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To improve the abrasion resistance of polycarbonate, which can be used as a replacement for glass, SiN x , SiO x N y , and SiO x thin films were deposited at low temperatures using a slot antenna electron cyclotron resonance (SLAN ECR) plasma source. The SLAN ECR plasma source has a high ionization rate even at low pressure and can thus rapidly deposit films with good mechanical properties at low temperatures. When SiH 4 gas is used as the Si precursor, the deposition rates of thin films can exceed 100 nm/min at 6.65 Pa. As the N 2 or O 2 flow decreases, the deposition rate is decreased, but the hardness H and elastic modulus E of the films gradually increases. The maximum hardness values of the prepared SiN x , SiO x N y , and SiO x films are 16.8, 14.9, and 11.4 GPa, respectively. The H / E and H 3 / E 2 values of such films are associated with abrasion resistance. However, the correlation between the H / E and H 3 / E 2 values and the abrasion resistances of our films is not strong. It is shown by annealing and abrasion experiments that the porosities of these films are more closely related than the H / E and H 3 / E 2 values to their abrasion resistances. When a hyper-thermal neutral beam (HNB) is used at low pressures, denser films are deposited. The hardness values of these films are also significantly higher. [ABSTRACT FROM AUTHOR]

The use of lattice kinetic Monte Carlo techniques for reproducing epitaxial growth of silicon using H 2 /SiH 4 chemistry is described in this work. The implementation of the surface mechanisms is limited to silane and hydrogen adsorption, surface dissociation of higher order hydrides and recombinative hydrogen desorption. Good agreement between simulation and experimental results available in the literature was obtained for H 2 desorption peak positions, equilibrium hydrogen coverages and Si growth rates. The formation of (111) and (113) planes is also reproduced, however no evidence of (131) was found even at 850° C, and (119) planes were not formed at the same position than actual grown structures. [ABSTRACT FROM AUTHOR]

Intrinsic amorphous silicon oxide (a-Si 1 − x O x :H) buffer layers were deposited on both sides of crystalline silicon (c-Si) wafers using plasma-enhanced chemical vapor deposition (PECVD) technique. The input gas flow ratio of carbon dioxide (CO 2 ) to silane (SiH 4 ) was varied in a wide range to study the passivation and structural properties of the a-Si 1 − x O x :H buffer layers. In this work, when the a-Si 1 − x O x :H layer was quite thick (> 15 nm), an extremely high effective lifetime of ~ 10 ms was achieved on the n-type float-zone c-Si (~ 3 Ω-cm, ~ 280 μm) at moderate CO 2 /SiH 4 flow ratios, resulting in an exceptionally low surface recombination velocity (< 1.4 cm/s). However, when CO 2 /SiH 4 flow ratio was either rather low (< 0.13) or extremely high (> 0.47), the surface passivation quality would deteriorate significantly. In addition, a certain amount of epitaxial phase (epi-Si) was observed in some excellent buffer layers made at the moderate CO 2 /SiH 4 ratios. Moreover, it was found that the epi-Si content could be gradually suppressed by slightly increasing the CO 2 /SiH 4 ratio without affecting passivation quality. When the a-Si 1 − x O x :H buffer layer thickness was kept at only a few nanometers as required by silicon heterojunction (SHJ) solar cells, the PECVD optimum condition (CO 2 /SiH 4 ratio) for buffer layers was revealed by applying the a-Si 1 − x O x :H buffer layers directly in a practical SHJ solar cell. We found that when the a-Si 1 − x O x :H buffer layer containing a certain amount (~ 22%) of epi-Si was employed at the back-surface-field side of the solar cell, a high open-circuit voltage ( V OC ) and a high fill factor (FF) were obtained at the same time. By contrast, at the emitter side of the solar cell, only the buffer layer without any epi-Si can be used to provide high-quality surface passivation for an excellent SHJ solar cell. [ABSTRACT FROM AUTHOR]

This work investigates the crystal quality of SiGe layers grown at low temperatures using trisilane, and germane precursors. The crystal quality sensitivity was monitored for hydrogen chloride and/or minor oxygen amount during SiGe epitaxy or at the interface of SiGe/Si layers. The quality of the epi-layers was examined by quantifying noise parameter, K 1/f obtained from the power spectral density vs. 1/f curves. The results indicate that while it is difficult to detect small defect densities in SiGe layers by physical material characterization, the noise measurement could reveal the effects of oxygen contamination as low as 0.16 mPa inside and in the interface of the layers. [ABSTRACT FROM AUTHOR]

Polydihydrosilane with pendant hexyl groups was synthesized to obtain silicon-rich amorphous silicon carbide (a-SiC) films via the solution route. Unlike conventional polymeric precursors, this polymer requires neither catalysts nor oxidation for its synthesis and cross-linkage. Therefore, the polymer provides sufficient purity for the fabrication of semiconducting a-SiC. Here, we investigated the correlation of Si/C stoichiometry between the polymer and the resultant a-SiC film. The structural, optical, and electrical properties of the films with various carbon contents were also explored. Experimental results suggested that the excess carbon that did not participate in Si C configurations was decomposed and was evaporated during polymer-to-SiC conversion. Consequently, the upper limit of the carbon in resultant a-SiC film was < 50 at.%; namely, the polymer provided silicon-rich a-SiC, whereas the conventionally used polycarbosilane inevitably provides carbon-rich one. These features of this unusual polymer open up a frontier of polymer-derived SiC and solution-processed SiC electronics. [ABSTRACT FROM AUTHOR]

Tetrasilane and digermane were used to grow epitaxial silicon germanium layers on silicon substrates in a commercial ultra-high vacuum chemical vapor deposition tool. Films with concentrations up to 19% germanium were grown at temperatures from 400 °C to 550 °C. For all alloy compositions, the growth rates were much higher compared to using mono-silane and mono-germane. The quality of the material was assessed using X-ray diffraction, atomic force microscopy, and spectroscopic ellipsometry; all indicating high quality epitaxial films with low surface roughness suitable for commercial applications. Studies of the decomposition kinetics with regard to temperature were performed, revealing an unusual growth rate maximum between the high and low temperature deposition regimes. [ABSTRACT FROM AUTHOR]

Silicon (Si) thin films were produced using an aerosol assisted atmospheric pressure chemical vapor deposition technique with liquid hydrosilane precursors cyclopentasilane (CPS, Si 5 H 10 ) and cyclohexasilane (CHS, Si 6 H 12 ). Thin films were deposited at temperatures between 300 and 500 °C, with maximum observed deposition rates of 55 and 47 nm/s for CPS and CHS, respectively, at 500 °C. Atomic force microscopic analyses of the films depict smooth surfaces with roughness of 4–8 nm. Raman spectroscopic analysis indicates that the Si films deposited at 300 °C and 350 °C consist of a hydrogenated amorphous Si (a-Si:H) phase while the films deposited at 400, 450, and 500 °C are comprised predominantly of a hydrogenated nanocrystalline Si (nc-Si:H) phase. The wide optical bandgaps of 2–2.28 eV for films deposited at 350–400 °C and 1.7–1.8 eV for those deposited at 450–500 °C support the Raman data and depict a transition from a-Si:H to nc-Si:H. Films deposited at 450 o C possess the highest photosensitivity of 10 2 –10 3 under AM 1.5G illumination. Based on the growth model developed for other silanes, we suggest a mechanism that governs the film growth using CPS and CHS. [ABSTRACT FROM AUTHOR]

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

The thin-film crystal growth of hydrogenated microcrystalline silicon (μc-Si:H) on SiO 2 was investigated by using a very-high-frequency hollow-electrode-enhanced glow plasma system with an ultrahigh-vacuum reactor. The properties of the μc-Si:H thin films deposited with different flow rates of both mono-silane and hydrogen were characterized. We achieved fabrication of a μc-Si:H thin film with a growth rate of 4.0 nm/s, good photosensitivity, high crystallinity, and highly preferred crystal orientation along the < 110 > direction at a gas pressure of 80 Pa. To study the crystallographic structure in detail, cross-sectional transmission electron microscopy (TEM), limited-visual-field electron beam diffraction imaging, and high-resolution TEM were applied for the thin films deposited with the highest (4.0 nm/s) and lowest (0.25 nm/s) growth rates, respectively. The crystallographic images clearly show columnar growth of microcrystalline silicon in every region of the films, with a very thin transition layer less than 2 nm thick, suggesting direct growth from the substrate surface. [ABSTRACT FROM AUTHOR]

A dual hot-wire arrangement has been designed and investigated for the deposition of various thin film materials by the hot-wire chemical vapor deposition (HWCVD) technique. Tantalum and rhenium wires were used for silicon and silicon carbide depositions with hydrogen diluted silane and monomethylsilane, respectively. It is shown that the both types of filaments are mechanically stable after alternate depositions of silicon and silicon carbide with a total deposition time of about 80 h. Good material quality of the deposited films is demonstrated. By taking advantage of this dual hot-wire arrangement, it is possible to deposit both kinds of thin film materials with the individual optimum deposition conditions in a single HWCVD chamber. [ABSTRACT FROM AUTHOR]

A capacitively coupled hydrogen diluted silane discharge operated at pressures above 500 Pa and driven by a combination of 13.56 MHz and 27.12 MHz is investigated by infrared laser absorption spectroscopy. Adjusting the phase angle between the two applied frequencies enables the control of the discharge symmetry via the Electrical Asymmetry Effect (EAE). The absorption measurements prove that the degree of dissociation of SiH 4 and, thus, the radical flux remains approximately constant, independently of the phase angle. Furthermore, the results show that the DC self-bias can be adjusted by tuning the phase, so that the sheath voltages change. Thus, the ion properties at the electrodes can be controlled via the EAE. This has an effect on the deposition of thin films, which are grown on glass substrates at various phase angles and analyzed using Raman spectrometry: Reducing the ion energy at the substrate leads to a decrease of the amorphous fraction in the predominantly microcrystalline film. [ABSTRACT FROM AUTHOR]

The disilane (Si2H6)+germane (GeH4) chemistry has been evaluated for the reduced pressure (2660Pa, i.e. 20Torr), low temperature growth of intrinsic and heavily boron-doped SiGe. A SiGe growth rate “plateau” has been evidenced between 650°C and 750°C. Meanwhile, the Ge concentration x was rather steady in the 500°C–700°C range. A linear increase of the SiGe growth rate with the GeH4 flow occurred at 500°C, 550°C and 675°C. The increase of x with the GeH4 mass-flow otherwise changed from linear to sub-linear as the growth temperature was reduced from 675°C down to 500°C–550°C. Be it with Si2H6 or SiH4, the SiGe growth rate fell by a factor of ~7–8 when switching from 550°C to 500°C. For the same x, growth rate was nevertheless 3–9 times higher with Si2H6 than with SiH4. We have also studied the impact of B2H6 on the 500°C growth kinetics of SiGe with Si2H6. Large substitutional boron concentrations were obtained in single-crystalline SiGe:B layers: [B]subst. ~3.7×1020 cm−3. Surface B atoms otherwise catalysed H desorption, resulting in growth rates ~5 times higher for SiGe:B than for intrinsic SiGe. Finally, a monotonic decrease of the SiGe(:B) growth rate together with a significant increase of the Ge concentration were evidenced at 500°C and 675°C when adding HCl to the gaseous mixture. At 500°C, SiGe:B growth rates still stayed 3 times higher than the intrinsic SiGe ones. Adding HCl had otherwise no clear impact on [B]subst. [ABSTRACT FROM AUTHOR]

Abstract: Band engineered Si/O superlattices are promising channel materials for ultimately scaled complementary metal oxide semiconductor devices. Theoretical calculations have indicated that insertion of O monolayers into Si lattice creates anisotropy in the Si band structure with an enhanced carrier mobility in the channel direction. However, the experimental demonstration of such superlattices is not straightforward, as it requires processes for the deposition of a monolayer of O on Si, and to continue the Si epitaxy thereon. In this work, we investigate processes for the fabrication of Si/O superlattices using the chemical vapor deposition technique. Ozone is used for the O deposition with control of the deposited O content at the monolayer level. The SiH4 based Si deposition is performed at low temperatures (500°C–550°C) in order to obtain a confined O monolayer in the Si superlattice. Si deposited on O layer of 1.2 O monolayers is completely amorphous. This indicates that this O layer is extremely uniform as it prevents any epitaxial ordering with the substrate. Reducing the O content to 0.9 O monolayers in combination with a slower Si deposition favors epitaxial ordering of Si on O/Si. Finally a defect free Si epitaxy is demonstrated on the O monolayer. Such ordering of epitaxial Si on the O layer provides a promising outlook for the growth of superlattices. [Copyright &y& Elsevier]

Abstract: Intrinsic hydrogenated amorphous silicon (i-a-Si:H) films were deposited by very high frequency (VHF) plasma enhanced chemical vapor deposition (PECVD) technique. It was found that there were three distinct deposition rate regions, when the deposition pressure and power were varied according to Paschen's law. The silane depletion fraction (SDF) is related to the reaction rates and the sticking probability of the radicals, which is smaller in the 1st region, where the SiH3 radical is the dominant deposition precursor giving rise to higher film density and a low Urbach energy (~68meV). The third region has higher SDF, where more SiH2 radicals are generated resulting in a reduction in film density and increased structural disorder due to polyhydride formation. The good quality films obtained with the condition of the 1st region, showed low SDF at lower pressure and power, following Paschen's law. Some of these i-a-Si:H films were used to fabricate p–i–n type solar cells. The measured photo voltaic parameters of one of the cells are as follows, open circuit voltage (Voc)=800mV, short circuit current density (Jsc) of 16.3mA/cm2, fill-factor (FF) of 72%, and photovoltaic conversion efficiency (η) of 9.4%, which may be due to improved intrinsic layer. Jsc, FF and Voc of the cell can be improved further with optimized cell structure and with i-a-Si:H having a lower number of defects. [Copyright &y& Elsevier]

Abstract: In this paper, the structural and optical properties of a series of silicon (Si) thin-films deposited using hot-wire chemical vapor deposition with different silane concentrations (SCs) are presented. All the films are characterized by Raman spectroscopy, scanning electron microscopy (SEM) and photoluminescence (PL). In the Raman analysis, the first order and specifically the second order Raman spectra indicate increase in crystalline grain size as well as crystalline volume fraction in the films with a reduction in SC, which is also confirmed by the SEM analysis. At the higher SC, the Si microcrystalline grains get embedded in the nanocrystalline Si network. The Gaussian fitted peaks in the PL analysis reveal the emission due to either band to band tail-state transitions or tail-state to mid-gap defect-state transitions due to Si-dangling bonds present in the films. [Copyright &y& Elsevier]

Abstract: Thermoplastic elastomers (TPE) are multifunctional polymeric materials that are characterized by moderate cost, excellent mechanical properties (high elasticity, good flexibility, hardness, etc.), high tensile strength, oxidation and wettability. With an objective of reducing the superficial friction coefficient of TPE, this work analyzes the characteristics of coating films that are based on aminopropyltriethoxysilane (APTES) over a TPE substrate. Since this material is heat-sensitive, it is necessary to use a technology that permits the deposition of coatings at low temperatures without affecting the substrate integrity. Thus, an atmospheric-pressure plasma jet system (APPJ) with a dielectric barrier discharge (DBD) was used in this study. The coated samples were analyzed by Scanning Electron Microscopy, Atomic Force Microscopy, Fourier-Transform Infrared with Attenuated Total Reflectance Spectroscopy, X-ray Photoelectron Spectroscopy and tribological tests (friction coefficient and wear rate). The studies showed that the coated samples that contain a higher amount of forms of silicon (SiOSi) and nitrogen (amines, amides and imines) have lower friction coefficients. The sample coated at a specific plasma power of 550W and an APTES flow rate of 1.5slm had the highest values of SiOSi and nitrogen-containing groups peak intensity and atomic percentages of Si2p and SiO4, and the lowest percentages of C1s and average friction coefficient. The results of this research permit one to conclude that APPJ with a DBD is a promising technique to use in coating SiOx and nitrogen-containing groups layers on polymeric materials. [Copyright &y& Elsevier]

Abstract: In this study, the inhibiting and healing effects of potassium permanganate for silane films were investigated, and the optimal mole ratio of MnO4 −/Cl− was also obtained. The inhibiting process and healing mechanism were studied by electrochemical measurements and scanning electron microcopy coupled with energy dispersive spectroscopy. Results demonstrated that the introduction of potassium permanganate to electrolyte could stop the development of corrosion process and the optimal inhibiting mole ratio of MnO4 −/Cl− is 2×10−1 with a protective efficiency about 99.24%. According to its high protective efficiency and the nice results of long-term immersion test, potassium permanganate as an inhibitor could prolong the lifetime of silane films and expand its scope of application. [Copyright &y& Elsevier]

Abstract: We prepared Ag thin films on glass substrates with an interlayer of 3-mercaptopropyl trimethoxysilane (MPTMS) for use as transparent anodes in organic light emitting diodes (OLEDs) as substitutes for conventionally used tin-doped indium oxide (ITO) films. The measured OLED properties reveal that a Ag (8nm)/MPTMS film can be used as the anode, despite having inferior optical properties to ITO films. Experiments also revealed that employing a thicker Ag film anode improved the emission properties of OLEDs. These results demonstrate that Ag/MPTMS anodes are promising for producing high-performance OLEDs. [Copyright &y& Elsevier]

Abstract: Surface treatment techniques were deployed to alter the surface of indium tin oxide (ITO) samples to attain a favorable interface between printed nano-inks and ITO surface. Surface free energy components of treated ITO substrates were calculated for each treatment using the van Oss–Chaudhury–Good method. The surface treatments of ITO changed the Lifshitz–van der Waals and Lewis acid–base components, and contact angle hysteresis significantly. Among all the surface treatments, air plasma treated samples showed high polar in nature, whereas dodecyltrichlorosilane self-assembled monolayer treated sample showed the lowest. In addition to the polarity and homogeneity, the surface roughness of the ITO was studied with respect to the surface treatment. Silver nanoparticulate ink was printed on treated ITO surfaces using aerosol jet printing system. Printed silver nano-ink line width and morphology strongly depended on the surface treatment of the ITO, ink properties and printing parameters. [Copyright &y& Elsevier]

Abstract: Nanostructured TiO2 arrays were prepared through a facile and environmentally friendly hydrothermal method on fluorine-doped tin oxide coated glass substrates with tunable surface morphologies without using any catalysts, seeds or templates. Their crystal structure, surface morphology, compositions and wettability were investigated by X-ray diffraction, field emission scanning electron microscope, X-ray photoelectron spectroscope and contact angle measurements, respectively. It is found that the concentration of hydrochloric acid has a great influence on the morphology and wettability of TiO2 nanorod films. Typically, the film prepared with 7.0M HCl exhibits a high water contact angle of 157.3±1.5° with an advancing contact angle of 154.2±1.3° and a receding contact angle of 161.2±1.3° and a small sliding angle of 7° after hydrophobic treatment. The Cassie theory was used to analyze the hydrophobic phenomenon of the as-prepared film, and it reveals that only about 9% of the water surface is contacted with the TiO2 film and the remaining 91% is contacted with the air cushion, which is reasonable for the hydrophobicity of a TiO2 nanorod film. [Copyright &y& Elsevier]

Abstract: Photosensitive TiO2/organically modified silane hybrid films were prepared by combining a low-temperature sol–gel process with a spin-coating technique. Optical properties and photochemical activities of the as-prepared hybrid sol–gel films under different UV irradiation time were characterized and monitored by prism coupling technique, UV–visible spectroscopy, and Fourier transform infrared spectroscopy. Surface morphology of the hybrid films was also observed by an atomic force microscopy. Advantages for fabrication of ridge waveguide structure based on the photosensitive hybrid films were demonstrated by an ultraviolet soft imprint technique. Effects of imprint force, imprint time, and UV irradiation time on high replication fidelity of the ridge waveguide structure were also investigated. An altitude replication fidelity of 99.7% can be obtained when the imprint force of 2MPa, imprint time of 30min and UV irradiation time of 45min were chosen. Scanning electron microscopy and surface profiler were used to characterize the morphological and surface profile properties of the as fabricated ridge waveguide structure. Results indicate that the as-prepared photosensitive hybrid materials have great applicability for the fabrication of micro-optical elements and advantage as the imprint layer under the ultraviolet soft imprint technique. [Copyright &y& Elsevier]

Abstract: In this work, a water-based silanization solution was prepared using a biphasic hydrolysis system composed of 85% (V/V) water and 15% (V/V) bis-[triethoxysilylpropyl] tetrasulfide (BTESPT)/n-heptane/ethanol mixture for efficiently coating aluminum with silane layer against corrosion. The BTESPT-based coatings on several pretreated aluminum samples were characterized by scanning electron microscopy and X-ray energy dispersive spectroscopy, and their electrochemical behaviors were assessed in 0.1M NaCl neutral solution by means of electrochemical impedance spectroscopy and Tafel polarization. The BTESPT-based coating of about 180nm thick was found to be uniform and compact, and the maximum corrosion resistance of 106 Ω of the BTESPT-treated aluminum samples was observed, which is larger than that of bare aluminum by two orders of magnitude. Durability tests in NaCl solution demonstrated that the BTESPT coating can provide superior protection of alumina substrate from corrosion for 10-day immersion in the corrosive media. [Copyright &y& Elsevier]

Abstract: Direct stamping of functional materials has been developed to reduce the number of processes and cost, and to increase throughput. However, there remain several challenging issues. One of the challenging issues is the residue-remaining problem after direct stamping. This significantly reduces reliability of stamping of micro-patterns and life-span of stamps. Here we present that direct stamping of silver nanoparticle generated conductive pattern with super-oleophobic stamp. A stamp was fabricated with UV-curable urethane rubber modified by perfluorinated silane. A master fabricated by photolithography and Bosch type etching enabled us to obtain a stamp patterned with a 2D array of voids with nano-scale re-entrant walls. And complete residue-free direct stamping of silver nanoparticles onto a glass substrate has been achieved using the stamp for little contact between the silver nanoparticle ink and the stamp was allowed by super-oleophobicity which resulted from the stamp material and pattern. [Copyright &y& Elsevier]

Abstract: The growth per cycle (GPC) temperature dependence was investigated for SiO2 films prepared by plasma-enhanced atomic layer deposition (PEALD). During preparation of PEALD-SiO2 using bis-diethyl-amino-silane, the GPC was saturated via increasing the precursor dose time and flow rate. The saturated GPC decreased with increasing deposition temperature. GPC saturation curves as a function of precursor dose time were analyzed by a two-step adsorption model, where the amino-silane reversibly adsorbed (physisorption) during the first step, and then irreversibly adsorbed (chemisorption) on the SiO2 surface upon reaction with surface OH absorbents. This model is in good quantitative agreement with the saturation curve. The GPC value was determined by the surface reaction of amino-silane with OH sites, whose surface density was decreased by increasing the deposition temperature. The GPC saturation became slower with increasing deposition temperature, because the desorption rate of the physisorbed precursor increased with increasing temperature. [Copyright &y& Elsevier]

Abstract: The decisive criterion associated with the species emission intensity ratio (Hα/SiH*) which characterizes the crystallinity of microcrystalline silicon (μc-Si) film was found to display an unstable behavior resulting from species concentration variation during μc-Si film growth with optical emission spectroscopy (OES) tool. In this study, a real-time process control system i.e. closed-loop system was developed. It aims to control the species intensity ratio with OES device in a very high frequency (VHF) plasma enhanced chemical vapor deposition reactor, via modulating the VHF power and silane dilution to improve μc-Si film growth for high efficiency a-Si/μc-Si tandem solar cell. The experiment results show that the closed-loop system stabilized the Hα/SiH* intensity ratio within a variation of 5% during the μc-Si film deposition process. Higher growth rate of μc-Si film with the same crystallinity was obtained in the closed loop system which consumed less power and SiH4 gas than in the open loop system, i.e. without process control. [Copyright &y& Elsevier]

Abstract: In a 300mm industrial Reduced Pressure–Chemical Vapour Deposition tool we have assessed the advantages and drawbacks of disilane for the low temperature growth of Si and SiGe. Four distinct regions can be noticed on the Arrhenius plot of the Si growth rate at 2660Pa (i.e. 20Torr) from Si2H6 as a function of the reverse growth temperature. For T>850°C, we are in the high temperature, Si precursor supply-limited regime (as with SiH4). For T≤850°C, the situation is more complicated, with the presence of a growth rate “plateau” between 575°C and 675°C (not present for SiH4 or SiH2Cl2), surrounded by domains where the Si growth rate increases with the temperature at different rates (Ea =1.39eV (T>675°C)⇔Ea =2.30eV (T<575°C)). This translates into Si growth rates which, for T<575°C, are approximately ten times higher with Si2H6 than with SiH4, which are in turn roughly ten times higher than with SiH2Cl2. For given GeH4 and Si precursor mass–flow ratios, lower Ge contents and much higher SiGe growth rates are obtained at 550°C, 2660Pa with Si2H6 than with SiH4 and especially SiH2Cl2. SiGe and Si layers grown with disilane are generally of high crystalline quality, however moderate Si2H6 mass-flows should be used in the growth rate plateau, in order to avoid the formation of defective Si. [Copyright &y& Elsevier]

Abstract: The Chemical Vapor Deposition growth mechanism of a hafnium silicate film deposited by means of the co-flow of two precursors, TDEAH (tetrakis-diethyl-amino-hafnium) and 4DMAS (tetrakis-dimethyl-amino-silane), is characterized. Typical growth kinetics demand that the deposition rate increases and the silicon concentration remain stable with increasing reactor pressure. Though the deposition rate follows the expected growth kinetics, the silicon concentration in the silicate does not and exhibits an abnormal increase with increasing reactor pressure. To understand this atypical behavior the formation of pure HfO2 from TDEAH and pure SiO x from 4DMAS is first studied. Experimental results show that whereas the HfO2 deposition is well behaved and fits a diffusion-based model defined by assuming diffusion of TDEAH through a boundary layer, the deposition of SiO x with 4DMAS requires Hf-O nucleation sites and self-saturates after a single Si―O monolayer is formed. Based on these observations, a model is developed for hafnium silicate formation. The Atomic Layer Deposition like behavior of 4DMAS decomposition results in a deposition rate and film stoichiometry that are weakly sensitive to the 4DMAS partial pressure, and instead are driven by the TDEAH reaction. Since TDEAH operates within a transport-limited regime, the deposition rate is insensitive to substrate temperature, and is only controlled by the TDEAH partial pressure and the gas phase kinematics, rendering the process robust and easily controllable with excellent reproducibility. [Copyright &y& Elsevier]

Abstract: Among an extremely large number of possible fullerene applications in the field of electronics, optics and photovoltaics, C60-cages are also considered as a promising dopant for low dielectric constant (low-k) materials. In this study, we incorporated C60 species into a 3-aminopropyltrimethoxysilane (APTMS) based material. We prepared thin films by spin coating. Using X-ray photoelectron spectroscopy we analyzed the time-related interactions between the components of the prepared samples and the influence of the C60 replacement by its better soluble derivative [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) on the chemical properties of the material. We applied atomic force microscopy to investigate the surface texture and thicknesses of the obtained films. In order to obtain information concerning the electrical properties of the material we performed capacitance-voltage characterization. We have proven that the increase of C60 species realized by PCBM incorporation within the APTMS-based matrix reduces the dielectric constant of the examined films while preserving its homogeneity. [Copyright &y& Elsevier]

Abstract: Homogeneously modified methyltrimethoxysilane (MTMS) films used as the barrier layers were fabricated on stainless steel substrates by introducing only very low amount of metal alkoxide, e.g. tetrabutyl orthotitanate or tetrabutyl orthozirconate into the silane/ethanol/water precursors. The modified films exhibit tremendous improvement in their barrier performance, along with higher compactness, hydrophobicity and thickness. Solution analysis of the silane precursors indicated that both the hydrolysis and condensation reactions of MTMS were significantly facilitated in the presence of metal alkoxide. A schematic description for the promoted formation of metal alkoxide-modified silane films which is in accordance with our findings is given. [Copyright &y& Elsevier]

Abstract: Superhydrophobic ZnO submicrorod films have been fabricated on zinc sheets through an H2O2-assisted surface etching process and subsequent surface modification with a monolayer of 1H,1H,2H,2H-perfluorodecyltriethoxysilane (FDS). The crystal structure, chemical compositions, morphologies, and wettability of the resultant ZnO films were analyzed by means of X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy, and water contact angle measurements. It is found that the surface of the as-prepared ZnO films on zinc substrate was hydrophobic with a water contact angle of 95±2°, whereas after modification with FDS, the film exhibited superhydrophobicity and the water CA increased to 154±2°. It is shown that both the higher surface roughness and the lower surface free energy play an important role in creating the superhydrophobic films. [Copyright &y& Elsevier]

Abstract: Amorphous and microcrystalline silicon thin films are used in solar cells as a multi-junction photovoltaic device. Plasma enhanced chemical vapor deposition is used and high deposition rate of a few nm/s is required while keeping film quality. SiH4 is used as a precursor diluted with H2. Electron impact processes give complex interdependent plasma chemical reactions. Many researchers suggest keeping high H/SiHx ratio is important. Numerical modeling of this process for capacitively coupled plasma and inductively coupled plasma is done to investigate which process parameters are playing key roles in determining it. A full set of 67 volume reactions and reduced set are used. Under most of conditions, CCP shows 100 times higher H/SiH3 ratio over ICP case due to its spatially localized two electron temperature distribution. Multi hollow cathode type CCP is also modeled as a 2×2 hole array. For Ar, the discharge is well localized at the neck of the hole at a few Torr of gas pressure. H2 and SiH4 +H2 needed higher gas pressure and power density to get a multi hole localized density profile. H/SiH3 was calculated to be about 1/10. [Copyright &y& Elsevier]

Abstract: A one-dimensional fluid model is developed to investigate the behavior of plasma in the afterglow of pulsed voltage modulated SiH4/N2/NH3 discharges at radio-frequency (400kHz), which are used for the deposition of silicon nitride (SiNx) films. The model incorporates particle balances, electron energy balance, and Poisson''s equation, allowing the equations solved self-consistently. The current work is an attempt to understand the effect of duty cycle on the characteristics of silicon nitride (SiNx) films. Therefore, the influences of duty cycle on the plasma density, electron temperature, and ion energy at the powered electrode were carefully discussed. We find that by decreasing the duty cycle, the negative ions can be able to escape during the off-time, and the positive ion energy is effectively decreased. On the other hand, the positive ion density is slightly decreased. [Copyright &y& Elsevier]

Abstract: Low-dielectric constant SiOC(were deposited on p-type Si(100) substrates by plasma-enhanced chemical-vapor deposition (PECVD) using dimethyldimethoxy silane (DMDMS, C4H12O2Si) and oxygen gas as precursors. To improve the physicochemical properties of the SiOC( the deposited SiOC(were exposed to ultraviolet (UV) irradiation in a vacuum. The bonding structure of the SiOC(was investigated by Fourier transform infrared (FTIR) spectroscopy and X-ray photoelectron spectroscopy (XPS). The electrical characterization of SiOC(were carried out through I–V measurements using the comb-like patterns of the TiN/Al/Ti/SiOC(/Ti metal–insulator–metal (MIM) structure. Excessive UV treatment adversely affected the SiOC(which resulted in an increased dielectric constant. Our results provide insight into the UV irradiation of low-k SiOC( [Copyright &y& Elsevier]

Abstract: In this paper, a one-dimensional self-consistent fluid model is applied to simulate high frequency atmospheric pressure glow discharges. The results show that the plasma density and current density depend strongly on the excitation frequency. When the excitation frequency is below 13.56MHz, the discharge operates in the α mode, and when the excitation frequency is above 13.56MHz, the discharge operates in a γ-like mode. The densities of species including SiH3 +, SiH3 −, SiH3, SiH2, H, Ar+, Ar⁎ and electron are enhanced with the frequency increasing from 6.78 to 27.12MHz. Similar discharge mode transition was observed experimentally in radio frequency atmospheric pressure He glow discharges. The effects of excitation frequency on plasma characteristics and densities of precursors for μc-Si:H film are further discussed. This study reveals that an appropriate excitation frequency is important for the growth of μc-Si:H film. [Copyright &y& Elsevier]

Abstract: Epitaxial silicon thick films have been deposited at around 400°C by mesoplasma chemical vapor deposition with trichlorosilane (TCS) as source gas. The deposition rate of the Si films increases linearly with the TCS flow rate and reaches 30nm/s at 15sccm of TCS. These films have exhibited relatively high hall mobility (~200cm2/V-s) independently of the deposition rate. [Copyright &y& Elsevier]

Abstract: Doped silicon nanoparticles have successfully been produced by hot wire thermal catalytic pyrolysis at 40mbar and a filament temperature of 1800°C, using a mixture of silane and diborane or phosphine. All particles are monocrystalline with shapes ranging from an octahedron to varying degrees of truncation of this basic shape, with an average diameter of 22nm. To determine the doping activity, the resistivity of the nanopowders was measured at successive compression levels. While boron doped particles have clean surfaces and are electrically active, with compacted powder having a resistivity of the order of 103 Ω m, phosphorus doped particles are covered by an oxide layer whose thickness increases from 0.3nm to 0.6nm with higher phosphine concentrations. Furthermore, the phosphor atoms are localised at the interface to this surface layer, where they are electrically inactive. These powders have a resistivity in the order of 107 Ω m. [Copyright &y& Elsevier]

Abstract: The structural properties of microcrystalline Si films prepared by hot-wire/catalytic chemical vapor deposition, with various dilution ratios of silane in hydrogen, were investigated as regards to the role of hydrogen. A large surface roughness correlated with a low crystalline nuclei density was observed for microcrystalline Si films deposited near the transition from amorphous to microcrystalline growth. Investigations of hydrogen-related properties suggest the presence of molecular hydrogen in these films. We tentatively propose that the diffusion of atomic hydrogen into the subsurface layer of growing films, which leads to the relaxation of amorphous Si network and to the generation of molecular hydrogen, plays an important role for determining the film properties, besides top surface reactions. [Copyright &y& Elsevier]

Abstract: The effect of filament temperature and deposition time on the formation of tungsten silicide upon exposure to the SiH4 gas in a hot wire chemical vapor deposition process was studied using the techniques of cross-sectional scanning electron microscopy and Auger electron spectroscopy. At a relatively low temperature of 1500°C, the decomposition of WSi2 phase and the diffusion of Si towards the silicide/W interface produce a thick W5Si3 layer. The diffusional nature leads to a parabolic rate law for silicide growth. An exponential decrease of silicide thickness with temperature between 1600 and 2000°C illustrates the dominance of Si evaporation at higher temperatures (T≥1600°C) over the silicide formation. [Copyright &y& Elsevier]

Abstract: “Super H2O-barrier film” with a water vapor transmission rate (WVTR) less than 1mg/m2/day has been developed. The barrier layer is a single layer of amorphous SiCN grown by organic Cat-CVD (O-Cat-CVD) with a thickness of 100nm. SiCN has been grown by using a gas mixture of monomethylsilane (MMS; Si (CH3)H3), NH3 and H2 on polyethylene-naphthalate (PEN) film substrates. It has been found that the WVTR drastically depends on the W-filament temperature of O-Cat-CVD. The WVTR changed from 5×10−1 to 1×10−3, corresponding to the W-filament temperature increase from 1100 to 1200C. We have recently succeeded in developing the “super H2O-barrier film” by the coating of single layers of SiCN for both sides of the PEN film without using the widely used polymer/inorganic multilayer coating. The both-side coating has been found to be crucial to avoid the H2O penetration into PEN films and also to avoid the breakdown of the SiCN/PEN interface caused by the H2O accumulation at the interface. [Copyright &y& Elsevier]

Abstract: Microcrystalline silicon carbide (μc-SiC:H) thin films in stoichiometric form were deposited from the gas mixture of monomethylsilane (MMS) and hydrogen by Hot-Wire Chemical Vapor Deposition (HWCVD). These films are highly conductive n-type. The optical gap E 04 is about 3.0–3.2eV. Such μc-SiC:H window layers were successfully applied in n-side illuminated n-i-p microcrystalline silicon thin film solar cells. By increasing the absorber layer thickness from 1 to 2.5μm, the short circuit current density (j SC) increases from 23 to 26mA/cm2 with Ag back contacts. By applying highly reflective ZnO/Ag back contacts, j SC =29.6mA/cm2 and η =9.6% were achieved in a cell with a 2-μm-thick absorber layer. [Copyright &y& Elsevier]

Abstract: Organic–inorganic polymers formed by hydrolysis/condensation reactions of alkoxide precursors, such as organically modified silanes (Ormosils) are used for several industrial applications such as electronic, optical and protective anticorrosion coatings. Such materials possess superior chemical stability, physical strength and scratch resistance characteristics when compared to organic polymers. Further performance improvement can be achieved through the incorporation of zirconium and titanium based nanoparticles, also formed through from precursors via the sol–gel process. However due to the inherent reactivity differences of the above precursors, they must be hydrolysed separately before being combined for final condensation. Zirconium precursors are commonly chelated using acetic acid or acetyl acetonate prior to hydrolysis, to lower the hydrolysis rate. In this body of work, 3,4-diaminobenzoic acid (DABA) and acetyl acetonate (acac) were compared as chelating ligands for controlling the hydrolysis reactions of zirconium n-propoxide to form nanoparticles within a silane sol matrix. The sols were applied as coatings on aerospace grade aluminium alloy AA 2024-T3 and characterised by physical, spectroscopical, microscopical, electrochemical and calorimetric techniques. The electrochemical properties of the coatings, as characterised by EIS and PDS, correlated with neutral salt spray evaluations confirming that the use of DABA as a chelating ligand significantly improved the coating performance when compared to the traditional diketone ligand. The data indicates the anticorrosion properties of the nitrogen rich chelate have a key role in protecting the alloy through the formation of smaller zirconium nanoparticles, thus improving the polymer network stability. [Copyright &y& Elsevier]

Abstract: In this work, 29Si nuclear magnetic resonance and Fourier-transformed infrared spectroscopy were combined to study the hydrolysis and polycondensation of γ-aminopropyltriethoxysilane (γ-APS), both in the liquid sol state and in the film state. γ-APS sols were prepared in methanol or ethanol solvent in the pH range from 5.7 to 11 and deposited. The aim of the present study was to get the most complete picture in regard to the chemical events and time scale of these events. Transesterification reactions between γ-APS and methanol result in faster kinetics in methanol compared to ethanol. γ-APS films were deposited on aluminium and dried at ambient conditions (23°C, 55% relative humidity). The silane films reached a chemical equilibrium in a couple of minutes (natural pH of 11) to 1h (pH 7) depending on the pH of the silane solution. From a practical perspective, the results obtained here might give some clues to define an optimized schedule for the application of γ-APS coupling agent to metals. [Copyright &y& Elsevier]

Abstract: We have previously described nanoparticle nanotubes (NPNTs), i.e., tubular metallic nanostructures comprising coalesced nanoparticles (NPs), obtained by passing citrate-stabilized metal (Au, Ag, Pd) NP solutions through aminosilane-modified nanoporous alumina membranes. Here we show that the mechanism of NPNT formation involves two stages: (i) electrostatic binding of a monolayer of metal NPs to the amine groups on the membrane pore walls; and (ii) accumulation of NP multilayers and room-temperature coalescence to form solid nanotubes. Free-standing NPNTs are obtained by post-dissolution of the membrane template. An improved fabrication apparatus enabled evaluation of the role of drying and other preparation parameters on the NP coalescence and NPNT formation and structure. Intermittent drying during the NP accumulation stage is necessary for the formation of solid NPNTs, while a slow flow rate of the colloid solution through the membrane pores and reversal of the flow direction promote the formation of more uniform and longer NPNTs. [Copyright &y& Elsevier]

Abstract: Surface relief gratings on organic polysilane thin films are fabricated by holographic exposure of ultra-violet light, and Au gratings are subsequently prepared on polysilane gratings by vapor deposition of Au. The anchoring energies of 4-pentyl-4′-cyanobiphenyl (5CB) nematic liquid crystal on the fabricated gratings are determined with a saturation voltage method. The anchoring energies of Au gratings are weaker than those of organic polysilane gratings because of suppression of π–π interaction between the liquid crystal and the alignment layer. The polar anchoring energies of Au gratings are also weaker than those reported in literature. [Copyright &y& Elsevier]

Abstract: The effect of adding clay, modified by a silane coupling agent, into the carbon nanotube (CNT) paste on the field electron emission and a lifetime of screen printed CNT film was studied. The composition of organophilic clay and CNTs was characterized by a combination of X-ray diffraction, and scanning electron microscopy. The incorporation of clay improved the dispersivity, adhesiveness, and conductive networking of paste, therewith enhancing the field emission''s uniformity and stability. The improvement of this gas barrier on the CNT film by clay loading prevents emission degradation. [Copyright &y& Elsevier]

Abstract: Magnesium and its alloys have desirable physical and mechanical properties for a number of applications. Unfortunately, these materials are highly susceptible to corrosion, particularly in the presence of aqueous solutions. The purpose of this study is to develop a uniform, non-toxic surface treatment to enhance the corrosion resistance of magnesium alloys. This paper reports the influence of the coating bath parameters and alloy microstructure on the deposition of 3-mercaptopropyltrimethoxysilane (MPTS) coatings on magnesium alloy AZ91. The surface chemistry at the magnesium/MPTS interface has also been explored. The results indicate that the deposition of MPTS onto AZ91 was influenced by both the pH and MPTS concentration in the coating bath. Furthermore, scanning electron microscopy results showed that the MPTS film deposited uniformly on all phases of the magnesium alloy surface. X-ray photoelectron spectroscopy studies revealed that at the magnesium/MPTS interface, the molecules bond to the surface through the thiol group in an acid–base interaction with the Mg(OH)2 layer, whereas in the bulk of the film, the molecules are randomly oriented. [Copyright &y& Elsevier]