin alumina films were grown on a Cu-9 at. % Al(111) substrate by selective oxidation of Al in the alloy in ultrahigh vacuum. The photoelectron spectra of Al 2p and valence band were measured in situ during oxidation. By analyzing multiple peaks of Al 2p, the interface atomic structure was discussed. The energy difference between the Fermi level of the substrate and the valence band maximum of alumina (band offset) was obtained. The relation between the interface atomic structure and the band offset was compared with the reported first-principles calculations. A novel method for controlling the band offset was proposed.

  4. Characterization of conducting polymer films grown via surface polymerization by ion-assisted deposition

    Science.gov (United States)

    Tepavcevic, Sanja

    2006-04-01

    Optimization of photonic and electronic devices based on conductive polymers, such as polythiophene and polyphenyl, requires the development of processing methods that can control both film chemistry and morphology on the nanoscale. One such method is explored in this thesis: surface polymerization by ion-assisted deposition (SPIAD). Polythiophene and polyphenyl thin films are grown on a silicon surface by SPIAD which uses hyperthermal, mass-selected thiophene cations coincident with alpha-thermal beam of aterthiophene (3T) or p-terphenyl (3P) neutrals. Mass spectrometry and x-ray photoelectron spectroscopy are used to verify polymerization of both 3T and 3P. The optimal conditions for the most efficient polymerization reaction and film growth are found by varying ion/neutral ratio and ion energy. The electronic structures of these films are probed by ultraviolet photoelectron spectroscopy (UPS) and polarized near-edge x-ray absorption fine structure spectroscopy (NEXAFS). The conducting polymer films formed by SPIAD display new valence band features resulting from a reduction in both their band gap and barrier to hole injection. These changes in film electronic structure result from an increase in the electron conjugation length and other changes in film structure induced by SPIAD. Scanning electron microscopy and x-ray diffraction are used to demonstrate that SPIAD can control the overall polythiophene and polyphenyl film morphology through the mediation of adsorption, diffusion, sublimation (desorption), and other thermal film growth events by ion-induced processes including polymerization, sputtering, bond breakage, and energetic mixing. Predicting the electronic properties, growth mechanism and morphology of the SPIAD films should be possible through computer simulations of the controlling phenomenon. Study with first principles density functional theory-molecular dynamics (DFT-MD) simulations indicates that polymerization and fragmentation of ions and

  5. Electrochemical delamination of CVD-grown graphene film: toward the recyclable use of copper catalyst.

    Science.gov (United States)

    Wang, Yu; Zheng, Yi; Xu, Xiangfan; Dubuisson, Emilie; Bao, Qiaoliang; Lu, Jiong; Loh, Kian Ping

    2011-12-27

    The separation of chemical vapor deposited (CVD) graphene from the metallic catalyst it is grown on, followed by a subsequent transfer to a dielectric substrate, is currently the adopted method for device fabrication. Most transfer techniques use a chemical etching method to dissolve the metal catalysts, thus imposing high material cost in large-scale fabrication. Here, we demonstrate a highly efficient, nondestructive electrochemical route for the delamination of CVD graphene film from metal surfaces. The electrochemically delaminated graphene films are continuous over 95% of the surface and exhibit increasingly better electronic quality after several growth cycles on the reused copper catalyst, due to the suppression of quasi-periodical nanoripples induced by copper step edges. The electrochemical delamination process affords the advantages of high efficiency, low-cost recyclability, and minimal use of etching chemicals.

  6. Direct fabrication of hybrid nanofibres composed of SiO2-PMMA nanospheres via electrospinning.

    Science.gov (United States)

    Zhang, Ran; Shang, Tinghua; Yang, Guang; Jia, Xiaolong; Cai, Qing; Yang, Xiaoping

    2016-08-01

    The direct fabrication of hybrid nanofibres composed of poly(methyl methacrylate)-grafted SiO2 (SiO2-PMMA) nanospheres via electrospinning was investigated in detail. SiO2-PMMA nanospheres were successfully prepared, with the SiO2 nanospheres synthesized via the Stober method, followed by in situ surface-initiated atom transfer radical polymerization of methyl methacrylate (MMA). Electrospinning was carried out with N,N-dimethylformamide (DMF) as the solvent to disperse SiO2-PMMA nanospheres. The size of the SiO2 core, the molecular weight of the PMMA shell and the concentration of the SiO2-PMMA/DMF solution all had substantial effects on the morphology and structure of electrospun nanofibres composed of SiO2-PMMA nanospheres. When these determining factors were well-tailored, it was found that one-dimensional necklace-like nanofibres were obtained, with SiO2-PMMA nanospheres aligned one by one along the fibre. The successful fabrication of nanofibres by directly electrospinning the SiO2-PMMA/DMF solution verified that polymer-grafted particles possess polymer-like characteristics, which endowed them with the ability to be processed into desirable shapes and structures. Copyright © 2016 Elsevier B.V. All rights reserved.

  7. HfO2/SiO2 multilayer based reflective and transmissive optics from the IR to the UV

    Science.gov (United States)

    Wang, Jue; Hart, Gary A.; Oudard, Jean Francois; Wamboldt, Leonard; Roy, Brian P.

    2016-05-01

    HfO2/SiO2 multilayer based reflective optics enable threat detection in the short-wave/middle-wave infrared and high power laser targeting capability in the near infrared. On the other hand, HfO2/SiO2 multilayer based transmissive optics empower early missile warning by taking advantage of the extremely low noise light detection in the deep-ultraviolet region where solar irradiation is strongly absorbed by the ozone layer of the earth's atmosphere. The former requires high laser damage resistance, whereas the latter needs a solar-blind property, i.e., high transmission of the radiation below 290 nm and strong suppression of the solar background from 300 nm above. The technical challenges in both cases are revealed. The spectral limits associated with the HfO2 and SiO2 films are discussed and design concepts are schematically illustrated. Spectral performances are realized for potential A and D and commercial applications.

  8. Review of 1064-nm damage tests of electron-beam deposited Ta2O5/SiO2 antireflection coatings

    International Nuclear Information System (INIS)

    Milam, D.; Rainer, F.; Lowdermilk, W.H.; Swain, J.E.; Carniglia, C.K.; Hart, T.T.

    1981-01-01

    Damage tests of Ta 2 O 5 /SiO 2 antireflection films deposited under a variety of conditions showed that thresholds of films deposited at 175 0 C were greater than thresholds of films deposited at either 250 0 C or 325 0 C. Deposition at high rate and low oxygen pressure produced highly absorptive films with low thresholds. Thresholds did not correlate with film reflectivity or net stress in the films, and correlated with film absorption only when the film absorption was greater than 10 4 ppM. Baking the films for four hours at 400 0 C reduced film absorption, altered net film stress, and produced an increase in the average damage threshold

  9. Heterojunction oxide thin-film transistors with unprecedented electron mobility grown from solution

    KAUST Repository

    Faber, Hendrik

    2017-04-28

    Thin-film transistors made of solution-processed metal oxide semiconductors hold great promise for application in the emerging sector of large-area electronics. However, further advancement of the technology is hindered by limitations associated with the extrinsic electron transport properties of the often defect-prone oxides. We overcome this limitation by replacing the single-layer semiconductor channel with a low-dimensional, solution-grown In2O3/ZnO heterojunction. We find that In2O3/ZnO transistors exhibit band-like electron transport, with mobility values significantly higher than single-layer In2O3 and ZnO devices by a factor of 2 to 100. This marked improvement is shown to originate from the presence of free electrons confined on the plane of the atomically sharp heterointerface induced by the large conduction band offset between In2O3 and ZnO. Our finding underscores engineering of solution-grown metal oxide heterointerfaces as an alternative strategy to thin-film transistor development and has the potential for widespread technological applications.

  10. Influence of different carrier gases on the properties of ZnO films grown by MOCVD

    Directory of Open Access Journals (Sweden)

    Wang, Jinzhong

    2008-08-01

    Full Text Available ZnO films were grown on sapphire (001 substrate by atmospheric MOCVD using diethyl zinc and tertiary butanol precursors. The influence of different carrier gases (H2 and He on the properties was analyzed by their structural (XRD, microstructural (SEM and compositional (SIMS characterization. The intensity of the strongest diffraction peak from ZnO (002 plane was increased by about 2 orders of magnitude when He is used as carrier gas, indicating the significant enhancement in crystallinity. The surface of the samples grown using H2 and He carrier gases was composed of leaf-like and spherical grains respectively. Hydrogen [H] content in the film grown using H2 is higher than that using He, indicating that the [H] was influenced by the H2 carrier gas. Ultraviolet emission dominates the low temperature PL spectra. The emission from ZnO films grown using He show higher optical quality and more emission centers.

    Se depositaron películas de ZnO sobre sustratos de zafiro (001 utilizando dietil zinc y butanol terciario como precursores. La influencia de los diferentes gases portadores (H2 y He sobre las propiedades se estudió mediante la caracterización estructural (XRD, microestructural (SEM y composicional (SIMS. La intensidad del pico de difracción más importante del plano (002 del ZnO aumentó en dos órdenes de magnitud cuando se utiliza He como gas portador indicando un incremento significativo de la cristalinidad. La superficie de las muestras crecidas utilizando H2 y He está formada por granos en forma de hoja y de forma esférica respectivamente. El contenido en hidrógeno (H en la película es mayor cuando se utiliza H2 que cuando se utiliza He, indicando que la cantidad de hidrógeno está influenciada por el H2 del gas portador. La emisión ultravioleta domina el espectro PL de baja temperatura. La emisión de las películas de ZnO utilizando

  11. The frequency-dependent AC photoresistance behavior of ZnO thin films grown on different sapphire substrates.

    Science.gov (United States)

    Cholula-Díaz, Jorge L; Barzola-Quiquia, José; Videa, Marcelo; Yin, Chunhai; Esquinazi, Pablo

    2017-09-13

    Zinc oxide (ZnO) thin films were grown by pulsed layer deposition under an N 2 atmosphere at low pressures on a- and r-plane sapphire substrates. Structural studies using X-ray diffraction confirmed that all films had a wurtzite phase. ZnO thin films on a- and r-plane sapphire have grown with orientations along the [0002] and [112[combining macron]0] directions, respectively. Room temperature photoluminescence measurements indicate that the presence of native point defects (interstitial zinc, oxygen vacancies, oxygen antisites and zinc vacancies) is more preponderant for ZnO thin films grown on the r-plane sapphire substrate than the sample grown on the a-plane sapphire substrate. Room temperature impedance spectroscopy measurements were performed in an alternating current frequency range from 40 to 10 5 Hz in the dark and under normal light. An unusual positive photoresistance effect is observed at frequencies above 100 kHz, which we suggest to be due to intrinsic defects present in the ZnO thin films. Furthermore, an analysis of the optical time response revealed that the film grown on the r-plane sapphire substrate responds faster (characteristic relaxation times for τ 1 , τ 2 and τ 3 of 0.05, 0.26 and 6.00 min, respectively) than the film grown on the a-plane sapphire substrate (characteristic relaxation times for τ 1 , τ 2 and τ 3 of 0.10, 0.73 and 4.02 min, respectively).

  12. Effect of disorder on carrier transport in ZnO thin films grown by atomic layer deposition at different temperatures

    Science.gov (United States)

    Saha, D.; Das, Amit. K.; Ajimsha, R. S.; Misra, P.; Kukreja, L. M.

    2013-07-01

    We have grown ˜200 nm thick ZnO films on (0001) sapphire substrates using atomic layer deposition at different substrate temperatures ranging from ˜150 to 350 °C. X-ray diffraction and photoluminescence spectra of these films showed that crystalline and compositional native defects were strongly dependent on the substrate temperature. Room temperature Hall measurement showed that all the films were degenerate with carrier concentration exceeding the Mott's critical density nc required for metallic conduction. The lowest value of room temperature resistivity ˜3.6 × 10-3 Ω cm was achieved for the film deposited at ˜200 °C, which had an estimated carrier concentration ˜5.7 × 1019 cm-3 and mobility ˜30 cm2/V s. The films deposited both below and above ˜200 °C showed increased resistivity and decreased mobility presumably due to the intensified defects and deteriorated crystalline quality of these films. To investigate the effect of disorder on the underlying charge transport mechanisms in these films, the electrical resistivity was measured in the temperature range of ˜4.2 to 300 K. The films grown at ˜150, 300, and 350 °C were found to be semiconducting in the entire range of the measurement temperature due to the intensified disorder which impeded the metallic transport in these films. However, the films grown at ˜200 and 250 °C showed a transition from metallic to semiconducting transport behaviour at lower temperatures due to the reduced defects and improved crystalline quality of these films. The observed semiconducting behaviour below the transition temperature for these films could be well explained by considering quantum corrections to the Boltzmann conductivity which includes the effect of disorder induced weak localization and coulomb electron-electron interactions.

  13. Roughening instability and ion-induced viscous relaxation of SiO2 surfaces

    International Nuclear Information System (INIS)

    Mayer, T.M.; Chason, E.; Howard, A.J.

    1994-01-01

    We characterize the development of nanometer scale topography (roughness) on SiO 2 surfaces as a result of low energy, off-normal ion bombardment, using in situ energy dispersive x-ray reflectivity and atomic force microscopy. Surfaces roughen during sputtering by heavy ions (Xe), with roughness increasing approximately linearly with ion fluence up to 10 17 cm -2 . A highly coherent ripple structure with wavelength of 30 nm and oriented with the wave vector parallel to the direction of incidence is observed after Xe sputtering at 1 keV. Lower frequency, random texture is also observed. Subsequent light ion (H, He) bombardment smoothens preroughened surfaces. The smoothing kinetics are first order with ion fluence and strongly dependent on ion energy in the range 0.2--1 eV. We present a linear model to account for the experimental observations which includes roughening both by random stochastic processes and by development of a periodic surface instability due to sputter yield variations with surface curvature which leads to ripple development. Smoothing occurs via ion bombardment induced viscous flow and surface diffusion. From the smoothing kinetics with H and He irradiation we measure the radiation enhanced viscosity of SiO 2 and find values on the order of 1--20x10 12 N s m -2 . The viscous relaxation per ion scales as the square root of the ion induced displacements in the film over the range of the ion penetration, suggesting short-lived defects with a bimolecular annihilation mechanism. The surface instability mechanism accounts for the ripple formation, while inclusion of stochastic roughening produces the random texture and reproduces the observed linear roughening kinetics and the magnitude of the overall roughness

  14. Growth of HfN thin films by reactive high power impulse magnetron sputtering

    Directory of Open Access Journals (Sweden)

    D. Ö. Thorsteinsson

    2018-03-01

    Full Text Available Thin hafnium nitride films were grown on SiO2 by reactive high power impulse magnetron sputtering (HiPIMS and reactive direct current magnetron sputtering (dcMS. The conditions during growth were kept similar and the film properties were compared as growth temperature, nitrogen flow rate, and in the case of HiPIMS, duty cycle were independently varied. The films were characterized with grazing incidence X-ray diffraction (GIXRD, X-ray reflection (XRR and X-ray stress analysis (XSA. HiPIMS growth had a lower growth rate for all grown films, but the films surfaces were smoother. The film density of HiPIMS deposited films grown at low duty cycle was comparable to dcMS grown films. Increasing the duty cycle increased the density of the HiPIMS grown films almost to the bulk density of HfN as well as increasing the growth rate, while the surface roughness did not change significantly. The HiPIMS grown films had large compressive stress while the dcMS grown films had some tensile stress. The dcMS grown films exhibit larger grains than HiPIMS grown films. The grain size of HiPIMS grown films decreases with increasing nitrogen flow rate, while the dcMS grain size increased with increasing nitrogen flow rate. This work shows that duty cycle during HiPIMS growth of HfN films has a significant effect on the film density and growth rate while other film properties seem mostly unaffected.

  15. Interface States Densities Effect at SiO2/ Polysilicon and SiO2/ Monosilicon Surfaces on N-polysilicon /Oxide/ P-Monosilicon Capacitance

    Directory of Open Access Journals (Sweden)

    H. Dib

    2014-05-01

    Full Text Available the interface states have a very significant role in the components containing MOS structures. In this paper we study the interface states densities effect at SiO2/ N-polysilicon and SiO2/ P- monosilicon surfaces on metal/polysilicon /oxide/ monosilicon capacitance. The numerical solution of poisson's equation and the determination of the charge variation in the structure induced by application of external bias (Vg allow simulating the capacitance-voltage MSPOS characteristics. The results show that the interface states at SiO2/ polysilicon and SiO2/ monosilicon surfaces translate the CT (V curve about positive voltage and cause the increase of the minimum value of capacitance. The effect of interface states on C (V curves is neglected for the polysilicon doping concentration in order to 1019 cm-3. For this doping level, the C (V curves are identical to the C (V of the monocristalline MOS structure.

  16. Optical investigations of Be doped ZnO films grown by molecular beam epitaxy

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Mingming, E-mail: andychain@live.cn [Faculty of Science, Jiangsu University, Zhenjiang, Jiangsu 212013 (China); Zhu, Yuan, E-mail: zhuy9@mail.sysu.edu.cn [State Key Laboratory of Optoelectronic Materials and Technologies, School of Physics and Engineering, Sun Yat-sen University, Guangzhou 510275 (China); Chen, Anqi; Shen, Zhen [State Key Laboratory of Optoelectronic Materials and Technologies, School of Physics and Engineering, Sun Yat-sen University, Guangzhou 510275 (China); Tang, Zikang, E-mail: phzktang@ust.hk [State Key Laboratory of Optoelectronic Materials and Technologies, School of Physics and Engineering, Sun Yat-sen University, Guangzhou 510275 (China); The Institute of Applied Physics and Materials Engineering, University of Macau, Avenida da Universidade, Taipa, Macau (China)

    2016-06-15

    Highlights: • The optical properties of Be doped ZnO films were investigated. • Low temperature photoluminescence spectrum was dominated by D°X and DAP emissions. • Shallow acceptor state with ionization energy of 116 meV was found in ZnO:Be films. • It is suggested that the incorporated Be atom might favor formation of Zn vacancies defects. • This work demonstrates that N doping BeZnO might be suitable for fabricating reliable p-type ZnO materials. - Abstract: In this article, the optical properties of ZnO:Be films grown by plasma-assisted molecular beam epitaxy were investigated by the excitation density-dependent and temperature-dependent photoluminescence measurements. The low temperature photoluminescence spectra showed a dominant excitons bound to neutral donors (D°X) emission centered at 3.3540 eV and strong donor-acceptor pair (DAP) transitions at 3.3000 eV. In addition, it showed that the intensity ratio of the DAP and D°X peaks changed with background electron concentration. Furthermore, a shallow acceptor state with ionization energy of 116 meV was found and attributed to Zn vacancy. The present study further suggests that Be and N codoping ZnO might be suitable for fabricating reliable p-type ZnO materials.

  17. Reproducibility and off-stoichiometry issues in nickelate thin films grown by pulsed laser deposition

    Directory of Open Access Journals (Sweden)

    Daniele Preziosi

    2017-01-01

    Full Text Available Rare-earth nickelates are strongly correlated oxides displaying a metal-to-insulator transition at a temperature tunable by the rare-earth ionic radius. In PrNiO3 and NdNiO3, the transition is very sharp and shows an hysteretic behavior akin to a first-order transition. Both the temperature at which the transition occurs and the associated resistivity change are extremely sensitive to doping and therefore to off-stoichiometry issues that may arise during thin film growth. Here we report that strong deviations in the transport properties of NdNiO3 films can arise in films grown consecutively under nominally identical conditions by pulsed laser deposition; some samples show a well-developed transition with a resistivity change of up to five orders of magnitude while others are metallic down to low temperatures. Through a detailed analysis of in-situ X-ray photoelectron spectroscopy data, we relate this behavior to large levels of cationic off-stoichoimetry that also translate in changes in the Ni valence and bandwidth. Finally, we demonstrate that this lack of reproducibility can be remarkably alleviated by using single-phase NdNiO3 targets.

  18. Electrochemical Energy Storage Applications of CVD Grown Niobium Oxide Thin Films.

    Science.gov (United States)

    Fiz, Raquel; Appel, Linus; Gutiérrez-Pardo, Antonio; Ramírez-Rico, Joaquín; Mathur, Sanjay

    2016-08-24

    We report here on the controlled synthesis, characterization, and electrochemical properties of different polymorphs of niobium pentoxide grown by CVD of new single-source precursors. Nb2O5 films deposited at different temperatures showed systematic phase evolution from low-temperature tetragonal (TT-Nb2O5, T-Nb2O5) to high temperature monoclinic modifications (H-Nb2O5). Optimization of the precursor flux and substrate temperature enabled phase-selective growth of Nb2O5 nanorods and films on conductive mesoporous biomorphic carbon matrices (BioC). Nb2O5 thin films deposited on monolithic BioC scaffolds produced composite materials integrating the high surface area and conductivity of the carbonaceous matrix with the intrinsically high capacitance of nanostructured niobium oxide. Heterojunctions in Nb2O5/BioC composites were found to be beneficial in electrochemical capacitance. Electrochemical characterization of Nb2O5/BioC composites showed that small amounts of Nb2O5 (as low as 5%) in conjunction with BioCarbon resulted in a 7-fold increase in the electrode capacitance, from 15 to 104 F g(-1), while imparting good cycling stability, making these materials ideally suited for electrochemical energy storage applications.

  19. Characterization for rbs of Titanium Oxide thin films grown by Dip Coating in a coloidal suspension of nano structured Titanium Oxide

    International Nuclear Information System (INIS)

    Pedrero, E.; Vigil, E.; Zumeta, I.

    1999-01-01

    The depth of Titanium Oxide thin films grown by Dip Coating in a coloidal suspension of nano structured Titanium Oxide was characterized using Rutherford Backscattering Spectrometry. Film depths are compared in function of bath and suspension parameters

  20. Electrical and mechanical stability of aluminum-doped ZnO films grown on flexible substrates by atomic layer deposition

    International Nuclear Information System (INIS)

    Luka, G.; Witkowski, B.S.; Wachnicki, L.; Jakiela, R.; Virt, I.S.; Andrzejczuk, M.; Lewandowska, M.; Godlewski, M.

    2014-01-01

    Highlights: • Transparent and conductive ZnO:Al films were grown by atomic layer deposition. • The films were grown on flexible substrates at low growth temperatures (110–140 °C). • So-obtained films have low resistivities, of the order of 10 −3 Ω cm. • Bending tests indicated a critical bending radius of ≈1.2 cm. • Possible sources of the film resistivity changes upon bending are proposed. - Abstract: Aluminum-doped zinc oxide (AZO) films were grown on polyethylene terephthalate (PET) substrates by atomic layer deposition (ALD) at low deposition temperatures (110–140 °C). The films have low resistivities, ∼10 −3 Ω cm, and high transparency (∼90%) in the visible range. Bending tests indicated a critical bending radius of ≈1.2 cm, below which the resistivity changes became irreversible. The films deposited on PET with additional buffer layer are more stable upon bending and temperature changes

  1. Phonon spectra in SiO2 glasses

    International Nuclear Information System (INIS)

    Perez R, J.F.; Jimenez S, S.; Gonzalez H, J.; Vorobiev, Y.V.; Hernandez L, M.A.; Parga T, J.R.

    1999-01-01

    Phonon spectra in SiO 2 sol-gel made glasses annealed under different conditions are investigated using infrared absorption and Raman scattering. These data are compared with those obtained in commercial optical-quality quartz. All the materials exhibit the same phonon bands, the exact position and the intensity depend on the measuring technique and on the sample preparation method. The phonon spectra in this material are interpreted on the basis of a simple quasi-linear description of elastic waves in an O-Si-O chain. It is shown that the main features observed in the range 400-1400 cm -1 can be predicted using a quasi-linear chain model in which the band at 1070 cm -1 is assigned to the longitudinal optical waves in the O-Si-O chain with the smallest possible wavelength at the Brillouin zone boundary, the band located around 450 cm -1 is assigned to the transversal optical waves and the band at 800 cm -1 to the longitudinal acoustical waves with the same wavelength. The degree of structural disorder can be also deduced within the framework of the proposed model. (Author)

  2. Scintillator based on SiO2-aerogel

    International Nuclear Information System (INIS)

    Boyko, I.R.; Ignatenko, M.A.; Esenak, K.; Kuhta, L.; Ruzicka, J.; Fainor, V.

    1995-01-01

    For increasing the light output of SiO 2 -aerogel two aerogel samples were doped with the wavelength shifter POPOP. As a result a scintillator with intermediate density between the gas and the solid state has been produced. The light pulse shapes of the both samples are well approximated by a sum of two exponents with the decay times 1.4±0.1 ns (58% of total light output) and 5.2±0.4 ns (42%). Under irradiation of 5.5 MeV α-particles the light output of the sample with smaller wavelength shifter concentration was 30% and that of the sample with larger concentration was 8% of the light output of a plastic scintillator (polysterene, 2% paraterphenil, 0.2% POPOP). The obtained data indicate that the α/β ratio for both samples is close to 1. This material can be used in experiments where the amount of substance in the way of particles to be detected is a critical factor. (orig.)

  3. Functionalized sio2 microspheres for extracting oil from produced water

    KAUST Repository

    Mishra, Himanshu

    2017-03-16

    Functionalized material, methods of producing the functionalized material, and use thereof for separation processes such as but not limited to use for separating and extracting a dissolved organic foulant, charged contaminant or oily matter or any combination thereof from water, such as produced water, are provided. In an embodiment, the functionalized material is a mineral material, such as mica, silica (e.g. an SiO2 microsphere) or a metal oxide, and the outer surface of the material is functionalized with an alkyl chain or a perfluorinated species. In an embodiment, the method of making the functionalized material, includes: a) providing a mineral material; b) providing an alkyl chain and/or a perfluorinated species, the alkyl chain or perfluorinated species selected to dissolve organic foulants, charged contaminants or oily matter from water or any combination thereof; c) hydroxylating the material via a concentrated acid solution or a basic solution; and d) grafting the alkyl chain and/or the perfluorinated species onto the material via a silanation reaction.

  4. ZnO and ZnSe thin films grown by Atomic Layer Epitaxy in a gas flow system

    Science.gov (United States)

    Godlewski, Marek; Guziewicz, Elzbieta; Kopalko, Krzysztof; Lusalowska, Elzbieta

    2003-03-01

    In the presentation we will briefly review our recent works on thin films of ZnO and ZnSe for possible applications in opto-electronics. Thin films of ZnO were grown by four different methods on either semiconductor substrates or on a glass plates. The latter system was successfully used as a substrate for deposition of amorphous GaN epilayers, using low temperature plasma-assisted MOCVD technique. Properties of ALE-grown ZnO films and of GaN epilayers grown on ZnO buffer layer will be shortly analyzed. Thin films of ZnSe were grown using synthesis from Zn and Se. These films show bright white color light emission. Temperature of the emission and brightness can be optimized by either modifications in a growth procedure or variations in excitation conditions. Nature of white emission and optimization procedures will be described. This work was partly supported by grant no. PBZ-KBN-044/P03/2001 of KBN. The ALE reactor was bought using SEZAM grant of Foundation for Polish Science.

  5. Structural characterization of Al xGa1-xSb films grown at low temperatures by liquid phase epitaxy

    International Nuclear Information System (INIS)

    Rosendo, E.; Diaz, T.; Martinez, J.; Juarez, H.; Juarez, G.

    2005-01-01

    High resolution X-ray diffraction (HRXRD) and far-infrared reflectivity techniques were applied to characterize Al x Ga 1-x Sb alloys. Layers of Al x Ga 1-x Sb grown by the liquid phase epitaxy technique and deposited on GaSb (100) substrates were obtained in the temperature range of 250 to 450 deg. C. From the HRXRD measurements it can be inferred that the films have good structural characteristics, this is because the lattice mismatch values were no bigger than 0.02% and from the rocking curves the Al concentration was ranged from 0.04 to 0.058. The presence of the ternary alloy in the films was confirmed by reflectivity. A change of the conductivity type in the film was observed for films grown at temperatures lower than 350 deg. C

  6. Microstructural Evolution and Domain Structures of Flux-grown Ferroelectric Thin Films

    Science.gov (United States)

    Burch, Matthew James

    Barium titanate is one of the most commonly utilized dielectric materials for commercial applications. As devices continue to scale smaller, it is necessary to find processing routes that allow for the integration of high-permittivity barium titanate into the thin film geometry. In the bulk, high permittivity barium titanate can be produced at high processing temperatures (>1250°C). This is several hundred degrees higher than many low temperature substrates are able to withstand, which makes integration of high-permittivity barium titanate onto these substrates a challenge.One method to lower the processing temperature and maintain bulk-like permittivity of barium titanate thin films is through the addition of a liquid forming flux. The fluxing agent increases the kinetics of the system while encouraging densification. This increase in kinetics results in large-grained, dense samples, with high dielectric properties at relatively low processing temperatures. In this dissertation, the underlying mechanisms of how the flux system actually impacts the microstructural evolution of physically vapor deposited barium titanate thin films on sapphire substrates is explored. The flux-system utilized is the barium-borate system (BaOB2O3). It will be shown that the flux system results in large-grained, dense barium titanate thin films grown on sapphire. However, the evolution of the microstructure depends on a complex interaction between the liquid forming flux, a reaction between the sapphire substrate and barium titanate, the resulting reactionary phase of BaAl2O4, and {111}-barium titanate twins. (Abstract shortened by ProQuest.).

  7. Non-iridescent structural colors from uniform-sized SiO2 colloids

    Science.gov (United States)

    Topçu, Gökhan; Güner, Tuğrul; Demir, Mustafa M.

    2018-05-01

    Structural colors have recently attracted interest from diverse fields of research due to their ease of fabrication and eco-friendliness. These types of colors are, in principle, achieved by periodically arranged submicron-diameter colloidal particles. The interaction of light with a structure containing long-range ordered colloidal particles leads to coloration; this usually varies depending on the angle of observation (iridescence). However, the majority of the applications demand constant color that is independent of the viewing angle (non-iridescence). In this work, silica colloids were obtained using the Stöber method at different sizes from 150 to 300 nm in an alcoholic dispersion. The casting of the dispersion on a substrate leaves behind a photonic crystal showing a colorful iridescent film. However, centrifugation and redispersion of the SiO2 particles into fresh solvent may cause the formation of small, aggregated silica domains in the new dispersion. The casting of this dispersion allows for the development of photonic glass, presumably due to the accumulation of aggregates showing stable colloidal film independent of viewing angle. Moreover, depending on the size of the silica colloids, non-iridescent photonic glasses with various colors (violet, blue, green, and orange) are obtained.

  8. Potassium ions in SiO2: electrets for silicon surface passivation

    Science.gov (United States)

    Bonilla, Ruy S.; Wilshaw, Peter R.

    2018-01-01

    This manuscript reports an experimental and theoretical study of the transport of potassium ions in thin silicon dioxide films. While alkali contamination was largely researched in the context of MOSFET instability, recent reports indicate that potassium ions can be embedded into oxide films to produce dielectric materials with permanent electric charge, also known as electrets. These electrets are integral to a number of applications, including the passivation of silicon surfaces for optoelectronic devices. In this work, electric field assisted migration of ions is used to rapidly drive K+ into SiO2 and produce effective passivation of silicon surfaces. Charge concentrations of up to ~5  ×  1012 e cm‑2 have been achieved. This charge was seen to be stable for over 1500 d, with decay time constants as high as 17 000 d, producing an effectively passivated oxide–silicon interface with SRV  <  7 cm s‑1, in 1 Ω cm n-type material. This level of charge stability and passivation effectiveness has not been previously reported. Overall, this is a new and promising methodology to enhance surface passivation for the industrial manufacture of silicon optoelectronic devices.

  9. Tuning of electrical and structural properties of indium oxide films grown by metal organic chemical vapor deposition

    International Nuclear Information System (INIS)

    Wang, Ch.Y.; Cimalla, V.; Romanus, H.; Kups, Th.; Niebelschuetz, M.; Ambacher, O.

    2007-01-01

    Tuning of structural and electrical properties of indium oxide (In 2 O 3 ) films by means of metal organic chemical vapor deposition is demonstrated. Phase selective growth of rhombohedral In 2 O 3 (0001) and body-centered cubic In 2 O 3 (001) polytypes on (0001) sapphire substrates was obtained by adjusting the substrate temperature and trimethylindium flow rate. The specific resistance of the as-grown films can be tuned by about two orders of magnitude by varying the growth conditions

  10. High electron mobility in Ga(In)NAs films grown by molecular beam epitaxy

    International Nuclear Information System (INIS)

    Miyashita, Naoya; Ahsan, Nazmul; Monirul Islam, Muhammad; Okada, Yoshitaka; Inagaki, Makoto; Yamaguchi, Masafumi

    2012-01-01

    We report the highest mobility values above 2000 cm 2 /Vs in Si doped GaNAs film grown by molecular beam epitaxy. To understand the feature of the origin which limits the electron mobility in GaNAs, temperature dependences of mobility were measured for high mobility GaNAs and referential low mobility GaInNAs. Temperature dependent mobility for high mobility GaNAs is similar to the GaAs case, while that for low mobility GaInNAs shows large decrease in lower temperature region. The electron mobility of high quality GaNAs can be explained by intrinsic limiting factor of random alloy scattering and extrinsic factor of ionized impurity scattering.

  11. Thermal activation of nitrogen acceptors in ZnO thin films grown by MOCVD

    Energy Technology Data Exchange (ETDEWEB)

    Dangbegnon, J.K.; Talla, K.; Botha, J.R. [Department of Physics, Nelson Mandela Metropolitan University, P.O. Box 77000, Port Elizabeth (South Africa)

    2010-06-15

    Nitrogen doping in ZnO is inhibited by spontaneous formation of compensating defects. Perfect control of the nitrogen doping concentration is required, since a high concentration of nitrogen could induce the formation of donor defects involving nitrogen. In this work, the effect of post-growth annealing in oxygen ambient on ZnO thin films grown by Metalorganic Chemical Vapor Deposition, using NO as both oxidant and nitrogen dopant, is studied. After annealing at 700 C and above, low-temperature photoluminescence shows the appearance of a transition at {proportional_to}3.23 eV which is interpreted as pair emission involving a nitrogen acceptor. A second transition at {proportional_to}3.15 eV is also discussed. This work suggests annealing as a potential means for p-type doping using nitrogen (copyright 2010 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  12. High resolution x-ray scattering studies of strain in epitaxial thin films of yttrium silicide grown on silicon (111)

    International Nuclear Information System (INIS)

    Marthinez-Miranda, L.J.; Santiago-Aviles, J.J.; Siegal, M.P.; Graham, W.R.; Heiney, P.A.

    1990-01-01

    The authors have used high resolution grazing incidence x-ray scattering (GIXS) to study the in- plane and out-of-plane structure of epitaxial YSi 2-x films grown on Si(111), with thicknesses ranging from 85 Angstrom to 510 Angstrom. Their results indicate that the films are strained, and that film strain increases as a function of thickness, with lattice parameters varying from a = 3.846 Angstrom/c = 4.142 Angstrom for the 85 Angstrom film to a = 3.877 Angstrom/c = 4.121 Angstrom for the 510 Angstrom film. The authors correlate these results with an increase in pinhole areal coverage as a function of thickness. In addition, the authors' measurements show no evidence for the existence of ordered silicon vacancies in the films

  13. Effect of cesium assistance on the electrical and structural properties of indium tin oxide films grown by magnetron sputtering

    Energy Technology Data Exchange (ETDEWEB)

    Song, Jaewon; Hwang, Cheol Seong; Park, Sung Jin; Yoon, Neung Ku [Department of Materials Science and Engineering and Inter-university Semiconductor Research Center, Seoul National University, Seoul 151-742 (Korea, Republic of); Sorona Inc., Pyeongtaek, Gyeonggi 451-841 (Korea, Republic of)

    2009-07-15

    Indium tin oxide (ITO) thin films were deposited by cesium (Cs)-assisted dc magnetron sputtering in an attempt to achieve a high performance at low temperatures. The films were deposited on SiO{sub 2}/Si wafer and glass (Eagle 2000) substrates at a substrate temperature of 100 degree sign C with a Cs vapor flow during the deposition process. The ITO thin films deposited in the presence of Cs vapor showed better crystallinity than the control films grown under normal Ar/O{sub 2} plasma conditions. The resistivity of the films with the Cs assistance was lower than that of the control films. The lowest resistivity of 6.2x10{sup -4} {Omega} cm, which is {approx}20% lower than that of the control sample, was obtained without any postdeposition thermal annealing. The surface roughness increased slightly when Cs vapor was added. The optical transmittance was >80% at wavelengths ranging from 380 to 700 nm.

  14. Zinc sulfide and terbium-doped zinc sulfide films grown by traveling wave reactor atomic layer epitaxy

    CERN Document Server

    Yun, S J; Nam, K S

    1998-01-01

    Zinc sulfide (ZnS) and terbium-doped ZnS (ZnS:Tb) thin films were grown by traveling wave reactor atomic layer epitaxy (ALE). In the present work, ZnCl sub 2 , H sub 2 S, and tris (2,2,6,6-tetramethyl-3,5-heptandionato) terbium (Tb(tmhd) sub 3) were used as the precursors. The dependence of crystallinity and Cl content of ZnS films was investigated on the growth temperature. ZnS and ZnS:Tb films grown at temperatures ranging from 400 to 500 .deg. C showed a hexagonal-2H crystalline structure. The crystallinity of ZnS film was greatly enhanced as the temperature increased. At growth temperatures higher than 450.deg.C, the films showed preferred orientation with mainly (002) diffraction peak. The Cl content decreased from approximately 9 to 1 at.% with the increase in growth temperature from 400 to 500 .deg. C. The segregation of Cl near the surface region and the incorporation of O from Tb(tmhd) sub 3 during ALE process were also observed using Auger electron spectroscopy. The ALE-grown ZnS and ZnS:Tb films re...

  15. As-grown enhancement of spinodal decomposition in spinel cobalt ferrite thin films by Dynamic Aurora pulsed laser deposition

    Energy Technology Data Exchange (ETDEWEB)

    Debnath, Nipa [Graduate School of Science and Technology, Shizuoka University, Hamamatsu 432-8561 (Japan); Department of Physics, Jagannath University, Dhaka 1100 (Bangladesh); Kawaguchi, Takahiko; Kumasaka, Wataru [Department of Electronics and Materials Science, Shizuoka University, Hamamatsu 432-8561 (Japan); Das, Harinarayan [Materials Science Division, Atomic Energy Centre, Dhaka 1000 (Bangladesh); Shinozaki, Kazuo [School of Materials and Chemical Technology, Tokyo Institute of Technology, Tokyo 152-8550 (Japan); Sakamoto, Naonori [Department of Electronics and Materials Science, Shizuoka University, Hamamatsu 432-8561 (Japan); Research Institute of Electronics, Shizuoka University, Hamamatsu 432-8561 (Japan); Suzuki, Hisao [Graduate School of Science and Technology, Shizuoka University, Hamamatsu 432-8561 (Japan); Department of Electronics and Materials Science, Shizuoka University, Hamamatsu 432-8561 (Japan); Research Institute of Electronics, Shizuoka University, Hamamatsu 432-8561 (Japan); Wakiya, Naoki, E-mail: wakiya.naoki@shizuoka.ac.jp [Graduate School of Science and Technology, Shizuoka University, Hamamatsu 432-8561 (Japan); Department of Electronics and Materials Science, Shizuoka University, Hamamatsu 432-8561 (Japan); Research Institute of Electronics, Shizuoka University, Hamamatsu 432-8561 (Japan)

    2017-06-15

    Highlights: • As-grown enhancement of spinodal decomposition (SD) in Co{sub x}Fe{sub 3−x}O{sub 4} film is observed. • Magnetic-field-induced ion-impingement enhances SD without any post-annealing. • The enhancement of SD is independent of the lattice-mismatch-induced strain. • This approach can promote SD in any thin film without post-deposition annealing. - Abstract: Cobalt ferrite Co{sub x}Fe{sub 3−x}O{sub 4} thin films with composition within the miscibility gap were grown using Dynamic Aurora pulsed laser deposition. X-ray diffraction patterns reveal as-grown phase separation to Fe-rich and Co-rich phases with no post-deposition annealing. The interconnected surface microstructure of thin film shows that this phase separation occurs through spinodal decomposition enhanced by magnetic-field-induced ion-impingement. The lattice parameter variation of the thin films with the magnetic field indicates that the composition fluctuations can be enhanced further by increasing the magnetic field. Results show that spinodal decomposition enhancement by magnetic-field-induced ion-impingement is independent of the lattice-mismatch-induced strain. This approach can promote spinodal decomposition in any thin film with no post-deposition annealing process.

  16. Assembly of Fe3O4 nanoparticles on SiO2 monodisperse spheres

    Indian Academy of Sciences (India)

    Assembly of Fe3O4 nanoparticles on SiO2 monodisperse spheres. K C BARICK and D BAHADUR*. Department of Metallurgical Engineering and Materials Science, Indian Institute of Technology Bombay,. Mumbai 400 076, India. Abstract. The assembly of superparamagnetic Fe3O4 nanoparticles on submicroscopic SiO2 ...

  17. Assembly of Fe3O4 nanoparticles on SiO2 monodisperse spheres

    Indian Academy of Sciences (India)

    Abstract. The assembly of superparamagnetic Fe3O4 nanoparticles on submicroscopic SiO2 spheres have been prepared by an in situ reaction using different molar ratios of Fe3+/Fe2+ (50–200%). It has been observed that morphology of the assembly and properties of these hybrid materials composed of SiO2 as core ...

  18. Influence of substrate on structural, morphological and optical properties of TiO2 thin films deposited by reaction magnetron sputtering

    Directory of Open Access Journals (Sweden)

    Xinghua Zhu

    2017-12-01

    Full Text Available Titanium dioxide (TiO2 films have been prepared by DC reaction magnetron sputtering technique on different substrates (glass, SiO2, platinum electrode-Pt, Silicon-Si. X-ray diffraction (XRD patterns showed that all TiO2 films were grown along the preferred orientation of (110 plane. Samples on Si and Pt substrates are almost monophasic rutile, however, samples on glass and SiO2 substrates accompanied by a weak anatase structure. Atomic force microscopy (AFM images revealed uniform grain distribution except for films on Pt substrates. Photoluminescence (PL spectra showed obvious intrinsic emission band, but films on glass was accompanied by a distinct defect luminescence region. Raman spectroscopy suggested that all samples moved to high wavenumbers and films on glass moved obviously.

  19. Magnetic properties of Fe3O4 thin films grown on different substrates by laser ablation

    International Nuclear Information System (INIS)

    Parames, M.L.; Viskadourakis, Z.; Rogalski, M.S.; Mariano, J.; Popovici, N.; Giapintzakis, J.; Conde, O.

    2007-01-01

    Magnetite thin films have been grown onto (1 0 0)Si (1 0 0)GaAs and (0 0 0 1)Al 2 O 3 , at substrate temperatures varying from 473 to 673 K, by UV pulsed laser ablation of Fe 3 O 4 targets in reactive atmospheres of O 2 and Ar, at working pressure of 8 x 10 -2 Pa. The influence of the substrate on stoichiometry, microstructure and the magnetic properties has been studied by X-ray diffraction (XRD), conversion electron Moessbauer spectroscopy (CEMS) and magnetic measurements. Magnetite crystallites, with stoichiometry varying from Fe 2.95 O 4 to Fe 2.99 O 4 , are randomly oriented for (1 0 0)GaAs and (1 0 0)Si substrates and exhibit (1 1 1) texture if grown onto (0 0 0 1)Al 2 O 3 . Interfacial Fe 3+ diffusion, which is virtually absent for (1 0 0)Si substrates, was found for both (0 0 0 1)Al 2 O 3 and (1 0 0)GaAs, with some deleterious effect on the subsequent microstructure and magnetic behaviour

  20. Transport measurements on selective area grown Te-based topological insulator thin films

    Energy Technology Data Exchange (ETDEWEB)

    Weyrich, Christian; Schall, Melissa; Kampmeier, Joern; Lanius, Martin; Mussler, Gregor; Schaepers, Thomas; Gruetzmacher, Detlev [Peter Gruenberg Institute (PGI- 9) and JARA-Fundamentals of Future Information Technology, Forschungszentrum Juelich GmbH, 52425 Juelich (Germany); Virtual Institute for Topological Insulators (VITI), Forschungszentrum Juelich GmbH, 52425 Juelich (Germany)

    2015-07-01

    We present magnetotransport measurements on Bi{sub 2}Te{sub 3} and Sb{sub 2}Te{sub 3} thin films, grown on prepatterned structures atop silicon-on-insulator substrates by molecular beam epitaxy. The substrates contain Si mesa fabricated from the 70nm thick Si(111) top layer on a 300nm thick SiO{sub 2} buried oxide layer. Therefore, we were able to utilize the difference in surface configuration between the Si(111) and the amorphous SiO{sub 2}, since only the hexagonal silicon surface supports growth of the tellurides. Using transport we show that films of comparable or even higher quality can be achieved using this method which furthermore evades the need of any additionally ex-situ patterning of the layers. With this, we pave the road to a simple fabrication method for nanometer sized structures that circumvents common problems of conventional methods like ion etching including hardened remains of photo resist and the like.

  1. Electrical properties of GaAsN film grown by chemical beam epitaxy

    International Nuclear Information System (INIS)

    Nishimura, K.; Suzuki, H.; Saito, K.; Ohshita, Y.; Kojima, N.; Yamaguchi, M.

    2007-01-01

    The local vibrational modes (LVMs) observed by Fourier transform infrared (FTIR) spectroscopy in GaAsN films grown by chemical beam epitaxy (CBE) was studied, and the influence of the nitrogen-hydrogen bond (N-H) concentration on the hole concentration was investigated. The absorption peak around 936 cm -1 is suggested to be the second harmonic mode of the substitutional N, N As , LVM around 469 cm -1 . The absorption peak around 960 cm -1 is suggested to be the wagging mode of the N-H, where the stretch mode is observed around 3098 cm -1 . The hole concentration linearly increases with increasing N-H concentration, and the slope increases with increasing growth temperature. It indicates that the hole concentration in GaAsN film is determined by both the number of the N-H and unknown defect, such as impurities, vacancies, and interstitials. This defect concentration increases with increasing growth temperature, suggesting that it is determined by Arrhenius type reaction

  2. Effect of growth temperature on defects in epitaxial GaN film grown by plasma assisted molecular beam epitaxy

    Directory of Open Access Journals (Sweden)

    S. S. Kushvaha

    2014-02-01

    Full Text Available We report the effect of growth temperature on defect states of GaN epitaxial layers grown on 3.5 μm thick GaN epi-layer on sapphire (0001 substrates using plasma assisted molecular beam epitaxy. The GaN samples grown at three different substrate temperatures at 730, 740 and 750 °C were characterized using atomic force microscopy and photoluminescence spectroscopy. The atomic force microscopy images of these samples show the presence of small surface and large hexagonal pits on the GaN film surfaces. The surface defect density of high temperature grown sample is smaller (4.0 × 108 cm−2 at 750 °C than that of the low temperature grown sample (1.1 × 109 cm−2 at 730 °C. A correlation between growth temperature and concentration of deep centre defect states from photoluminescence spectra is also presented. The GaN film grown at 750 °C exhibits the lowest defect concentration which confirms that the growth temperature strongly influences the surface morphology and affects the optical properties of the GaN epitaxial films.

  3. Ferrocene carboxaldehyde thin films grown by matrix-assisted pulsed laser evaporation for non linear optical applications

    International Nuclear Information System (INIS)

    Constantinescu, Catalin; Matei, Andreea; Ion, Valentin; Mitu, Bogdana; Ionita, Iulian; Dinescu, Maria; Luculescu, Catalin R.; Vasiliu, Cristina; Emandi, Ana

    2014-01-01

    Thin films of ferrocene carboxaldehyde, also known as cyclopentadienyl(formylcyclopentadienyl)iron, were grown on silicon and glass substrates by matrix-assisted pulsed laser evaporation technique, using a Nd:YAG device operating at 266 nm (4ω). Spectroscopic-ellipsometry, Fourier transform infrared spectroscopy, scanning electron microscopy and atomic force microscopy investigations revealed that the films are homogeneous in thickness, with dense morphology and without cracks, low surface roughness (∼11 nm), and no significant chemical damage. Second harmonic generation capabilities of the thin films were evidenced by using a femtosecond Ti:sapphire laser.

  4. Ordered Ag nanocluster structures by vapor deposition on pre-patterned SiO2.

    Science.gov (United States)

    Numazawa, Satoshi; Ranjan, Mukesh; Heinig, Karl-Heinz; Facsko, Stefan; Smith, Roger

    2011-06-08

    Highly ordered Ag nanocluster structures have been grown on pre-patterned amorphous SiO(2) surfaces by oblique angle physical vapor deposition at room temperature. Despite the small undulation of the rippled surface, the stripe-like Ag nanoclusters are very pronounced, reproducible and well separated. Computer modeling of the growth has been performed with a lattice-based kinetic Monte Carlo (KMC) method using a combination of a simplified inter-atomic potential and experimental transition barriers taken from the literature. An effective transition event classification method is introduced which allows a boost factor of several thousand compared to a traditional KMC approach, thus allowing experimental time scales to be modeled. The simulation predicts a low sticking probability for the arriving atoms, millisecond order lifetimes for single Ag adatoms and ≈1 nm square surface migration ranges of Ag adatoms. It is also shown that metal nucleations can trigger even on defect free surfaces. The simulations give excellent reproduction of the experimentally observed nanocluster growth patterns.

  5. Distribution of electron traps in SiO2/HfO2 nMOSFET

    Science.gov (United States)

    Xiao-Hui, Hou; Xue-Feng, Zheng; Ao-Chen, Wang; Ying-Zhe, Wang; Hao-Yu, Wen; Zhi-Jing, Liu; Xiao-Wei, Li; Yin-He, Wu

    2016-05-01

    In this paper, the principle of discharge-based pulsed I-V technique is introduced. By using it, the energy and spatial distributions of electron traps within the 4-nm HfO2 layer have been extracted. Two peaks are observed, which are located at ΔE ˜ -1.0 eV and -1.43 eV, respectively. It is found that the former one is close to the SiO2/HfO2 interface and the latter one is close to the gate electrode. It is also observed that the maximum discharge time has little effect on the energy distribution. Finally, the impact of electrical stress on the HfO2 layer is also studied. During stress, no new electron traps and interface states are generated. Meanwhile, the electrical stress also has no impact on the energy and spatial distribution of as-grown traps. The results provide valuable information for theoretical modeling establishment, material assessment, and reliability improvement for advanced semiconductor devices. Project supported by the National Natural Science Foundation of China (Grant Nos. 61334002, 61106106, and 61474091), the New Experiment Development Funds for Xidian University, China (Grant No. SY1434), and the Scientific Research Foundation for the Returned Overseas Chinese Scholars, State Education Ministry, China (Grant No. JY0600132501).

  6. A comparative study of physico-chemical properties of CBD and SILAR grown ZnO thin films

    International Nuclear Information System (INIS)

    Jambure, S.B.; Patil, S.J.; Deshpande, A.R.; Lokhande, C.D.

    2014-01-01

    Graphical abstract: Schematic model indicating ZnO nanorods by CBD (Z 1 ) and nanograins by SILAR (Z 2 ). - Highlights: • Simple methods for the synthesis of ZnO thin films. • Comparative study of physico-chemical properties of ZnO thin films prepared by CBD and SILAR methods. • CBD outperforms SILAR method. - Abstract: In the present work, nanocrystalline zinc oxide (ZnO) thin films have been successfully deposited onto glass substrates by simple and economical chemical bath deposition (CBD) and successive ionic layer adsorption reaction (SILAR) methods. These films were further characterized for their structural, optical, surface morphological and wettability properties. The X-ray diffraction (XRD) patterns for both CBD and SILAR deposited ZnO thin films reveal the highly crystalline hexagonal wurtzite structure. From optical studies, band gaps obtained are 2.9 and 3.0 eV for CBD and SILAR deposited thin films, respectively. The scanning electron microscope (SEM) patterns show growth of well defined randomly oriented nanorods and nanograins on the CBD and SILAR deposited samples, respectively. The resistivity of CBD deposited films (10 2 Ω cm) is lower than that of SILAR deposited films (10 5 Ω cm). Surface wettability studies show hydrophobic nature for both films. From the above results it can be concluded that CBD grown ZnO thin films show better properties as compared to SILAR method

  7. Ultra-low power thin film transistors with gate oxide formed by nitric acid oxidation method

    International Nuclear Information System (INIS)

    Kobayashi, H.; Kim, W. B.; Matsumoto, T.

    2011-01-01

    We have developed a low temperature fabrication method of SiO 2 /Si structure by use of nitric acid, i.e., nitric acid oxidation of Si (NAOS) method, and applied it to thin film transistors (TFT). A silicon dioxide (SiO 2 ) layer formed by the NAOS method at room temperature possesses 1.8 nm thickness, and its leakage current density is as low as that of thermally grown SiO 2 layer with the same thickness formed at ∼900 deg C. The fabricated TFTs possess an ultra-thin NAOS SiO 2 /CVD SiO 2 stack gate dielectric structure. The ultrathin NAOS SiO 2 layer effectively blocks a gate leakage current, and thus, the thickness of the gate oxide layer can be decreased from 80 to 20 nm. The thin gate oxide layer enables to decrease the operation voltage to 2 V (cf. the conventional operation voltage of TFTs with 80 nm gate oxide: 12 V) because of the low threshold voltages, i.e., -0.5 V for P-ch TFTs and 0.5 V for N-ch TFTs, and thus the consumed power decreases to 1/36 of that of the conventional TFTs. The drain current increases rapidly with the gate voltage, and the sub-threshold voltage is ∼80 mV/dec. The low sub-threshold swing is attributable to the thin gate oxide thickness and low interface state density of the NAOS SiO 2 layer. (authors)

  8. Optical properties of aluminum nitride thin films grown by direct-current magnetron sputtering close to epitaxy

    Energy Technology Data Exchange (ETDEWEB)

    Stolz, A. [Institut d' Electronique de Microélectronique et de Nanotechnologie (IEMN), UMR CNRS 8520, PRES Lille, Université Nord de France, Avenue Poincaré, 59652 Villeneuve d' Ascq Cedex (France); Soltani, A., E-mail: ali.soltani@iemn.univ-lille1.fr [Institut d' Electronique de Microélectronique et de Nanotechnologie (IEMN), UMR CNRS 8520, PRES Lille, Université Nord de France, Avenue Poincaré, 59652 Villeneuve d' Ascq Cedex (France); Abdallah, B. [Department of Materials Physics, Atomic Energy Commission of Syria, Damascus, P.O. Box 6091 (Syrian Arab Republic); Charrier, J. [Fonctions Optiques pour les Technologies de l' informatiON (FOTON), UMR CNRS 6082, 6, rue de Kerampont CS 80518, 22305 Lannion Cedex (France); Deresmes, D. [Institut d' Electronique de Microélectronique et de Nanotechnologie (IEMN), UMR CNRS 8520, PRES Lille, Université Nord de France, Avenue Poincaré, 59652 Villeneuve d' Ascq Cedex (France); Jouan, P.-Y.; Djouadi, M.A. [Institut des Matériaux Jean Rouxel – IMN, UMR CNRS 6502, 2, rue de la Houssinère BP 32229, 44322 Nantes (France); Dogheche, E.; De Jaeger, J.-C. [Institut d' Electronique de Microélectronique et de Nanotechnologie (IEMN), UMR CNRS 8520, PRES Lille, Université Nord de France, Avenue Poincaré, 59652 Villeneuve d' Ascq Cedex (France)

    2013-05-01

    Low-temperature Aluminum Nitride (AlN) thin films with a thickness of 3 μm were deposited by Direct-Current magnetron sputtering on sapphire substrate. They present optical properties similar to those of epitaxially grown films. Different characterization methods such as X-Ray Diffraction, Transmission Electron Microscopy and Atomic Force Microscopy were used to determine the structural properties of the films such as its roughness and crystallinity. Newton interferometer was used for stress measurement of the films. Non-destructive prism-coupling technique was used to determine refractive index and thickness homogeneity by a mapping on the whole sample area. Results show that AlN films grown on AlGaN layer have a high crystallinity close to epitaxial films, associated to a low intrinsic stress for low thickness. These results highlight that it is possible to grow thick sample with microstructure and optical properties close to epitaxy, even on a large surface. - Highlights: ► Aluminum Nitride sputtering technique with a low temperature growth process ► Epitaxial quality of two microns sputtered Aluminum Nitride film ► Optics as a non-destructive accurate tool for acoustic wave investigation.

  9. Microstructures of InN film on 4H-SiC (0001) substrate grown by RF-MBE

    Science.gov (United States)

    Jantawongrit, P.; Sanorpim, S.; Yaguchi, H.; Orihara, M.; Limsuwan, P.

    2015-08-01

    InN film was grown on 4H-SiC (0001) substrate by RF plasma-assisted molecular beam epitaxy (RF-MBE). Prior to the growth of InN film, an InN buffer layer with a thickness of ∼5.5 nm was grown on the substrate. Surface morphology, microstructure and structural quality of InN film were investigated. Micro-structural defects, such as stacking faults and anti-phase domain in InN film were carefully investigated using transmission electron microscopy (TEM). The results show that a high density of line contrasts, parallel to the growth direction (c-axis), was clearly observed in the grown InN film. Dark field TEM images recorded with diffraction vectors g=11\\bar{2}0 and g = 0002 revealed that such line contrasts evolved from a coalescence of the adjacent misoriented islands during the initial stage of the InN nucleation on the substrate surface. This InN nucleation also led to a generation of anti-phase domains. Project supported by the Thailand Center of Excellence in Physics (ThEP) and the King Mongkut's University of Technology Thonburi under The National Research University Project. One of the authors (S. Sanorpim) was supported by the National Research Council of Thailand (NRCT) and the Thai Government Stimulus Package 2 (TKK2555), under the Project for Establishment of Comprehensive Center for Innovative Food, Health Products and Agriculture.

  10. Hydrothermally synthesized PZT film grown in highly concentrated KOH solution with large electromechanical coupling coefficient for resonator

    Science.gov (United States)

    Feng, Guo-Hua; Lee, Kuan-Yi

    2017-12-01

    This paper presents a study of lead zirconate titanate (PZT) films hydrothermally grown on a dome-shaped titanium diaphragm. Few articles in the literature address the implementation of hydrothermal PZT films on curved-diaphragm substrates for resonators. In this study, a 50-μm-thick titanium sheet is embossed using balls of designed dimensions to shape a dome-shaped cavity array. Through single-process hydrothermal synthesis, PZT films are grown on both sides of the processed titanium diaphragm with good adhesion and uniformity. The hydrothermal synthesis process involves a high concentration of potassium hydroxide solution and excess amounts of lead acetate and zirconium oxychloride octahydrate. Varied deposition times and temperatures of PZT films are investigated. The grown films are characterized by X-ray diffraction and scanning electron microscopy. The 10-μm-thick PZT dome-shaped resonators with 60- and 20-μm-thick supporting layers are implemented and further tested. Results for both resonators indicate that large electromechanical coupling coefficients and a series resonance of 95 MHz from 14 MHz can be attained. The device is connected to a complementary metal-oxide-semiconductor integrated circuit for analysis of oscillator applications. The oscillator reaches a Q value of 6300 in air. The resonator exhibits a better sensing stability when loaded with water when compared with air.

  11. Self-organized single crystal mixed magnetite/cobalt ferrite films grown by infrared pulsed-laser deposition

    Energy Technology Data Exchange (ETDEWEB)

    Figuera, Juan de la, E-mail: juan.delafiguera@iqfr.csic.es [Instituto de Química Física “Rocasolano”, CSIC, Madrid E-28006 (Spain); Quesada, Adrián [Instituto de Cerámica y Vidrio, CSIC, Madrid E-28049 (Spain); Martín-García, Laura; Sanz, Mikel; Oujja, Mohamed; Rebollar, Esther; Castillejo, Marta [Instituto de Química Física “Rocasolano”, CSIC, Madrid E-28006 (Spain); Prieto, Pilar; Muñoz-Martín, Ángel [Universidad Autónoma de Madrid, E-28049 (Spain); Aballe, Lucía [Alba Synchrotron Light Facility, CELLS, Barcelona (Spain); Marco, José F. [Instituto de Química Física “Rocasolano”, CSIC, Madrid E-28006 (Spain)

    2015-12-30

    Highlights: • Infrared pulsed deposition is used to grow single crystal mixed magnetite-cobalt ferrite films. • Distinct topography with two mound types on the surface of the film. • Suggested origin of segregation into two phases is oxygen deficiency during growth. • Mössbauer is required to quantify the two components. - Abstract: We have grown mixed magnetite/cobalt ferrite epitaxial films on SrTiO{sub 3} by infrared pulsed-laser deposition. Diffraction experiments indicate epitaxial growth with a relaxed lattice spacing. The films are flat with two distinct island types: nanometric rectangular mounds in two perpendicular orientations, and larger square islands, attributed to the two main components of the film as determined by Mössbauer spectroscopy. The origin of the segregation is suggested to be the oxygen-deficiency during growth.

  12. Thickness-Dependent Properties of YBCO Films Grown on GZO/CLO-Buffered NiW Substrates

    DEFF Research Database (Denmark)

    Malmivirta, M.; Huhtinen, H.; Yue, Zhao

    2017-01-01

    To study the role of novel Gd2Zr2O7/Ce0.9La0.1O2 buffer layer structure on a biaxially textured NiW substrate, a set of YBa2Cu3O7−δ (YBCO) films with different thicknesses were prepared by pulsed laser deposition (PLD). Interface imperfections as well as thickness-dependent structural properties...... were observed in the YBCO thin films. The structure is also reflected into the improved superconducting properties with the highest critical current densities in films with intermediate thicknesses. Therefore,it can be concluded that the existing buffer layers need more optimization before they can...... be successfully used for films with various thicknesses. This issue is linked to the extremely susceptible growth method of PLD when compared to the commonly used chemical deposition methods. Nevertheless, PLD-grown films can give a hint on what to concentrate to be able to further improve the buffer layer...

  13. Crystal orientations of InSb films grown on a Si(111) substrate by inserting AlSb buffer layer

    International Nuclear Information System (INIS)

    Murata, K.; Ahmad, N.B.; Mori, M.; Tambo, T.; Maezawa, K.

    2008-01-01

    The heteroepitaxial growth of InSb film via AlSb buffer layer on a Si(111) substrate was performed in an ultra high vacuum. The grown InSb films were characterized by X-ray diffraction and atomic force microscopy. XRD patterns (Φ-scan) of the samples showed different epitaxial relationship between InSb/Si and InSb/AlSb/Si. It is found that surface condition has a significant influence on the growth of InSb films and the surface of InSb films became rough due to the high mixture ratio of domains. The two-step growth procedure was also tried to further improve the crystal quality of the InSb films. (copyright 2008 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  14. Conformal SiO2 coating of sub-100 nm diameter channels of polycarbonate etched ion-track channels by atomic layer deposition

    Directory of Open Access Journals (Sweden)

    Nicolas Sobel

    2015-02-01

    Full Text Available Polycarbonate etched ion-track membranes with about 30 µm long and 50 nm wide cylindrical channels were conformally coated with SiO2 by atomic layer deposition (ALD. The process was performed at 50 °C to avoid thermal damage to the polymer membrane. Analysis of the coated membranes by small angle X-ray scattering (SAXS reveals a homogeneous, conformal layer of SiO2 in the channels at a deposition rate of 1.7–1.8 Å per ALD cycle. Characterization by infrared and X-ray photoelectron spectroscopy (XPS confirms the stoichiometric composition of the SiO2 films. Detailed XPS analysis reveals that the mechanism of SiO2 formation is based on subsurface crystal growth. By dissolving the polymer, the silica nanotubes are released from the ion-track membrane. The thickness of the tube wall is well controlled by the ALD process. Because the track-etched channels exhibited diameters in the range of nanometres and lengths in the range of micrometres, cylindrical tubes with an aspect ratio as large as 3000 have been produced.

  15. Preparation and Characterization of SiO2/SiCN Core-shell Ceramic Microspheres

    Directory of Open Access Journals (Sweden)

    ZHANG Hai-yuan

    2017-05-01

    Full Text Available The SiO2/PSN core-shell microspheres were prepared via an emulsion reaction combined with the polymer-derived ceramics (PDCs method using polysilazane (PSN in situ polymerization on the surface of SiO2 modified by silane coupling agents MPS, followed by pyrolysis process to obtain SiO2/SiCN core-shell ceramic microspheres. The effects of raw mass ratio, curing time and pyrolysis temperature on the formation and the morphology of core-shell microspheres were studied. The morphology, chemical composition and phase transformation were characterized by SEM, EDS, TEM, FT-IR and XRD. The results show that after reaction for 4h at 200℃, SiO2 completely coated PSN forms a core-shell microsphere with rough surface when the mass ratio of SiO2 and PSN is 1:4; when pyrolysis temperature is at 800-1200℃, amorphous SiO2/SiCN core-shell ceramic microspheres are prepared; at 1400℃, the amorphous phase partially crystallizes to produce SiO2, SiC and Si3N4 phase.

  16. Enhanced antioxidation and microwave absorbing properties of SiO2-coated flaky carbonyl iron particles

    Science.gov (United States)

    Zhou, Yingying; Xie, Hui; Zhou, Wancheng; Ren, Zhaowen

    2018-01-01

    SiO2 was successfully coated on the surface of flaky carbonyl iron particles using a chemical bath deposition method in the presence of 3-aminopropyl triethoxysilane (APTES). The morphologies, composition, valence states of elements, as well as antioxidation and electromagnetic properties of the samples were characterized by scanning electron microscope (SEM), energy dispersive spectrometer (EDS), X-ray photoelectron spectroscopy (XPS), thermogravimetric (TG) and microwave network analyzer. TG curve shows the obvious weight gain of carbonyl iron was deferred to 360 °C after SiO2-coated, which can be ascribed to the exits of SiO2 overlayer. Compared with the raw carbonyl iron, SiO2-coated sample shows good wave absorption performance due to its impedance matching. The electromagnetic properties of raw and SiO2-coated carbonyl iron particles were characterized in X band before and after heat treatment at 250 °C for 10 h. It was established that SiO2-coated carbonyl iron demonstrate good thermal stability, indicating SiO2-coating is useful in the usage of microwave absorbers operating at temperature up to 250 °C.

  17. Effect of SiO2 addition and gamma irradiation on the lithium borate glasses

    Science.gov (United States)

    Raut, A. P.; Deshpande, V. K.

    2018-01-01

    The physical properties like density, glass transition temperature (Tg), and ionic conductivity of lithium borate (LB) glasses with SiO2 addition were measured before and after gamma irradiation. Remarkable changes in properties have been obtained in the physical properties of LB glasses with SiO2 addition and after gamma irradiation. The increase in density and glass transition temperature of LB glasses with SiO2 addition has been explained with the help of increase in density of cross linking due to SiO4 tetrahedra formation. The increase in ionic conductivity with SiO2 addition was explained with the help of ‘mixed glass former effect’. The increase in density and Tg of LB glasses with SiO2 addition after gamma irradiation has been attributed to fragmentation of bigger ring structure into smaller rings, which increases the density of cross linking and hence compaction. The exposure of gamma irradiation has lead to decrease in ionic conductivity of LB glasses with SiO2 addition. The atomic displacement caused by gamma irradiation resulted in filling of interstices and decrease in trapping sites. This explains the obtained decrease in ionic conductivity after gamma irradiation of glasses. The obtained results of effect of SiO2 addition and gamma irradiation on the density, Tg and ionic conductivity has been supported by FTIR results.

  18. Kinetics of Valeric Acid Ketonization and Ketenization in Catalytic Pyrolysis on Nanosized SiO2, γ-Al2O3, CeO2/SiO2, Al2O3/SiO2and TiO2/SiO2.

    Science.gov (United States)

    Kulyk, Kostiantyn; Palianytsia, Borys; Alexander, John D; Azizova, Liana; Borysenko, Mykola; Kartel, Mykola; Larsson, Mats; Kulik, Tetiana

    2017-07-19

    Valeric acid is an important renewable platform chemical that can be produced efficiently from lignocellulosic biomass. Upgrading of valeric acid by catalytic pyrolysis has the potential to produce value added biofuels and chemicals on an industrial scale. Understanding the different mechanisms involved in the thermal transformations of valeric acid on the surface of nanometer-sized oxides is important for the development of efficient heterogeneously catalyzed pyrolytic conversion techniques. In this work, the thermal decomposition of valeric acid on the surface of nanoscale SiO 2 , γ-Al 2 O 3 , CeO 2 /SiO 2 , Al 2 O 3 /SiO 2 and TiO 2 /SiO 2 has been investigated by temperature-programmed desorption mass spectrometry (TPD MS). Fourier transform infrared spectroscopy (FTIR) has also been used to investigate the structure of valeric acid complexes on the oxide surfaces. Two main products of pyrolytic conversion were observed to be formed depending on the nano-catalyst used-dibutylketone and propylketene. Mechanisms of ketene and ketone formation from chemisorbed fragments of valeric acid are proposed and the kinetic parameters of the corresponding reactions were calculated. It was found that the activation energy of ketenization decreases in the order SiO 2 >γ-Al 2 O 3 >TiO 2 /SiO 2 >Al 2 O 3 /SiO 2 , and the activation energy of ketonization decreases in the order γ-Al 2 O 3 >CeO 2 /SiO 2 . Nano-oxide CeO 2 /SiO 2 was found to selectively catalyze the ketonization reaction. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  19. Dewetting induced Au-Ge composite nanodot evolution in SiO2

    Science.gov (United States)

    Datta, D. P.; Chettah, A.; Siva, V.; Kanjilal, D.; Sahoo, P. K.

    2018-01-01

    A composite nanostructure comprising of Au and Ge gradually evolves on SiO2 surface when a bilayer of Au and Ge is irradiated by medium keV Xe-ion beam. The morphology progresses through different stages from nucleating patches to extended islands and finally a Au-Ge composite nanodot array develops on the insulator surface. While ion energy and fluence are found to determine dimensions of the nanostructures, existence of a characteristic lateral length scale is also detected at every stage of evolution. Through morphological and compositional analysis, the observed evolution is understood as an effect of ion beam induced dewetting of Au top layer. Numerical estimation based on the unified thermal spike model using the present experimental condition demonstrates formation of molten zones around the ion track due to nuclear and electronic energy deposition in the target. Dewetting results from mass flow onto the surface driven by local melting along the ion track and combines with sputter erosion of the bilayer film to lead to composite nanodot evolution. The generality of the ion induced processes provides possible route towards metal-semiconductor hybrid nanostructure synthesis on insulator surface.

  20. Porous asymmetric SiO2-g-PMMA nanoparticles produced by phase inversion

    KAUST Repository

    Munirasu, Selvaraj

    2014-07-22

    A new kind of asymmetric organic-inorganic porous structure has been proposed. Asymmetric lattices of polymer grafted silica nanoparticles were manufactured by casting and phase inversion in water. Silica nanoparticles were first functionalized with 3-(dimethylethoxysilyl)propyl-2-bromoisobutyrate, followed by grafting of poly(methylmethacrylate) (PMMA) segments, performed by atom-transfer radical polymerization. Mechanically stable self-standing films were prepared by casting a dispersion of functionalized nanoparticles in different solvents and immersion in water. The resulting asymmetrically porous morphology and nanoparticle assembly was characterized by scanning electron and atomic force microscopy. The PMMA functionalized SiO2 hybrid material in acetone or acetone/dioxane led to the best-assembled structures. Porous asymmetric membranes were prepared by adding free PMMA and PMMA terminated with hydrophilic hydroxyl group. Nitrogen flow of 2800 L m-2 h -1 was measured at 1.3 bar demonstrating the porosity and potential application for membrane technology. © 2014 Springer Science+Business Media New York.

  1. 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.

  2. Cytotoxicity and effect on GJIC of SiO2 nanoparticles in HL-7702 cells

    International Nuclear Information System (INIS)

    Pan Tao; Jin Minghua; Liu Xiaomei; Du Zhongjun; Zhou Xianqing; Huang Peili; Sun Zhiwei

    2013-01-01

    Objective: To study the cytotoxicity and effect on gap junction intracellular communication (GJIC) of SiO 2 nanoparticles in HL-7702 cells, and to provide experimental basis for toxicity assessment and the security applications of SiO 2 nanoparticles. Methods: Transmission electron microscope (TEM) was used to characterize two kinds of SiO 2 nanoparticles, verifying their size, dispersion and shape; dynamic light scattering (DLS) method was used to analyze the water dispersion and culture medium dispersion of the SiO 2 nanoparticles; MTT assay was carried out to examine the cytotoxicities of the two sizes SiO 2 nanoparticles on the cells; lactate dehydrogenase (LDH) release assay was performed to examine the integrity nano of the cell membrane; Scrape-loading and dye transfer assay was performed to examine the effect of SiO 2 nanoparticles on GJIC. Results: Based on the result of TEM, two kinds of SiO 2 nanoparticles were spherically shaped, uniformly sized and sporadically dispersed; the statistical analysis results showed the diameters of the two nanoparticles were (447.60±20.78) nm and (67.42±5.69) nm, respectively, thus they could be categorized as submicron scale and nano scale. The DLS method results manifested that the hydration nanoparticle sizes of the two SiO 2 nanoparticles were (684.37±18.76) nm, (128.31±7.64) nm in high purity water and (697.02±19.57) nm, (133.74±8.97) nm in RPMI-1640 solution, all the two nanoparticles were well dispersed without aggregation. MTT assay indicated that 24 h after treatment of SiO 2 nanoparticles, the cell viabilities were affected by both the size and the dose of the SiO 2 nanoparticles; the higher the dose was, the less viability the cells exhibited. Moreover, the nano scale particles inflicted more damage to the cells. LDH release assay indicated that the SiO 2 particles could also damage the cell membrane in a dose-dependent and size-dependent way. Scrape-loading and dye transfer assay indicated that the nano scale particles could cause GJIC inhibition in a dose-dependent way; and when at the same dose, the nanoparticles could cause a more obvious inhibition of GJIC than the submicron particles. Conclusion: SiO 2 nanoparticles have cytotoxicity on HL-7702 cells, and would cause GJIC inhibition. (authors)

  3. Facile synthesis of microporous SiO2/triangular Ag composite nanostructures for photocatalysis

    Science.gov (United States)

    Sirohi, Sidhharth; Singh, Anandpreet; Dagar, Chakit; Saini, Gajender; Pani, Balaram; Nain, Ratyakshi

    2017-11-01

    In this article, we present a novel fabrication of microporous SiO2/triangular Ag nanoparticles for dye (methylene blue) adsorption and plasmon-mediated degradation. Microporous SiO2 nanoparticles with pore size green 26 and curcumin crystalline. Amine-functionalized microporous SiO2/triangular Ag nanostructures were used for plasmon-mediated photocatalysis of methylene blue. The experimental results revealed that the large surface area of microporous silica facilitated adsorption of dye. Triangular Ag nanoparticles, due to their better charge carrier generation and enhanced surface plasmon resonance, further enhanced the photocatalysis performance.

  4. Formation of radiative centers in SiO2 by tin high-dose implantation

    International Nuclear Information System (INIS)

    Komarov, F.F.; Parkhomenko, I.N.; Vlasukova, L.A.; Mil'chanin, O.V.; Mokhovikov, M.A.; Wendler, E.; Wesch, W.

    2013-01-01

    The structural transformations in SiO 2 layers implanted with high fluence of Sn ions have been investigated. It has been found that post-implantation annealing results in the β-Sn precipitation as well as the formation of SnO 2 -enriched regions in SiO 2 :Sn matrix. The intensive emission in the range of photon energies 1.5 – 3.5 eV is registered for the implanted and annealed samples. We attribute it to the oxygen deficiency centers created in the SiO 2 :Sn matrix and at the 'nanocluster/SiO 2 ' interfaces. (authors)

  5. Optical properties of amorphous SiO2-TiO2 multi-nanolayered coatings for 1064-nm mirror technology

    Science.gov (United States)

    Magnozzi, M.; Terreni, S.; Anghinolfi, L.; Uttiya, S.; Carnasciali, M. M.; Gemme, G.; Neri, M.; Principe, M.; Pinto, I.; Kuo, L.-C.; Chao, S.; Canepa, M.

    2018-01-01

    The use of amorphous, SiO2-TiO2 nanolayered coatings has been proposed recently for the mirrors of 3rd-generation interferometric detectors of gravitational waves, to be operated at low temperature. Coatings with a high number of low-high index sub-units pairs with nanoscale thickness were found to preserve the amorphous structure for high annealing temperatures, a key factor to improve the mechanical quality of the mirrors. The optimization of mirror designs based on such coatings requires a detailed knowledge of the optical properties of sub-units at the nm-thick scale. To this aim we have performed a Spectroscopic Ellipsometry (SE) study of amorphous SiO2-TiO2 nanolayered films deposited on Si wafers by Ion Beam Sputtering (IBS). We have analyzed films that are composed of 5 and 19 nanolayers (NL5 and NL19 samples) and have total optical thickness nominally equivalent to a quarter of wavelength at 1064 nm. A set of reference optical properties for the constituent materials was obtained by the analysis of thicker SiO2 and TiO2 homogeneous films (∼ 120 nm) deposited by the same IBS facility. By flanking SE with ancillary techniques, such as TEM and AFM, we built optical models that allowed us to retrieve the broad-band (250-1700 nm) optical properties of the nanolayers in the NL5 and NL19 composite films. In the models which provided the best agreement between simulation and data, the thickness of each sub-unit was fitted within rather narrow bounds determined by the analysis of TEM measurements on witness samples. Regarding the NL5 sample, with thickness of 19.9 nm and 27.1 nm for SiO2 and TiO2 sub-units, respectively, the optical properties presented limited variations with respect to the thin film counterparts. For the NL19 sample, which is composed of ultrathin sub-units (4.4 nm and 8.4 nm for SiO2 and TiO2, respectively) we observed a significant decrease of the IR refraction index for both types of sub-units; this points to a lesser mass density with

  6. Wafer bowing control of free-standing heteroepitaxial diamond (100) films grown on Ir(100) substrates via patterned nucleation growth

    International Nuclear Information System (INIS)

    Yoshikawa, Taro; Kodama, Hideyuki; Kono, Shozo; Suzuki, Kazuhiro; Sawabe, Atsuhito

    2015-01-01

    The potential of patterned nucleation growth (PNG) technique to control the wafer bowing of free-standing heteroepitaxial diamond films was investigated. The heteroepitaxial diamond (100) films were grown on an Ir(100) substrate via PNG technique with different patterns of nucleation regions (NRs), which were dot-arrays with 8 or 13 μm pitch aligned to < 100 > or < 110 > direction of the Ir(100) substrate. The wafer bows and the local stress distributions of the free-standing films were measured using a confocal micro-Raman spectrometer. For each NR pattern, the stress evolutions within the early stage of diamond growth were also studied together with a scanning electron microscopic observation of the coalescing diamond particles. These investigations revealed that the NR pattern, in terms of pitch and direction of dot-array, strongly affects the compressive stress on the nucleation side of the diamond film and dominantly contributes to the elastic deformation of the free-standing film. This indicates that the PNG technique with an appropriate NR pattern is a promising solution to fabricate free-standing heteroepitaxial diamond films with extremely small bows. - Highlights: • Wafer bowing control of free-standing heteroepitaxial diamond (100) films • Effect of patterned nucleation and growth (PNG) technique on wafer bowing reduction • Influence of nucleation region patterns of PNG on wafer bowing • Internal stress analysis of PNG films via confocal micro-Raman spectroscopy

  7. Elucidating doping driven microstructure evolution and optical properties of lead sulfide thin films grown from a chemical bath

    Science.gov (United States)

    Mohanty, Bhaskar Chandra; Bector, Keerti; Laha, Ranjit

    2018-03-01

    Doping driven remarkable microstructural evolution of PbS thin films grown by a single-step chemical bath deposition process at 60 °C is reported. The undoped films were discontinuous with octahedral-shaped crystallites after 30 min of deposition, whereas Cu doping led to a distinctly different surface microstructure characterized by densely packed elongated crystallites. A mechanism, based on the time sequence study of microstructural evolution of the films, and detailed XRD and Raman measurements, has been proposed to explain the contrasting microstructure of the doped films. The incorporation of Cu forms an interface layer, which is devoid of Pb. The excess Cu ions in this interface layer at the initial stages of film growth strongly interact and selectively stabilize the charged {111} faces containing either Pb or S compared to the uncharged {100} faces that contain both Pb and S. This interaction interferes with the natural growth habit resulting in the observed surface features of the doped films. Concurrently, the Cu-doping potentially changed the optical properties of the films: A significant widening of the bandgap from 1.52 eV to 1.74 eV for increase in Cu concentration from 0 to 20% was observed, making it a highly potential absorber layer in thin film solar cells.

  8. Perpendicular Magnetic Anisotropy and Spin Glass-like Behavior in Molecular Beam Epitaxy Grown Chromium Telluride Thin Films.

    Science.gov (United States)

    Roy, Anupam; Guchhait, Samaresh; Dey, Rik; Pramanik, Tanmoy; Hsieh, Cheng-Chih; Rai, Amritesh; Banerjee, Sanjay K

    2015-04-28

    Reflection high-energy electron diffraction (RHEED), scanning tunneling microscopy (STM), vibrating sample magnetometry, and other physical property measurements are used to investigate the structure, morphology, magnetic, and magnetotransport properties of (001)-oriented Cr2Te3 thin films grown on Al2O3(0001) and Si(111)-(7×7) surfaces by molecular beam epitaxy. Streaky RHEED patterns indicate flat smooth film growth on both substrates. STM studies show the hexagonal arrangements of surface atoms. Determination of the lattice parameter from the atomically resolved STM image is consistent with the bulk crystal structures. Magnetic measurements show the film is ferromagnetic, having a Curie temperature of about 180 K, and a spin glass-like behavior was observed below 35 K. Magnetotransport measurements show the metallic nature of the film with a perpendicular magnetic anisotropy along the c-axis.

  9. Microstructure of epitaxial YBa2Cu3O7-x thin films grown on LaAlO3 (001)

    International Nuclear Information System (INIS)

    Hsieh, Y.; Siegal, M.P.; Hull, R.; Phillips, J.M.

    1990-01-01

    We report a microstructural investigation of the epitaxial growth of YBa 2 Cu 3 O 7-x (YBCO) thin films on LaAlO 3 (001) substrates using transmission electron microscopy (TEM). Epitaxial films grow with two distinct modes: c epitaxy (YBCO) single crystal with the c (axis normal to the surface and a epitaxy (YBCO) single crystal with the c axis in the interfacial plane), where c epitaxy is the dominant mode grown in all samples 35--200 nm thick. In 35 nm YBCO films annealed at 850 degree C, 97±1% of the surface area is covered by c epitaxy with embedded anisotropic a-epitaxial grains. Quantitative analysis reveals the effect of film thickness and annealing temperature on the density, grain sizes, areal coverages, and anisotropic growth of a epitaxy

  10. The role of defects in the electrical properties of NbO2thin film vertical devices

    Science.gov (United States)

    Joshi, Toyanath; Borisov, Pavel; Lederman, David

    Epitaxial NbO2 thin films were grown on Si:GaN layers deposited on Al2O3 substrates using pulsed laser deposition. Pulsed current-voltage (IV) curves and self-sustained current oscillations were measured across a 31 nm NbO2 film and compared with a similar device made from polycrystalline NbO2 film grown on TiN-coated SiO2/Si substrate. Crystal quality of the as grown films was determined from x-ray diffractometric, x-ray photoelectron spectroscopy and atomic force microscopy data. The epitaxial film device was found to be more stable than the defect-rich polycrystalline sample in terms of current switching and oscillation behaviors. This work was supported in part by FAME, one of six centers of STARnet, a Semiconductor Research Corporation program sponsored by MARCO and DARPA (Contract 2013-MA-2382), and the WVU Shared Research Facilities.

  11. The role of defects in the electrical properties of NbO2 thin film vertical devices

    Directory of Open Access Journals (Sweden)

    Toyanath Joshi

    2016-12-01

    Full Text Available Epitaxial NbO2 thin films were grown on Si:GaN layers deposited on Al2O3 substrates using pulsed laser deposition. Pulsed current-voltage (IV curves and self-sustained current oscillations were measured across a 31 nm NbO2 film and compared with a similar device made from polycrystalline NbO2 film grown on TiN-coated SiO2/Si substrate. Crystal quality of the as grown films was determined from x-ray diffractometry, x-ray photoelectron spectroscopy and atomic force microscopy data. The epitaxial film device was found to be more stable than the defect-rich polycrystalline sample in terms of current switching and oscillation behaviors.

  12. Radiation-induced redistribution of gold in SiO2-Si structures

    International Nuclear Information System (INIS)

    Bolotov, V.V.; Emeksuzyan, V.M.; Spiridonov, V.N.

    1989-01-01

    Gold distribution in SiO 2 -Si structures after diffusion and its redistribution under irradiation by high-energy electrons are studied by DLTS and SIMS methods. It is shown that the concentration of substitutional gold increases at radiation doses of 10 13 to 10 14 cm -2 , which is due to the presence of a previously inactive interstitial component Au I and its dissolution in vacancies. A radiation dose increase results in radiation-induced gettering of gold by the SiO 2 -Si interface with subsequent penetration of gold into SiO 2 . The state of the SiO 2 -Si interface affects the behaviour of gold at irradiation. (author)

  13. Experimental determination of nanofluid specific heat with SiO2 nanoparticles in different base fluids

    Science.gov (United States)

    Akilu, S.; Baheta, A. T.; Sharma, K. V.; Said, M. A.

    2017-09-01

    Nanostructured ceramic materials have recently attracted attention as promising heat transfer fluid additives owing to their outstanding heat storage capacities. In this paper, experimental measurements of the specific heats of SiO2-Glycerol, SiO2-Ethylene Glycol, and SiO2-Glycerol/Ethylene Glycol mixture 60:40 ratio (by mass) nanofluids with different volume concentrations of 1.0-4.0% have been carried out using differential scanning calorimeter at temperatures of 25 °C and 50 °C. Experimental results indicate lower specific heat capacities are found with SiO2 nanofluids compared to their respective base fluids. The specific heat was decreasing with the increase of concentration, and this decrement depends on upon the type of the base fluid. It is observed that temperature has a positive impact on the specific heat capacity. Furthermore, the experimental values were compared with the theoretical model predictions, and a satisfactory agreement was established.

  14. Synthesis of unidirectional structures of SiO2-Ag using Au nanoparticles as nucleation centers

    International Nuclear Information System (INIS)

    Villa S, G.; Mendoza A, D.; Gutierrez W, C.; Perez H, R.

    2008-01-01

    This paper reports a method to synthesize Ag unidirectional structures covered with SiO 2 by sol-gel technique using Au nanoparticles as nucleation centers of the unidirectional structures. In the first phase unidirectional structures of SiO 2 -Ag CI are obtained by sol-gel, using TEOS as a precursor of metallic structures (Ag) and the incorporation of Au nanoparticles as nucleation centers for growth of unidirectional structures. In the second stage, one-way systems are subjected to thermal treatment in H 2 atmosphere for obtain AG 0 particles through mechanisms that diffusion and coalescence of silver to form structures that have a thin cover of SiO 2 . Analysis by scanning electron microscopy, transmission and atomic force microscopy allowed to determine the chemical composition and microstructural properties of unidirectional systems SiO 2 -Ag. (Author)

  15. Hole-dominated transport in InSb nanowires grown on high-quality InSb films

    Energy Technology Data Exchange (ETDEWEB)

    Algarni, Zaina; George, David; Singh, Abhay; Lin, Yuankun; Philipose, U., E-mail: usha.philipose@unt.edu [University of North Texas, Department of Physics (United States)

    2016-12-15

    We have developed an effective strategy for synthesizing p-type indium antimonide (InSb) nanowires on a thin film of InSb grown on glass substrate. The InSb films were grown by a chemical reaction between Sb{sub 2}S{sub 3} and In and were characterized by structural, compositional, and optical studies. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) studies reveal that the surface of the substrate is covered with a polycrystalline InSb film comprised of sub-micron sized InSb islands. Energy dispersive X-ray (EDX) results show that the film is stoichiometric InSb. The optical constants of the InSb film, characterized using a variable-angle spectroscopic ellipsometer (VASE) shows a maximum value for refractive index at 3.7 near 1.8 eV, and the extinction coefficient (k) shows a maximum value 3.3 near 4.1 eV. InSb nanowires were subsequently grown on the InSb film with 20 nm sized Au nanoparticles functioning as the metal catalyst initiating nanowire growth. The InSb nanowires with diameters in the range of 40–60 nm exhibit good crystallinity and were found to be rich in Sb. High concentrations of anions in binary semiconductors are known to introduce acceptor levels within the band gap. This un-intentional doping of the InSb nanowire resulting in hole-dominated transport in the nanowires is demonstrated by the fabrication of a p-channel nanowire field effect transistor. The hole concentration and field effect mobility are estimated to be ≈1.3 × 10{sup 17} cm{sup −3} and 1000 cm{sup 2} V{sup −1} s{sup −1}, respectively, at room temperature, values that are particularly attractive for the technological implications of utilizing p-InSb nanowires in CMOS electronics.

  16. Application of pentacene thin-film transistors with controlled threshold voltages to enhancement/depletion inverters

    Science.gov (United States)

    Takahashi, Hajime; Hanafusa, Yuki; Kimura, Yoshinari; Kitamura, Masatoshi

    2018-03-01

    Oxygen plasma treatment has been carried out to control the threshold voltage in organic thin-film transistors (TFTs) having a SiO2 gate dielectric prepared by rf sputtering. The threshold voltage linearly changed in the range of ‑3.7 to 3.1 V with the increase in plasma treatment time. Although the amount of change is smaller than that for organic TFTs having thermally grown SiO2, the tendency of the change was similar to that for thermally grown SiO2. To realize different plasma treatment times on the same substrate, a certain region on the SiO2 surface was selected using a shadow mask, and was treated with oxygen plasma. Using the process, organic TFTs with negative threshold voltages and those with positive threshold voltages were fabricated on the same substrate. As a result, enhancement/depletion inverters consisting of the organic TFTs operated at supply voltages of 5 to 15 V.

  17. Preparation and characterization of ZnO particles embedded in SiO2 matrix by reactive magnetron sputtering

    International Nuclear Information System (INIS)

    Ma, J.G.; Liu, Y.C.; Xu, C.S.; Liu, Y.X.; Shao, C.L.; Xu, H.Y.; Zhang, J.Y.; Lu, Y.M.; Shen, D.Z.; Fan, X.W.

    2005-01-01

    ZnO particles embedded in SiO 2 thin films were prepared by a radio-frequency magnetron sputtering technique. X-ray diffraction (XRD) and optical-absorption spectra showed that ZnO particles with hexagonal wurtzite structure had been embedded in the SiO 2 matrix, and the size of ZnO particles increased with increasing annealing temperature from 773 to 973 K. Raman-scattering and Fourier transform infrared (FTIR) spectrum measurements also confirmed the presence of ZnO particles. When the annealing temperature was lower than 973 K, room-temperature photoluminescence (PL) spectra showed dominative deep-level emissions in the visible region and very weak ultraviolet emissions. As the annealing temperature increased to 973 K, an emission band in the ultraviolet region besides the emissions from free and bound excitons recombination was observed in the low-temperature PL spectra. The origin of the ultraviolet emission bands was discussed with the help of temperature-dependent PL spectra. When the annealing temperature was higher than 973 K, Zn 2 SiO 4 particles were formed, as shown by XRD and FTIR results

  18. Single electron transistors with hydrogen treatment of ALD SiO2 in nanoscale metal-insulator-metal tunnel junctions

    Science.gov (United States)

    Karbasian, Golnaz; McConnell, Michael S.; Orlov, Alexei O.; Nazarov, Alexei N.; Snider, Gregory L.

    2017-05-01

    Over the past five years, fabrication of metal-insulator-metal (MIM) single electron transistors (SET) featuring atomic layer deposition (ALD) of ultrathin tunnel barrier dielectrics (SiO2, Al2O3) has been reported. However, the performance of fabricated devices was significantly compromised by the presence of native metal oxide and problems associated with the nucleation of ALD dielectrics on metal substrates. To overcome the difficulty of dielectric ALD nucleation on metal substrates, we recently developed a fabrication technique in which the native metal oxide naturally forming in the presence of the ALD oxidant precursor is first used to promote the nucleation of ALD dielectrics, and then is chemically reduced by forming gas anneal (FGA) at temperatures near 400 °C. However, despite the elimination of native oxide, low temperature characterization of the devices fabricated using FGA reveals excess ‘switching’ noise of a very large magnitude resulting from charged defects within the junctions. It has been previously reported that remote hydrogen plasma (RHP) treatment of SiO2 thin films effectively eradicates fabrication defects. This work reports a comparative study of Ni-based MIM SET treated with FGA and/or RHP. We show that, using a combination of FGA and RHP treatments, it is possible to obtain MIM junctions free of switching noise and without a detectable contribution of native oxide.

  19. Interface properties of SiO2/n-GaN metal-insulator-semiconductor structures

    OpenAIRE

    Yoshitaka, Nakano; Takashi, Jimbo

    2002-01-01

    Electrical characterization of SiO2/n-GaN metal-insulator-semiconductor structures fabricated on sapphire substrates was performed by using high-frequency pulsed capacitance-voltage and capacitance-transient techniques. Fast and slow capacitance transients are clearly seen after applying reverse voltages, reflecting thermal emissions of carriers from the SiO2/GaN interface. The temperature dependence of the capacitance-voltage characteristics shows capacitance saturation in deep depletion (>1...

  20. Tetrazoles in the Presence of Nano-TiCl 4 .SiO 2

    African Journals Online (AJOL)

    Nano-TiCl4.SiO2 was found to be an extremely efficient catalyst for the preparation of 5-substituted 1H-tetrazole derivatives. Nano-TiCl4.SiO2 is a solid Lewis-acid was synthesized by the reaction of nano-SiO2 and TiCl4. The structure characterization of this acid was achieved with X-ray diffraction, thermogravimetric ...

  1. Core-exsolved SiO2 Dispersal in the Earth's Mantle

    Science.gov (United States)

    Helffrich, G. R.; Ballmer, M.; Hirose, K.

    2017-12-01

    SiO2 may have been expelled from the core following its formation in the early stages of Earth's accretion and onwards through the present day. On account of SiO2's low density with respect to both the core and the lowermost mantle, we examine the process of SiO2 accumulation at the core-mantle boundary (CMB) and its incorporation into the mantle by buoyant rise. Today, the if SiO2 is 100-10000 times more viscous than lower mantle material, the dimensions of SiO2 diapirs formed by the viscous Rayleigh-Taylor instability at the CMB would cause them to be swept into the mantle as inclusions of 100 m - 10 km diameter. Under early Earth conditions of rapid heat loss after core formation, SiO2 diapirs of 5-80 km diameter could have risen independently of mantle flow to their level of neutral buoyancy in the mantle, trapping them there due to a combination of high viscosity and neutral buoyancy. We examine the SiO2 yield by assuming Si+O saturation at the conditions found at the base of a magma ocean and find that for a range of conditions, dispersed bodies could reach as high as 2 volume percent in shallow parts of the lower mantle, with their abundance decreasing with depth. At such low concentrations, their effect on aggregate seismic wavespeeds would be within the uncertainty of the radial Earth model PREM. However, their presence would be revealed by small-scale scattering in the lower mantle due to the bodies' large velocity contrast. We conclude that the shallow lower mantle (700-1500 km depth) could harbor SiO2 released in early Earth times.

  2. Nano-Ticl 4 .SiO 2 : a Versatile and Efficient Catalyst for Synthesis of ...

    African Journals Online (AJOL)

    Nano-TiCl4.SiO2 has been found to be an extremely efficient catalyst for the preparation of 3,4-dihydropyrimidinones/thiones via three-component reactions of an aldehyde, β-ketoester or β-diketone and urea or thiourea under mild conditions. Nano-TiCl4.SiO2 as a solid Lewis acid has been synthesized by reaction of ...

  3. Growth Stress in SiO2 during Oxidation of SiC Fibers (Preprint)

    Science.gov (United States)

    2011-11-01

    calculating the average self-pressure ( pav ) in the SiO2 scale throughout its thickness, as a function of total scale thickness (w), temperature, and fiber...2 ∑ p(bj2 − bj−12 )ij=1 [54] The average pressure ( pav ) was calculated for 6 and 3 µm...for public release; distribution unlimited. Fig. 13. Average SiO2 scale self-pressure ( pav ) for 6 and 3 µm radius fibers as a function of scale

  4. Superconducting NbN films grown using pulsed laser deposition for potential application in internally shunted Josephson junctions

    Energy Technology Data Exchange (ETDEWEB)

    Bhat, Anupama; Meng, Xiaofan; Wong, Andre; Van Duzer, Theodore [Department of Electrical Engineering and Computer Sciences and the Electronics Research Laboratory, University of California, Berkeley, CA 720 1770 (United States)

    1999-11-01

    We have grown superconducting NbN films using a pulsed KrF laser for potential use as superconducting electrodes in SNS Josephson junctions being developed for nonlatching logic applications. The NbN films show a superconducting transition of 16 K using an Nb target in background N{sub 2} gas. The T{sub c} dependence on N{sub 2} pressure in the range of 50-80 mTorr was investigated at a growth temperature of 600 deg. C. The NbN films were grown on MgO(100) and amorphous SiN{sub x}/Si substrates. In the latter case, the films had a lower T{sub c}, and appeared amorphous from x-ray diffraction measurements, while those on the MgO(100) substrates were strongly textured. AFM measurements reveal RMS surface roughness as low as 1 nm, over a 5 {mu}m x 5 {mu}m area, indicating that these films appear suitable for SNS junctions. (author)

  5. Calcium phosphate formation on porous sol-gel-derived SiO2 and CaO-P2O5-SiO2 substrates in vitro.

    Science.gov (United States)

    Peltola, T; Jokinen, M; Rahiala, H; Levänen, E; Rosenholm, J B; Kangasniemi, I; Yli-Urpo, A

    1999-01-01

    Sol-gel-derived SiO2 and CaO-P2O5-SiO2 have been shown to be bioactive and bone bonding. In this study bioactive sol-gel-derived SiO2 and CaO-P2O5-SiO2 systems were tested for in in vitro bioactivity. The calcined ceramic monoliths were immersed in a simulated body fluid and analyzed to follow the hydroxyapatite formation on the ceramic surface. Apatite-forming ability was investigated in terms of structural changes by changing the composition and the preparation method. The role of Ca and P dopants in the substrate structure is complicated, and careful characterization is needed. The composition and structure together determine the in vitro bioactivity. The pore structure was analyzed using N2-adsorption/desorption isotherms. The results indicate that a great mesopore volume and a wide mesopore size distribution favor hydroxycarbonate apatite nucleation and a great surface area is not needed. The performed preparation process for silica in a basic environment provides a convenient way to prepare a mesoporous material. Copyright 1999 John Wiley & Sons, Inc.

  6. Effect of Growth Temperature and Mn Incorporation on GaN:Mn Thin Films Grown by Plasma-Assisted MOCVD

    Directory of Open Access Journals (Sweden)

    Budi Mulyanti

    2008-09-01

    Full Text Available In this paper, the growth of GaN:Mn thin films by plasma-assisted metalorganic chemical vapor deposition (PAMOCVD method is reported. The method used in this study, utilizes a microwave cavity as a cracking cell to produce nitrogen radicals, which in turn reduce the growth temperature. Trimethylgallium (TMGa, nitrogen (N2 and cyclopentadienyl manganese tricarbonyl (CpMnT were used as a source of Ga, N and Mn, respectively, while hydrogen gas was used as a carrier gas for both TMGa and CpMnT. The effect of growth temperature and Mn incorporation on structural properties and surface morphology of GaN:Mn films are presented. The growth of GaN:Mn thin films were conducted at varied growth temperature in range of 625 oC to 700 oC and the Mn/Ga molar fraction in the range of 0.2 to 0.5. Energy dispersive of X-ray (EDX and X-ray diffraction (XRD methods were used to analyze atomic composition and crystal structure of the grown films, respectively. The surface morphology was then characterized using both atomic force microscopy (AFM and scanning electron microscopy (SEM images. A systematic XRD analysis reveal that maximum Mn incorporation that still produces single phase GaN:Mn (0002 is 6.4 % and 3.2 % for the film grown at 650 oC and 700 oC, respectively. The lattice constant and full width at half maximum (FWHM of the single phase films depend on the Mn concentration. The decrease in lattice constant accompanied by the increase in FWHM is due to incorporation of substitutional Mn on the Ga sub-lattice. The maximum values of doped Mn atoms incorporated in the wurtzite structure of GaN:Mn as substitutional atoms on Ga sub-lattice are 2.0 % and 2.5 % at 650 oC and 700 oC, respectively. AFM and SEM images show that the film grown at lower growth temperature and Mn concentration has a better surface than that of film grown at higher growth temperature and Mn concentration.

  7. 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.

  8. Enhanced Formation of Si Nanocrystals in SiO2 by Light-Filtering Rapid Thermal Annealing

    Science.gov (United States)

    Chen, Xiaobo; Chen, Guangping

    2015-04-01

    In this work, silicon-rich oxide (SRO) films with designed thickness of 100 nm were deposited by a bipolar pulse and radio frequency magnetron co-sputtering. For comparison, the samples were then treated in a nitrogen atmosphere by conventional rapid thermal annealing (CRTA) or light-filtering rapid thermal annealing (LRTA) at 900-1100°C for 2 min. Raman spectra, grazing incident X-ray diffraction (XRD), transmission electron microscopy (TEM), Hall measurements, and current density-voltage measurements were carried out to analyze the microstructural and electrical properties of samples. Compared with the control sample using CRTA method, the crystalline volume fraction and number density of Si nanocrystals (SiNCs) in silicon oxide prepared by LRTA were greatly increased. The quantum effects of the short wave-length light (less than 800 nm) of these tungsten halogen lamps during the rapid thermal annealing process have negative effects on the formation of SiNCs in SiO2 films. SiNCs with crystal volume fraction of 73%, average size of 2.53 nm, and number density of 1.1 × 1012 cm-2 embedded in the amorphous SiO2 matrix can be formed by LRTA at 1100°C. Enhancement of more than one order of magnitude in conductivity and higher current density were obtained from the LRTA annealed sample compared to the CRTA annealed sample. The improvements in conductivity and current density were attributed to the high density SiNCs. Our results show that the LRTA method is a suitable annealing tool for the formation of SiNC in thin SiOx films.

  9. The effects of ZnO buffer layers on the properties of phosphorus doped ZnO thin films grown on sapphire by pulsed laser deposition

    International Nuclear Information System (INIS)

    Kim, K-W; Lugo, F J; Lee, J H; Norton, D P

    2012-01-01

    The properties of phosphorus doped ZnO thin films grown on sapphire by pulsed laser deposition were examined, specifically focusing on the effects of undoped ZnO buffer layers. In particular, buffer layers were grown under different conditions; the transport properties of as-deposited and rapid thermal annealed ZnO:P films were then examined. As-deposited films showed n-type conductivity. After rapid thermal annealing, the film on buffer layer grown at a low temperature showed the conversion of carrier type to p-type for specific growth conditions while the films deposited on buffer layer grown at a high temperature remained n-type regardless of growth condition. The films deposited on buffer layer grown at a low temperature showed higher resistivity and more significant change of the transport properties upon rapid thermal annealing. These results suggest that more dopants are incorporated in films with higher defect density. This is consistent with high resolution x-ray diffraction results for phosphorus doped ZnO films on different buffer layers. In addition, the microstructure of phosphorus doped ZnO films is substantially affected by the buffer layer.

  10. Copper-vapor-assisted chemical vapor deposition for high-quality and metal-free single-layer graphene on amorphous SiO2 substrate.

    Science.gov (United States)

    Kim, Hyungki; Song, Intek; Park, Chibeom; Son, Minhyeok; Hong, Misun; Kim, Youngwook; Kim, Jun Sung; Shin, Hyun-Joon; Baik, Jaeyoon; Choi, Hee Cheul

    2013-08-27

    We report that high-quality single-layer graphene (SLG) has been successfully synthesized directly on various dielectric substrates including amorphous SiO2/Si by a Cu-vapor-assisted chemical vapor deposition (CVD) process. The Cu vapors produced by the sublimation of Cu foil that is suspended above target substrates without physical contact catalyze the pyrolysis of methane gas and assist nucleation of graphene on the substrates. Raman spectra and mapping images reveal that the graphene formed on a SiO2/Si substrate is almost defect-free and homogeneous single layer. The overall quality of graphene grown by Cu-vapor-assisted CVD is comparable to that of the graphene grown by regular metal-catalyzed CVD on a Cu foil. While Cu vapor induces the nucleation and growth of SLG on an amorphous substrate, the resulting SLG is confirmed to be Cu-free by synchrotron X-ray photoelectron spectroscopy. The SLG grown by Cu-vapor-assisted CVD is fabricated into field effect transistor devices without transfer steps that are generally required when SLG is grown by regular CVD process on metal catalyst substrates. This method has overcome two important hurdles previously present when the catalyst-free CVD process is used for the growth of SLG on fused quartz and hexagonal boron nitride substrates, that is, high degree of structural defects and limited size of resulting graphene, respectively.

  11. Fabrication of ZIF-8@SiO2 Micro/Nano Hierarchical Superhydrophobic Surface on AZ31 Magnesium Alloy with Impressive Corrosion Resistance and Abrasion Resistance.

    Science.gov (United States)

    Wu, Cuiqing; Liu, Qi; Chen, Rongrong; Liu, Jingyuan; Zhang, Hongsen; Li, Rumin; Takahashi, Kazunobu; Liu, Peili; Wang, Jun

    2017-03-29

    Superhydrophobic coatings are highly promising for protecting material surfaces and for wide applications. In this study, superhydrophobic composites, comprising a rhombic-dodecahedral zeolitic imidazolate framework (ZIF-8@SiO 2 ), have been manufactured onto AZ31 magnesium alloy via chemical etching and dip-coating methods to enhance stability and corrosion resistance. Herein, we report on a simple strategy to modify hydrophobic hexadecyltrimethoxysilan (HDTMS) on ZIF-8@SiO 2 to significantly improve the property of repelling water. We show that various liquids can be stable on its surface and maintain a contact angle higher than 150°. The morphologies and chemical composition were characterized by means of scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FI-IR). In addition, the anticorrosion and antiattrition properties of the film were assessed by electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization and HT, respectively. Such a coating shows promising potential as a material for large-scale fabrication.

  12. A facile approach to fabricate Au nanoparticles loaded SiO2 microspheres for catalytic reduction of 4-nitrophenol

    International Nuclear Information System (INIS)

    Tang, Mingyi; Huang, Guanbo; Li, Xianxian; Pang, Xiaobo; Qiu, Haixia

    2015-01-01

    Hydrophilic and biocompatible macromolecules were used to improve and simplify the process for the fabrication of core/shell SiO 2 @Au composite particles. The influence of polymers on the morphology of SiO 2 @Au particles with different size of SiO 2 cores was analyzed by transmission electron microscopy and scanning electron microscopy. The optical property of the SiO 2 @Au particles was studied with UV–Vis spectroscopy. The results indicate that the structure and composition of macromolecules affect the morphology of Au layers on SiO 2 microspheres. The SiO 2 @Au particles prepared in the presence of polyvinyl alcohol (PVA) or polyvinylpyrrolidone (PVP) have thin and complete Au nanoshells owing to their inducing act in preferential growth of Au nanoparticles along the surface of SiO 2 microspheres. SiO 2 @Au particles can be also prepared from SiO 2 microspheres modified with 3-aminopropyltrimethoxysilane in the presence of PVA or PVP. This offers a simple way to fabricate a Au layer on SiO 2 or other microspheres. The SiO 2 @Au particles demonstrated high catalytic activity in the reduction of 4-nitrophenol. - Highlights: • Facile direct deposition method for Au nanoparticles on silica microspheres. • Influence of different types of macromolecule on the formation of Au shell. • High catalytic performance of Au nanoparticles on silica microspheres

  13. Dielectric properties of thin C r2O3 films grown on elemental and oxide metallic substrates

    Science.gov (United States)

    Mahmood, Ather; Street, Michael; Echtenkamp, Will; Kwan, Chun Pui; Bird, Jonathan P.; Binek, Christian

    2018-04-01

    In an attempt to optimize leakage characteristics of α-C r2O3 thin films, its dielectric properties were investigated at local and macroscopic scale. The films were grown on Pd(111), Pt(111), and V2O3 (0001), supported on A l2O3 substrate. The local conductivity was measured by conductive atomic force microscopy mapping of C r2O3 surfaces, which revealed the nature of defects that formed conducting paths with the bottom Pd or Pt layer. A strong correlation was found between these electrical defects and the grain boundaries revealed in the corresponding topographic scans. In comparison, the C r2O3 film on V2O3 exhibited no leakage paths at similar tip bias value. Electrical resistance measurements through e-beam patterned top electrodes confirmed the resistivity mismatch between the films grown on different electrodes. The x-ray analysis attributes this difference to the twin free C r2O3 growth on V2O3 seeding.

  14. The Luminescent Properties and Atomic Structures of As-Grown and Annealed Nanostructured Silicon Rich Oxide Thin Films

    Directory of Open Access Journals (Sweden)

    N. D. Espinosa-Torres

    2016-01-01

    Full Text Available Not long ago, we developed a theoretical model to describe a set of chemical reactions that can potentially occur during the process of obtaining Silicon Rich Oxide (SRO films, an off stoichiometry material, notwithstanding the technique used to grow such films. In order to elucidate the physical chemistry properties of such material, we suggested the chemical reactions that occur during the process of growing of SRO films in particular for the case of the Low Pressure Chemical Vapor Deposition (LPCVD technique in the aforementioned model. The present paper represents a step further with respect to the previous (published work, since it is dedicated to the calculation by Density Functional Theory (DFT of the optical and electronic properties of the as-grown and annealed SRO structures theoretically predicted on the basis of the previous work. In this work, we suggest and evaluate either some types of molecules or resulting nanostructures and we predict theoretically, by applying the DFT, the contribution that they may have to the phenomenon of luminescence (PL, which is experimentally measured in SRO films. We evaluated the optical and electronic properties of both the as-grown and the annealed structures.

  15. Tunable graphene doping by modulating the nanopore geometry on a SiO2/Si substrate

    KAUST Repository

    Lim, Namsoo

    2018-02-28

    A tunable graphene doping method utilizing a SiO2/Si substrate with nanopores (NP) was introduced. Laser interference lithography (LIL) using a He–Cd laser (λ = 325 nm) was used to prepare pore size- and pitch-controllable NP SiO2/Si substrates. Then, bottom-contact graphene field effect transistors (G-FETs) were fabricated on the NP SiO2/Si substrate to measure the transfer curves. The graphene transferred onto the NP SiO2/Si substrate showed relatively n-doped behavior compared to the graphene transferred onto a flat SiO2/Si substrate, as evidenced by the blue-shift of the 2D peak position (∼2700 cm−1) in the Raman spectra due to contact doping. As the porosity increased within the substrate, the Dirac voltage shifted to a more positive or negative value, depending on the initial doping type (p- or n-type, respectively) of the contact doping. The Dirac voltage shifts with porosity were ascribed mainly to the compensation for the reduced capacitance owing to the SiO2–air hetero-structured dielectric layer within the periodically aligned nanopores capped by the suspended graphene (electrostatic doping). The hysteresis (Dirac voltage difference during the forward and backward scans) was reduced when utilizing an NP SiO2/Si substrate with smaller pores and/or a low porosity because fewer H2O or O2 molecules could be trapped inside the smaller pores.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2016-11-01

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

  17. Positive magnetoresistance in ferromagnetic Nd-doped In2O3 thin films grown by pulse laser deposition

    KAUST Repository

    Xing, G. Z.

    2014-05-23

    We report the magnetic and magnetotransport properties of (In 0.985Nd0.015)2O2.89 thin films grown by pulse laser deposition. The clear magnetization hysteresis loops with the complementary magnetic domain structure reveal the intrinsic room temperature ferromagnetism in the as-prepared films. The strong sp-f exchange interaction as a result of the rare earth doping is discussed as the origin of the magnetotransport behaviours. A positive magnetoresistance (∼29.2%) was observed at 5 K and ascribed to the strong ferromagnetic sp-f exchange interaction in (In0.985Nd0.015)2O 2.89 thin films due to a large Zeeman splitting in an external magnetic field of 50 KOe. © 2014 AIP Publishing LLC.

  18. Memory and learning behaviors mimicked in nanogranular SiO2-based proton conductor gated oxide-based synaptic transistors.

    Science.gov (United States)

    Wan, Chang Jin; Zhu, Li Qiang; Zhou, Ju Mei; Shi, Yi; Wan, Qing

    2013-11-07

    In neuroscience, signal processing, memory and learning function are established in the brain by modifying ionic fluxes in neurons and synapses. Emulation of memory and learning behaviors of biological systems by nanoscale ionic/electronic devices is highly desirable for building neuromorphic systems or even artificial neural networks. Here, novel artificial synapses based on junctionless oxide-based protonic/electronic hybrid transistors gated by nanogranular phosphorus-doped SiO2-based proton-conducting films are fabricated on glass substrates by a room-temperature process. Short-term memory (STM) and long-term memory (LTM) are mimicked by tuning the pulse gate voltage amplitude. The LTM process in such an artificial synapse is due to the proton-related interfacial electrochemical reaction. Our results are highly desirable for building future neuromorphic systems or even artificial networks via electronic elements.

  19. Structural color in porous, superhydrophilic, and self-cleaning SiO2/TiO2 Bragg stacks.

    Science.gov (United States)

    Wu, Zhizhong; Lee, Daeyeon; Rubner, Michael F; Cohen, Robert E

    2007-08-01

    Thin-film Bragg stacks exhibiting structural color have been fabricated by a layer-by-layer (LbL) deposition process involving the sequential adsorption of nanoparticles and polymers. High- and low-refractive-index regions of quarter-wave stacks were generated by calcining LbL-assembled multilayers containing TiO(2) and SiO(2) nanoparticles, respectively. The physical attributes of each region were characterized by a recently developed ellipsometric method. The structural color characteristics of the resultant nanoporous Bragg stacks could be precisely tuned in the visible region by varying the number of stacks and the thickness of the high- and low-refractive-index stacks. These Bragg stacks also exhibited potentially useful superhydrophilicity and self-cleaning properties.

  20. Thin yttrium iron garnet films grown by pulsed laser deposition: Crystal structure, static, and dynamic magnetic properties

    Energy Technology Data Exchange (ETDEWEB)

    Sokolov, N. S., E-mail: nsokolov@fl.ioffe.ru; Fedorov, V. V.; Korovin, A. M.; Suturin, S. M.; Baranov, D. A.; Gastev, S. V.; Krichevtsov, B. B.; Bursian, V. E.; Lutsev, L. V. [Ioffe Physical-Technical Institute of Russian Academy of Sciences, St. Petersburg 194021 (Russian Federation); Maksimova, K. Yu.; Grunin, A. I. [Immanuel Kant Baltic Federal University, Kaliningrad 236041 (Russian Federation); Tabuchi, M. [Synchrotron Radiation Research Center, Nagoya University, Nagoya 464-8603 (Japan)

    2016-01-14

    Pulsed laser deposition has been used to grow thin (10–84 nm) epitaxial layers of Yttrium Iron Garnet Y{sub 3}Fe{sub 5}O{sub 12} (YIG) on (111)–oriented Gadolinium Gallium Garnet substrates at different growth conditions. Atomic force microscopy showed flat surface morphology both on micrometer and nanometer scales. X-ray diffraction measurements revealed that the films are coherent with the substrate in the interface plane. The interplane distance in the [111] direction was found to be by 1.2% larger than expected for YIG stoichiometric pseudomorphic film indicating presence of rhombohedral distortion in this direction. Polar Kerr effect and ferromagnetic resonance measurements showed existence of additional magnetic anisotropy, which adds to the demagnetizing field to keep magnetization vector in the film plane. The origin of the magnetic anisotropy is related to the strain in YIG films observed by XRD. Magneto-optical Kerr effect measurements revealed important role of magnetization rotation during magnetization reversal. An unusual fine structure of microwave magnetic resonance spectra has been observed in the film grown at reduced (0.5 mTorr) oxygen pressure. Surface spin wave propagation has been demonstrated in the in-plane magnetized films.

  1. Engineering the mechanical properties of ultrabarrier films grown by atomic layer deposition for the encapsulation of printed electronics

    Energy Technology Data Exchange (ETDEWEB)

    Bulusu, A.; Singh, A.; Kim, H. [Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332 (United States); Wang, C. Y.; Dindar, A.; Fuentes-Hernandez, C.; Kippelen, B. [School of Electrical and Computer Engineering, Georgia Institute of Technology, and Center for Organic Photonics and Electronics, Atlanta, Georgia 30332 (United States); Cullen, D. [Oak Ridge National Laboratory, P.O. Box 2008 MS-6064, Oak Ridge, Tennessee 37831 (United States); Graham, S., E-mail: sgraham@gatech.edu [Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332 (United States); Oak Ridge National Laboratory, P.O. Box 2008 MS-6064, Oak Ridge, Tennessee 37831 (United States)

    2015-08-28

    Direct deposition of barrier films by atomic layer deposition (ALD) onto printed electronics presents a promising method for packaging devices. Films made by ALD have been shown to possess desired ultrabarrier properties, but face challenges when directly grown onto surfaces with varying composition and topography. Challenges include differing nucleation and growth rates across the surface, stress concentrations from topography and coefficient of thermal expansion mismatch, elastic constant mismatch, and particle contamination that may impact the performance of the ALD barrier. In such cases, a polymer smoothing layer may be needed to coat the surface prior to ALD barrier film deposition. We present the impact of architecture on the performance of aluminum oxide (Al{sub 2}O{sub 3})/hafnium oxide (HfO{sub 2}) ALD nanolaminate barrier films deposited on fluorinated polymer layer using an optical calcium (Ca) test under damp heat. It is found that with increasing polymer thickness, the barrier films with residual tensile stress are prone to cracking resulting in rapid failure of the Ca sensor at 50 °C/85% relative humidity. Inserting a SiN{sub x} layer with residual compressive stress between the polymer and ALD layers is found to prevent cracking over a range of polymer thicknesses with more than 95% of the Ca sensor remaining after 500 h of testing. These results suggest that controlling mechanical properties and film architecture play an important role in the performance of direct deposited ALD barriers.

  2. Thin yttrium iron garnet films grown by pulsed laser deposition: Crystal structure, static, and dynamic magnetic properties

    International Nuclear Information System (INIS)

    Sokolov, N. S.; Fedorov, V. V.; Korovin, A. M.; Suturin, S. M.; Baranov, D. A.; Gastev, S. V.; Krichevtsov, B. B.; Bursian, V. E.; Lutsev, L. V.; Maksimova, K. Yu.; Grunin, A. I.; Tabuchi, M.

    2016-01-01

    Pulsed laser deposition has been used to grow thin (10–84 nm) epitaxial layers of Yttrium Iron Garnet Y 3 Fe 5 O 12 (YIG) on (111)–oriented Gadolinium Gallium Garnet substrates at different growth conditions. Atomic force microscopy showed flat surface morphology both on micrometer and nanometer scales. X-ray diffraction measurements revealed that the films are coherent with the substrate in the interface plane. The interplane distance in the [111] direction was found to be by 1.2% larger than expected for YIG stoichiometric pseudomorphic film indicating presence of rhombohedral distortion in this direction. Polar Kerr effect and ferromagnetic resonance measurements showed existence of additional magnetic anisotropy, which adds to the demagnetizing field to keep magnetization vector in the film plane. The origin of the magnetic anisotropy is related to the strain in YIG films observed by XRD. Magneto-optical Kerr effect measurements revealed important role of magnetization rotation during magnetization reversal. An unusual fine structure of microwave magnetic resonance spectra has been observed in the film grown at reduced (0.5 mTorr) oxygen pressure. Surface spin wave propagation has been demonstrated in the in-plane magnetized films

  3. Photo- and Electrochromic Properties of Activated Reactive Evaporated MoO3 Thin Films Grown on Flexible Substrates

    Directory of Open Access Journals (Sweden)

    K. Hari Krishna

    2008-01-01

    Full Text Available The molybdenum trioxide (MoO3 thin films were grown onto ITO-coated flexible Kapton substrates using plasma assisted activated reactive evaporation technique. The film depositions were carried out at constant glow power and oxygen partial pressures of 8 W and 1×10−3 Torr, respectively. The influence of substrate temperature on the microstructural and optical properties was investigated. The MoO3 thin films prepared at a substrate temperature of 523 K were found to be composed of uniformly distributed nanosized grains with an orthorhombic structure of α-MoO3. These nanocrystalline MoO3 thin films exhibited higher optical transmittance of about 80% in the visible region with an evaluated optical band gap of 3.29 eV. With the insertion of 12.5 mC/cm2, the films exhibited an optical modulation of 40% in the visible region with coloration efficiency of 22 cm2/C at the wavelength of 550 nm. The MoO3 films deposited at 523 K demonstrated better photochromic properties and showed highest color center concentration for the irradiation time of 30 minutes at 100 mW/cm2.

  4. Comparative Study of Furnace and Flash Lamp Annealed Silicon Thin Films Grown by Plasma Enhanced Chemical Vapor Deposition

    Directory of Open Access Journals (Sweden)

    Maheshwar Shrestha

    2018-03-01

    Full Text Available Low-temperature growth of microcrystalline silicon (mc-Si is attractive for many optoelectronic device applications. This paper reports a detailed comparison of optical properties, microstructure, and morphology of amorphous silicon (a-Si thin films crystallized by furnace annealing and flash lamp annealing (FLA at temperatures below the softening point of glass substrate. The initial a-Si films were grown by plasma enhanced chemical vapor deposition (PECVD. Reflectance measurement indicated characteristic peak in the UV region ~280 nm for the furnace annealed (>550 °C and flash lamp annealed films, which provided evidence of crystallization. The film surface roughness increased with increasing the annealing temperature as well as after the flash lamp annealing. X-ray diffraction (XRD measurement indicated that the as-deposited samples were purely amorphous and after furnace crystallization, the crystallites tended to align in one single direction (202 with uniform size that increased with the annealing temperature. On the other hand, the flash lamp crystalized films had randomly oriented crystallites with different sizes. Raman spectroscopy showed the crystalline volume fraction of 23.5%, 47.3%, and 61.3% for the samples annealed at 550 °C, 650 °C, and with flash lamp, respectively. The flash lamp annealed film was better crystallized with rougher surface compared to furnace annealed ones.

  5. SnO{sub 2} thin films grown by atomic layer deposition using a novel Sn precursor

    Energy Technology Data Exchange (ETDEWEB)

    Choi, Min-Jung [Electronic Materials Research Center, Korea Institute of Science and Technology, Seoul, 136-791 (Korea, Republic of); Department of Materials Science and Engineering, Yonsei University, Seoul, 120-749 (Korea, Republic of); Cho, Cheol Jin [Electronic Materials Research Center, Korea Institute of Science and Technology, Seoul, 136-791 (Korea, Republic of); Department of Materials Science and Engineering, Seoul National University, Seoul, 151-744 (Korea, Republic of); Kim, Kwang-Chon; Pyeon, Jung Joon [Electronic Materials Research Center, Korea Institute of Science and Technology, Seoul, 136-791 (Korea, Republic of); Park, Hyung-Ho [Department of Materials Science and Engineering, Yonsei University, Seoul, 120-749 (Korea, Republic of); Kim, Hyo-Suk; Han, Jeong Hwan; Kim, Chang Gyoun; Chung, Taek-Mo [Division of Advanced Materials, Korea Research Institute of Chemical Technology (KRICT), Daejeon, 305-600 (Korea, Republic of); Park, Tae Joo [Department of Materials Science and Engineering, Hanyang University, Ansan, 426-791 (Korea, Republic of); Kwon, Beomjin [Electronic Materials Research Center, Korea Institute of Science and Technology, Seoul, 136-791 (Korea, Republic of); Jeong, Doo Seok; Baek, Seung-Hyub [Electronic Materials Research Center, Korea Institute of Science and Technology, Seoul, 136-791 (Korea, Republic of); Department of Nanomaterials, Korea University of Science and Technology, Daejeon, 305-333 (Korea, Republic of); Kang, Chong-Yun; Kim, Jin-Sang [Electronic Materials Research Center, Korea Institute of Science and Technology, Seoul, 136-791 (Korea, Republic of); Kim, Seong Keun, E-mail: s.k.kim@kist.re.kr [Electronic Materials Research Center, Korea Institute of Science and Technology, Seoul, 136-791 (Korea, Republic of); Department of Nanomaterials, Korea University of Science and Technology, Daejeon, 305-333 (Korea, Republic of)

    2014-11-30

    Highlights: • We developed a new ALD process for SnO{sub 2} films using dimethylamino-2-methyl-2-propoxy-tin(II) as a novel Sn precursor. • The SnO{sub 2} films grown from Sn(dmamp){sub 2} has negligible impurity contents. • Sn ions in the films had a single binding state corresponding to Sn{sup 4+} in SnO{sub 2}. - Abstract: SnO{sub 2} thin films were grown by atomic layer deposition (ALD) with dimethylamino-2-methyl-2-propoxy-tin(II) (Sn(dmamp){sub 2}) and O{sub 3} in a temperature range of 100–230 °C. The ALD window was found to be in the range of 100–200 °C. The growth per cycle of the films in the ALD window increased with temperature in the range from 0.018 to 0.042 nm/cycle. Above 230 °C, the self-limiting behavior which is a unique characteristic of ALD, was not observed in the growth because of the thermal decomposition of the Sn(dmamp){sub 2} precursor. The SnO{sub 2} films were amorphous in the ALD window and exhibited quite a smooth surface. Sn ions in all films had a single binding state corresponding to Sn{sup 4+} in SnO{sub 2}. The concentration of carbon and nitrogen in the all SnO{sub 2} films was below the detection limit of the auger electron spectroscopy technique and a very small amount of carbon, nitrogen, and hydrogen was detected by secondary ions mass spectroscopy only. The impurity contents decreased with increasing the growth temperature. This is consistent with the increase in the density of the SnO{sub 2} films with respect to the growth temperature. The ALD process with Sn(dmamp){sub 2} and O{sub 3} shows excellent conformality on a hole structure with an aspect ratio of ∼9. This demonstrates that the ALD process with Sn(dmamp){sub 2} and O{sub 3} is promising for growth of robust and highly pure SnO{sub 2} films.

  6. Ultrathin NbN Films for Superconducting Single-Photon Detectors

    International Nuclear Information System (INIS)

    Slysz, W.; Guziewicz, M.; Borysiewicz, M.

    2011-01-01

    We present our research on fabrication and structural and transport characterization of ultrathin superconducting NbN layers deposited on both single-crystal Al 2 O 3 and Si wafers, and SiO 2 and Si 3 N 4 buffer layers grown directly on Si wafers. The thicknesses of our films varied from 6 nm to 50 nm and they were grown using reactive RF magnetron sputtering on substrates maintained at the temperature 850 o C. We have performed extensive morphology characterization of our films using the X-ray diffraction method and atomic force microscopy, and related the results to the type of the substrate used for the film deposition. Our transport measurements showed that even the thinnest, 6 nm thick NbN films had the superconducting critical temperature of 10-12 K, which was increased to 14 K for thicker films. (author)

  7. Bonding structure and morphology of chromium oxide films grown by pulsed-DC reactive magnetron sputter deposition

    Energy Technology Data Exchange (ETDEWEB)

    Gago, R., E-mail: rgago@icmm.csic.es [Instituto de Ciencia de Materiales de Madrid, Consejo Superior de Investigaciones Científicas, E-28049 Madrid (Spain); Vinnichenko, M. [Fraunhofer-Institut für Keramische Technologien und Systeme IKTS, D-01277 Dresden (Germany); Hübner, R. [Helmholtz-Zentrum Dresden – Rossendorf, Institute of Ion Beam Physics and Materials Research, Bautzner Landstraße 400, 01328 Dresden (Germany); Redondo-Cubero, A. [Departamento de Física Aplicada and Centro de Microanálisis de Materiales, Universidad Autónoma de Madrid, E-28049 Madrid (Spain)

    2016-07-05

    Chromium oxide (CrO{sub x}) thin films were grown by pulsed-DC reactive magnetron sputter deposition in an Ar/O{sub 2} discharge as a function of the O{sub 2} fraction in the gas mixture (ƒ) and for substrate temperatures, T{sub s}, up to 450 °C. The samples were analysed by Rutherford backscattering spectrometry (RBS), spectroscopic ellipsometry (SE), atomic force microscopy (AFM), scanning (SEM) and transmission (TEM) electron microscopy, X-ray diffraction (XRD), and X-ray absorption near-edge structure (XANES). On unheated substrates, by increasing ƒ the growth rate is higher and the O/Cr ratio (x) rises from ∼2 up to ∼2.5. Inversely, by increasing T{sub s} the atomic incorporation rate drops and x falls to ∼1.8. XRD shows that samples grown on unheated substrates are amorphous and that nanocrystalline Cr{sub 2}O{sub 3} (x = 1.5) is formed by increasing T{sub s}. In amorphous CrO{sub x}, XANES reveals the presence of multiple Cr environments that indicate the growth of mixed-valence oxides, with progressive promotion of hexavalent states with ƒ. XANES data also confirms the formation of single-phase nanocrystalline Cr{sub 2}O{sub 3} at elevated T{sub s}. These structural changes also reflect on the optical and morphological properties of the films. - Highlights: • XANES of CrO{sub x} thin films grown by pulsed-DC reactive magnetron sputtering. • Identification of mixed-valence amorphous CrO{sub x} oxides on unheated substrates. • Promotion of amorphous chromic acid (Cr{sup VI}) by increasing O{sub 2} partial pressure. • Production of single-phase Cr{sub 2}O{sub 3} films by increasing substrate temperature. • Correlation of bonding structure with morphological and optical properties.

  8. Thermodynamics of Bi2O3-SiO2 system

    Directory of Open Access Journals (Sweden)

    Onderka B.

    2017-01-01

    Full Text Available Thermodynamic properties of the liquid Bi2O3-SiO2 solutions were determined from the results of the electrochemical measurements by use of the solid oxide galvanic cells with YSZ (Yttria-Stabilized-Zirconia electrolyte. Activities of Bi2O3 in the solutions were determined for 0.2, 0.3, 0.4, and 0.5 SiO2 mole fractions in the temperature range 1073-1293 K from measured electromotive force (e.m.f of the solid electrolyte galvanic cell: Bi, Bi2O3-SiO2 | YSZ | air (pO2 = 0.213 bar Additionally, heat capacity data obtained for two solid phases 6Bi2O3•SiO2 and 2Bi2O3•3SiO2 were included into optimization of thermodynamic properties of the system. Optimization procedure was supported by differential thermal analysis (DTA data obtained in this work as well as those accepted from the literature. Using the data obtained in this work, and the information about phase equilibria found in the literature, binary system Bi2O3-SiO2 was assessed with the ThermoCalc software.

  9. Integrated nanophotonic hubs based on ZnO-Tb(OH3/SiO2 nanocomposites

    Directory of Open Access Journals (Sweden)

    Lin Yu

    2011-01-01

    Full Text Available Abstract Optical integration is essential for practical application, but it remains unexplored for nanoscale devices. A newly designed nanocomposite based on ZnO semiconductor nanowires and Tb(OH3/SiO2 core/shell nanospheres has been synthesized and studied. The unique sea urchin-type morphology, bright and sharply visible emission bands of lanthanide, and large aspect ratio of ZnO crystalline nanotips make this novel composite an excellent signal receiver, waveguide, and emitter. The multifunctional composite of ZnO nanotips and Tb(OH3/SiO2 nanoparticles therefore can serve as an integrated nanophotonics hub. Moreover, the composite of ZnO nanotips deposited on a Tb(OH3/SiO2 photonic crystal can act as a directional light fountain, in which the confined radiation from Tb ions inside the photonic crystal can be well guided and escape through the ZnO nanotips. Therefore, the output emission arising from Tb ions is truly directional, and its intensity can be greatly enhanced. With highly enhanced lasing emissions in ZnO-Tb(OH3/SiO2 as well as SnO2-Tb(OH3/SiO2 nanocomposites, we demonstrate that our approach is extremely beneficial for the creation of low threshold and high-power nanolaser.

  10. Integrated nanophotonic hubs based on ZnO-Tb(OH)3/SiO2 nanocomposites

    Science.gov (United States)

    Lin, Hsia Yu; Cheng, Chung Liang; Lin, Yu Shen; Hung, Yann; Mou, Chung Yuan; Chen, Yang Fang

    2011-08-01

    Optical integration is essential for practical application, but it remains unexplored for nanoscale devices. A newly designed nanocomposite based on ZnO semiconductor nanowires and Tb(OH)3/SiO2 core/shell nanospheres has been synthesized and studied. The unique sea urchin-type morphology, bright and sharply visible emission bands of lanthanide, and large aspect ratio of ZnO crystalline nanotips make this novel composite an excellent signal receiver, waveguide, and emitter. The multifunctional composite of ZnO nanotips and Tb(OH)3/SiO2 nanoparticles therefore can serve as an integrated nanophotonics hub. Moreover, the composite of ZnO nanotips deposited on a Tb(OH)3/SiO2 photonic crystal can act as a directional light fountain, in which the confined radiation from Tb ions inside the photonic crystal can be well guided and escape through the ZnO nanotips. Therefore, the output emission arising from Tb ions is truly directional, and its intensity can be greatly enhanced. With highly enhanced lasing emissions in ZnO-Tb(OH)3/SiO2 as well as SnO2-Tb(OH)3/SiO2 nanocomposites, we demonstrate that our approach is extremely beneficial for the creation of low threshold and high-power nanolaser.

  11. Photoluminescence of nanocrystalline ZnS thin film grown by sol-gel method.

    Science.gov (United States)

    Anila, E I; Safeera, T A; Reshmi, R

    2015-03-01

    Nano and polycrystalline ZnS thin films play a crucial role in photovoltaic technology and optoelectronic devices. In this work, we report the photoluminescence (PL) characterization of nanocrystalline ZnS thin films synthesized by dip coating method. The PL spectra exhibit broad nature with multiple emission peaks which are due to the different defect levels in the prepared film.

  12. Optical properties and structure of HfO{sub 2} thin films grown by high pressure reactive sputtering

    Energy Technology Data Exchange (ETDEWEB)

    MartInez, F L [Departamento de Electronica y TecnologIa de Computadoras, Universidad Politecnica de Cartagena, Campus Universitario Muralla del Mar, E-30202 Cartagena (Spain); Toledano-Luque, M [Departamento de Fisica Aplicada III, Universidad Complutense de Madrid, E-28040 Madrid (Spain); GandIa, J J [Departamento de EnergIa, CIEMAT, Avda. Complutense 22, E-28040 Madrid (Spain); Carabe, J [Departamento de EnergIa, CIEMAT, Avda. Complutense 22, E-28040 Madrid (Spain); Bohne, W [Hahn-Meitner-Institut Berlin, Abteilung SF4, D-14109 Berlin (Germany); Roehrich, J [Hahn-Meitner-Institut Berlin, Abteilung SF4, D-14109 Berlin (Germany); Strub, E [Hahn-Meitner-Institut Berlin, Abteilung SF4, D-14109 Berlin (Germany); Martil, I [Departamento de Fisica Aplicada III, Universidad Complutense de Madrid, E-28040 Madrid (Spain)

    2007-09-07

    Thin films of hafnium oxide (HfO{sub 2}) have been grown by high pressure reactive sputtering on transparent quartz substrates (UV-grade silica) and silicon wafers. Deposition conditions were adjusted to obtain polycrystalline as well as amorphous films. Optical properties of the films deposited on the silica substrates were investigated by transmittance and reflectance spectroscopy in the ultraviolet, visible and near infrared range. A numerical analysis method that takes into account the different surface roughness of the polycrystalline and amorphous films was applied to calculate the optical constants (refractive index and absorption coefficient). Amorphous films were found to have a higher refractive index and a lower transparency than polycrystalline films. This is attributed to a higher density of the amorphous samples, which was confirmed by atomic density measurements performed by heavy-ion elastic recoil detection analysis. The absorption coefficient gave an excellent fit to the Tauc law (indirect gap), which allowed a band gap value of 5.54 eV to be obtained. The structure of the films (amorphous or polycrystalline) was found to have no significant influence on the nature of the band gap. The Tauc plots also give information about the structure of the films, because the slope of the plot (the Tauc parameter) is related to the degree of order in the bond network. The amorphous samples had a larger value of the Tauc parameter, i.e. more order than the polycrystalline samples. This is indicative of a uniform bond network with percolation of the bond chains, in contrast to the randomly oriented polycrystalline grains separated by grain boundaries.

  13. Petrogenesis of coexisting SiO 2-undersaturated to SiO 2-oversaturated felsic igneous rocks: The alkaline complex of Itatiaia, southeastern Brazil

    Science.gov (United States)

    Brotzu, P.; Gomes, C. B.; Melluso, L.; Morbidelli, L.; Morra, V.; Ruberti, E.

    1997-07-01

    The Itatiaia alkaline complex is a Late Cretaceous intrusion (72 Myr) made up of felsic differentiates, with syenitic rocks dominant throughout and with presence of both nepheline- and quartz-rich varieties. Dykes with phonolitic or trachytic composition cross-cut the coarse-grained facies. The rocks are arranged concentrically, with the core of the complex being formed by SiO 2-oversaturated syenites (with a small outcrop of granites), and are radially displaced by faults related to regional tectonic lineaments. The minerals show gradual but significant changes in composition (salitic and augitic to aegirine-rich pyroxenes, hastingsite and actinolite to richterite and arfvedsonite amphiboles, sodic plagioclase to orthoclase feldspars and so on) and the whole-rock trends are broadly consistent with fractional crystallization processes dominated by alkali feldspar removal. Sr-isotopic data indicate more radiogenic ratios for the SiO 2-oversaturated rocks (0.7062-0.7067 against 0.7048-0.7054 for the SiO 2-undersaturated syenites), consistent with small amounts of crustal input. The favored hypothesis for the petrogenesis of the different syenitic groups is the prolonged differentiation starting from differently SiO 2-undersaturated mafic parental magmas (potassic alkali basalts to ankaratrites, present in the Late Cretaceous dyke swarms of the area), accompanied by variable crustal contamination prior to the final emplacement. The lack of carbonatite as a significant lithotype, the potassic affinity of the Itatiaia complex, and the relatively high Sr-isotopic ratios match the characteristics of the other complexes of the Rio de Janeiro-Sa˜o Paulo states coastline and confirm the ultimate derivation of these differentiated rocks from an enriched lithospheric mantle source.

  14. Luminescence of SiO2 and GeO2 crystals with rutile structure. Comparison with α-quartz crystals and relevant glasses (Review Article)

    Science.gov (United States)

    Trukhin, A. N.

    2016-07-01

    Luminescence properties of SiO2 in different structural states are compared. Similar comparison is made for GeO2. Rutile and α-quartz structures as well as glassy state of these materials are considered. Main results are that for α-quartz crystals the luminescence of self-trapped exciton is the general phenomenon that is absent in the crystal with rutile structure. In rutile structured SiO2 (stishovite) and GeO2 (argutite) the main luminescence is due to a host material defect existing in as-received (as-grown) samples. The defect luminescence possesses specific two bands, one of which has a slow decay (for SiO2 in the blue and for GeO2, in green range) and another, a fast ultraviolet (UV) band (4.75 eV in SiO2 and at 3 eV in GeO2). In silica and germania glasses, the luminescence of self-trapped exciton coexists with defect luminescence. The latter also contains two bands: one in the visible range and another in the UV range. The defect luminescence of glasses was studied in details during last 60-70 years and is ascribed to oxygen deficient defects. Analogous defect luminescence in the corresponding pure nonirradiated crystals with α-quartz structure is absent. Only irradiation of a α-quartz crystal by energetic electron beam, γ-rays and neutrons provides defect luminescence analogous to glasses and crystals with rutile structure. Therefore, in glassy state the structure containing tetrahedron motifs is responsible for existence of self-trapped excitons and defects in octahedral motifs are responsible for oxygen deficient defects.

  15. Control of Ga-oxide interlayer growth and Ga diffusion in SiO2/GaN stacks for high-quality GaN-based metal–oxide–semiconductor devices with improved gate dielectric reliability

    Science.gov (United States)

    Yamada, Takahiro; Watanabe, Kenta; Nozaki, Mikito; Yamada, Hisashi; Takahashi, Tokio; Shimizu, Mitsuaki; Yoshigoe, Akitaka; Hosoi, Takuji; Shimura, Takayoshi; Watanabe, Heiji

    2018-01-01

    A simple and feasible method for fabricating high-quality and highly reliable GaN-based metal–oxide–semiconductor (MOS) devices was developed. The direct chemical vapor deposition of SiO2 films on GaN substrates forming Ga-oxide interlayers was carried out to fabricate SiO2/GaO x /GaN stacked structures. Although well-behaved hysteresis-free GaN-MOS capacitors with extremely low interface state densities below 1010 cm‑2 eV‑1 were obtained by postdeposition annealing, Ga diffusion into overlying SiO2 layers severely degraded the dielectric breakdown characteristics. However, this problem was found to be solved by rapid thermal processing, leading to the superior performance of the GaN-MOS devices in terms of interface quality, insulating property, and gate dielectric reliability.

  16. Effect of interface layer on growth behavior of atomic-layer-deposited Ir thin film as novel Cu diffusion barrier

    International Nuclear Information System (INIS)

    Choi, Bum Ho; Lee, Jong Ho; Lee, Hong Kee; Kim, Joo Hyung

    2011-01-01

    Growth and nucleation behavior of Ir films grown by atomic layer deposition (ALD) on different interfacial layers such as SiO 2 , surface-treated TaN, and 3-nm-thick TaN were investigated. To grow Ir thin film by ALD, (1,5-cyclooctadiene) (ethylcyclopentadienyl) iridium (Ir(EtCp)(COD)) and oxygen were employed as the metalorganic precursor and reactant, respectively. To obtain optimal deposition conditions, the deposition temperature was varied from 240 to 420 deg. C and the number of deposition cycles was changed from 150 to 300. The Ir film grown on the 3-nm-thick TaN surface showed the smoothest and most uniform layer for all the deposition cycles, whereas poor nucleation and three-dimensional island-type growth of the Ir layer were observed on Si, SiO 2 , and surface-treated TaN after fewer number of deposition cycles. The uniformity of the Ir film layer was maintained for all the different substrates up to 300 deposition cycles. Therefore we suggest that the growth behavior of the Ir layer on different interface layer is related to the chemical bonding pattern of the substrate film or interface layer, resulting in better understand the growth mechanism of Ir layer as a copper diffusion barrier. The ALD-grown Ir films show the preferential direction of (1 1 1) for all the reflections, which indicates the absence of IrO 2 in metallic Ir.

  17. Temperature dependent electrical properties of polyaniline film grown on paper through aniline vapor polymerization

    Energy Technology Data Exchange (ETDEWEB)

    Deb, K.; Bera, A.; Saha, B., E-mail: biswajit.physics@gmail.com [Department of Physics, National Institute of Technology Agartala, Jirania, West Tripura 799046 (India); Bhowmik, K. L. [Department of Physics, National Institute of Technology Agartala, Jirania, West Tripura 799046 (India); Department of Chemistry, Bir Bikram Memorial College, Agartala, West Tripura 799004 (India); Chattopadhyay, K. K. [Department of Physics, Jadavpur University, Kolkata 700 032 (India)

    2016-05-23

    Polyaniline thin film has been prepared on paper by aniline vapor deposition technique. Ferric chloride has been used as polymerizing agent in this approach. The prepared films were studied through electrical resistivity and optical properties measurements. The electrical resistivity of the polyaniline film shows significant temperature dependence. The resistance sharply falls with the increase in temperature. The optical absorbance measurements shows characteristics absorbance peak indicating the formation of conducting emeraldine salt form of polyaniline. The optical energy band gap of the film was calculated from the transmittance spectra. The optical energy band gap and electrical conductivity of the polyaniline film is well suited for their applications in electronic devices.

  18. Preparation and Characterization of ZnO Nanoparticles Supported on Amorphous SiO2

    Directory of Open Access Journals (Sweden)

    Ying Chen

    2017-08-01

    Full Text Available In order to reduce the primary particle size of zinc oxide (ZnO and eliminate the agglomeration phenomenon to form a monodisperse state, Zn2+ was loaded on the surface of amorphous silica (SiO2 by the hydrogen bond association between hydroxyl groups in the hydrothermal process. After calcining the precursors, dehydration condensation among hydroxyl groups occurred and ZnO nanoparticles supported on amorphous SiO2 (ZnO–SiO2 were prepared. Furthermore, the SEM and TEM observations showed that ZnO nanoparticles with a particle size of 3–8 nm were uniformly and dispersedly loaded on the surface of amorphous SiO2. Compared with pure ZnO, ZnO–SiO2 showed a much better antibacterial performance in the minimum inhibitory concentration (MIC test and the antibacterial properties of the paint adding ZnO–SiO2 composite.

  19. Semiconductor nanocrystals formed in SiO2 by ion implantation

    International Nuclear Information System (INIS)

    Zhu, J.G.; White, C.W.; Budai, J.D.; Withrow, S.P.; Chen, Y.

    1994-11-01

    Nanocrystals of group IV (Si, Ge and SiGe), III-V (GaAs), and II-VI (CdSe) semiconductor materials have been fabricated inside SiO 2 by ion implantation and subsequent thermal annealing. The microstructure of these nanocrystalline semiconductor materials has been studied by transmission electron microscopy (TEM). The nanocrystals form in near-spherical shape with random crystal orientations in amorphous SiO 2 . Extensive studies on the nanocrystal size distributions have been carried out for the Ge nanocrystals by changing the implantation doses and the annealing temperatures. Remarkable roughening of the nanocrystals occurs when the annealing temperature is raised over the melting temperature of the implanted semiconductor material. Strong red photoluminescence peaked around 1.67 eV has been achieved in samples with Si nanocrystals in SiO 2

  20. The hydrophobic and omnidirectional antireflection coating of SiO2 nanospheres with C18-TEOS

    Science.gov (United States)

    Hsu, Cheng-Chih; Lan, Wen-Lin; Chen, Nien-Po; Wu, Chyan-Chyi

    2014-06-01

    This paper demonstrates the antireflection coating of SiO2 nanospheres applied to cover glass by using the optimal spin-coating method. Because of the hydrolysis and condensation reactions between the SiO2 nanosphere antireflection (AR) coating and n-octadecyltriethoxysilane solution (C18-TEOS), the contact angle of the AR coating with hydrophobic treatment is improved approximately 38%, and the moisture-resistance remains unchanged, which preserved similar transmittance for six weeks. Furthermore, the AR coating with hydrophobic treatment exhibits approximately 3% and 7% improvement in the transmittance at normal and oblique incidence, respectively. The hydrophobic and omnidirectional AR coating with nanoscale SiO2 particles can be fabricated using the proposed simple and economical method.

  1. Nitrogen lattice location in MOVPE grown Ga1-xInxNyAs1-y films using ion beam channeling

    International Nuclear Information System (INIS)

    Nebiki, Takuya; Narusawa, Tadashi; Kumagai, Akiko; Doi, Hideyuki; Saito, Tadashi; Takagishi, Shigenori

    2006-01-01

    We have investigated the nitrogen lattice location in MOVPE grown Ga 1-x In x N y As 1-y with x=0.07 and y=0.025 by means of ion beam channeling technique. In this system, the lattice constant of the Ga 1-x In x N y As 1-y film is equal to GaAs lattice. Therefore, we can grow apparently no strain, high quality and very thick GaInNAs film on GaAs substrate. The quality of the films as well as the lattice location of In and N were characterized by channeling Rutherford backscattering spectrometry and nuclear reaction analysis using 3.95 MeV He 2+ beam. The fraction of substitutional nitrogen in the film was measured using the 14 N(α,p) 17 O endothermic nuclear reaction. Our results indicate that more than 90% of In and N atoms are located the substitutional site, however, N atoms are slightly displaced by ∼0.2 A from the lattice site. We suggest that the GaInNAs film has a local strain or point defects around the N atoms. (author)

  2. Structural, Optical Constants and Photoluminescence of ZnO Thin Films Grown by Sol-Gel Spin Coating

    Directory of Open Access Journals (Sweden)

    Abdel-Sattar Gadallah

    2013-01-01

    Full Text Available We report manufacturing and characterization of low cost ZnO thin films grown on glass substrates by sol-gel spin coating method. For structural properties, X-ray diffraction measurements have been utilized for evaluating the dominant orientation of the thin films. For optical properties, reflectance and transmittance spectrophotometric measurements have been done in the spectral range from 350 nm to 2000 nm. The transmittance of the prepared thin films is 92.4% and 88.4%. Determination of the optical constants such as refractive index, absorption coefficient, and dielectric constant in this wavelength range has been evaluated. Further, normal dispersion of the refractive index has been analyzed in terms of single oscillator model of free carrier absorption to estimate the dispersion and oscillation energy. The lattice dielectric constant and the ratio of free carrier concentration to free carrier effective mass have been determined. Moreover, photoluminescence measurements of the thin films in the spectral range from 350 nm to 900 nm have been presented. Electrical measurements for resistivity evaluation of the films have been done. An analysis in terms of order-disorder of the material has been presented to provide more consistency in the results.

  3. Growth and optical properties of sol-gel ZnO thin films grown on R-plane sapphire substrates

    Science.gov (United States)

    Nam, Giwoong; Kim, Min Su; Lee, Jewon; Leem, Jae-Young; Lee, Sang-heon; Jung, Jae Hak; Kim, Jin Soo; Kim, Jong Su

    2013-04-01

    Zinc-oxide (ZnO) thin films were grown on R-plane sapphire substrates by using the sol-gel spincoating method. They were annealed at temperatures ranging from 600 to 800 °C. The effects of the annealing temperature on the properties of the ZnO thin films were investigated using scanning electron microscopy, X-ray diffraction, and photoluminescence. When the annealing temperature was increased to 700 °C, the grains of the ZnO thin films coalesced, their size increased, and the residual stress in the ZnO thin films was relaxed. In addition, the intensity of the deep-level emission peak caused by defects decreased, and the full width at half maximum of the near-bandedge emission peak decreased as the annealing temperature was increased to 700 °C. However, when the annealing temperature was increased further, degradation of the structural and the optical properties was observed. The reflective index of the ZnO thin films in the UV region increased as the annealing temperature was increased to 700 °C, and n in the visible region decreased with increasing wavelength. The extinction coefficient in the UV and the visible regions decreased as the annealing temperature was increased to 700 °C. However, inflection points in the reflective index and the extinction coefficient were observed with a further increase in the annealing temperature.

  4. Effects of Various Parameters on Structural and Optical Properties of CBD-Grown ZnS Thin Films: A Review

    Science.gov (United States)

    Sinha, Tarkeshwar; Lilhare, Devjyoti; Khare, Ayush

    2018-02-01

    Zinc sulfide (ZnS) thin films deposited by chemical bath deposition (CBD) technique have proved their capability in a wide area of applications including electroluminescent and display devices, solar cells, sensors, and field emitters. These semiconducting thin films have attracted a much attention from the scientific community for industrial and research purposes. In this article, we provide a comprehensive review on the effect of various parameters on various properties of CBD-grown ZnS films. In the first part, we discuss the historical background of ZnS, its basic properties, and the advantages of the CBD technique. Detailed discussions on the film growth, structural and optical properties of ZnS thin films affected by various parameters, such as bath temperature and concentration, deposition time, stirring speed, complexing agents, pH value, humidity in the environment, and annealing conditions, are also presented. In later sections, brief information about the recent studies and findings is also added to explore the scope of research work in this field.

  5. Preparation and luminescence properties of SiO2@LaBO3:Eu3+ nanoparticles

    Science.gov (United States)

    Qin, Chuanxiang; Qin, Lin; Chen, Guoqiang; Xu, Haitao; Lin, Tong

    2013-08-01

    Spherical SiO2 particles having a LaBO3:Eu3+ shell have been prepared by coating of silica nanoparticles (size around 130-150 nm) with a LaBO3:Eu3+ sol-gel precursor and subsequent calcination. The SiO2@LaBO3:Eu3+ nanoparticles were characterized by X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy, and transmission electron microscopy. The XRD and FTIR results revealed that the LaBO3:Eu3+ layer on SiO2 nanoparticles formed an H-LaBO3 crystal phase when calcination at a temperature up to 700 °C. Both excitation and emission properties were characterized. The strong excitation lines at 393 and 465 nm of SiO2@LaBO3:Eu3+ indicated that the core-shell phosphor matched well with the output wavelength of near-UV (350-400 nm) or blue LED (450 nm) chips in phosphor-converted W-LEDs. The emission spectra of the 5D0 → 7F J ( J = 0, 1, 2, 3, and 4) transitions at blue/near-UV light showed strong emission lines around 615 nm which were attributed to the induced electric dipole transition of 5D0 → 7F2. The coating cycles affected the luminescence of SiO2@LaBO3:Eu3+ nanoparticles and their CIE chromaticity coordinate shifted from orange-red to the deep red zone with the increase in the coating cycles (up to 3). The luminescence lifetime of the Eu3+ ions in SiO2@LaBO3:Eu3+ was 2.32 ms. Such a luminescent material may be useful for display and light applications.

  6. Nanostructured and wide bandgap CdS:O thin films grown by reactive RF sputtering

    International Nuclear Information System (INIS)

    Islam, M. A.; Rahman, K. S.; Haque, F.; Rashid, M. J.; Akhtaruzzaman, M.; Sopian, K.; Sulaiman, Y.; Amin, N.

    2015-01-01

    In this study, CdS:O thin films were prepared from a 99.999% CdS target by reactive sputtering in a Ar:O 2 (99:1) ambient with different RF power at room temperature. The deposited films were studied by means of XRD, SEM, EDX, Hall Effect and UV-Vis spectrometry. The incorporations of O 2 into the films were observed to increase with the decrease of deposition power. The cryatallinity of the films were reduced, whereas the band gaps of the films were increased by the increase of O 2 content on the films. The films were found in nano-structured grains with a compact surface. It has been seen that the highest carrier density is observed in the film with O 2 at.% 21.10, while the values decreased with the further increase or decrease of O 2 content on the films; indicating that specific amount of donor like O 2 atoms substitute to the S atoms can improve the carrier density of the CdS:O thin film

  7. Nanostructured and wide bandgap CdS:O thin films grown by reactive RF sputtering

    Energy Technology Data Exchange (ETDEWEB)

    Islam, M. A.; Rahman, K. S.; Haque, F.; Rashid, M. J.; Akhtaruzzaman, M.; Sopian, K.; Sulaiman, Y. [Solar Energy Research Institute (SERI), National University of Malaysia, 43600 Bangi (Malaysia); Amin, N. [Solar Energy Research Institute (SERI), National University of Malaysia, 43600 Bangi (Malaysia); Department of Electrical, Electronic and System Engineering, Faculty of Engineering and Built Environment, National University of Malaysia, 43600 Bangi (Malaysia)

    2015-05-15

    In this study, CdS:O thin films were prepared from a 99.999% CdS target by reactive sputtering in a Ar:O{sub 2} (99:1) ambient with different RF power at room temperature. The deposited films were studied by means of XRD, SEM, EDX, Hall Effect and UV-Vis spectrometry. The incorporations of O{sub 2} into the films were observed to increase with the decrease of deposition power. The cryatallinity of the films were reduced, whereas the band gaps of the films were increased by the increase of O{sub 2} content on the films. The films were found in nano-structured grains with a compact surface. It has been seen that the highest carrier density is observed in the film with O{sub 2} at.% 21.10, while the values decreased with the further increase or decrease of O{sub 2} content on the films; indicating that specific amount of donor like O{sub 2} atoms substitute to the S atoms can improve the carrier density of the CdS:O thin film.

  8. Fractal features of CdTe thin films grown by RF magnetron sputtering

    Energy Technology Data Exchange (ETDEWEB)

    Hosseinpanahi, Fayegh, E-mail: f.hosseinpanahi@yahoo.com [Department of Physics, Payame Noor University, P.O. Box 19395-4697, Tehran (Iran, Islamic Republic of); Raoufi, Davood [Department of Physics, University of Bu Ali Sina, P.O. Box 65174, Hamedan (Iran, Islamic Republic of); Ranjbarghanei, Khadijeh [Department of Physics, Plasma Physics Research Center, Science & Research Branch Islamic Azad University, Tehran (Iran, Islamic Republic of); Karimi, Bayan [Department of Physics, Payame Noor University, P.O. Box 19395-4697, Tehran (Iran, Islamic Republic of); Babaei, Reza [Department of Physics, Plasma Physics Research Center, Science & Research Branch Islamic Azad University, Tehran (Iran, Islamic Republic of); Hasani, Ebrahim [Department of Physics, University of Bu Ali Sina, P.O. Box 65174, Hamedan (Iran, Islamic Republic of)

    2015-12-01

    Graphical abstract: - Highlights: • CdTe thin films were deposited on glass substrates by RF magnetron sputtering at room temperature with different deposition time 5, 10 and 15 min. • Nanostructure of CdTe layer indicates that CdTe films are polycrystalline and have zinc blende structure, irrespective of their deposition time. • Complexity and roughness of the CdTe films and strength of multifractality increase with increasing deposition time. • Detrended fluctuation analysis (DFA) and also multifractal detrended fluctuation analysis (MFDFA) methods showed that prepared CdTe films have multifractal nature. - Abstract: Cadmium telluride (CdTe) thin films were prepared by RF magnetron sputtering on glass substrates at room temperature (RT). The film deposition was performed for 5, 10, and 15 min at power of 30 W with a frequency of 13.56 MHz. The crystal structure of the prepared CdTe thin films was studied by X-ray diffraction (XRD) technique. XRD analyses indicate that the CdTe films are polycrystalline, having zinc blende structure of CdTe irrespective of their deposition time. All CdTe films showed a preferred orientation along (1 1 1) crystalline plane. The surface morphology characterization of the films was studied using atomic force microscopy (AFM). The quantitative AFM characterization shows that the RMS surface roughness of the prepared CdTe thin films increases with increasing the deposition time. The detrended fluctuation analysis (DFA) and also multifractal detrended fluctuation analysis (MFDFA) methods showed that prepared CdTe thin films have multifractal nature. The complexity, roughness of the CdTe thin films and strength of the multifractality increase as deposition time increases.

  9. Fractal features of CdTe thin films grown by RF magnetron sputtering

    International Nuclear Information System (INIS)

    Hosseinpanahi, Fayegh; Raoufi, Davood; Ranjbarghanei, Khadijeh; Karimi, Bayan; Babaei, Reza; Hasani, Ebrahim

    2015-01-01

    Graphical abstract: - Highlights: • CdTe thin films were deposited on glass substrates by RF magnetron sputtering at room temperature with different deposition time 5, 10 and 15 min. • Nanostructure of CdTe layer indicates that CdTe films are polycrystalline and have zinc blende structure, irrespective of their deposition time. • Complexity and roughness of the CdTe films and strength of multifractality increase with increasing deposition time. • Detrended fluctuation analysis (DFA) and also multifractal detrended fluctuation analysis (MFDFA) methods showed that prepared CdTe films have multifractal nature. - Abstract: Cadmium telluride (CdTe) thin films were prepared by RF magnetron sputtering on glass substrates at room temperature (RT). The film deposition was performed for 5, 10, and 15 min at power of 30 W with a frequency of 13.56 MHz. The crystal structure of the prepared CdTe thin films was studied by X-ray diffraction (XRD) technique. XRD analyses indicate that the CdTe films are polycrystalline, having zinc blende structure of CdTe irrespective of their deposition time. All CdTe films showed a preferred orientation along (1 1 1) crystalline plane. The surface morphology characterization of the films was studied using atomic force microscopy (AFM). The quantitative AFM characterization shows that the RMS surface roughness of the prepared CdTe thin films increases with increasing the deposition time. The detrended fluctuation analysis (DFA) and also multifractal detrended fluctuation analysis (MFDFA) methods showed that prepared CdTe thin films have multifractal nature. The complexity, roughness of the CdTe thin films and strength of the multifractality increase as deposition time increases.

  10. Interfacial charge trapping in extrinsic Y2O3/SiO2 bilayer gate dielectric based MIS devices on Si(100)

    Science.gov (United States)

    Rastogi, A. C.; Sharma, R. N.

    2001-08-01

    Metal-insulator-semiconductor (MIS) structures based on an extrinsic Y2O3 dielectric film on Si show high leakage currents due to roughness-related highly localized fields. Oxygen annealing increases the dielectric constant and strength and reduces leakage currents by transforming Y2O3 (film)/Si(100) into a bilayer Y2O3 (film)/SiO2/Si(100) dielectric structure. Evolution of interfacial SiO2 causes generation of mid-gap interface states at Ev + 0.23 eV and Ev + 0.43 eV, which act as electron traps and are responsible for hysteresis effects in capacitance-voltage (C-V) and current-voltage (I-V) behaviour in the accumulation-inversion modes. The electron trapping reduces the cathodic field and causes lowering of the current and the shift in current to higher fields after successive ramps. The charge trapping effects cause varied and unstable C-V and I-V behaviour of MIS structures based on a Y2O3/SiO2 bilayer gate dielectric. Its origin has been attributed to microstructure and defect state modification at the Y2O3 film-Si interface. This limits its application in high-density dynamic random access memory and ultra-large-scale integration devices.

  11. Bond length contraction in Au nanocrystals formed by ion implantation into thin SiO2

    International Nuclear Information System (INIS)

    Kluth, P.; Johannessen, B.; Giraud, V.; Cheung, A.; Glover, C.J.; Azevedo, G. de M; Foran, G.J.; Ridgway, M.C.

    2004-01-01

    Au nanocrystals (NCs) fabricated by ion implantation into thin SiO 2 and annealing were investigated by means of extended x-ray absorption fine structure (EXAFS) spectroscopy and transmission electron microscopy. A bond length contraction was observed and can be explained by surface tension effects in a simple liquid-drop model. Such results are consistent with previous reports on nonembedded NCs implying a negligible influence of the SiO 2 matrix. Cumulant analysis of the EXAFS data suggests surface reconstruction or relaxation involving a further shortened bond length. A deviation from the octahedral closed shell structure is apparent for NCs of size 25 A

  12. High-resolution electron microscopy study of SiGeC thin films grown on Si(1 0 0) by laser-assisted techniques

    International Nuclear Information System (INIS)

    Lioutas, Ch.B.; Frangis, N.; Soumelidis, S.; Chiussi, S.; Lopez, E.; Leon, B.

    2006-01-01

    PLIE was used for rapid crystallisation of a-SiGeC films deposited by LCVD on Si(1 0 0) substrates. HRTEM study of thin films grown with several laser energies shows that the combination of the two laser techniques gives an almost completely crystallised alloy, even for the lowest laser fluence. Island formation is observed below a certain threshold of fluence (about 450 mJ/cm 2 ). In the case of the lowest energy (100 mJ/cm 2 ) the material was partially crystallised (with the crystalline material being the predominant state), to a nanocrystalline alloy with a considerable amount of epitaxialy grown grains and with grain sizes of several tens of nanometers. Above the threshold of 450 mJ/cm 2 a rather smooth thin film is grown. The crystallisation is almost complete and the alloy is grown in an almost perfect epitaxial way

  13. Characterization of Pb-Doped GaN Thin Films Grown by Thermionic Vacuum Arc

    Science.gov (United States)

    Özen, Soner; Pat, Suat; Korkmaz, Şadan

    2018-03-01

    Undoped and lead (Pb)-doped gallium nitride (GaN) thin films have been deposited by a thermionic vacuum arc (TVA) method. Glass and polyethylene terephthalate were selected as optically transparent substrates. The structural, optical, morphological, and electrical properties of the deposited thin films were investigated. These physical properties were interpreted by comparison with related analysis methods. The crystalline structure of the deposited GaN thin films was hexagonal wurtzite. The optical bandgap energy of the GaN and Pb-doped GaN thin films was found to be 3.45 eV and 3.47 eV, respectively. The surface properties of the deposited thin films were imaged using atomic force microscopy and field-emission scanning electron microscopy, revealing a nanostructured, homogeneous, and granular surface structure. These results confirm that the TVA method is an alternative layer deposition system for Pb-doped GaN thin films.

  14. Aluminum-doped zinc oxide thin films grown on various substrates using facing target sputtering system

    Science.gov (United States)

    Kim, Hwa-Min; Lee, Chang Hyun; Shon, Sun Young; Kim, Bong Hwan

    2017-11-01

    Aluminum-doped zinc oxide (AZO) films were fabricated on various substrates, such as glass, polyethylene naphthalate (PEN), and polyethylene terephthalate (PET), at room temperature using a facing target sputtering (FTS) system with hetero ZnO and Al2O3 targets, and their electrical and optical properties were investigated. The AZO film on glass exhibited compressive stress while the films on the plastic substrates showed tensile stress. These stresses negatively affected the crystalline quality of the AZO films, and it is suggested that the poor crystalline quality of the films may be related to the neutral Al-based defect complexes formed in the films; these complexes act as neutral impurity scattering centers. AZO films with good optoelectronic properties could be formed on the glass and plastic substrates by the FTS technique using the hetero targets. The AZO films deposited on the glass, PEN, and PET substrates showed very low resistivities, of 5.0 × 10-4 Ω cm, 7.0 × 10-4 Ω cm, and 7.4 × 10-4 Ω cm, respectively. Further, the figure merit of the AZO film formed on the PEN substrate in the visible range (400-700 nm) was significantly higher than that of the AZO film on PET and similar to that of the AZO film on glass. Finally, the average transmittances of the films in the visible range (400-700 nm) were 83.16% (on glass), 76.3% (on PEN), and 78.16% (on PET).

  15. Elastically strained and relaxed La0.67Ca0.33MnO3 films grown on lanthanum aluminate substrates with different orientations

    Science.gov (United States)

    Boikov, Yu. A.; Serenkov, I. T.; Sakharov, V. I.; Claeson, T.

    2016-12-01

    Structure of 40-nm thick La0.67Ca0.33MnO3 (LCMO) films grown by laser evaporation on (001) and (110) LaAlO3 (LAO) substrates has been investigated using the methods of medium-energy ion scattering and X-ray diffraction. The grown manganite layers are under lateral biaxial compressive mechanical stresses. When (110)LAO wafers are used as the substrates, stresses relax to a great extent; the relaxation is accompanied by the formation of defects in a (3-4)-nm thick manganite-film interlayer adjacent to the LCMO-(110)LAO interface. When studying the structure of the grown layers, their electro- and magnetotransport parameters have been measured. The electroresistance of the LCMO films grown on the substrates of both types reached a maximum at temperature T M of about 250 K. At temperatures close to T M magnetoresistance of the LCMO/(110)LAO films exceeds that of the LCMO/(001)LAO films by 20-30%; however, the situation is inverse at low temperatures ( T < 150 K). At T < T M , the magnetotransport in the grown manganite films significantly depends on the spin ordering in ferromagnetic domains, which increase with a decrease in temperature.

  16. Structural and magnetic properties of cobalt nanostructures on SiO2/Si(1 1 1) substrates

    International Nuclear Information System (INIS)

    Bounour-Bouzamouche, W.; Chérif, S.M.; Farhat, S.; Roussigné, Y.; Tallaire, A.; Gicquel, A.; Lungu, C.P.; Guerioune, M.

    2014-01-01

    Highlights: • Heat and plasma treatments of ultrathin cobalt films deposited on SiO 2 /Si(1 1 1) create highly auto-organized structures. • Direct correlation between the film thickness and the size of the nanoparticles formed after thermal annealing. • Modification of the surface morphology strongly influences the magnetic response of the investigated films. • Formation of Co islands in triangular shapes is found to play a key role in the enhancement of the coercive field. - Abstract: 2D architectures of cobalt onto silicon (1 1 1) surfaces were elaborated by patterning of magnetic cobalt in the nanometer scale. A continuous cobalt layer of 1, 3 and 10 nm thickness, respectively, was first deposited by means of thermoionic vacuum arc technique and then, thermally annealed in vacuum at temperatures ranging from 450 to 800 °C. Surface structure was analyzed by atomic force and field emission-scanning electron microscopies. Above 750 °C, regular triangular shape cobalt nanostructures are formed with pattern dimensions varying between 10 and 200 nm. Good control of shape and packing density could be achieved by adjusting the initial thickness and the thermal and hydrogen plasma treatments. Magnetic properties were investigated using vibrating sample magnetometer technique. The evolution of the coercive field versus packing density and dimensions of the nanostructures was studied and compared to micromagnetic calculations. The observed nanostructures have been modeled by a series of shapes tending to a fractal curve

  17. Effect of SiO2-acryl nanohybrid coating layers on transparent conducting oxide-poly(ethylene terephthalate) superstrate.

    Science.gov (United States)

    Kang, Y T; Kang, D P; Kang, D J; Chung, I D

    2013-05-01

    SiO2-acryl nanohybrid coating layers were produced by hybridizing acrylic resin and surface-modified colloidal silica (CS) nanoparticles. First, CS nanoparticles were modified with methyltrimethoxysilane (MTMS) and vinyltrimethoxysilane (VTMS) by a sol-gel process. The surface-modified CS nanoparticles were then solvent-exchanged to be homogeneous in acrylic resin. The Hybrid materials were mixed in variation with the amount of surface-modified CS nanoparticles, coated with poly(ethylene terephthalate) (PET), then finally cured by UV light to obtain a hybrid coating layer. Field emission scanning electron microscopy (FE-SEM), particle size analysis (using a Zetasizer), and atomic force microscopy (AFM) were performed to determine the morphology of the hybrid thin-films. Thermogravimetric analysis (TGA) was used to investigate the thermal properties. Fourier-transform infrared (FTIR), ultraviolet-visible (UVNis) spectroscopies, and pencil hardness were used to obtain the details of chemical structures, optical properties, and hardness, respectively. The hybrid thin films had shown to be enhanced properties compared to their urethane acrylate prepolymer (UAP) coating film.

  18. Improving stability of photoluminescence of ZnSe thin films grown by molecular beam epitaxy by incorporating Cl dopant

    International Nuclear Information System (INIS)

    Wang, J. S.; Shen, J. L.; Chen, W. J.; Tsai, Y. H.; Wang, H. H.; Yang, C. S.; Chen, R. H.; Tsai, C. D.

    2011-01-01

    This investigation studies the effect of chlorine (Cl) dopant in ZnSe thin films that were grown by molecular beam epitaxy on their photoluminescence (PL) and the stability thereof. Free excitonic emission was observed at room-temperature in the Cl-doped sample. Photon irradiation with a wavelength of 404 nm and a power density of 9.1 W/cm 2 has a much stronger effect on PL degradation than does thermal heating to a temperature of 150 deg. C. Additionally, this study shows that the generation of nonradiative centers by both photon irradiation and thermal heating can be greatly inhibited by incorporating Cl dopant.

  19. Investigation of humidity-dependent nanotribology behaviors of Si(1 0 0)/SiO2 pair moving from stick to slip

    International Nuclear Information System (INIS)

    Yu Jiaxin; Chen Lei; Qian Linmao; Song Danlu; Cai Yong

    2013-01-01

    Highlights: ► The effect of humidity on the motion behavior of Si(1 0 0)/SiO 2 pair was clarified. ► With increase in humidity, adhesion force increases slowly firstly, then sharply. ► With increase in humidity, friction force increases sharply firstly, then slowly. ► The wear degree of Si is relative to the physical state of absorbed water film. ► The tribochemical reaction of Si(1 0 0) in humid air was verified by ToF-SIMS. - Abstract: With an atomic force microscopy, the humidity-dependent nanotribology behaviors of Si(1 0 0) against SiO 2 microsphere were investigated while the relative movement translated from stick to slip. The relative humidity RH of air exhibits a strong effect on the motion behavior of Si(1 0 0)/SiO 2 pair. With the increase in RH, relative movement of Si(1 0 0)/SiO 2 pair is easier to keep into stick state, namely, the relative slip becomes more difficult to occur in a higher humidity range. The adhesion F a will increase with the increase in RH in the given humidity range. In the low RH range ( a increases very slowly. However, in relative higher RH range (>20%), F a increases very sharply once ‘liquid-like’ adsorbed water layer forms, because it increases the capillary force. The initial friction forces F t of Si(1 0 0)/SiO 2 pair also increase with the increase in RH in the given humidity range. However, different from F a , it increases sharply in the low RH range ( 30%). During the cyclic friction process, under the higher RH, relative stable tangential force is easier to be observed at higher displacement amplitude, here, the relative movement usually keeps into stick state. With the increase in RH, the surface damage of Si(1 0 0) transforms from mechanical deformation (forming hillock) to tribochemical wear (material removal). The tribochemical wear is sensitive to the absorbed water film with ‘solid-like’ structure, here, the wear volume increases drastically in this RH range (<20%); further increase of wear is

  20. Thin films of copper oxide and copper grown by atomic layer deposition for applications in metallization systems of microelectronic devices

    Energy Technology Data Exchange (ETDEWEB)

    Waechtler, Thomas

    2010-05-25

    Copper-based multi-level metallization systems in today's ultralarge-scale integrated electronic circuits require the fabrication of diffusion barriers and conductive seed layers for the electrochemical metal deposition. Such films of only several nanometers in thickness have to be deposited void-free and conformal in patterned dielectrics. The envisaged further reduction of the geometric dimensions of the interconnect system calls for coating techniques that circumvent the drawbacks of the well-established physical vapor deposition. The atomic layer deposition method (ALD) allows depositing films on the nanometer scale conformally both on three-dimensional objects as well as on large-area substrates. The present work therefore is concerned with the development of an ALD process to grow copper oxide films based on the metal-organic precursor bis(trin- butylphosphane)copper(I)acetylacetonate [({sup n}Bu{sub 3}P){sub 2}Cu(acac)]. This liquid, non-fluorinated {beta}-diketonate is brought to react with a mixture of water vapor and oxygen at temperatures from 100 to 160 C. Typical ALD-like growth behavior arises between 100 and 130 C, depending on the respective substrate used. On tantalum nitride and silicon dioxide substrates, smooth films and selfsaturating film growth, typical for ALD, are obtained. On ruthenium substrates, positive deposition results are obtained as well. However, a considerable intermixing of the ALD copper oxide with the underlying films takes place. Tantalum substrates lead to a fast self-decomposition of the copper precursor. As a consequence, isolated nuclei or larger particles are always obtained together with continuous films. The copper oxide films grown by ALD can be reduced to copper by vapor-phase processes. If formic acid is used as the reducing agent, these processes can already be carried out at similar temperatures as the ALD, so that agglomeration of the films is largely avoided. Also for an integration with subsequent

  1. Effect of deposition conditions on the growth rate and electrical properties of ZnO thin films grown by MOCVD

    Energy Technology Data Exchange (ETDEWEB)

    Roro, K.T.; Botha, J.R.; Leitch, A.W.R. [Department of Physics, Nelson Mandela Metropolitan University, P.O. Box 77000, Port Elizabeth 6031 (South Africa)

    2008-07-01

    ZnO thin films have been grown on glass substrates by MOCVD. The effect of deposition conditions such as VI/II molar ratio, DEZn flow rate and total reactor pressure on the growth rate and electrical properties of the films was studied. It is found that the growth rate decreases with an increase in the VI/II molar ratio. This behaviour is ascribed to the competitive adsorption of reactant species on the growth surface. The growth rate increases with an increase in DEZn flow rate, as expected. It is shown that the carrier concentration is independent of the DEZn flow rate. An increase in the total reactor pressure yields a decrease in growth rate. This phenomenon is attributed to the depletion of the gas phase due to parasitic prereactions between zinc and oxygen species at high pressure. (copyright 2008 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  2. Microcrystalline GaN film grown on Si(1 0 0) and its application to MSM photodiode

    International Nuclear Information System (INIS)

    Hassan, Z.; Lee, Y.C.; Yam, F.K.; Abdullah, M.J.; Ibrahim, K.; Kordesch, M.E.

    2004-01-01

    The properties and application of gallium nitride (GaN) films grown on silicon at a low temperature (873 K) by electron cyclotron resonance (ECR) plasma-assisted metalorganic chemical vapor deposition (MOCVD) were investigated. Structural analysis revealed microcrystalline structure (μc-GaN) with crystallite size of 167 nm for these smooth and transparent films. Ni/μc-GaN metal-semiconductor-metal (MSM) photodiode have been fabricated and analyzed by means of electrical characterization, using current-voltage (I-V) and capacitance-voltage (C-V) measurements to evaluate the Schottky contact parameters for the study of current transport mechanism of the MSM photodiode. The barrier height phi b determined from the C-V method is 0.734 eV

  3. Post deposition annealing of epitaxial Ce(1-x)Pr(x)O(2-δ) films grown on Si(111).

    Science.gov (United States)

    Wilkens, H; Spiess, W; Zoellner, M H; Niu, G; Schroeder, T; Wollschläger, J

    2015-04-21

    In this work the structural and morphological changes of Ce1-xPrxO2-δ (x = 0.20, 0.35 and 0.75) films grown on Si(111) due to post deposition annealing are investigated by low energy electron diffraction combined with a spot profile analysis. The surface of the oxide films exhibit mosaics with large terraces separated by monoatomic steps. It is shown that the Ce/Pr ratio and post deposition annealing temperature can be used to tune the mosaic spread, terrace size and step height of the grains. The morphological changes are accompanied by a phase transition from a fluorite type lattice to a bixbyite structure. Furthermore, at high PDA temperatures a silicate formation via a polycrystalline intermediate state is observed.

  4. Phase-coherent electron transport in (Zn, Al)Ox thin films grown by atomic layer deposition

    Science.gov (United States)

    Saha, D.; Misra, P.; Ajimsha, R. S.; Joshi, M. P.; Kukreja, L. M.

    2014-11-01

    A clear signature of disorder induced quantum-interference phenomena leading to phase-coherent electron transport was observed in (Zn, Al)Ox thin films grown by atomic layer deposition. The degree of static-disorder was tuned by varying the Al concentration through periodic incorporation of Al2O3 sub-monolayer in ZnO. All the films showed small negative magnetoresistance due to magnetic field suppressed weak-localization effect. The temperature dependence of phase-coherence length ( l φ ∝ T - 3 / 4 ), as extracted from the magnetoresistance measurements, indicated electron-electron scattering as the dominant dephasing mechanism. The persistence of quantum-interference at relatively higher temperatures up to 200 K is promising for the realization of ZnO based phase-coherent electron transport devices.

  5. Physical properties of lanthanum monosulfide thin films grown on (100) silicon substrates

    Science.gov (United States)

    Cahay, M.; Garre, K.; Wu, X.; Poitras, D.; Lockwood, D. J.; Fairchild, S.

    2006-06-01

    Thin films of lanthanum monosulfide (LaS) have been deposited on Si (100) substrates by pulsed laser deposition. The films are golden yellow in appearance with a mirrorlike surface morphology and a sheet resistance around 0.1 Ω/□, as measured using a four-probe measurement technique. The thin films are characterized by atomic force microscopy (AFM), x-ray diffraction (XRD) analysis, high resolution transmission electron microscopy (HRTEM), ellipsometry, and Raman spectroscopy. The root-mean-square variation of (1 μm thick) film surface roughness measured over a 1 μm2 area by AFM was found to be 1.74 nm. XRD analysis of fairly thick films (micrometer size) reveals the growth of the cubic rocksalt structure with a lattice constant of 5.863(7) A˚, which is close to the bulk LaS value. HRTEM images reveal that the films are comprised of nanocrystals separated by regions of amorphous material. Two beam bright field TEM images show that there is a strain contrast in the Si substrate right under the interface with the LaS film and penetrating into the Si substrate. This suggests that there is an initial epitaxial-like growth of the LaS film on the Si substrate that introduces a strain as a result of the 8% lattice mismatch between the film and substrate. Ellipsometry measurements of the LaS films are well characterized by a Drude-Lorentz model from which an electron concentration of about 2.52×1022 cm-3 and a mobility around 8.5 cm2/V s are derived. Typical crystalline LaS features were evident in Raman spectra of the films, but the spectra also revealed their disordered (polycrystalline) nature.

  6. Improvement of thermoelectric properties of Bi{sub 2}Te{sub 3} and Sb{sub 2}Te{sub 3} films grown on graphene substrate

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Chang Wan [Thin Film Materials Research Group, Korea Research Institute of Chemical Technology, Daejeon (Korea, Republic of); School of Electrical and Electronic Engineering, Yonsei University, Seoul (Korea, Republic of); Kim, Gun Hwan; Choi, Ji Woon; An, Ki-Seok; Lee, Young Kuk [Thin Film Materials Research Group, Korea Research Institute of Chemical Technology, Daejeon (Korea, Republic of); Kim, Jin-Sang [Center for Electronic Materials, Korea Institute of Science and Technology, Seoul (Korea, Republic of); Kim, Hyungjun [School of Electrical and Electronic Engineering, Yonsei University, Seoul (Korea, Republic of)

    2017-06-15

    A study of substrate effect on the thermoelectric (TE) properties of Bi{sub 2}Te{sub 3} (BT) and Sb{sub 2}Te{sub 3} (ST) thin films grown by plasma-enhanced chemical vapor deposition (PECVD) was performed. Graphene substrates which have small lattice mismatch with BT and ST were used for the preparation of highly oriented BT and ST thin films. Carrier mobility of the epitaxial BT and ST films grown on the graphene substrates increased as the deposition temperature increased, which was not observed in that of SiO{sub 2}/Si substrates. Seebeck coefficients of the as-grown BT and ST films were observed to be maintained even though carrier concentration increased in the epitaxial BT and ST films on graphene substrate. Although Seebeck coefficient was not improved, power factor of the as-grown BT and ST films was considerably enhanced due to the increase of electrical conductivity resulting from the high carrier mobility and moderate carrier concentration in the epitaxial BT and ST films. (copyright 2017 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  7. Growth, luminescence and magnetic properties of GaN:Er semiconductor thin films grown by molecular beam epitaxy

    Science.gov (United States)

    Dasari, K.; Wu, J.; Huhtinen, H.; Jadwisienczak, W. M.; Palai, R.

    2017-05-01

    We report on the growth, surface, luminescence and magnetic properties of 180 nm thick Er-doped GaN thin films grown by molecular beam epitaxy (MBE) on c-sapphire substrates with no buffer layer and with different Er concentrations. In situ reflection high-energy electron diffraction (RHEED) patterns revealed crystalline and uniform growth of the films. The x-ray diffraction (XRD) pattern showed c-axis-oriented growth. Atomic force microscopy (AFM) analysis showed enhancement of surface morphology and smoothness with increasing Er doping, which could be due to minimization of surface defects because of the gettering effect of the rare earth. Scanning area-dependent surface morphology analysis showed a power law dependence indicating the fractal nature of the surface, which is confirmed by the observation of a non-integer D (fractal dimension) value. X-ray photoluminescence spectroscopy (XPS) revealed the formation of a GaN:Er phase and ruled out the presence of Ga and Er metallic and native oxide phases. The semi-quantitative elemental composition of the films was determined using N 1s, Ga 2p3/2 and Er 4d photoemission lines. The Er concentration was estimated from the x-ray photoelectron spectra and found to be between 3.0 and 9.0 at.% (˜1021 atoms cm-3). Photoluminescence (PL) and cathodoluminescence (CL) studies showed visible emission and concentration quenching of Er3+ ions in agreement with reported results. Excitation of the Er3+ ion might be affected by charge trapping due to Er-doping-induced defect complexes. The magnetic measurements carried out by a superconducting quantum interference device (SQUID) showed a ferromagnetic-paramagnetic phase transition at low temperature, contrary to the reported room temperature ferromagnetism in metalorganic chemical vapor deposition (MOCVD)-grown GaN:Er thick films of 550 nm.

  8. Fabrication of an ordered mesoporous nanoparticle SiO2/Mc and their CMP of fused silica application

    Science.gov (United States)

    Xu, L.; Zou, C. L.; Zhang, X.; Kang, C. X.; Luo, G. H.; Pan, G. S.

    2018-02-01

    Here we developed an inorganic SiO2 core/mesoporous carbon shell structured (SiO2/Mc) nano-composite particle with an average size ∼50 nm as abrasives with improved dispersibility and distribution via a hydro-thermal route to obtain reserved fused silica surface and subsurface. The obtained SiO2/Mc were characterized by scanning electronic microscope. Atomic force microscopy was used to assess the surface before and after planarization. The results indicated the as-prepared SiO2/Mc composite abrasives gave a much lower surface roughness as well as lower topographical variations than that of traditional colloidal silica abrasives.

  9. Influence of Substrate-Film Reactions on YBCO Grown by Fluorine-Free MOD Route

    DEFF Research Database (Denmark)

    Zhao, Yue; Tang, Xiao; Wu, W.

    2017-01-01

    Recently, fluorine-free metal organic deposition routes (FF-MOD) for growth of YBCO superconducting films have attracted increased attentions. In this paper, a comparison study was performed on the YBCO-Ag superconducting thin films deposited on two types substrates, LaAlO3 and CSD-Ce0.9La0.1O2-y...

  10. Terahertz and M4PP conductivity mapping of large area CVD grown graphene films

    DEFF Research Database (Denmark)

    Buron, Jonas Christian Due; Petersen, Dirch Hjorth; Bøggild, Peter

    We demonstrate mapping of magnitude and variation of the electrical conductance of large area CVD graphene films by terahertz time-domain spectroscopy (THz-TDS) and micro four-point-probe (M4PP). Non-trivial correlations between results obtained with the two techniques are discussed in relation...... to electrical properties of the graphene films....

  11. High-Mobility Aligned Pentacene Films Grown by Zone-Casting

    DEFF Research Database (Denmark)

    Duffy, Claudia M.; Andreasen, Jens Wenzel; Breiby, Dag W.

    2008-01-01

    We investigate the growth and field-effect transistor performance of aligned pentacene thin films deposited by zone-casting from a solution of unsubstituted pentacene molecules in a chlorinated solvent. Polarized optical microscopy shows that solution processed pentacene films grow as large cryst...

  12. Solution-based deposition of ceramic thin films for electronic applications

    Science.gov (United States)

    Yu, Shijun

    With the requirement of a low-temperature process which is compatible with flexible electronics, solution-based processes for ceramic thin films have received substantial attention in recent years. In this study, two different variations of solution processing were explored. Liquid phase deposition (LPD) was used to prepare for F-doped SiO2 and F-doped SnO2, and hydrothermal processing was used to prepare ZnO thin films consisting of vertically aligned nanorods. F-doped SiO2 thin films were developed from supersaturated hydrofluorosilicic acid (H2SiF6) solution with the addition of boric acid (H3BO3). The microstructure dependence of LPD SiO2 films on solution parameters and deposition temperature was systematically investigated. The dielectric constant is lower than that of thermal SiO2, resulting from the fluorine doping. The remarkably low dielectric constant, relatively low leakage current and fairly high elastic modulus make these low temperature processed LPD SiO2 films very promising for an interlayer dielectric for flexible substrates. Using the same LPD method, smooth SnO2 films were deposited on both silicon and glass substrates at 60 ºC through supersaturated solutions of SnF 2 with a concentration range from 10 mM to 40 mM. They consist of nanoscale crystallites and the degree of crystallinity increase with annealing temperature. A hydrothermal process was employed to deposit ZnO films for energy harvesting devices. A polymer mask was patterned on top of a zinc acetate seed layer to generate a regular array of open holes (200 nm in diameter) using a nanoimprint. Vertically aligned ZnO nanorod arrays were grown on these open holes that expose the seed layer. The morphology and microstrucutre of the nanorods were studied according to chemical composition of the solution. Equimolar reduce of the concentration of ZnAc and HMTA results in decrease in nanorod diameter, as well as in length. The nanorods become thinner and slightly better aligned with

  13. Wet chemically grown composite thin film for room temperature LPG sensor

    Science.gov (United States)

    Birajadar, Ravikiran; Desale, Dipalee; Shaikh, Shaheed; Mahajan, Sandip; Upadhye, Deepak; Ghule, Anil; Sharma, Ramphal

    2014-04-01

    We have synthesized thin film of zinc oxide-polyaniline (ZnO/PANI) composite using a simple wet chemical approach. As-synthesized ZnO/PANI composite thin film studied using different characterization techniques. The optical study reveals the penetration and interaction of PANI molecules with ZnO thin film. Prominent blue shift in UV-vis due to interaction between ZnO and PANI indicate presence of zinc oxide in polyaniline matrix. It is observed that ZnO thin film is not sensitive to LPG (liquefied petroleum gas) at room temperature. On the other hand ZnO/PANI composite thin film shows good response and recovery behaviors at room temperature.

  14. Properties of CdTe nanocrystalline thin films grown on different substrates by low temperature sputtering

    International Nuclear Information System (INIS)

    Chen Huimin; Guo Fuqiang; Zhang Baohua

    2009-01-01

    CdTe nanocrystalline thin films have been prepared on glass, Si and Al 2 O 3 substrates by radio-frequency magnetron sputtering at liquid nitrogen temperature. The crystal structure and morphology of the films were characterized by X-ray diffraction (XRD) and field-emission scanning electron microscopy (FESEM). The XRD examinations revealed that CdTe films on glass and Si had a better crystal quality and higher preferential orientation along the (111) plane than the Al 2 O 3 . FESEM observations revealed a continuous and dense morphology of CdTe films on glass and Si substrates. Optical properties of nanocrystalline CdTe films deposited on glass substrates for different deposited times were studied.

  15. Study of structural and optical properties of ZnO films grown by pulsed laser deposition

    International Nuclear Information System (INIS)

    Lemlikchi, S.; Abdelli-Messaci, S.; Lafane, S.; Kerdja, T.; Guittoum, A.; Saad, M.

    2010-01-01

    Wurtzite zinc oxides films (ZnO) were deposited on silicon (0 0 1) and corning glass substrates using the pulsed laser deposition technique. The laser fluence, target-substrate distance, substrate temperature of 300 deg. C were fixed while varying oxygen pressures from 2 to 500 Pa were used. It is observed that the structural properties of ZnO films depend strongly on the oxygen pressure and the substrate nature. The film crystallinity improves with decreasing oxygen pressure. At high oxygen pressure, the films are randomly oriented, whereas, at low oxygen pressures they are well oriented along [0 0 1] axis for Si substrates and along [1 0 3] axis for glass substrates. A honeycomb structure is obtained at low oxygen pressures, whereas microcrystalline structures were obtained at high oxygen pressures. The effect of oxygen pressure on film transparency, band gap E g and Urbach energies was investigated.

  16. Atomic layer-deposited Al–HfO2/SiO2 bi-layers towards 3D charge trapping non-volatile memory

    International Nuclear Information System (INIS)

    Congedo, Gabriele; Wiemer, Claudia; Lamperti, Alessio; Cianci, Elena; Molle, Alessandro; Volpe, Flavio G.; Spiga, Sabina

    2013-01-01

    A metal/oxide/high-κ dielectric/oxide/silicon (MOHOS) planar charge trapping memory capacitor including SiO 2 as tunnel oxide, Al–HfO 2 as charge trapping layer, SiO 2 as blocking oxide and TaN metal gate was fabricated and characterized as test vehicle in the view of integration into 3D cells. The thin charge trapping layer and blocking oxide were grown by atomic layer deposition, the technique of choice for the implementation of these stacks into 3D structures. The oxide stack shows a good thermal stability for annealing temperature of 900 °C in N 2 , as required for standard complementary metal–oxide–semiconductor processes. MOHOS capacitors can be efficiently programmed and erased under the applied voltages of ± 20 V to ± 12 V. When compared to a benchmark structure including thin Si 3 N 4 as charge trapping layer, the MOHOS cell shows comparable program characteristics, with the further advantage of the equivalent oxide thickness scalability due to the high dielectric constant (κ) value of 32, and an excellent retention even for strong testing conditions. Our results proved that high-κ based oxide structures grown by atomic layer deposition can be of interest for the integration into three dimensionally stacked charge trapping devices. - Highlights: ► Charge trapping device with Al–HfO 2 storage layer is fabricated and characterized. ► Al–HfO 2 and SiO 2 blocking oxides are deposited by atomic layer deposition. ► The oxide stack shows a good thermal stability after annealing at 900 °C. ► The device can be efficiently programmed/erased and retention is excellent. ► The oxide stack could be used for 3D-stacked Flash non-volatile memories

  17. Si nanocrystals embedded in SiO2: Optical studies in the vacuum ultraviolet range

    DEFF Research Database (Denmark)

    Pankratov, V.; Osinniy, Viktor; Kotlov, A.

    2011-01-01

    Photoluminescence excitation and transmission spectra of Si nanocrystals of different diameters embedded in a SiO2 matrix have been investigated in the broad visible-vacuum ultraviolet spectral range using synchrotron radiation. The dependence of the photoluminescence excitation spectra...

  18. FeCl3.nano SiO2: An Efficient Heterogeneous Nano Catalyst for the ...

    African Journals Online (AJOL)

    NICO

    2012-05-28

    May 28, 2012 ... Solid acids have attracted much attention in organic synthesis owing to their easy work-up procedures, ... including the reaction of aryloxy magnesium halides and triethylorthoformate,13 cyclodehydration ... trichloroacetic acid,27 bismuth(III) chlo- ride,28 sulfonic acid functionalized silica (SiO2-Pr-SO3H),29.

  19. Preparation of TiO2-SiO2 composite photocatalysts for environmental applications

    Czech Academy of Sciences Publication Activity Database

    Paušová, Š.; Krýsa, J.; Jirkovský, Jaromír; Prevot, V.; Mailhot, G.

    2014-01-01

    Roč. 89, č. 8 (2014), s. 1129-1135 ISSN 0268-2575 Institutional support: RVO:61388955 Keywords : photocatalysis * TiO2/SiO2 * composite Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 2.349, year: 2014

  20. Nanoimprint lithography using TiO2-SiO2 ultraviolet curable materials

    Science.gov (United States)

    Takei, Satoshi

    2015-05-01

    Ultraviolet nanoimprint lithography has great potential for commercial device applications that are closest to production such as optical gratings, planar waveguides, photonic crystals, semiconductor, displays, solar cell panel, sensors, highbrightness LEDs, OLEDs, and optical data storage. I report and demonstrate the newly TiO2-SiO2 ultraviolet curable materials with 20-25 wt% ratio of high titanium for CF4/O2 etch selectivity using nanoimprint lithography process. The multiple structured three-dimensional micro- and nanolines patterns were observed to be successfully patterned over the large areas. The effect of titanium concentration on CF4/O2 etch selectivity with pattern transferring carbon layer imprinting time was investigated. CF4/O2 etching rate of the TiO2-SiO2 ultraviolet curable material was approximately 3.8 times lower than that of the referenced SiO2 sol-gel ultraviolet curable material. The TiO2-SiO2 ultraviolet curable material with high titanium concentration has been proved to be versatile in advanced nanofabrication.

  1. Theory of Al2O3 incorporation in SiO2

    DEFF Research Database (Denmark)

    Lægsgaard, Jesper

    2002-01-01

    Different possible forms of Al2O3 units in a SiO2 network are studied theoretically within the framework of density-functional theory. Total-energy differences between the various configurations are obtained, and simple thermodynamical arguments are used to provide an estimate of their relative...

  2. Electrical impedance spectroscopic investigations of monodispersed SiO2 nanospheres

    Science.gov (United States)

    Sakthisabarimoorthi, A.; Martin Britto Dhas, S. A.; Jose, M.

    2018-01-01

    Dielectric analysis of uniform and monodispersed SiO2 nanospheres at various temperatures in the frequency range 1 Hz-1 MHz is reported. The high optical transmittance and the presence of silica network in the synthesized product are evident from UV-vis and FTIR spectroscopic techniques respectively. The amorphous structure of SiO2 nanospheres is investigated by powder XRD pattern and uniform spherical morphology is visualized by FESEM analysis. The X-ray photoelectron spectroscopy elucidated the exact valence states of the SiO2 nanospheres. The temperature dependent dielectric parameters such as, dielectric constant (εr) and loss factor (tan δ) are decreased with increasing applied frequency and became static at higher frequencies. SiO2 nanospheres exhibited high dielectric constant (εr = 68) and low loss factor (tan δ = 0.0079) at 40 °C at 1 MHz. The activation energy (Ea) and relaxation time constant (τ) are calculated and the equivalent circuit model is developed to describe the electrical behaviour of the material.

  3. CoFe2O4-SiO2 Composites: Preparation and Magnetodielectric Properties

    Directory of Open Access Journals (Sweden)

    T. Ramesh

    2016-01-01

    Full Text Available Cobalt ferrite (CoFe2O4 and silica (SiO2 nanopowders have been prepared by the microwave hydrothermal (M-H method using metal nitrates as precursors of CoFe2O4 and tetraethyl orthosilicate as a precursor of SiO2. The synthesized powders were characterized by XRD and FESEM. The (100-x (CoFe2O4 + xSiO2 (where x = 0%, 10%, 20%, and 30% composites with different weight percentages have been prepared using ball mill method. The composite samples were sintered at 800°C/60 min using the microwave sintering method and then their structural and morphological studies were investigated using X-ray diffraction (XRD, Fourier transformation infrared (FTIR spectra, and scanning electron microscopy (SEM, respectively. The effect of SiO2 content on the magnetic and electrical properties of CoFe2O4/SiO2 nanocomposites has been studied via the magnetic hysteresis loops, complex permeability, permittivity spectra, and DC resistivity measurements. The synthesized nanocomposites with adjustable grain sizes and controllable magnetic properties make the applicability of cobalt ferrite even more versatile.

  4. Catalytic combustion of trichloroethylene over TiO2-SiO2 supported catalysts

    NARCIS (Netherlands)

    Kulazynski, M.; van Ommen, J.G.; Trawczynski, J.; Walendziewski, J.

    2002-01-01

    Combustion of trichloroethylene (TCE) on Cr2O3, V2O5, Pt or Pd catalysts supported on TiO2-SiO2 as a carrier has been investigated. It was found that oxide catalysts are very active but their activity quickly diminishes due to loss of the active component, especially at higher reaction temperatures

  5. Selective SiO2 etching in three dimensional structures using parylene-C as mask

    NARCIS (Netherlands)

    Veltkamp, Henk-Willem; Zhao, Yiyuan; de Boer, Meint J.; Wiegerink, Remco J.; Lötters, Joost Conrad

    2017-01-01

    This abstract describes an application of an easy and straightforward method for selective SiO2 etching in three dimensional structures, which is developed by our group. The application in this abstract is the protection of the buried-oxide (BOX) layer of a silicon-on-insulator (SOI) wafer against

  6. SiO2 Glass Density to Lower-Mantle Pressures

    DEFF Research Database (Denmark)

    Petitgirard, Sylvain; Malfait, Wim J.; Journaux, Baptiste

    2017-01-01

    and present Earth. SiO2 is the main constituent of Earth's mantle and is the reference model system for the behavior of silicate melts at high pressure. Here, we apply our recently developed x-ray absorption technique to the density of SiO2 glass up to 110 GPa, doubling the pressure range...... for such measurements. Our density data validate recent molecular dynamics simulations and are in good agreement with previous experimental studies conducted at lower pressure. Silica glass rapidly densifies up to 40 GPa, but the density trend then flattens to become asymptotic to the density of SiO2 minerals above 60...... GPa. The density data present two discontinuities at similar to 17 and similar to 60 GPa that can be related to a silicon coordination increase from 4 to a mixed 5/6 coordination and from 5/6 to sixfold, respectively. SiO2 glass becomes denser than MgSiO3 glass at similar to 40 GPa, and its density...

  7. Enhanced Photocatalytic Activity of ZrO2-SiO2 Nanoparticles by Platinum Doping

    Directory of Open Access Journals (Sweden)

    Mohammad W. Kadi

    2013-01-01

    Full Text Available ZrO2-SiO2 mixed oxides were prepared via the sol-gel method. Photo-assisted deposition was utilized for doping the prepared mixed oxide with 0.1, 0.2, 0.3, and 0.4 wt% of Pt. XRD spectra showed that doping did not result in the incorporation of Pt within the crystal structure of the material. UV-reflectance spectrometry showed that the band gap of ZrO2-SiO2 decreased from 3.04 eV to 2.48 eV with 0.4 wt% Pt doping. The results show a specific surface area increase of 20%. Enhanced photocatalysis of Pt/ZrO2-SiO2 was successfully tested on photo degradation of cyanide under illumination of visible light. 100% conversion was achieved within 20 min with 0.3 wt% of Pt doped ZrO2-SiO2.

  8. Friction and wear studies on nylon-6/SiO2 nanocomposites

    NARCIS (Netherlands)

    de la Luz Garcia-Curiel, M.M.; de Rooij, Matthias B.; Winnubst, Aloysius J.A.; van Zyl, W.E.; Verweij, H.

    2004-01-01

    Composites of nanometer-sized silica (SiO2) filler incorporated in nylon-6 polymer were prepared by compression molding. Their friction and wear properties were investigated on a pin on disk tribometer by running a flat pin of steel against a composite disc. The morphologies of the composites as

  9. Enhanced field emission properties of carbon nanotube bundles confined in SiO2 pits

    Science.gov (United States)

    Lim, Yu Dian; Grapov, Dmitry; Hu, Liangxing; Kong, Qinyu; Tay, Beng Kang; Labunov, Vladimir; Miao, Jianmin; Coquet, Philippe; Aditya, Sheel

    2018-02-01

    It has been widely reported that carbon nanotubes (CNTs) exhibit superior field emission (FE) properties due to their high aspect ratios and unique structural properties. Among the various types of CNTs, random growth CNTs exhibit promising FE properties due to their reduced inter-tube screening effect. However, growing random growth CNTs on individual catalyst islands often results in spread out CNT bundles, which reduces overall field enhancement. In this study, significant improvement in FE properties in CNT bundles is demonstrated by confining them in microfabricated SiO2 pits. Growing CNT bundles in narrow (0.5 μm diameter and 2 μm height) SiO2 pits achieves FE current density of 1–1.4 A cm‑2, which is much higher than for freestanding CNT bundles (76.9 mA cm‑2). From the Fowler Nordheim plots, confined CNT bundles show a higher field enhancement factor. This improvement can be attributed to the reduced bundle diameter by SiO2 pit confinement, which yields bundles with higher aspect ratios. Combining the obtained outcomes, it can be conclusively summarized that confining CNTs in SiO2 pits yields higher FE current density due to the higher field enhancement of confined CNTs.

  10. Nano-TiCl4/SiO2: An efficient heterogeneous solid acid catalyst for ...

    Indian Academy of Sciences (India)

    Abstract. Nano-TiCl4/SiO2 was found to be an inexpensive and efficient heterogeneous solid acid catalyst for the synthesis of one-pot cascade synthesis of highly functionalized asymmetric tetrahydropyridines from the five-component condensation reaction of the para-substituted anilines and aromatic aldehydes with ethyl.

  11. Synthesis and characterization of silica–gold core-shell (SiO2@Au ...

    Indian Academy of Sciences (India)

    Synthesis and characterization of silica–gold core-shell (SiO2@Au) nanoparticles. DEEPIKA KANDPAL. 1,∗. , SUCHITA KALELE. 2 and S K KULKARNI. 2. 1. Department of Physics, G.B. Pant University of Agriculture & Technology,. Pantnagar 263 145, India. 2. Department of Physics, University of Pune, Pune 411 007, ...

  12. A microbiological evaluation of SiO2-coated textiles in hospital interiors

    DEFF Research Database (Denmark)

    Mogensen, Jeppe; Jørgensen, Poul-Erik; Thomsen, Trine Rolighed

    2016-01-01

    contact plates through a three-week period. By determining the level of contamination on these surfaces, the study illustrates that the SiO2-coated textile is possible to clean to an acceptable level below the critical limit value of 2,5 Colony Forming Units (CFU) per cm2. In comparison, the traditional...

  13. Hazards of TiO2 and amorphous SiO2 nanoparticles

    NARCIS (Netherlands)

    Reijnders, L.; Kahn, H.A.; Arif, I.A.

    2012-01-01

    TiO2 and amorphous SiO2 nanoparticles have been described as ‘safe’, ‘non-toxic’ and ‘environment friendly’ in scientific literature. However, though toxicity data are far from complete, there is evidence that these nanoparticles are hazardous. TiO2 nanoparticles have been found hazardous to humans

  14. Sol-Gel SiO2-CaO-P2O5 biofilm with surface engineered for medical application

    Directory of Open Access Journals (Sweden)

    Sonia Regina Federman

    2007-06-01

    Full Text Available Sol-gel film in the SiO2-CaO-P2O5 system was prepared from TEOS, TEP, alcohol and hydrated calcium nitrate in an acidic medium. The coatings were deposited on stainless steel using the dip-coating technique. After deposition, the composite was submitted to heat treatment, at different temperatures and exposure times to investigate the influence of such parameters on the surface morphology of the composite. The coated surfaces were characterized by AFM, SEM and FTIR. The present study showed that the formation of different textures (an important parameter in implant fixation could be controlled by temperature and time of heat treatment.

  15. Controlled fabrication of Si nanocrystal delta-layers in thin SiO2 layers by plasma immersion ion implantation for nonvolatile memories

    International Nuclear Information System (INIS)

    Bonafos, C.; Ben-Assayag, G.; Groenen, J.; Carrada, M.; Spiegel, Y.; Torregrosa, F.; Normand, P.; Dimitrakis, P.; Kapetanakis, E.; Sahu, B. S.; Slaoui, A.

    2013-01-01

    Plasma Immersion Ion Implantation (PIII) is a promising alternative to beam line implantation to produce a single layer of nanocrystals (NCs) in the gate insulator of metal-oxide semiconductor devices. We report herein the fabrication of two-dimensional Si-NCs arrays in thin SiO 2 films using PIII and rapid thermal annealing. The effect of plasma and implantation conditions on the structural properties of the NC layers is examined by transmission electron microscopy. A fine tuning of the NCs characteristics is possible by optimizing the oxide thickness, implantation energy, and dose. Electrical characterization revealed that the PIII-produced-Si NC structures are appealing for nonvolatile memories

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2013-09-30

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

  17. Effect of annealing on pulse laser deposition grown copper oxide thin film

    Science.gov (United States)

    Mistry, Vaibhavi H.; Mistry, Bhaumik V.; Modi, B. P.; Joshi, U. S.

    2017-05-01

    Cuprous oxide (Cu2O) is a promising non-toxic and low cost semiconductor with potential applications in photovoltaic devices and sensor applications. Copper oxide thin films were prepared on glass substrate by pulse laser deposition. The effects of annealing on the structural, optical and electrical properties of copper oxide thin films were studied. The films were annealed in air for different temperature ranging from 200 to 450 °C. X-ray diffraction patterns reveals that the films as-deposited and annealed at 200 and 250 °C are of cuprite structure with composition Cu2O. Annealing at 300 °C and above converts these films to CuO phase. The atomic force microscopy results show that both the phase has nanocrystalline and particle size of the films is increasing with increase in annealing temperature. The conversion from Cu2O to CuO phase was confirmed by a shift in the optical band gap from 2.20 eV to 1.74 eV. The annealing conditions play a major role in the structural properties of copper oxide thin films.

  18. Characterization of ZnO thin films grown on different p-Si substrate elaborated by solgel spin-coating method

    Energy Technology Data Exchange (ETDEWEB)

    Chebil, W., E-mail: Chbil.widad@live.fr [Laboratoire Physico-chimie des Matériaux, Unité de Service Commun de Recherche “High resolution X-ray diffractometer”, Département de Physique, Université de Monastir, Faculté des Sciences de Monastir, Avenue de l’Environnement, 5019 Monastir (Tunisia); Fouzri, A. [Laboratoire Physico-chimie des Matériaux, Unité de Service Commun de Recherche “High resolution X-ray diffractometer”, Département de Physique, Université de Monastir, Faculté des Sciences de Monastir, Avenue de l’Environnement, 5019 Monastir (Tunisia); Institut Supérieur des Sciences Appliquées et de Technologie de Sousse, Université de Sousse (Tunisia); Fargi, A. [Laboratoire de Microélectronique et Instrumentation, Faculté des Sciences de Monastir, Université de Monastir, Avenue de l’environnement, 5019 Monastir (Tunisia); Azeza, B.; Zaaboub, Z. [Laboratoire Micro-Optoélectroniques et Nanostructures, Faculté des Sciences de Monastir, Université de Monastir, Avenue de l' environnement, 5019 Monastir (Tunisia); and others

    2015-10-15

    Highlights: • High quality ZnO thin films grown on different p-Si substrates were successful obtained by sol–gel process. • PL measurement revealed that ZnO thin film grown on porous Si has the better optical quality. • I–V characteristics for all heterojunctions exhibit successful diode formation. • The diode ZnO/PSi shows a better photovoltaic effect under illumination with a maximum {sub Voc} of 0.2 V. - Abstract: In this study, ZnO thin films are deposited by sol–gel technique on p-type crystalline silicon (Si) with [100] orientation, etched silicon and porous silicon. The structural analyses showed that the obtained thin films were polycrystalline with a hexagonal wurtzite structure and preferentially oriented along the c-axis direction. Morphological study revealed the presence of rounded and facetted grains irregularly distributed on the surface of all samples. PL spectra at room temperature revealed that ZnO thin film grown on porous Si has a strong UV emission with low defects in the visible region comparing with ZnO grown on plat Si and etched Si surface. The heterojunction parameters were evaluated from the (I–V) under dark and illumination at room temperature. The ideality factor, barrier height and series resistance of heterojunction grown on different p-Si substrates are determined by using different methods. Best electrical properties are obtained for ZnO layer deposited on porous silicon.

  19. Nitrogen doping in atomic layer deposition grown titanium dioxide films by using ammonium hydroxide

    Energy Technology Data Exchange (ETDEWEB)

    Kaeaeriaeinen, M.-L., E-mail: marja-leena.kaariainen@lut.fi; Cameron, D.C.

    2012-12-30

    Titanium dioxide films have been created by atomic layer deposition using titanium chloride as the metal source and a solution of ammonium hydroxide in water as oxidant. Ammonium hydroxide has been used as a source of nitrogen for doping and three thickness series have been deposited at 350 Degree-Sign C. A 15 nm anatase dominated film was found to possess the highest photocatalytic activity in all film series. Furthermore almost three times better photocatalytic activity was discovered in the doped series compared to undoped films. The doped films also had lower resistivity. The results from X-ray photoemission spectroscopy showed evidence for interstitial nitrogen in the titanium dioxide structure. Besides, there was a minor red shift observable in the thickest samples. In addition the film conductivity was discovered to increase with the feeding pressure of ammonium hydroxide in the oxidant precursor. This may indicate that nitrogen doping has caused the decrease in the resistivity and therefore has an impact as an enhanced photocatalytic activity. The hot probe test showed that all the anatase or anatase dominant films were p-type and all the rutile dominant films were n-type. The best photocatalytic activity was shown by anatase-dominant films containing a small amount of rutile. It may be that p-n-junctions are formed between p-type anatase and n-type rutile which cause carrier separation and slow down the recombination rate. The combination of nitrogen doping and p-n junction formation results in superior photocatalytic performance. - Highlights: Black-Right-Pointing-Pointer We found all N-doped and undoped anatase dominating films p-type. Black-Right-Pointing-Pointer We found all N-doped and undoped rutile dominating films n-type. Black-Right-Pointing-Pointer We propose that p-n junctions are formed in anatase-rutile mixture films. Black-Right-Pointing-Pointer We found that low level N-doping has increased TiO{sub 2} conductivity. Black

  20. Amorphization and recrystallization of epitaxial ReSi2 films grown on Si(100)

    Science.gov (United States)

    Kim, Kun HO; Bai, G.; Nicolet, MARC-A.; Mahan, John E.; Geib, Kent M.

    1991-01-01

    The effects of implantation damage and the chemical species of the implant on structural and electrical properties of epitaxial ReSi2 films on Si(100) implanted with Si-28 or Ar-40 ions, at doses ranging from 10 to the 13th/sq cm to 10 to the 15th/sq cm, were investigated using the backscattering spectrometry, XRD, and the van der Pauw techniques. Results showed that ion implantation produces damage in the film, which increases monotonically with dose; the resistivity of the film decreases monotonically with dose.

  1. Bismuth onion thin film in situ grown on silicon wafer synthesized through a hydrothermal approach

    International Nuclear Information System (INIS)

    Zhao Yue; Liu Hong; Liu Jin; Hu Chenguo; Wang Jiyang

    2010-01-01

    Bismuth onion structured nanospheres with the same structure as carbon onions have been synthesized and observed. The nanospheres were synthesized through a hydrothermal method using bismuth hydroxide and silicon wafer as reactants. By controlling the heating temperature, heating time, and the pressure, nanoscale bismuth spheres can be in situ synthesized on silicon wafer, and forms a bismuth onion film on the substrate. The electronic property of the films was investigated. A formation mechanism of the formation of bismuth onions and the onion film has been proposed on the basis of experimental observations.

  2. Electron-diffraction and spectroscopical characterisation of ultrathin ZnS films grown by molecular beam epitaxy on GaP(0 0 1)

    International Nuclear Information System (INIS)

    Zhang, L.; Szargan, R.; Chasse, T.

    2004-01-01

    ZnS films were grown by molecular beam epitaxy employing a single compound effusion cell on GaP(0 0 1) substrate at different temperatures, and characterised by means of low energy electron diffraction, X-ray and ultra-violet photoelectron spectroscopy, angle-resolved ultra-violet photoelectron spectroscopy and X-ray emission spectroscopy. The GaP(0 0 1) substrate exhibits a (4x2) reconstruction after Ar ion sputtering and annealing at 370 deg. C. Crystal quality of the ZnS films depends on both film thickness and growth temperature. Thinner films grown at higher temperatures and thicker films grown at lower temperatures have better crystal quality. The layer-by-layer growth mode of the ZnS films at lower (25, 80 and 100 deg. C) temperatures changes to layer-by-layer-plus-island mode at higher temperatures (120, 150 and 180 deg. C). A chemical reaction takes place and is confined to the interface. The valence band offset of the ZnS-GaP heterojunction was determined to be 0.8±0.1 eV. Sulphur L 2,3 emission spectra of ZnS powder raw material and the epitaxial ZnS films display the same features, regardless of the existence of the Ga-S bonding in the film samples

  3. Efficient photocatalytic activity with carbon-doped SiO2 nanoparticles

    KAUST Repository

    Zhang, Dongen

    2013-01-01

    Photocatalysis provides a \\'green\\' approach to completely eliminate various kinds of contaminants that are fatal for current environmental and energy issues. Semiconductors are one of the most frequently used photocatalysts as they can absorb light over a wide spectral range. However, it is also well known that naked SiO2 is not an efficient photocatalyst due to its relatively large band gap, which could only absorb shortwave ultraviolet light. In this report, nanoscale particles of carbon-doped silicon dioxide (C-doped SiO2) for use in photocatalysis were successfully prepared by a facile one-pot thermal process using tetraethylorthosilicate (TEOS) as the source of both silicon and carbon. These particles were subsequently characterized by thermogravimetric analysis, X-ray diffraction, standard and high resolution transmission electron microscopy and X-ray photoelectron spectroscopy. The C-doped SiO2 displayed outstanding photocatalytic properties, as evidenced by its catalysis of Rhodamine B degradation under near-UV irradiation. We propose that carbon doping of the SiO2 lattice creates new energy states between the bottom of the conduction band and the top of the valence band, which narrows the band gap of the material. As a result, the C-doped SiO2 nanoparticles exhibit excellent photocatalytic activities in a neutral environment. The novel synthesis reported herein for this material is both energy efficient and environmentally friendly and as such shows promise as a technique for low-cost, readily scalable industrial production. © 2013 The Royal Society of Chemistry.

  4. Ultrathin Microporous SiO2 Membranes Photodeposited on Hydrogen Evolving Catalysts Enabling Overall Water Splitting

    KAUST Repository

    Bau, Jeremy A.

    2017-10-17

    Semiconductor systems for photocatalytic overall water splitting into H2 and O2 gases typically require metal cocatalyst particles, such as Pt, to efficiently catalyze H2 evolution. However, such metal catalyst surfaces also serve as recombination sites for H2 and O2, forming H2O. We herein report the photon-induced fabrication of microporous SiO2 membranes that can selectively restrict passage of O2 and larger hydrated ions while allowing penetration of protons, water, and H2. The SiO2 layers were selectively photodeposited on Pt nanoparticles on SrTiO3 photocatalyst by using tetramethylammonium (TMA) as a structure-directing agent (SDA), resulting in the formation of core–shell Pt@SiO2 cocatalysts. The resulting photocatalyst exhibited both improved overall water splitting performance under irradiation and with no H2/O2 recombination in the dark. The function of the SiO2 layers was investigated electrochemically by fabricating the SiO2 layers on a Pt electrode via an analogous cathodic deposition protocol. The uniform, dense, yet amorphous layers possess microporosity originating from ring structures formed during the hydrolysis of the silicate precursor in the presence of TMA, suggesting a double-role for TMA in coordinating silicate to cathodic surfaces and in creating a microporous material. The resulting layers were able to function as a molecular sieve, allowing for exclusive H2 generation while excluding unwanted side reactions by O2 or ferricyanide. The SiO2 layer is stable for extended periods of time in photocatalytic conditions, demonstrating promise as a nontoxic material for selective H2 evolution.

  5. Layer-dependent supercapacitance of graphene films grown by chemical vapor deposition on nickel foam

    KAUST Repository

    Chen, Wei

    2013-03-01

    High-quality, large-area graphene films with few layers are synthesized on commercial nickel foams under optimal chemical vapor deposition conditions. The number of graphene layers is adjusted by varying the rate of the cooling process. It is found that the capacitive properties of graphene films are related to the number of graphene layers. Owing to the close attachment of graphene films on the nickel substrate and the low charge-transfer resistance, the specific capacitance of thinner graphene films is almost twice that of the thicker ones and remains stable up to 1000 cycles. These results illustrate the potential for developing high-performance graphene-based electrical energy storage devices. © 2012 Elsevier B.V. All rights reserved.

  6. Thin-Film Solar Cells with InP Absorber Layers Directly Grown on Nonepitaxial Metal Substrates

    KAUST Repository

    Zheng, Maxwell

    2015-08-25

    The design and performance of solar cells based on InP grown by the nonepitaxial thin-film vapor-liquid-solid (TF-VLS) growth technique is investigated. The cell structure consists of a Mo back contact, p-InP absorber layer, n-TiO2 electron selective contact, and indium tin oxide transparent top electrode. An ex situ p-doping process for TF-VLS grown InP is introduced. Properties of the cells such as optoelectronic uniformity and electrical behavior of grain boundaries are examined. The power conversion efficiency of first generation cells reaches 12.1% under simulated 1 sun illumination with open-circuit voltage (VOC) of 692 mV, short-circuit current (JSC) of 26.9 mA cm-2, and fill factor (FF) of 65%. The FF of the cell is limited by the series resistances in the device, including the top contact, which can be mitigated in the future through device optimization. The highest measured VOC under 1 sun is 692 mV, which approaches the optically implied VOC of ≈795 mV extracted from the luminescence yield of p-InP. The design and performance of solar cells based on indium phosphide (InP) grown by the nonepitaxial thin-film vapor-liquid-solid growth technique is investigated. The cell structure consists of a Mo back contact, p-InP absorber layer, n-TiO2 electron selective contact, and an indium tin oxide transparent top electrode. The highest measured open circuit voltage (VOC) under 1 sun is 692 mV, which approaches the optically implied VOC of ≈795 mV extracted from the luminescence yield of p-InP.

  7. Single orientation graphene synthesized on iridium thin films grown by molecular beam epitaxy

    OpenAIRE

    Dangwal Pandey, A.; Krausert, Konstantin; Franz, D.; Grånäs, E.; Shayduk, R.; Müller, P.; Keller, Thomas F.; Noei, H.; Vonk, V.; Stierle, A.

    2016-01-01

    Heteroepitaxial iridium thin films were deposited on (0001) sapphire substrates by means of molecular beam epitaxy, and subsequently, one monolayer of graphene was synthesized by chemical vapor deposition. The influence of the growth parameters on the quality of the Ir films, as well as of graphene, was investigated system atically by means of low energy electron diffraction, x-ray reflectivity, x-ray diffraction, Auger electron spectroscopy, scanning electron microscopy, and atomic force mic...

  8. Structural characterization and magnetic properties of L10-MnAl films grown on different underlayers by molecular beam epitaxy

    Science.gov (United States)

    Takata, Fumiya; Gushi, Toshiki; Anzai, Akihito; Toko, Kaoru; Suemasu, Takashi

    2018-03-01

    We grow MnAl films on different underlayers by molecular beam epitaxy (MBE), and investigate their structural and magnetic properties. L10-ordered MnAl films were successfully grown both on an MgO(0 0 1) single-crystalline substrate and on an Mn4N(0 0 1) buffer layer formed on MgO(0 0 1) and SrTiO3(0 0 1) substrates. For the MgO substrate, post rapid thermal annealing (RTA) drastically improved the crystalline quality and the degree of L10-ordering, whereas no improvement in the crystallinity was achieved by altering the substrate temperature (TS) during MBE growth. However, high-quality L10-MnAl films were formed on the Mn4N buffer layer by simply varying TS. Structural analysis using X-ray diffraction showed MnAl on an MgO substrate had a cubic structure whereas MnAl on the Mn4N buffer had a tetragonal structure. This difference in crystal structure affected the magnetic properties of the MnAl films. The uniaxial magnetic anisotropy constant (Ku) was drastically improved by inserting an Mn4N buffer layer. We achieved a perpendicular magnetic anisotropy of Ku = 5.0 ± 0.7 Merg/cm3 for MnAl/Mn4N film on MgO and 6.0 ± 0.2 Merg/cm3 on STO. These results suggest that Mn4N has potential as an underlayer for L10-MnAl.

  9. Ethanol-to-Butadiene Conversion over SiO2-MgO Catalysts: Synthesis-Structure-Performance Relationships

    NARCIS (Netherlands)

    Angelici, C.

    2015-01-01

    The work presented in this PhD Thesis provides new insights into the underlying reasons that make SiO2-MgO materials excellent catalysts for the ethanol-to-butadiene Lebedev process. In particular, the preparation technique of choice affects the structural properties of the resulting SiO2-MgO

  10. The electrorheological properties of nano-sized SiO2 particle materials doped with rare earths

    International Nuclear Information System (INIS)

    Liu Yang; Liao Fuhui; Li Junran; Zhang Shaohua; Chen Shumei; Wei Chenguan; Gao Song

    2006-01-01

    Electrorheological (ER) materials of pure SiO 2 and SiO 2 doped with rare earths (RE = Ce, Gd, Y) (non-metallic glasses (silicates)) were prepared using Na 2 SiO 3 and RECl 3 as starting materials. The electrorheological properties are not enhanced by all rare earth additions. The material doped with Ce exhibits the best ER performance

  11. Sensitizing effects of ZnO quantum dots on red-emitting Pr3+-doped SiO2 phosphor

    CSIR Research Space (South Africa)

    Mbule, PS

    2012-05-01

    Full Text Available In this study, red cathodoluminescence (CL) ( emission=614 nm) was observed from Pr3+ ions in a glassy (amorphous) SiO2 host. This emission was enhanced considerably when ZnO quantum dots (QDs) were incorporated in the SiO2:Pr3+ suggesting...

  12. Preparation of Raspberry-like Superhydrophobic SiO2 Particles by Sol-gel Method and Its Potential Applications

    Directory of Open Access Journals (Sweden)

    Xu Gui-Long

    2011-12-01

    Full Text Available Raspberry‐like SiO2 particles with a nano‐micro‐binary structure were prepared by a simple sol‐gel method using tetraethoxysilane (TEOS and methyltriethoxysilane (MTES as precursors. The chemical components and morphology of the SiO2 particles were characterized by Fourier transform infrared spectroscopy (FT‐IR and a Transmission electron microscope (TEM. The surface topography and wetting behaviour of the raspberry‐like SiO2 surface were observed with a Scanning electron microscope (SEM and studied by the water/oil contact angle (CA, respectively. The thermal stability of the prepared SiO2 particles was characterized by TGA analysis. The results show that the highly dispersed SiO2 particles initially prepared by the sol‐gel method turn into raspberry‐like particles with during the aging process. The raspberry‐like SiO2 particles show superhydrophobicity and superoleophilicity across a wide range of pH values. The SiO2 particles were thermally stable up to 475°C, while above this temperature the hydrophobicity decreases and finally becomes superhydrophobic when the temperature reaches 600°C. The raspberry‐like SiO2 particles which were prepared have potential applications in the fields of superhydrophobic surfaces, water‐oil separation, anti‐corrosion and fluid transportation.

  13. Permeation barrier performance of Hot Wire-CVD grown silicon-nitride films treated by argon plasma

    International Nuclear Information System (INIS)

    Majee, S.; Cerqueira, M.F.; Tondelier, D.; Vanel, J.C.; Geffroy, B.; Bonnassieux, Y.; Alpuim, P.; Bourée, J.E.

    2015-01-01

    In this work SiN x thin films have been deposited by Hot-Wire Chemical Vapor Deposition (HW-CVD) technique to be used as encapsulation barriers for flexible organic electronic devices fabricated on polyethylene terephthalate (PET) substrates. First results of SiN x multilayers stacked and stacks of SiN x single-layers (50 nm each) separated by an Ar-plasma surface treatment are reported. The encapsulation barrier properties of these different multilayers are assessed using the electrical calcium degradation test by monitoring changes in the electrical conductance of encapsulated Ca sensors with time. The water vapor transmission rate is found to be slightly minimized (7 × 10 −3 g/m 2 day) for stacked SiN x single-layers exposed to argon plasma treatment during a short time (2 min) as compared to that for stacked SiN x single-layers without Ar plasma treatment. - Highlights: • SiN x films are grown using HW-CVD to be used as permeation barrier layer. • Ar plasma treatment is made between two successive SiN x films. • Electrical calcium degradation test is used to evaluate the WVTR values. • Lowest WVTR value of ~ 7 × 10 -3 g/m 2 .day is reported

  14. Characterization of Optical and Electrical Properties of Transparent Conductive Boron-Doped Diamond thin Films Grown on Fused Silica

    Directory of Open Access Journals (Sweden)

    Bogdanowicz Robert

    2014-12-01

    Full Text Available Abstract A conductive boron-doped diamond (BDD grown on a fused silica/quartz has been investigated. Diamond thin films were deposited by the microwave plasma enhanced chemical vapor deposition (MW PECVD. The main parameters of the BDD synthesis, i.e. the methane admixture and the substrate temperature were investigated in detail. Preliminary studies of optical properties were performed to qualify an optimal CVD synthesis and film parameters for optical sensing applications. The SEM micro-images showed the homogenous, continuous and polycrystalline surface morphology; the mean grain size was within the range of 100-250 nm. The fabricated conductive boron-doped diamond thin films displayed the resistivity below 500 mOhm cm-1 and the transmittance over 50% in the VIS-NIR wavelength range. The studies of optical constants were performed using the spectroscopic ellipsometry for the wavelength range between 260 and 820 nm. A detailed error analysis of the ellipsometric system and optical modelling estimation has been provided. The refractive index values at the 550 nm wavelength were high and varied between 2.24 and 2.35 depending on the percentage content of methane and the temperature of deposition.

  15. Flexible Al-doped ZnO films grown on PET substrates using linear facing target sputtering for flexible OLEDs

    International Nuclear Information System (INIS)

    Jeong, Jin-A; Shin, Hyun-Su; Choi, Kwang-Hyuk; Kim, Han-Ki

    2010-01-01

    We report the characteristics of flexible Al-doped zinc oxide (AZO) films prepared by a plasma damage-free linear facing target sputtering (LFTS) system on PET substrates for use as a flexible transparent conducting electrode in flexible organic light-emitting diodes (OLEDs). The electrical, optical and structural properties of LFTS-grown flexible AZO electrodes were investigated as a function of dc power. We obtained a flexible AZO film with a sheet resistance of 39 Ω/□ and an average transmittance of 84.86% in the visible range although it was sputtered at room temperature without activation of the Al dopant. Due to the effective confinement of the high-density plasma between the facing AZO targets, the AZO film was deposited on the PET substrate without plasma damage and substrate heating caused by bombardment of energy particles. Moreover, the flexible OLED fabricated on the AZO/PET substrate showed performance similar to the OLED fabricated on a ITO/PET substrate in spite of a lower work function. This indicates that LFTS is a promising plasma damage-free and low-temperature sputtering technique for deposition of flexible and indium-free AZO electrodes for use in cost-efficient flexible OLEDs.

  16. Cr2O3 thin films grown at room temperature by low pressure laser chemical vapour deposition

    International Nuclear Information System (INIS)

    Sousa, P.M.; Silvestre, A.J.; Conde, O.

    2011-01-01

    Chromia (Cr 2 O 3 ) has been extensively explored for the purpose of developing widespread industrial applications, owing to the convergence of a variety of mechanical, physical and chemical properties in one single oxide material. Various methods have been used for large area synthesis of Cr 2 O 3 films. However, for selective area growth and growth on thermally sensitive materials, laser-assisted chemical vapour deposition (LCVD) can be applied advantageously. Here we report on the growth of single layers of pure Cr 2 O 3 onto sapphire substrates at room temperature by low pressure photolytic LCVD, using UV laser radiation and Cr(CO) 6 as chromium precursor. The feasibility of the LCVD technique to access selective area deposition of chromia thin films is demonstrated. Best results were obtained for a laser fluence of 120 mJ cm -2 and a partial pressure ratio of O 2 to Cr(CO) 6 of 1.0. Samples grown with these experimental parameters are polycrystalline and their microstructure is characterised by a high density of particles whose size follows a lognormal distribution. Deposition rates of 0.1 nm s -1 and mean particle sizes of 1.85 μm were measured for these films.

  17. Zn{sub x}Zr{sub y}O{sub z} thin films grown by DC magnetron sputtering

    Energy Technology Data Exchange (ETDEWEB)

    Sanchez, O. [Instituto de Ciencia de Materiales de Madrid (CSIC), Madrid (Spain); Hernandez-Velez, M. [Departamento de Fisica Aplicada, Universidad Autonoma de Madrid (Spain)

    2017-10-15

    The structural and optical properties of thin films deposited by DC reactive magnetron co-sputtering using Zn and Zr targets in argon and oxygen gas mixtures at room temperature are reported. The power applied to the Zr cathode was kept constant, while that applied to the Zn cathode was varied between 0 and 150 W to produce very different Zn{sub x}Zr{sub y}O{sub z} ternary compounds with Zn/Zr atomic ratios in the range of 0.1-10. The composition, crystalline structure, and optical properties of the samples were determined by EDX, XRD, FTIR, and UV-visible spectroscopies. The grown films are polycrystalline, and the preferred crystallographic orientation depends on the Zn atomic concentration in the film. The optical transmission in the UV-visible range is approximately 80% in all cases, and as the Zn atomic content increases, the absorption edge shifts to longer wavelengths. The optical band gap, E{sub g}, shifted from 5.5 to 3.5 eV when the Zn/Zr atomic ratio was increased. The results indicate the potential use of these materials in optoelectronic applications. (copyright 2017 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  18. Crystallinity and superconductivity of as-grown MgB2 thin films with AlN buffer layers

    International Nuclear Information System (INIS)

    Tsujimoto, K.; Shimakage, H.; Wang, Z.; Kaya, N.

    2005-01-01

    The effects of aluminum nitride (AlN) buffer layers on the superconducting properties of MgB 2 thin film were investigated. The AlN buffer layers and as-grown MgB 2 thin films were deposited in situ using the multiple-target sputtering system. The best depositing condition for the AlN/MgB 2 bi-layer occurred when the AlN was deposited on c-cut sapphire substrates at 290 deg. C. The crystallinity of the AlN/MgB 2 bi-layer was studied using the XRD φ-scan and it showed that AlN and MgB 2 had the same in-plane alignment rotated at an angle of 30 deg. as compared to c-cut sapphire. The critical temperature of the MgB 2 film was 29.8 K and the resistivity was 50.0 μΩ cm at 40 K

  19. Single orientation graphene synthesized on iridium thin films grown by molecular beam epitaxy

    Energy Technology Data Exchange (ETDEWEB)

    Dangwal Pandey, A., E-mail: arti.pandey@desy.de; Grånäs, E.; Shayduk, R.; Noei, H.; Vonk, V. [Deutsches Elektronen-Synchrotron (DESY), D-22607 Hamburg (Germany); Krausert, K.; Franz, D.; Müller, P.; Keller, T. F.; Stierle, A., E-mail: andreas.stierle@desy.de [Deutsches Elektronen-Synchrotron (DESY), D-22607 Hamburg (Germany); Fachbereich Physik, Universität Hamburg, D-22607 Hamburg (Germany)

    2016-08-21

    Heteroepitaxial iridium thin films were deposited on (0001) sapphire substrates by means of molecular beam epitaxy, and subsequently, one monolayer of graphene was synthesized by chemical vapor deposition. The influence of the growth parameters on the quality of the Ir films, as well as of graphene, was investigated systematically by means of low energy electron diffraction, x-ray reflectivity, x-ray diffraction, Auger electron spectroscopy, scanning electron microscopy, and atomic force microscopy. Our study reveals (111) oriented iridium films with high crystalline quality and extremely low surface roughness, on which the formation of large-area epitaxial graphene is achieved. The presence of defects, like dislocations, twins, and 30° rotated domains in the iridium films is also discussed. The coverage of graphene was found to be influenced by the presence of 30° rotated domains in the Ir films. Low iridium deposition rates suppress these rotated domains and an almost complete coverage of graphene was obtained. This synthesis route yields inexpensive, air-stable, and large-area graphene with a well-defined orientation, making it accessible to a wider community of researchers for numerous experiments or applications, including those which use destructive analysis techniques or irreversible processes. Moreover, this approach can be used to tune the structural quality of graphene, allowing a systematic study of the influence of defects in various processes like intercalation below graphene.

  20. Investigation of mechanical properties of CVD grown titanium silicon nitride thin films under reduced atmosphere

    Science.gov (United States)

    Guha, Spandan; Das, Soham; Bandyopadhyay, Asish; Das, Santanu; Swain, Bibhu P.

    2018-01-01

    Titanium silicon nitride (TiSiN) thin films were deposited by thermal chemical vapour deposition using TiO2 + Si3N4 powder with different H2 flow rates. Morphological, structural, and mechanical properties of deposited TiSiN films were characterized using different techniques by SEM, XRD, Raman, and nano-indentation. SEM images reveal that surface roughness of TiSiN thin films decreased with increasing of H2 flow rate. The Raman spectroscopy indicated that the intensity of acoustic phonon mode decreases, whereas intensity of optical phonon mode increases with increasing of H2 flow rate. The maximum hardness, Young's modulus, and yield strength of the TiSiN films are 18.23, 185.26, and 83.2 GPa, respectively. The crystallite size and lattice strain of TiSiN thin films vary 2.08-4.43 nm and 0.02-0.055, respectively, for different H2 flow rates. The quantitative and qualitative analyses of TiSiN thin were carried out using the Origin 9.0 software.

  1. Intermediate phase evolution in YBCO thin films grown by the TFA process

    International Nuclear Information System (INIS)

    Zalamova, K; Pomar, A; Palau, A; Puig, T; Obradors, X

    2010-01-01

    The YBCO thin film growth process from TFA precursors involves a complex reaction path which includes several oxide, fluoride and oxyfluoride intermediate phases, and the final microstructure and properties of the films are strongly influenced by the morphological and chemical evolution of these intermediate phases. In this work we present a study of the evolution of the intermediate phases involved in the TFA YBCO growth process under normal pressure conditions and we show that the oxygen partial pressure during pyrolysis of the TFA precursors is an important parameter. The Cu phase after the TFA pyrolysis can be either CuO, Cu 2 O or a mixture of both as the oxygen partial pressure is modified. The kinetics evolution of the intermediate phases has been determined for films pyrolysed in oxygen and nitrogen atmospheres and it is concluded that non-equilibrium phase transformations influence the reaction path towards epitaxial YBCO films and its microstructure. The intermediate phase evolution in these two series of films is summarized in kinetic phase diagrams.

  2. Electrochromism in surface modified crystalline WO3 thin films grown by reactive DC magnetron sputtering

    Science.gov (United States)

    Karuppasamy, A.

    2013-10-01

    In the present work, tungsten oxide thin films were deposited at various oxygen chamber pressures (1.0-5.0 × 10-3 mbar) by maintaining the sputtering power density and argon pressure constant at 3.0 W/cm2 and 1.2 × 10-2 mbar, respectively. The role of surface morphology and porosity on the electrochromic properties of crystalline tungsten oxide thin films has been investigated. XRD and Raman studies reveal that all the samples post annealed at 450 ̊C in air for 3.0 h settle in monoclinic crystal system of tungsten oxide (W18O49). Though the phase of material is indifferent to oxygen pressure variations (PO2), morphology and film density shows a striking dependence on PO2. A systematic study on plasma (OES), morphology, optical and electrochromic properties of crystalline tungsten oxide reveal that the films deposited at PO2 of 2.0 × 10-3 mbar exhibit better coloration efficiency (58 cm2/C), electron/ion capacity (Qc: -25 mC/cm2), and reversibility (92%). This is attributed to the enhanced surface properties like high density of pores and fine particulates (100 nm) and to lesser bulk density of the film (ρ/ρo = 0.84) which facilitates the process of intercalation/de-intercalation of protons and electrons. These results show good promise toward stable and efficient crystalline tungsten oxide based electrochromic device applications.

  3. Annealing effects on photoluminescence of SiNx films grown by PECVD

    International Nuclear Information System (INIS)

    Komarov, F.F.; Parkhomenko, I.N.; Vlasukova, L.A.; Milchanin, O.V.; Togambayeva, A.K.; Kovalchuk, N.S.

    2013-01-01

    Si-rich and N-rich silicon nitride films were deposited at low temperature 300 °C by using plasma-enhanced chemical vapor deposition (PECVD). The optical and structural properties of these films have been investigated by ellipsometry, Rutherford backscattering (RBS), transmission electron microscopy (TEM), Raman spectroscopy (RS) and photoluminescence (PL). The formation of silicon clusters in both Si-rich and N-rich silicon nitride films after annealing at 900 °C and 1000 °C for hour in N 2 ambient has been revealed by TEM. Dependency of PL spectra on stoichiometry and post-annealing temperature was analyzed. The contribution of Si and N-related defects in emitting properties of Si-rich and N-rich SiN x has been discussed. (authors)

  4. InAs film grown on Si(111) by metal organic vapor phase epitaxy

    International Nuclear Information System (INIS)

    Caroff, P; Jeppsson, M; Mandl, B; Wernersson, L-E; Wheeler, D; Seabaugh, A; Keplinger, M; Stangl, J; Bauer, G

    2008-01-01

    We report the successful growth of high quality InAs films directly on Si(111) by Metal Organic Vapor Phase Epitaxy. A nearly mirror-like and uniform InAs film is obtained at 580 0 C for a thickness of 2 μm. We measured a high value of the electron mobility of 5100 cm 2 /Vs at room temperature. The growth is performed using a standard two-step procedure. The influence of the nucleation layer, group V flow rate, and layer thickness on the electrical and morphological properties of the InAs film have been investigated. We present results of our studies by Atomic Force Microscopy, Scanning Electron Microscopy, electrical Hall/van der Pauw and structural X-Ray Diffraction characterization

  5. Characteristics of CuInSe2 thin films grown by the selenization method

    International Nuclear Information System (INIS)

    Kim, Sang Deok; Kim, Hyeong Joon; Adurodija, Frederick Ojo; Yoon, Kyeong Hoon; Song, Jin Soo

    1999-01-01

    CuInSe 2 thin films were formed from a selenization of co-sputtered Cu-In alloy layers which consisted of only two phases, CuIn 2 and Cu 11 In 9 . A linear dependence of the Cu-In alloy film composition on the Cu/In sputtering power was found. The metallic layers were selenized in vacuum or at 1 atm. A small number of Cu-Se and In-Se compounds was observed during the early stage of selenization, and single-phase CuInSe 2 was more easily formed in vacuum than at atmospheric pressure. Therefore, CuInSe 2 films selenized in vacuum showed larger grain sizes, smoother surfaces, and denser microstructures than those selenized at 1 atm

  6. Modeling the transport properties of epitaxially grown thermoelectric oxide thin films using spectroscopic ellipsometry

    KAUST Repository

    Sarath Kumar, S. R.

    2012-02-01

    The influence of oxygen vacancies on the transport properties of epitaxial thermoelectric (Sr,La)TiO3 thin films is determined using electrical and spectroscopic ellipsometry (SE) measurements. Oxygen vacancy concentration was varied by ex-situ annealing in Ar and Ar/H2. All films exhibited degenerate semiconducting behavior, and electrical conductivity decreased (258–133 S cm−1) with increasing oxygen content. Similar decrease in the Seebeck coefficient is observed and attributed to a decrease in effective mass (7.8–3.2 me ), as determined by SE. Excellent agreement between transport properties deduced from SE and direct electrical measurements suggests that SE is an effective tool for studying oxide thin film thermoelectrics.

  7. Characteristics of CuInSe sub 2 thin films grown by the selenization method

    CERN Document Server

    Kim, S D; Adurodija, F O; Yoon, K H; Song, J S

    1999-01-01

    CuInSe sub 2 thin films were formed from a selenization of co-sputtered Cu-In alloy layers which consisted of only two phases, CuIn sub 2 and Cu sub 1 sub 1 In sub 9. A linear dependence of the Cu-In alloy film composition on the Cu/In sputtering power was found. The metallic layers were selenized in vacuum or at 1 atm. A small number of Cu-Se and In-Se compounds was observed during the early stage of selenization, and single-phase CuInSe sub 2 was more easily formed in vacuum than at atmospheric pressure. Therefore, CuInSe sub 2 films selenized in vacuum showed larger grain sizes, smoother surfaces, and denser microstructures than those selenized at 1 atm.

  8. SiO2/polyacrylonitrile membranes via centrifugal spinning as a separator for Li-ion batteries

    Science.gov (United States)

    Yanilmaz, Meltem; Lu, Yao; Li, Ying; Zhang, Xiangwu

    2015-01-01

    Centrifugal spinning is a fast, cost-effective and safe alternative to the electrospinning technique, which is commonly used for making fiber-based separator membranes. In this work, SiO2/polyacrylonitrile (PAN) membranes were produced by using centrifugal spinning and they were characterized by using different electrochemical techniques for use as separators in Li-ion batteries. SiO2/PAN membranes exhibited good wettability and high ionic conductivity due to their highly porous fibrous structure. Compared with commercial microporous polyolefin membranes, SiO2/PAN membranes had larger liquid electrolyte uptake, higher electrochemical oxidation limit, and lower interfacial resistance with lithium. SiO2/PAN membrane separators were assembled into lithium/lithium iron phosphate cells and these cells delivered high capacities and exhibited good cycling performance at room temperature. In addition, cells using SiO2/PAN membranes showed superior C-rate performance compared to those using microporous PP membrane.

  9. Fluence dependent electrical conductivity in aluminium thin films grown by infrared pulsed laser deposition

    Energy Technology Data Exchange (ETDEWEB)

    Rebollar, Esther, E-mail: e.rebollar@csic.es [Instituto de Química Física Rocasolano, IQFR-CSIC, Serrano 19, 28006 Madrid (Spain); Martínez-Tong, Daniel E. [Instituto de Estructura de la Materia, IEM-CSIC, Serrano 121, 28006 Madrid (Spain); Sanz, Mikel; Oujja, Mohamed; Marco, José F. [Instituto de Química Física Rocasolano, IQFR-CSIC, Serrano 19, 28006 Madrid (Spain); Ezquerra, Tiberio A. [Instituto de Estructura de la Materia, IEM-CSIC, Serrano 121, 28006 Madrid (Spain); Castillejo, Marta [Instituto de Química Física Rocasolano, IQFR-CSIC, Serrano 19, 28006 Madrid (Spain)

    2016-11-30

    Highlights: • IR pulsed laser ablation of aluminium gives rise to smooth layers of several tens of nanometers. • Irradiation at fluences around 2.7 J/cm{sup 2} and above 7 J/cm{sup 2} resulted in deposition of amorphous aluminium oxide films and metallic aluminium films respectively. • Highly ionized species are more abundant in the ablation plumes generated at higher fluences. • It is possible to control by PLD the metal or dielectric character of the films. - Abstract: We studied the effect of laser fluence on the morphology, composition, structure and electric conductivity of deposits generated by pulsed laser ablation of a metallic aluminium target in vacuum using a Q-switched Nd:YAG laser (1064 nm, 15 ns). Upon irradiation for one hour at a repetition rate of 10 Hz, a smooth layer of several tens of nanometres, as revealed by atomic force microscopy (AFM) was deposited on glass. Surface chemical composition was determined by X-ray photoelectron spectroscopy, and to study the conductivity of deposits both I–V curves and conductive-AFM measurements were performed. Irradiation at fluences around 2.7 J/cm{sup 2} resulted in deposition of amorphous aluminium oxide films. Differently, at higher fluences above 7 J/cm{sup 2}, the films are constituted by metallic aluminium. Optical emission spectroscopy revealed that highly ionized species are more abundant in the ablation plumes generated at higher fluences. The results demonstrate the possibility to control by PLD the metal or dielectric character of the films.

  10. Effect of thermal annealing on the optical and electronic properties of ZnO thin films grown on p-Si substrates

    Energy Technology Data Exchange (ETDEWEB)

    Han, W.G. [Department of Materials Science and Engineering, Hanyang University, 17 Haengdang-dong, Seongdong-gu, Seoul 133-791 (Korea, Republic of); Kang, S.G. [Department of Materials Science and Engineering, Hanyang University, 17 Haengdang-dong, Seongdong-gu, Seoul 133-791 (Korea, Republic of); Kim, T.W. [Advanced Semiconductor Research Center, Division of Electrical and Computer Engineering, Hanyang University, 17 Haengdang-dong, Seongdong-gu, Seoul 133-791 (Korea, Republic of)]. E-mail: twk@hanyang.ac.kr; Kim, D.W. [Semiconductor Materials Laboratory, Nano-Device Research Center, Korea Institute of Science and Technology, P.O. Box 131, Cheongryang, Seoul 130-650 (Korea, Republic of); Cho, W.J. [Semiconductor Materials Laboratory, Nano-Device Research Center, Korea Institute of Science and Technology, P.O. Box 131, Cheongryang, Seoul 130-650 (Korea, Republic of)

    2005-05-30

    The effects of annealing on the optical and the electronics properties of ZnO thin films grown on p-Si(1 0 0) substrates by using radio frequency magnetron sputtering were investigated by X-ray diffraction (XRD), transmission electron microscopy (TEM), photoluminescence (PL), and X-ray photoelectron spectroscopy (XPS) measurements. The XRD patterns and pole figures showed that the crystallinity of the ZnO films grown on p-Si(1 0 0) substrates was improved by thermal treatment. XRD patterns, pole figures, and TEM images showed that the as-grown and the annealed ZnO films grown on Si(1 0 0) substrates had a c-axis preferential orientation in the [0 0 0 1] crystal direction. The PL spectra showed that luminescence peaks related to the free excitons and the deep levels appeared after annealing. The XPS spectra showed that the peak positions corresponding to the O 1s and the Zn 2p shifted slightly after thermal treatment. These results can help improve understanding of thermal effects on the optical and the electronic properties of ZnO thin films grown on p-Si(1 0 0) substrates.

  11. 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)

  12. Influence of annealing temperature on ZnO thin films grown by dual ...

    Indian Academy of Sciences (India)

    In electrical characterization as well, when annealing temperature was increased from 400 to 600 °C, room temperature electron mobility enhanced from 6.534 to 13.326 cm2/V s, and then reduced with subsequent increase in temperature. Therefore, 600 °C annealing temperature produced good-quality ZnO film, suitable ...

  13. Influence of interface reactions on the YBCO films grown by fluorine-free solution route

    DEFF Research Database (Denmark)

    Zhao, Yue; Wu, Wei; Tang, Xiao

    2015-01-01

    Fabrication of full-stacked coated conductors by all-chemical-solution routes exhibit a great potential in view of further reducing the cost and increasing the throughput for industrialization. Growth of YBa2Cu3O7−x (YBCO) superconducting films by fluorine-free metal organic deposition routes (FF...

  14. Effect of pulse biasing on the morphology of diamond films grown by hot filament CVD

    International Nuclear Information System (INIS)

    Beake, B.D.; Hussain, I.U.; Rego, C.; Ahmed, W.

    1999-01-01

    There has been considerable interest in the chemical vapour deposition (CVD) of diamond due to its unique mechanical, optical and electronic properties, which make it useful for many applications. For use in optical and electronic applications further developments in the CVD process are required to control the surface morphology and crystal size of the diamond films. These will require a detailed understanding of both the nucleation and growth processes that effect the properties. The technique of bias enhanced nucleation (BEN) of diamond offers better reproducibility than conventional pre-treatment methods such as mechanical abrasion. Atomic force microscopy (AFM) and scanning electron microscopy (SEM) have been used study the surface modification of diamond films on silicon substrates during pulse biased growth in a hot filament CVD reactor. Pre-abraded silicon substrates were subjected to a three-step sequential growth process: (i) diamond deposition under standard CVD conditions, (ii) bias pre-treatment and (iii) deposition under standard conditions. The results show that the bias pre-treatment time is a critical parameter controlling the surface morphology and roughness of the diamond films deposited. Biasing reduces the surface roughness from 152 nm for standard CVD diamond to 68 nm for the 2.5 minutes pulse biased film. Further increase in the bias time results in an increase in surface roughness and crystallite size. (author)

  15. Structural changes induced spin-reorientation of ultrathin Mn films grown on Ag(001)

    International Nuclear Information System (INIS)

    Ouarab, N.; Haroun, A.; Baadji, N.

    2016-01-01

    The strained body centered tetragonal (bct) Mn ultrathin film from lattice parameter a=2.89 Å to lattice value of 2.73 Å induces anti-ferromagnetic behavior between Mn layers. The magnetic easy axis of Mn film was demonstrated theoretically to switch from the in-plane to out-of-plane by magneto-optical Kerr effect investigation. By including spin–orbit coupling in full potential linearized augmented plane waves and linearized muffin-tin orbitals methods, manganese ultrathin film displays different magnetic behaviors and the spin-reorientation transition is shown to be correlated to these structural changes. The calculated magnetic moment of manganese planes are enhanced and reach a value of ~4.02 μ B . The polar magneto-optical Kerr effect is calculated for a photon energy range extended to 15 eV. It shows a pronounced peak in visible light. - Highlights: • The applied strain in Mn-bct structure induces anti-ferromagnetic behavior. • The easy magnetization axis is demonstrated to be out-of-plane. • The magnetic moment of Mn-layers are enhanced and reach a value of ~4.02 μ B . • Kerr spectra show significant polar responses for Mn films in the visible range. • The prominent structures in the Kerr spectra have been identified.

  16. Positron beam and RBS studies of thermally grown oxide films on stainless steel grade 304

    Science.gov (United States)

    Horodek, P.; Siemek, K.; Kobets, A. G.; Kulik, M.; Meshkov, I. N.

    2015-04-01

    The formation of oxide films on surfaces of stainless steel 304 AISI annealed at 800 °C in vacuum, air and in flow N2 atmospheres was studied using variable energy positron beam technique (VEP) and Rutherford backscattering/nuclear reaction (RBS/NR) methods. In frame of these studies, Doppler broadening of annihilation line (DB) measurements were performed. For a sample heated in vacuum the oxide film ca. 8 nm is observed. For specimens oxidized in air and N2 the multi-layered oxide films of about a few hundred nanometers are recognized. The RBS/NR measurements have shown that the sample annealed in vacuum contains a lower quantity of oxygen while for samples heated in the air and N2 non-linear and rather linear time-dependency are observed, respectively. The thicknesses of total oxide films obtained from RBS/NR tests are in good agreement with the VEP results. Time evolution of the oxide growing was studied as well.

  17. Carrier transport in polycrystalline silicon thin films solar cells grown on a highly textured structure

    Czech Academy of Sciences Publication Activity Database

    Honda, Shinya; Takakura, H.; Hamakawa, Y.; Muhida, R.; Kawamura, T.; Harano, T.; Toyama, T.; Okamoto, H.

    2004-01-01

    Roč. 43, 9A (2004), s. 5955-5959 ISSN 0021-4922 Institutional research plan: CEZ:AV0Z1010914 Keywords : polycrystalline silicon thin film * solar cells * substrate texture Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 1.142, year: 2004

  18. Influence of annealing temperature on ZnO thin films grown by dual ...

    Indian Academy of Sciences (India)

    Administrator

    ties were measured using four-probe Hall measurement set-up in Van der Pauw geometry with a magnetic field of. 0⋅50 Tesla. 3. Results and discussion. 3.1 Structural properties. Figure 1(a) demonstrated the variation of XRD spectra from ZnO films for different annealing temperatures. It should be mentioned at this point ...

  19. Thermally induced evolution of sol–gel grown WO3 films on ITO/glass substrates

    NARCIS (Netherlands)

    Caruso, T.; Castriota, M.; Policicchio, A.; Fasanella, A.; Santo, M.P. De; Ciuchi, F.; Desiderio, G.; Rosa, S. La; Rudolf, P.; Agostino, R.G.; Cazzanelli, E.

    2014-01-01

    The electronic, morphological and structural properties of WO3 thin films, synthesized via a sol-gel route and deposited on ITO/glass substrates by spin-coating, were analyzed as a function of annealing temperature (100-700 degrees C range) by Scanning Electron Microscopy, Atomic Force Microscopy,

  20. Tungsten oxide thin films grown by thermal evaporation with high resistance to leaching

    Energy Technology Data Exchange (ETDEWEB)

    Correa, Diogo S. [Universidade Federal de Pelotas (UFPel), RS (Brazil). Centro de Ciencias Quimicas, Farmaceuticas e de Alimentos; Pazinato, Julia C.O.; Freitas, Mauricio A. de; Radtke, Claudio; Garcia, Irene T.S., E-mail: irene@iq.ufrgs.br [Universidade Federal do Rio Grande do Sul (UFRGS), Porto Alegre, RS (Brazil). Instituto de Quimica; Dorneles, Lucio S. [Universidade Federal de Santa Maria (UFSM), RS (Brazil). Centro de Ciencias Naturais e Exatas

    2014-05-15

    Tungsten oxides show different stoichiometries, crystal lattices and morphologies. These characteristics are important mainly when they are used as photocatalysts. In this work tungsten oxide thin films were obtained by thermal evaporation on (100) silicon substrates covered with gold and heated at 350 and 600 °C, with different deposition times. The stoichiometry of the films, morphology, crystal structure and resistance to leaching were characterized through X-ray photoelectron spectroscopy, micro-Raman spectroscopy, scanning and transmission electron microscopy, X-ray diffractometry, Rutherford backscattering spectrometry and O{sup 16} (α,α')O{sup 16} resonant nuclear reaction. Films obtained at higher temperatures show well-defined spherical nanometric structure; they are composed of WO{sub 3.1} and the presence of hydrated tungsten oxide was also observed. The major crystal structure observed is the hexagonal. Thin films obtained through thermal evaporation present resistance to leaching in aqueous media and excellent performance as photocatalysts, evaluated through the degradation of the methyl orange dye. (author)

  1. Preparation and characterization of LaNiO3 films grown by metal ...

    Indian Academy of Sciences (India)

    Administrator

    Xi'an 710062, P.R. China; School of Chemistry and Chemical Engineering, Shaanxi Normal University, ... (h00) orientation depends on pyrolysis temperature, annealing temperature and thickness of LaNiO3 layers. The LaNiO3 films prepared under optimal condition indicate highly (h00) orientation and a rather smooth.

  2. Preparation and characterization of LaNiO3 films grown by metal ...

    Indian Academy of Sciences (India)

    The LaNiO3 films prepared under optimal condition indicate highly (ℎ00) orientation and a rather smooth surface. ... Key Laboratory of Applied Surface and Colloid Chemistry (Shaanxi Normal University), Ministry of Education, Xi'an 710062, P.R. China; School of Chemistry and Chemical Engineering, Shaanxi Normal ...

  3. Structural transformations in MoO{sub x} thin films grown by pulsed laser deposition

    Energy Technology Data Exchange (ETDEWEB)

    Camacho-Lopez, M.A.; Haro-Poniatowski, E. [Departamento de Fisica, Laboratorio de Optica Cuantica, Universidad Autonoma Metropolitana Iztapalapa, Apdo. Postal 55-534, 09340, Mexico D. F. (Mexico); Escobar-Alarcon, L. [Departamento de Fisica, Instituto Nacional de Investigaciones Nucleares, Apdo. Postal 18-1027, 11801, Mexico D. F. (Mexico)

    2004-01-01

    In this work, laser-induced crystallization in MoO{sub x} thin films (1.8{<=}x{<=}2.1) is reported. This transformation involves a MoO{sub x} oxidation and subsequently a crystallization process from amorphous MoO{sub 3} to crystalline {alpha}MoO{sub 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{sub x} to the thermodynamically stable {alpha}MoO{sub 3} crystalline phase. For the thin films deposited on Si(100) the structural transformation is from amorphous MoO{sub x} to a mixture of {alpha}MoO{sub 3} and the thermodynamically unstable {beta}MoO{sub 3} crystalline phases. The structural transformations are also characterized by scanning electron microscopy and light-transmission experiments. (orig.)

  4. Structural changes induced spin-reorientation of ultrathin Mn films grown on Ag(001)

    Energy Technology Data Exchange (ETDEWEB)

    Ouarab, N., E-mail: ouarab_nourdine@yahoo.fr [Quantum Physics and Dynamical Systems Laboratory, Ferhat Abbas University of Sétif (Algeria); Semiconductor Technology Research Center for Energetic-(CRTSE), 02, Bd Frantz Fanon Algiers, BP N° 140 (Algeria); Haroun, A. [Quantum Physics and Dynamical Systems Laboratory, Ferhat Abbas University of Sétif (Algeria); Baadji, N. [School of Physics and CRANN, Trinity College, Dublin 2 (Ireland)

    2016-12-01

    The strained body centered tetragonal (bct) Mn ultrathin film from lattice parameter a=2.89 Å to lattice value of 2.73 Å induces anti-ferromagnetic behavior between Mn layers. The magnetic easy axis of Mn film was demonstrated theoretically to switch from the in-plane to out-of-plane by magneto-optical Kerr effect investigation. By including spin–orbit coupling in full potential linearized augmented plane waves and linearized muffin-tin orbitals methods, manganese ultrathin film displays different magnetic behaviors and the spin-reorientation transition is shown to be correlated to these structural changes. The calculated magnetic moment of manganese planes are enhanced and reach a value of ~4.02 μ{sub B}. The polar magneto-optical Kerr effect is calculated for a photon energy range extended to 15 eV. It shows a pronounced peak in visible light. - Highlights: • The applied strain in Mn-bct structure induces anti-ferromagnetic behavior. • The easy magnetization axis is demonstrated to be out-of-plane. • The magnetic moment of Mn-layers are enhanced and reach a value of ~4.02 μ{sub B}. • Kerr spectra show significant polar responses for Mn films in the visible range. • The prominent structures in the Kerr spectra have been identified.

  5. Electrical and optical properties of mixed phase tungsten trioxide films grown by laser pyrolysis

    CSIR Research Space (South Africa)

    Govender, M

    2014-02-01

    Full Text Available Laser pyrolysis was chosen to synthesize tungsten trioxide starting with tungsten ethoxide precursor. The film was found to have a thickness that varied from 205 nm to 1 µm. X-ray diffraction and Raman spectroscopy confirmed the presence of a...

  6. Influence of cation off-stoichiometry on structural and transport properties of (Ba,La)SnO3 epitaxial thin films grown by pulsed laser deposition

    Science.gov (United States)

    Ozaki, Yusuke; Kan, Daisuke; Shimakawa, Yuichi

    2017-06-01

    We investigate the influences of cation off-stoichiometry on structural and transport properties of 3% La-doped BaSnO3 (BLSO) epitaxial thin films grown on SrTiO3 substrates by pulsed laser deposition. We show that cation off-stoichiometry, namely, Sn excess and Sn deficiency, is introduced by variations in either laser fluence or the cation composition of the target used for the film growth and that the cation off-stoichiometry influences the properties of the grown films. While all films investigated in this study undergo relaxations from the substrate-induced strain, the out-of-plane lattice constant decreases with the increase in the Sn content in the film. The electrical conductivity, carrier concentration, and mobility are strongly dependent on the type of the cation off-stoichiometry (Sn excess and Sn deficiency). The highest room-temperature mobility, 35 cm2/V-1s-1, is seen for a film grown by ablating the stoichiometric target with a fluence of 1.6 J/cm2, which keeps the cation ratio in the film close to the stoichiometric one. The conductivity and the carrier concentration of the Sn-excess films grown with the fluence smaller than 1.6 J/cm2 are as high as 2 × 103 S/cm and 5 × 1020 cm-3, respectively, while the mobility remains as low as 25 cm2/V-1s-1. The observed carrier concentration is slightly higher than that calculated from the stoichiometric composition of BLSO, implying that the excess Sn in the films provides additional carriers and also acts as scattering centers for the carriers. On the other hand, no measurable electrical conduction is observed in the Sn-deficient films grown with a fluence greater than 1.6 J/cm2, indicating that the carriers provided by the dopants are trapped by defects due to the Sn deficiency. We also show that cation off-stoichiometry influences the surface morphology of the films. Our results highlight that the cation stoichiometry of the BLSO films is an important factor influencing their properties.

  7. Formation of Mn-germanide nanodots on ultrathin SiO2 induced by remote hydrogen plasma

    Science.gov (United States)

    Wen, Yinghui; Makihara, Katsunori; Ohta, Akio; Ikeda, Mitsuhisa; Miyazaki, Seiichi

    2018-01-01

    High-density Mn-germanide nanodots [Mn x Ge1‑ x (x = 0.8) NDs] with an areal dot density as high as ∼1012 cm‑2 were formed on thermally grown SiO2 by exposing ∼1.0-nm-thick Mn/∼1.0-nm-thick amorphous Ge (a-Ge) bilayer stacked structures to a remote H2 plasma (H2-RP) without external heating. The germanidation reaction of the Mn/a-Ge bilayer was observed through high resolution X-ray photoelectron spectroscopy measurements. Electrical isolation among the Mn x Ge1‑ x (x = 0.8) NDs was verified from the changes in surface potential after charge injection using an atomic force microscope/Kelvin probe technique. As seen from the VHF input power and exposure time dependence of the ultrathin bilayer stacked structures, control of thickness and H-radical flux are important parameters for the high-density formation of MnGe alloy NDs induced by H2-RP.

  8. Versatile superamphiphobic cotton fabrics fabricated by coating with SiO2/FOTS

    Science.gov (United States)

    Li, Deke; Guo, Zhiguang

    2017-12-01

    A multifunctional superamphiphobic cotton fabric was fabricated by coating silica nanoparticles on the cotton fabric surface and further modification by 1H,1H,2H,2H-perfluorooctyltrichlorosilane (FOTS). The fluctuant woven fabric and the fluffy spherical SiO2 nanoparticles constructed a dual micro/nano-structures. The surface free energy of the fabric composite was reduced by FOTS modifier. The interplay of the structured and perfluorinated SiO2 nanoparticles could not only endow the fabric highly liquid repellent ability, but could also to enhance the coating stability. The prepared cotton fabrics exhibited high liquid repellency to water, colza oil and n-hexadecane with lower surface tension, showing a contact angle of 158°, 152°, and 153°, respectively. The results demonstrated that superamphiphobic cotton fabric possessed desirable chemical and mechanical durability, self-cleaning and self-healing property, the robust and multifunctional fabric would find innovative opportunities for practical applications.

  9. Electron irradiation response on Ge and Al-doped SiO 2 optical fibres

    Science.gov (United States)

    Yaakob, N. H.; Wagiran, H.; Hossain, I.; Ramli, A. T.; Bradley, D. A.; Hashim, S.; Ali, H.

    2011-05-01

    This paper describes the thermoluminescence response, sensitivity, stability and reproducibility of SiO 2 optical fibres with various electron energies and doses. The TL materials that comprise Al- and Ge-doped silica fibres were used in this experiment. The TL results are compared with those of the commercially available TLD-100. The doped SiO 2 optical fibres and TLD-100 are placed in a solid phantom and irradiated with 6, 9 and 12 MeV electron beams at doses ranging from 0.2 to 4.0 Gy using the LINAC at Hospital Sultan Ismail, Johor Bahru, Malaysia. It was found that the commercially available Al- and Ge-doped optical fibres have a linear dose-TL signal relationship. The intensity of TL response of Ge-doped fibre is markedly greater than that of the Al-doped fibre.

  10. Microwave absorption properties and mechanism of cagelike ZnO /SiO2 nanocomposites

    Science.gov (United States)

    Cao, Mao-Sheng; Shi, Xiao-Ling; Fang, Xiao-Yong; Jin, Hai-Bo; Hou, Zhi-Ling; Zhou, Wei; Chen, Yu-Jin

    2007-11-01

    In this paper, cagelike ZnO /SiO2 nanocomposites were prepared and their microwave absorption properties were investigated in detail. Dielectric constants and losses of the pure cagelike ZnO nanostructures were measured in a frequency range of 8.2-12.4GHz. The measured results indicate that the cagelike ZnO nanostructures are low-loss material for microwave absorption in X band. However, the cagelike ZnO /SiO2 nanocomposites exhibit a relatively strong attenuation to microwave in X band. Such strong absorption is related to the unique geometrical morphology of the cagelike ZnO nanostructures in the composites. The microcurrent network can be produced in the cagelike ZnO nanostructures, which contributes to the conductive loss.

  11. Fourier transform infrared spectroscopic study of gamma irradiated SiO2 nanoparticles

    Science.gov (United States)

    Huseynov, Elchin; Garibov, Adil; Mehdiyeva, Ravan; Huseynova, Efsane

    2018-03-01

    In the present work, nano SiO2 particles are investigated before and after gamma irradiation (25, 50, 75, 100 and 200 kGy) using Fourier transform infrared (FTIR) spectroscopy method for the wavenumber between 400-4000 cm-1. It is found that as a result of spectroscopic analysis, five new peaks have appeared after gamma radiation. Two of new obtained peaks (which are located at 687 cm-1 and 2357 cm-1 of wavenumber) were formed as a result of gamma radiation interaction with Si-O bonds. Another three new peaks (peaks appropriate to 941, 2052 and 2357 cm-1 values of wavenumber) appear as a result of interaction of water with nano SiO2 particles after gamma irradiation. It has been defined as asymmetrical bending vibration, symmetrical bending vibration, symmetrical stretching vibration and asymmetrical stretching vibration of Si-O bonds appropriate to peaks.

  12. Preparation of Mesoporous SiO2-Pillared Lamellar Titanoniobate Catalysts for Bioethanol Dehydration

    Directory of Open Access Journals (Sweden)

    Olivalter Pergentino

    2014-01-01

    Full Text Available The lamellar perovskite K0,8Ti0,8Nb1,2O5 was prepared by solid state reaction, and its protonic form was used in a sequence of intercalation steps with n-butylamine, cetyltrimethylammonium bromide (CTABr, and tetraethyl orthosilicate (TEOS. After calcination, a high surface area, mesoporous SiO2-pillared titanoniobate, was obtained. The samples were characterized by XRD, EDX, TG-DTG, N2 adsorption isotherms, and NH3-TPD. The pillarization procedure affected the textural properties, the amount, and strength distribution of acid sites. The influence of the pillarization procedure on the catalytic properties of the lamellar titanoniobates was investigated on ethanol dehydration. High ethanol conversions and ethylene yields (>90% were obtained in the presence of the SiO2-pillared titanoniobate catalyst, at 350–450°C.

  13. Electron irradiation response on Ge and Al-doped SiO2 optical fibres

    International Nuclear Information System (INIS)

    Yaakob, N.H.; Wagiran, H.; Hossain, I.; Ramli, A.T.; Bradley, D.A; Hashim, S.; Ali, H.

    2011-01-01

    This paper describes the thermoluminescence response, sensitivity, stability and reproducibility of SiO 2 optical fibres with various electron energies and doses. The TL materials that comprise Al- and Ge-doped silica fibres were used in this experiment. The TL results are compared with those of the commercially available TLD-100. The doped SiO 2 optical fibres and TLD-100 are placed in a solid phantom and irradiated with 6, 9 and 12 MeV electron beams at doses ranging from 0.2 to 4.0 Gy using the LINAC at Hospital Sultan Ismail, Johor Bahru, Malaysia. It was found that the commercially available Al- and Ge-doped optical fibres have a linear dose-TL signal relationship. The intensity of TL response of Ge-doped fibre is markedly greater than that of the Al-doped fibre.

  14. Formation of nucleoplasmic protein aggregates impairs nuclear function in response to SiO2 nanoparticles

    International Nuclear Information System (INIS)

    Chen Min; Mikecz, Anna von

    2005-01-01

    Despite of their exponentially growing use, little is known about cell biological effects of nanoparticles. Here, we report uptake of silica (SiO 2 ) nanoparticles to the cell nucleus where they induce aberrant clusters of topoisomerase I (topo I) in the nucleoplasm that additionally contain signature proteins of nuclear domains, and protein aggregation such as ubiquitin, proteasomes, cellular glutamine repeat (polyQ) proteins, and huntingtin. Formation of intranuclear protein aggregates (1) inhibits replication, transcription, and cell proliferation; (2) does not significantly alter proteasomal activity or cell viability; and (3) is reversible by Congo red and trehalose. Since SiO 2 nanoparticles trigger a subnuclear pathology resembling the one occurring in expanded polyglutamine neurodegenerative disorders, we suggest that integrity of the functional architecture of the cell nucleus should be used as a read out for cytotoxicity and considered in the development of safe nanotechnology

  15. Experimental observations of the chemistry of the SiO2/Si interface

    Science.gov (United States)

    Grunthaner, F. J.; Maserjian, J.

    1977-01-01

    Changes in silicon surface preparation prior to thermal oxidation are shown to leave a signature by altering the final SiO2/Si interface structure. Surface analytical techniques, including XPS, static SIMS, ion milling, and newly developed wet-chemical profiling procedures are used to obtain detailed information on the chemical structure of the interface. The oxides are shown to be essentially SiO2 down to a narrow transitional interface layer (3-7 A). A number of discrete chemical species are observed in this interface layer, including different silicon bonds (e.g., C-, OH-, H-) and a range of oxidation states of silicon (0 to +4). The effect of surface preparation and the observed chemical species are correlated with oxide growth rate, surface-state density, and flatband shifts after irradiation.

  16. Transistors and tunnel diodes enabled by large-scale MoS2 nanosheets grown on GaN

    Science.gov (United States)

    San Yip, Pak; Zou, Xinbo; Cho, Wai Ching; Wu, Kam Lam; Lau, Kei May

    2017-07-01

    We report growth, fabrication, and device results of MoS2-based transistors and diodes implemented on a single 2D/3D material platform. The 2D/3D platform consists of a large-area MoS2 thin film grown on SiO2/p-GaN substrates. Atomic force microscopy, scanning electron microscopy, and Raman spectroscopy were used to characterize the thickness and quality of the as-grown MoS2 film, showing that the large-area MoS2 nanosheet has a smooth surface morphology constituted by small grains. Starting from the same material, both top-gated MoS2 field effect transistors and MoS2/SiO2/p-GaN heterojunction diodes were fabricated. The transistors exhibited a high on/off ratio of 105, a subthreshold swing of 74 mV dec-1, field effect mobility of 0.17 cm2 V-1 s-1, and distinctive current saturation characteristics. For the heterojunction diodes, current-rectifying characteristics were demonstrated with on-state current density of 29 A cm-2 and a current blocking property up to -25 V without breakdown. The reported transistors and diodes enabled by the same 2D/3D material stack present promising building blocks for constructing future nanoscale electronics.

  17. Investigation of pentacene growth on SiO2 gate insulator after photolithography for nitrogen-doped LaB6 bottom-contact electrode formation

    Science.gov (United States)

    Maeda, Yasutaka; Hiroki, Mizuha; Ohmi, Shun-ichiro

    2018-04-01

    Nitrogen-doped (N-doped) LaB6 is a candidate material for the bottom-contact electrode of n-type organic field-effect transistors (OFETs). However, the formation of a N-doped LaB6 electrode affects the surface morphology of a pentacene film. In this study, the effects of surface treatments and a N-doped LaB6 interfacial layer (IL) were investigated to improve the pentacene film quality after N-doped LaB6 electrode patterning with diluted HNO3, followed by resist stripping with acetone and methanol. It was found that the sputtering damage during N-doped LaB6 deposition on a SiO2 gate insulator degraded the crystallinity of pentacene. The H2SO4 and H2O2 (SPM) and diluted HF treatments removed the damaged layer on the SiO2 gate insulator surface. Furthermore, the N-doped LaB6 IL improved the crystallinity of pentacene and realized dendritic grain growth. Owing to these surface treatments, the hole mobility improved from 2.8 × 10‑3 to 0.11 cm2/(V·s), and a steep subthreshold swing of 78 mV/dec for the OFET with top-contact configuration was realized in air even after bottom-contact electrode patterning.

  18. Highly conformal SiO2/Al2O3 nanolaminate gas-diffusion barriers for large-area flexible electronics applications

    International Nuclear Information System (INIS)

    Choi, Jin-Hwan; Kim, Young-Min; Park, Young-Wook; Park, Tae-Hyun; Jeong, Jin-Wook; Choi, Hyun-Ju; Song, Eun-Ho; Ju, Byeong-Kwon; Lee, Jin-Woo; Kim, Cheol-Ho

    2010-01-01

    The present study demonstrates a flexible gas-diffusion barrier film, containing an SiO 2 /Al 2 O 3 nanolaminate on a plastic substrate. Highly uniform and conformal coatings can be made by alternating the exposure of a flexible polyethersulfone surface to vapors of SiO 2 and Al 2 O 3 , at nanoscale thickness cycles via RF-magnetron sputtering deposition. The calcium degradation test indicates that 24 cycles of a 10/10 nm inorganic bilayer, top-coated by UV-cured resin, greatly enhance the barrier performance, with a permeation rate of 3.79 x 10 -5 g m -2 day -1 based on the change in the ohmic behavior of the calcium sensor at 20 deg. C and 50% relative humidity. Also, the permeation rate for 30 cycles of an 8/8 nm inorganic bilayer coated with UV resin was beyond the limited measurable range of the Ca test at 60 deg. C and 95% relative humidity. It has been found that such laminate films can effectively suppress the void defects of a single inorganic layer, and are significantly less sensitive against moisture permeation. This nanostructure, fabricated by an RF-sputtering process at room temperature, is verified as being useful for highly water-sensitive organic electronics fabricated on plastic substrates.

  19. Properties of HfO2/ultrathin SiO2/Si structures and their comparison with Si MOS structures passivated in KCN solution

    Science.gov (United States)

    Pinčík, Emil; Kobayashi, Hikaru; Matsumoto, Taketoshi; Takahashi, Masao; Mikula, Milan; Brunner, Róbert

    2014-05-01

    Electrical, optical and partly structural properties are investigated on very thin ALD HfO2/ultrathin NAOS SiO2/n-type Si structures. An ALD layer was deposited at 250 °C and it contains amorphous and crystalline-probably monoclinic HfO2 phases. HfO2 films with both types of structural phases were not stable if thermal treatment above 200 °C was applied. On as- prepared samples, deep interface traps with activation energy of ΔW = 0.23 eV have been determined. After annealing of the structure at 200 °C, the traps were partly transformed and a mid-gap level ΔW = 0.49 eV was detected. FTIR and AFM measurements confirmed presence of HfO2 monoclinic phase in the HfO2 films. On the other side, the density of interface defect states of the structure decreased from approx. 1012 eV-1 cm-2 to 1011 eV-1 cm-2 after low temperature annealing of the reference structure. The results are compared with very similar (almost identical) development of interface defect states on the very thin thermal SiO2/Si structure before and after passivation in a 0.1 M KCN methanol solution.PACS: 78.55.Qr; 78.66.Jg; 81.16.Pr; 85.40Ls

  20. Vaporization of SiO2 and MgSiO3

    Science.gov (United States)

    Stixrude, L. P.; Xiao, B.

    2016-12-01

    Vaporization of SiO2 and MgSiO3B Xiaoa and L Stixrude*a, a Department of Earth Sciences, University College London, WC1E 6BT London, UK *presenting author, email: l.stixrude@ucl.ac.uk Vaporization is an important process in Earth's earliest evolution during which giant impacts are thought to have produced a transient silicate atmosphere. As experimental data are very limited, little is known of the near-critical vaporization of Earth's major oxide components: MgO and SiO2. We have performed novel ab initio molecular dynamics simulations of vapor-liquid coexistence in the SiO2 and MgSiO3 systems. The simulations, based on density functional theory using the VASP code, begin with a suitably prepared liquid slab embedded in a vacuum. During the dynamical trajectory in the canonical ensemble, we see spontaneous vaporization, leading eventually to a steady-state chemical equilibrium between the two coexisting phases. We locate the liquid-vapor critical point at 6600 K and 0.40 g/cm3 for MgSiO3 and 5300 K and 0.43 g/cm3 for SiO2. By carefully examining the trajectories, we determine the composition and speciation of the vapor. For MgSiO3, We find that the vapor is significantly richer in Mg, O, and atomic (non-molecular) species than extrapolation of low-temperature experimental data has suggested. These results will have important implications for our understanding of the initial chemistry of the Earth and Moon and the initial thermal state of Earth.

  1. Generation of interface states by injection of electrons into SiO2

    Science.gov (United States)

    Lyon, S. A.

    1984-11-01

    Several techniques have been used to inject electrons into SiO2 with various energies. Interface states are found to be generated whenever electrons flow through the oxide. However, the efficiency of interface state generation depends upon the method of electron injection. At high enough fields, positive charge is produced in the oxide which enhances the production of interface states. All of the states are amphoteric and are probably dangling Si bonds at the interface (Pb-centers).

  2. Structural verification and optical characterization of SiO2–Au–Cu2O ...

    Indian Academy of Sciences (India)

    In this paper, SiO2–Au–Cu2O core/shell/shell nanoparticles were synthesized by reducing gold chloride on 3-amino-propyl-triethoxysilane molecules attached silica nanoparticle cores for several stages. Cu2O nanoparticles were synthesized readily with the size of 4–5 nm using a simple route of sol–gel method. Then, they ...

  3. Effect of SiO2 protective layer on the femtosecond laser-induced damage of HfO2/SiO2 multilayer high-reflective coatings

    International Nuclear Information System (INIS)

    Yuan Lei; Zhao Yuanan; Wang Congjuan; He Hongbo; Fan Zhengxiu; Shao Jianda

    2007-01-01

    Two kinds of HfO 2 /SiO 2 800 nm high-reflective (HR) coatings, with and without SiO 2 protective layer were deposited by electron beam evaporation. Laser-induced damage thresholds (LIDT) were measured for all samples with femtosecond laser pulses. The surface morphologies and the depth information of all samples were observed by Leica optical microscopy and WYKO surface profiler, respectively. It is found that SiO 2 protective layer had no positive effect on improving the LIDT of HR coating. A simple model including the conduction band electron production via multiphoton ionization and impact ionization is used to explain this phenomenon. Theoretical calculations show that the damage occurs first in the SiO 2 protective layer for HfO 2 /SiO 2 HR coating with SiO 2 protective layer. The relation of LIDT for two kinds of HfO 2 /SiO 2 HR coatings in calculation agrees with the experiment result

  4. Nano-regime Length Scales Extracted from the First Sharp Diffraction Peak in Non-crystalline SiO2 and Related Materials: Device Applications

    Directory of Open Access Journals (Sweden)

    Phillips James

    2010-01-01

    Full Text Available Abstract This paper distinguishes between two different scales of medium range order, MRO, in non-crystalline SiO2: (1 the first is ~0.4 to 0.5 nm and is obtained from the position of the first sharp diffraction peak, FSDP, in the X-ray diffraction structure factor, S(Q, and (2 the second is ~1 nm and is calculated from the FSDP full-width-at-half-maximum FWHM. Many-electron calculations yield Si–O third- and O–O fourth-nearest-neighbor bonding distances in the same 0.4–0.5 nm MRO regime. These derive from the availability of empty Si dπ orbitals for back-donation from occupied O pπ orbitals yielding narrow symmetry determined distributions of third neighbor Si–O, and fourth neighbor O–O distances. These are segments of six member rings contributing to connected six-member rings with ~1 nm length scale within the MRO regime. The unique properties of non-crystalline SiO2 are explained by the encapsulation of six-member ring clusters by five- and seven-member rings on average in a compliant hard-soft nano-scaled inhomogeneous network. This network structure minimizes macroscopic strain, reducing intrinsic bonding defects as well as defect precursors. This inhomogeneous CRN is enabling for applications including thermally grown ~1.5 nm SiO2 layers for Si field effect transistor devices to optical components with centimeter dimensions. There are qualitatively similar length scales in nano-crystalline HfO2 and phase separated Hf silicates based on the primitive unit cell, rather than a ring structure. Hf oxide dielectrics have recently been used as replacement dielectrics for a new generation of Si and Si/Ge devices heralding a transition into nano-scale circuits and systems on a Si chip.

  5. VO2 Thermochromic Films on Quartz Glass Substrate Grown by RF-Plasma-Assisted Oxide Molecular Beam Epitaxy

    Directory of Open Access Journals (Sweden)

    Dong Zhang

    2017-03-01

    Full Text Available Vanadium dioxide (VO2 thermochromic thin films with various thicknesses were grown on quartz glass substrates by radio frequency (RF-plasma assisted oxide molecular beam epitaxy (O-MBE. The crystal structure, morphology and chemical stoichiometry were investigated systemically by X-ray diffraction (XRD, atomic force microscopy (AFM, Raman spectroscopy and X-ray photoelectron spectroscopy (XPS analyses. An excellent reversible metal-to-insulator transition (MIT characteristics accompanied by an abrupt change in both electrical resistivity and optical infrared (IR transmittance was observed from the optimized sample. Remarkably, the transition temperature (TMIT deduced from the resistivity-temperature curve was reasonably consistent with that obtained from the temperature-dependent IR transmittance. Based on Raman measurement and XPS analyses, the observations were interpreted in terms of residual stresses and chemical stoichiometry. This achievement will be of great benefit for practical application of VO2-based smart windows.

  6. Stabilization of SiO2 nanoparticle foam system and evaluation of its performance

    Science.gov (United States)

    Sun, Chong; Fan, Zhenzhong; Liu, Qingwang; Wang, Jigang; Xu, Jianjun

    2017-05-01

    As tertiary recovery is applied in the oil field, foam flooding technology plays an important role in the oil field. Steam flooding is easy to generate a series of problems such as excessive pressure, gas channelling, heat loss ect. The foam flooding can be better used in the formation of plugging and profile control. However, the foam is not stabilizing in thermodynamics and breaks easily while it encounters oil. So the emphasis of the research is how to make the foam stable. The Warning Blender method is used to evaluate the foam In the course of experiment, which verifies that the modified Nano SiO2 solid not only works very well in coordination with SDS solution but also contributes to the generation of stable foam in solution. The optimum concentration of SDS is determined by 0.5%, and the best concentration is 1.4% of H20 type SiO2 particles that the concentration is 79.26°. Finally, the 0.5%SDS+1.4%H2O type SiO2 is chosen as the complete foam flooding system, and the performance of salt tolerance and oil displacement of composite foam system is evaluated. It is concluded that the stability of foam is the key to improve the oil recovery.

  7. Reduction of SiO2 to SiC Using Natural Gas

    Science.gov (United States)

    Ksiazek, Michal; Tangstad, Merete; Dalaker, Halvor; Ringdalen, Eli

    2014-09-01

    This paper presents a preliminary study of SiC production by use of natural gas for reduction of silica. Direct reduction of SiO2 by gas mixtures containing CH4, H2, and Ar was studied at temperatures between 1273 K and 1773 K (1000 °C and 1500 °C). Silica in form of particles between 1 and 3 mm and pellets with mean grain size 50 µm were exposed to the gas mixture for 6 hours. Influence of temperature and CH4H2 ratio was investigated. Higher temperature and CH4 concentration resulted in greater SiC production. Two kinds of SiC were found: one was deposited between SiO2 particles, the other one was deposited inside the SiO2 particles. Although the exact reaction mechanisms have not been determined, it is clear that gas-phase reactions play an important role in both cases. The reaction products were analyzed by Electron Probe Micro Analyzer.

  8. Current Tunnelling in MOS Devices with Al2O3/SiO2 Gate Dielectric

    Directory of Open Access Journals (Sweden)

    A. Bouazra

    2008-01-01

    Full Text Available With the continued scaling of the SiO2 thickness below 2 nm in CMOS devices, a large direct-tunnelling current flow between the gate electrode and silicon substrate is greatly impacting device performance. Therefore, higher dielectric constant materials are desirable for reducing the gate leakage while maintaining transistor performance for very thin dielectric layers. Despite its not very high dielectric constant (∼10, Al2O3 has emerged as one of the most promising high-k candidates in terms of its chemical and thermal stability as its high-barrier offset. In this paper, a theoretical study of the physical and electrical properties of Al2O3 gate dielectric is reported including I(V and C(V characteristics. By using a stack of Al2O3/SiO2 with an appropriate equivalent oxide thickness of gate dielectric MOS, the gate leakage exhibits an important decrease. The effect of carrier trap parameters (depth and width at the Al2O3/SiO2 interface is also discussed.

  9. Strong piezoelectricity in single-layer graphene deposited on SiO2 grating substrates.

    Science.gov (United States)

    da Cunha Rodrigues, Gonçalo; Zelenovskiy, Pavel; Romanyuk, Konstantin; Luchkin, Sergey; Kopelevich, Yakov; Kholkin, Andrei

    2015-06-25

    Electromechanical response of materials is a key property for various applications ranging from actuators to sophisticated nanoelectromechanical systems. Here electromechanical properties of the single-layer graphene transferred onto SiO2 calibration grating substrates is studied via piezoresponse force microscopy and confocal Raman spectroscopy. The correlation of mechanical strains in graphene layer with the substrate morphology is established via Raman mapping. Apparent vertical piezoresponse from the single-layer graphene supported by underlying SiO2 structure is observed by piezoresponse force microscopy. The calculated vertical piezocoefficient is about 1.4 nm V(-1), that is, much higher than that of the conventional piezoelectric materials such as lead zirconate titanate and comparable to that of relaxor single crystals. The observed piezoresponse and achieved strain in graphene are associated with the chemical interaction of graphene's carbon atoms with the oxygen from underlying SiO2. The results provide a basis for future applications of graphene layers for sensing, actuating and energy harvesting.

  10. A highly efficient g-C3N4/SiO2heterojunction: the role of SiO2in the enhancement of visible light photocatalytic activity.

    Science.gov (United States)

    Hao, Qiang; Niu, Xiuxiu; Nie, Changshun; Hao, Simeng; Zou, Wei; Ge, Jiangman; Chen, Daimei; Yao, Wenqing

    2016-11-23

    SiO 2 , an insulator, hardly has any photocatalytic acitivity due to its intrinsic property, and it is generally used as a hard template to increase the surface area of catalysts. However, in this work, we found that the surface state of the insulator SiO 2 can promote the migration of photogenerated charge carriers, leading to the enhancement of the photooxidation ability of graphitic carbon nitride (g-C 3 N 4 ). A one-pot calcination method was employed to prepare g-C 3 N 4 /SiO 2 composites using melamine and SiO 2 as precursors. The composites present considerably high photocatalytic degradation activities for 2,4-dichlorophenol (2,4-DCP) and rhodamine B (RhB) under visible light (λ > 420 nm) irradiation, which are about 1.53 and 4.18 times as high as those of bulk g-C 3 N 4 , respectively. The enhancement of the photocatalytic activity is due to the fact that the introduction of the insulator SiO 2 in g-C 3 N 4 /SiO 2 composites can greatly improve the specific surface area of the composites; more importantly, the impurity energy level of SiO 2 can help accelerate the separation and transfer of electron-hole pairs of g-C 3 N 4 . Electron paramagnetic resonance (EPR) spectroscopy and trapping experiments with different radical scavengers show that the main active species of g-C 3 N 4 are superoxide radicals, while holes also play a role in photodegradation. For g-C 3 N 4 /SiO 2 -5, besides superoxide radicals and holes, the effect of hydroxyl radicals was greatly improved. Finally, a possible mechanism for the photogenerated charge carrier migration of the g-C 3 N 4 /SiO 2 photocatalyst was proposed.

  11. Crystal orientation, crystallinity, and thermoelectric properties of Bi0.9Sr0.1CuSeO epitaxial films grown by pulsed laser deposition

    Science.gov (United States)

    Ishizawa, Mamoru; Fujishiro, Hiroyuki; Naito, Tomoyuki; Ito, Akihiko; Goto, Takashi

    2018-02-01

    We have grown Bi0.9Sr0.1CuSeO epitaxial thin films on MgO and SrTiO3 (STO) single-crystal substrates by pulsed laser deposition (PLD) under various growth conditions, and investigated the crystal orientation, crystallinity, chemical composition, and thermoelectric properties of the films. The optimization of the growth conditions was realized in the film grown on MgO at the temperature T s = 573 K and Ar pressure P Ar = 0.01 Torr in this study, in which there was no misalignment apart from the c-axis and no impurity phase. It was clearly found that the higher crystal orientation of the epitaxial film grown at a higher temperature under a lower Ar pressure mainly enhanced the thermoelectric power factor P (= S 2/ρ), where S is the Seebeck coefficient and ρ is the electrical resistivity. However, the thermoelectric properties of the films were lower than those of polycrystalline bulk because of lattice distortion from lattice mismatch, a low crystallinity caused by a lower T s, and Bi and Cu deficiencies in the films.

  12. Synthesis of TiO2-doped SiO2 composite films and its applications

    Indian Academy of Sciences (India)

    Wintec

    ity in order to provide vital information for the design and application of such highly efficient photocatalytic systems in the degradation of toxic compounds diluted in a liquid phase. Keywords. ... combines both the mechanical properties of silica and the chemical properties of active titania, recent studies reveal that TiO2–SiO2 ...

  13. Structural features of epitaxial NiFe2O4 thin films grown on different substrates by direct liquid injection chemical vapor deposition

    Science.gov (United States)

    Datta, R.; Loukya, B.; Li, N.; Gupta, A.

    2012-04-01

    NiFe2O4 (NFO) thin films are grown on four different substrates, i.e., Lead Zinc Niobate-Lead Titanate (PZN-PT), Lead Magnesium Niobate-Lead Titanate (PMN-PT), MgAl2O4 (MAO) and SrTiO3 (STO), by a direct liquid injection chemical vapor deposition technique (DLI-CVD) under optimum growth conditions where relatively high growth rate (˜20 nm/min), smooth surface morphology and high saturation magnetization values in the range of 260-290 emu/ cm3 are obtained. The NFO films with correct stoichiometry (Ni:Fe=1:2) grow epitaxially on all four substrates, as confirmed by energy dispersive X-ray spectroscopy, transmission electron microscopy and x-ray diffraction. While the films on PMN-PT and PZN-PT substrates are partially strained, essentially complete strain relaxation occurs for films grown on MAO and STO. The formations of threading dislocations along with dark diffused contrast areas related to antiphase domains having a different cation ordering are observed on all four substrates. These crystal defects are correlated with lattice mismatch between the film and substrate and result in changes in magnetic properties of the films. Atomic resolution HAADF imaging and EDX line profiles show formation of a sharp interface between the film and the substrate with no inter-diffusion of Pb or other elements across the interface. Antiphase domains are observed to originate at the film-substrate interface.

  14. Sulfurization effect on optical properties of Cu2SNS3 thin films grown by two-stage process

    Science.gov (United States)

    Reddy, G. Phaneendra; Reddy, K. T. Ramakrishna

    2017-05-01

    A good phase controlled and impurity free two stage process was used to prepare Cu2SnS3 layers on glass substrates. The layers were prepared by sulfurization of sputtered Cu-Sn metallic precursors by varying the sulfurization temperature (Ts) in the range, 150-450°C, keeping the other deposition parameters constant. A complete investigation of the optical properties of the layers with sulfurization temperature was made by using the optical transmittance and reflectance measurements versus wavelength. The absorption coefficient α, was evaluated using the optical data that showed a α > 104 cm-1 for all the as-grown films. The optical bandgap of the as grown layers was determined from the second derivative diffused reflectance spectra that varied from 1.96 eV to 0.99 eV. Consequently, refractive index and extinction coefficient were calculated from Pankov's relations. In addition, the other optical parameters such as the dielectric constants, dissipation factor and also optical conductivity calculated. A detailed analysis of the dependence of all the above parameters on Ts is reported and discussed.

  15. Measuring the dielectric and optical response of millimeter-scale amorphous and hexagonal boron nitride films grown on epitaxial graphene

    Science.gov (United States)

    Rigosi, Albert F.; Hill, Heather M.; Glavin, Nicholas R.; Pookpanratana, Sujitra J.; Yang, Yanfei; Boosalis, Alexander G.; Hu, Jiuning; Rice, Anthony; Allerman, Andrew A.; Nguyen, Nhan V.; Hacker, Christina A.; Elmquist, Randolph E.; Hight Walker, Angela R.; Newell, David B.

    2018-01-01

    Monolayer epitaxial graphene (EG), grown on the Si face of SiC, is an advantageous material for a variety of electronic and optical applications. EG forms as a single crystal over millimeter-scale areas and consequently, the large scale single crystal can be utilized as a template for growth of other materials. In this work, we present the use of EG as a template to form millimeter-scale amorphous and hexagonal boron nitride (a-BN and h-BN) films. The a-BN is formed with pulsed laser deposition and the h-BN is grown with triethylboron (TEB) and NH3 precursors, making it the first metal organic chemical vapor deposition (MOCVD) process of this growth type performed on epitaxial graphene. A variety of optical and non-optical characterization methods are used to determine the optical absorption and dielectric functions of the EG, a-BN, and h-BN within the energy range of 1 eV–8.5 eV. Furthermore, we report the first ellipsometric observation of high-energy resonant excitons in EG from the 4H polytype of SiC and an analysis on the interactions within the EG and h-BN heterostructure.

  16. Tribological evaluation of an Al2O3-SiO2 ceramic fiber candidate for high temperature sliding seals

    Science.gov (United States)

    Dellacorte, Christopher; Steinetz, Bruce

    1994-01-01

    A test program to determine the relative sliding durability of an alumina-silica candidate ceramic fiber for high temperature sliding seal applications is described. Pin-on-disk tests were used to evaluate the potential seal material by sliding a tow or bundle of the candidate ceramic fiber against a superalloy test disk. Friction was measured during the tests and fiber wear, indicated by the extent of fibers broken in the tow or bundle, was measured at the end of each test. Test variables studied included ambient temperatures from 25 to 900 C, loads from 1.3 to 21.2 N, and sliding velocities from 0.025 to 0.25 m/sec. In addition, the effects of fiber diameter and elastic modulus on friction and wear were measured. Thin gold films deposited on the superalloy disk surface were evaluated in an effort to reduce friction and wear of the fibers. In most cases, wear increased with test temperature. Friction ranged from 0.36 at 500 C and low velocity (0.025 m/sec) to over 1.1 at 900 C and high velocity (0.25 m/sec). The gold films resulted in satisfactory lubrication of the fibers at 25 C. At elevated temperatures diffusion of substrate elements degraded the films. These results indicate that the alumina-silica (Al2O3-SiO2) fiber is a good candidate material system for high temperature sliding seal applications. More work is needed to reduce friction.

  17. Transient Photoinduced Absorption in Ultrathin As-grown Nanocrystalline Silicon Films

    Directory of Open Access Journals (Sweden)

    Lioutas Ch

    2007-01-01

    Full Text Available AbstractWe have studied ultrafast carrier dynamics in nanocrystalline silicon films with thickness of a few nanometers where boundary-related states and quantum confinement play an important role. Transient non-degenerated photoinduced absorption measurements have been employed to investigate the effects of grain boundaries and quantum confinement on the relaxation dynamics of photogenerated carriers. An observed long initial rise of the photoinduced absorption for the thicker films agrees well with the existence of boundary-related states acting as fast traps. With decreasing the thickness of material, the relaxation dynamics become faster since the density of boundary-related states increases. Furthermore, probing with longer wavelengths we are able to time-resolve optical paths with faster relaxations. This fact is strongly correlated with probing in different points of the first Brillouin zone of the band structure of these materials.

  18. CeCo5 thin films with perpendicular anisotropy grown by molecular beam epitaxy

    Science.gov (United States)

    Sharma, S.; Hildebrandt, E.; Major, M.; Komissinskiy, P.; Radulov, I.; Alff, L.

    2018-04-01

    Buffer-free, highly textured (0 0 1) oriented CeCo5 thin films showing perpendicular magnetic anisotropy were synthesized on (0 0 1) Al2O3 substrates by molecular beam epitaxy. Ce exists in a mixture of Ce3+ and Ce4+ valence states as shown by X-ray photoelectron spectroscopy. The first anisotropy constant, K1, as measured by torque magnetometry was 0.82 MJ/m3 (8.2 ×106erg /cm3) . A maximum coercivity of 5.16 kOe with a negative temperature coefficient of -0.304%K-1 and a magnetization of 527.30 emu/cm3 was measured perpendicular to the film plane at 5 K. In addition, a large anisotropy of the magnetic moment of 15.5% was observed. These magnetic parameters make CeCo5 a potential candidate material for spintronic and magnetic recording applications.

  19. Biomolecular urease thin films grown by laser techniques for blood diagnostic applications

    Energy Technology Data Exchange (ETDEWEB)

    Gyoergy, E., E-mail: eniko.gyorgy@inflpr.ro [Consejo Superior de Investigaciones Cientificas, Institut de Ciencia de Materials de Barcelona and Centre d' Investigacions en Nanociencia i Nanotecnologia, Campus UAB, 08193 Bellaterra (Spain); National Institute for Lasers, Plasma and Radiations Physics, P. O. Box MG 36, 77125 Bucharest (Romania); Sima, F.; Mihailescu, I.N. [National Institute for Lasers, Plasma and Radiations Physics, P. O. Box MG 36, 77125 Bucharest (Romania); Smausz, T. [Department of Optics and Quantum Electronics, University of Szeged, H-6720 Szeged, Dom ter 9 (Hungary); Hopp, B. [Hungarian Academy of Sciences and University of Szeged, Research Group on Laser Physics, H-6720 Szeged, Dom ter 9 (Hungary); Predoi, D. [National Institute for Physics of Materials, P.O. Box MG 07, Bucharest, Magurele (Romania); Sima, L.E.; Petrescu, S.M. [Institute of Biochemistry, Romanian Academy, Splaiul Independentei 296, 060031 Bucharest (Romania)

    2010-05-10

    Matrix assisted pulsed laser evaporation (MAPLE) was used for growing urease thin films designed for bio-sensor applications in clinical diagnostics. The targets exposed to laser radiation were made from a frozen composite manufactured by dissolving biomaterials in distilled water. We used a UV KrF* ({lambda} = 248 nm, {tau}{sub FWHM} {approx_equal} 30 ns, {nu} = 10 Hz) excimer source for multipulse laser irradiation of the frozen targets cooled with Peltier elements. The laser source was operated at an incident fluence of 0.4 J/cm{sup 2}. Urease activity and kinetics were assayed by the Worthington method that monitors urea hydrolysis by coupling ammonia production to a glutamate dehydrogenase reaction. A decrease in absorbance was measured at 340 nm and correlated with the enzymatic activity of urease. We show that the urease films obtained by MAPLE techniques remain active up to three months after deposition.

  20. Efficient photovoltaic conversion of graphene–carbon nanotube hybrid films grown from solid precursors

    International Nuclear Information System (INIS)

    Gan, Xin; Lv, Ruitao; Bai, Junfei; Zhang, Zexia; Wei, Jinquan; Huang, Zheng-Hong; Zhu, Hongwei; Kang, Feiyu; Terrones, Mauricio

    2015-01-01

    Large-area (e.g. centimeter size) graphene sheets are usually synthesized via pyrolysis of gaseous carbon precursors (e.g. methane) on metal substrates like Cu using chemical vapor deposition (CVD), but the presence of grain boundaries and the residual polymers during transfer deteriorates significantly the properties of the CVD graphene. If carbon nanotubes (CNTs) can be covalently bonded to graphene, the hybrid system could possess excellent electrical conductivity, transparency and mechanical strength. In this work, conducting and transparent CNT–graphene hybrid films were synthesized by a facile solid precursor pyrolysis method. Furthermore, the synthesized CNT–graphene hybrid films display enhanced photovoltaic conversion efficiency when compared to devices based on CNT membranes or graphene sheets. Upon chemical doping, the graphene–CNT/Si solar cells reveal power conversion efficiencies up to 8.50%. (paper)