Hydrogen Dilution Research Articles

Intrinsic thin film properties study of hydrogenated silicon using the method of RF-PECVD

Effect of hydrogen dilution on deposition rate, energy band gap, localized state defect - through observation of energy absorption Urbach, and surface roughness of intrinsic thin film was investigated using RF-PECVD. Films were grown on ITO glass substrate. Analysis of energy band gap was conducted to determine changes in the structure of a thin film of a-Si:H. Energy band gap is important to determine the portion of the spectrum of sunlight that is absorbed solar cells. The sun’s rays with energy greater than the energy band gap will be absorbed by the solar cell, but the rest will be the thermal energy which results in low efficiency. Characterization using UV-Vis spectrometer and Tauc’s plot methods showed that wide energy band gap was greater for larger hydrogen dilution. Moreover, the increase of the hydrogen dilution will decrease the rate of deposition and the Urbach energy. It is estimated that with an increased dilution of hydrogen will be obtained μc-Si:H film structure. This structure is more conductive due to the reduction of residual bandtail defect or dangling bond defects.

Role of Hydrogen Flow Rate on Microstructure of a-Si:H(n) Films: Spectroscopic Ellipsometry Studies

The influence of hydrogen flow rate on the microstructure and optical properties of phosphorous doped hydrogenated amorphous silicon (a-Si:H(n)) films is studied through spectroscopic ellipsometry (SE). A series of a-Si:H(n) films were deposited using radio frequency plasma enhanced chemical vapour deposition (RFPECVD) technique by varying the hydrogen flow rate (HFR) in the range of 30–80 SCCM. The SE measurements showed a shift in peak position of pseudo dielectric function of these films from 3.6 eV (for pure a-Si:H) to 4.1 eV with a shoulder peak at 3.4 eV (nanocrystallites embedded a-Si:H) as the hydrogen flow rate was increased. A systematic increase in crystalline fraction along with a decrease in void fraction was observed as HFR was increased up to 70 SCCM during deposition. The results confirm that hydrogen dilution helps in improving the microstructure of films and favours the formation of strong Si–H bonds. Beyond 70 SCCM of HFR, a large flux of hydrogen resulted in an increase in void fraction and disorder in the films.

Improvement of Electrical Performance in P-Channel LTPS Thin-Film Transistor with a-Si:H Surface Passivation.

We report the effects of surface passivation by depositing a hydrogenated amorphous silicon (a-Si:H) layer on the electrical characteristics of low temperature polycrystalline silicon thin film transistors (LTPS TFTs). The intrinsic a-Si:H layer was optimized by hydrogen dilution and its structural and electrical characteristics were investigated. The a-Si:H layer in the transition region between a-Si:H and µc-Si:H resulted in superior device characteristics. Using a-Si:H passivation layer, the field-effect mobility of the LTPS TFT was increased by 78.4% compared with conventional LTPS TFT. Moreover, the leakage current measured at VGS of 5 V was suppressed because the defect sites at the poly-Si grain boundaries were well passivated. Our passivation layer, which allows thorough control of the crystallinity and passivation-quality, should be considered as a candidate for high performance LTPS TFTs.

Simulation and safety analysis of the leakage of liquefied hydrogen from high-pressure container

In this paper, the leakage and diffusion of liquefied hydrogen which is stored in high-pressure container were investigated and the safety arrangement in cosmodrome focused on the effects of external flow on the above process was proposed. The phase transition process of leakage of liquefied hydrogen at the initial stage was first analyzed by considering the motion of single particle and particle group. Furthermore, the rule of leakage and diffusion of liquefied hydrogen under different conditions was thoroughly examined by CFD modelling. Through this work, the leakage pressure, leakage location, external air-flow direction and external air-flow velocity are found to have great effects on the diffusion of leaking hydrogen. By increasing the leakage pressure and putting leakage port closer to ground, the diffusion and dilution of leaking hydrogen would be strongly expedited to spread much further away. By adopting upper air blow and raising the external air speed, the concentration can be fairly reduced.

Passivation optimization and performance improvement of planar a-Si:H/c-Si heterojunction cells in perovskite/silicon tandem solar cells

Recently, the monolithic spin-coating perovskite/planar silicon heterojunction tandem solar cells with high performance have attracted attention mainly due to simple fabrication, low preparation cost and high efficiency, especially compared with fully textured multi-junction perovskite/silicon tandem device. As is well known, the excellent passivation of a-Si:H/c-Si interface is the key to achieving a high-efficiency planar silicon heterojunction solar cell, which further improves the performance of the corresponding tandem cell. Therefore, we investigate the elements affecting a-Si:H/c-Si interface passivation, including the c-Si surface treatment technique, a-Si:H passivation layer and P-type emitter layer and so on. In these experiments, we adjust the immersed time of diluent hydrofluoric acid and pre-deposited hydrogen plasma with different gas mixture flows. Also, the suitable deposition parameters of intrinsic a-Si:H passivation layer are regulated by varying hydrogen dilution and time, and variously slight silane content is embedded into i-a-Si:H /P-type (I/P) emitter interface by hydrogen-rich plasma treating which is for acquiring optimal experimental processing conditions to promote the chemical passivation. In addition, the p-a-Si:H and p-nc-Si:H are comparatively studied as buffer layers to further improve the I/P interface passivation by varying the hydrogen dilution in the gas mixture during deposition. It can be found that p-nc-Si:H buffer layer with high conductivity and wide bandgap can not only reduce the defect density at the I/P interface, but also increase the conductivity of P-type emitter, which further improves the field passivation effect. By the above- mentioned optimization, the highest minority carrier lifetime and implied open-circuit voltage (<i>iV</i><sub>oc</sub>) of the structure of P-type emitter/a-Si:H(i)/c-Si/a-Si:H(i)/N-type layer (inip) sample can respectively reach 2855 μs and 709 mV, which demonstrates authentically outstanding passivation performance. An efficiency of 18.76% can be obtained for the planar a-Si/c-Si heterojunction solar cell with a <i>V</i><sub>oc</sub> of 681.5 mV, which is 34.3 mV higher than that of the reference device. Regarding the optimized planar a-Si:H/c-Si heterojunction solar cell as the bottom cell, we also obtain an efficiency of 21.24% for perovskite/silicon heterojunction tandem solar cell with an open-circuit voltage of 1780 mV, which proves that the above strategies are very effective for improving the passivation optimization and performance of bottom cell in the tandem device.

The Variation of Crystalline Structure Induced by Gas Dilution and Thermal Annealing in Silicon Layers Deposited by PECVD Technique

We prepared hydrogenated thick silicon film by plasma enhanced chemical vapor deposition (PECVD) method using SiH4 and H2 gas mixture and we investigated the effect of the hydrogen dilution ratio defined as $$ R=\frac{\left[{H}_2\right]}{\left[{SiH}_4\right]} $$ on the as-deposited and annealed films. With increase in hydrogen dilution ratio, amorphous to microcrystalline transition has been observed. The crystallization has been confirmed from Raman spectroscopy, UV reflectance, low angle X-ray diffraction (XRD), spectroscopic ellipsometry and atomic force microscopy (AFM) analysis. Tauc band gap shows a decreasing trend with increasing H2 dilution of silane. It decreases from 1.8 to 1.57 eV. It has been concluded that H2 dilution of silane in PECVD enhances the crystallinity of the film and affects its optical and structural properties.

Effect of incorporation of highly‐ordered a‐Ge:H nanoparticles on the performance of perovskite solar cells

To improve light absorption, in this study, the narrow band gap highly-ordered free-standing hydrogenated amorphous germanium nanoparticles (a-Ge:H NPs) were introduced into the CH3NH3PbI3−x Cl x films. Here, the NPs were fabricated by means of the radio frequency plasma enhanced chemical vapour deposition system. The effects of hydrogen dilution ratio (RH) on the microstructure and bonding configuration of a-Ge:H NPs were investigated by Raman, transmission electron microscopy and Fourier transform infrared spectroscopy measurements. As RH increases, an improvement in the structure order of a-Ge:H NPs was observed. Compared with the pure CH3NH3PbI3−x Cl x films, the light absorption of the hybrid a-Ge:H NPs/CH3NH3PbI3−x Cl x active layers was improved, and the surface coverage of the hybrid active layers nearly reached 100%. This new finding provided a novel way to solve the universal unfavourable surface coverage problem that existed in the ultrasonic spray-coating process. Meanwhile, compared with the device that is based on pure CH3NH3PbI3−x Cl x films, due to the enhanced light absorption in the visible range, a ∼14.6% enhancement in the power conversion efficiency was achieved based on the hybrid a-Ge:H NPs/CH3NH3PbI3−x Cl x active layers.

Laminar burning velocities and flame instabilities of diluted H2/CO/air mixtures under different hydrogen fractions

An experimental study was conducted using outwardly propagating flame to evaluate the laminar burning velocity and flame intrinsic instability of diluted H2/CO/air mixtures. The laminar burning velocity of H2/CO/air mixtures diluted with CO2 and N2 was measured at lean equivalence ratios with different dilution fractions and hydrogen fractions at 0.1 MPa; two fitting formulas are proposed to express the laminar burning velocity in our experimental scope. The flame instability was evaluated for diluted H2/CO/air mixtures under different hydrogen fractions at 0.3 MPa and room temperature. As the H2 fraction in H2/CO mixtures was more than 50%, the flame became more unstable with the decrease in equivalence ratio; however, the flame became more stable with the decrease in equivalence ratio when the hydrogen fraction was low. The flame instability of 70%H2/30%CO premixed flames hardly changed with increasing dilution fraction. However, the flames became more stable with increasing dilution fraction for 30%H2/70%CO premixed flames. The variation in cellular instability was analyzed, and the effects of hydrogen fraction, equivalence ratio, and dilution fraction on diffusive-thermal and hydrodynamic instabilities were discussed.

In Situ Plasma Monitoring of PECVD nc-Si:H Films and the Influence of Dilution Ratio on Structural Evolution

We report plasma-enhanced chemical vapor deposition (PECVD) hydrogenated nano-crystalline silicon (nc-Si:H) thin films. In particular, the effect of hydrogen dilution ratio (R = H2/SiH4) on structural and optical evolutions of the deposited nc-Si:H films were systematically investigated including Raman spectroscopy, Fourier-transform infrared spectroscopy (FTIR) and low angle X-ray diffraction spectroscopy (XRD). Measurement results revealed that the nc-Si:H structural evolution, primarily the transition of nano-crystallization from the amorphous state to the nanocrystalline state, can be carefully induced by the adjustment of hydrogen dilution ratio (R). In addition, an in situ plasma diagnostic tool of optical emission spectroscopy (OES) was used to further characterize the crystallization rate index (Hα*/SiH*) that increases when hydrogen dilution ratio (R) rises, whereas the deposition rate decreases. Another in situ plasma diagnostic tool of quadruple mass spectrometry (QMS) also confirmed that the “optimal” range of hydrogen dilution ratio (R = 30–40) can yield nano-crystalline silicon (n-Si:H) growth due to the depletion of higher silane radicals. A good correlation between the plasma characteristics by in situ OES/QMS and the film characteristics by XRD, Raman and FTIR, for the transition of a-Si:H to nc-Si:H film from the hydrogen dilution ratio, was obtained.

A quasi-2D transient model of proton exchange membrane fuel cell with anode recirculation

Anode recirculation of proton exchange membrane fuel cell (PEMFC) is considered as an effective way for self-humidification and efficient hydrogen utilization, but nitrogen crossover presents a problem. To investigate the transient characteristics of PEMFC with anode recirculation, a comprehensive quasi-2D non-isothermal transient model is developed. The simulation results show that for a PEMFC initially operated with dry hydrogen, anode recirculation leads to certain level of performance increase in the beginning due to self-humidification effect, and then the performance decreases caused by nitrogen crossover, hydrogen dilution and the increase of anode activation loss. The nitrogen accumulation in anode downstream is severer than upstream, and the performance decline rate decreases with increasing cathode inlet velocity under the simulated operating conditions. The performance and current density distribution uniformity of counter-flow configuration is better than co-flow under low inlet humidity, but the difference becomes smaller with anode recirculation. Anode recirculation and dead-ended anode (DEA) operation both have self-humidification effect, and compared to DEA, the advantages of anode recirculation can be summarized as lower performance decline rate, less chance of local hydrogen starvation and better current density distribution uniformity.

Autoignition of hydrogen in shear flows

In this paper, we compare the autoignition characteristics of laminar, nitrogen-diluted hydrogen jets in two different oxidizer flow configurations: (a) co-flowing heated air and (b) wake of heated air, using two-dimensional numerical simulations coupled with detailed chemical kinetics. In both cases, autoignition is observed to initiate at locations with low scalar dissipation rates and high HO2 depletion rates. It is found that the induction stage prior to autoignition is primarily dominated by chemical kinetics and diffusion while the improved scalar mixing imparted by the large-scale flow structures controls the ignition progress in later stages. We further investigate the ignition transience and its connection with mixing by varying the initial wake conditions and fuel jet to oxidizer velocity ratios. These studies reveal that the autoignition delay times are independent of initial wake flow conditions. However, with increased jet velocity ratios, the later stages of ignition are accelerated, mainly due to enhanced mixing facilitated by the higher scalar dissipation rates. Furthermore, the sensitivity studies for the jet in wake configuration show a significant reduction in ignition delay even for about 0.14% (by volume) hydrogen dilution in the oxidizer. In addition, the detailed autoignition chemistry and the relative roles of certain radical species in the initiation of the autoignition process in these non-premixed jets are investigated by tracking the evolution of important chain reactions using a Lagrangian particle tracking approach. The reaction H2 + O2 ↔ HO2 + H is recognized to be the dominant chain initiation reaction that provides H radicals essential for the progress of subsequent elementary reactions during the pre-ignition stage.

The effects of doping type on structural and electrical properties of silicon nanocrystals layers grown by plasma enhanced chemical vapor deposition

The purpose of this paper is to compare the influence of boron and phosphor doping on the optical, structural and electrical properties of hydrogenated amorphous silicon (a-Si:H) thin films elaborated at low radiofrequency power and low hydrogen dilution. Structural properties of deposited films were investigated by scanning electron microscopy (SEM), grazing incidence X-ray diffraction (GI-XRD) and Raman spectroscopy. The SEM analysis shows that the best homogeneity is observed in the layer doped with low diborane flow rate. Reflectance, XRD and Raman measurements show that the doping of thin films induces the formation of nanocrystallites (nc-Si) embedded in the amorphous matrix with higher density in the phosphorus-doped layers compared to those of boron-doped one. The temperature dependent electrical properties of Au/a-Si:H Schottky diodes were investigated using current–voltage characteristics (I–V), admittance spectroscopy technique and capacitance–voltage characteristics [C(V)] in the temperature range of 100–400 K. From the I–V analyses based on thermionic emission (TE) theory we notice the heterogeneity of the barrier height of the Schottky diodes. From the electrical conductivity measurements, we plotted the evolution of the logarithm of the conductivity σ·T as a function of 1000/T. Activation energies \({\text{E}}_{{\text{a}}}^{{{\text{Low}}}}\) and \({\text{E}}_{{\text{a}}}^{{{\text{High}}}}\) of the samples in low and high temperature ranges respectively are estimated. The decrease of \({\text{E}}_{{\text{a}}}^{{{\text{Low}}}}\) with increasing boron flow rate is attributed to an increase in the density of the traps in the band gap of silicon. On the other hand, we found that \({\text{E}}_{{\text{a}}}^{{{\text{High}}}}\)increases when the flow rate of boron increases and decreases when the flow rate of phosphorus increases. We attributed these behaviors to the increase in the crystallinity of the n-type layers and to the presence of a deep defect in the p-type layers. C−2(V) plots show the presence of two linear regions. We found that the response of the nanocrystalline phase becomes more pronounced at high doping flow rate. Optical, structural and electrical measurements confirmed that the type and the density of doping are important parameters that influence the electrical properties of nc-Si:H Schottky diodes.

Evolution of Structural and Electrical Properties of Carbon Films from Amorphous Carbon to Nanocrystalline Graphene on Quartz Glass by HFCVD.

Direct growth of graphene films on glass is of great importance but has so far met with limited success. The noncatalytic property of glass results in the low decomposition ability of hydrocarbon precursors, especially at reduced temperatures (<1000 °C), and therefore amorphous carbon (a-C) films are more likely to be obtained. Here, we report the hydrogen influence on the structural and electrical properties of carbon films deposited on quartz glass at 850 °C by hot-filament chemical vapor deposition (HFCVD). The results revealed that the obtained a-C films were all graphitelike carbon films. Structural transition of the deposited films from a-C to nanocrystalline graphene was achieved by raising the hydrogen dilution ratios from 10 to over 80%. On the basis of systematic structural and chemical characterizations, a schematic process with three steps including sp2 chain aggregation, aromatic ring formation, and sp3 bond etching was proposed to interpret the structural evolution. The nanocrystalline graphene films grown on glass by HFCVD exhibited good electrical performance with a carrier mobility of 36.76 cm2/(V s) and a resistivity of 5.24 × 10-3 Ω cm over an area of 1 cm2. Temperature-dependent electrical characterizations revealed that the electronic transport in carbon films was dominated by defect, localized, and extended states, respectively, when increasing the temperature from 75 to 292 K. The nanocrystalline graphene films presented higher carrier mobility and lower carrier concentration than those of a-C films, which was mainly attributed to their smaller conductive activation energy. The present investigation provides an effective way for direct growth of graphene films on glass at reduced temperatures and also offers useful insights into the understanding of structural and electrical relationship between a-C and graphene.

Wide-bandgap nanocrystalline silicon-carbon alloys for photovoltaic applications

p-Type hydrogenated silicon carbide (p-SiC:H) films were prepared using plasma-enhanced chemical vapor deposition by systematically incorporating carbon into nanocrystalline silicon networks. The carbon content of the films was varied by adjusting the methane/silane (CH4/SiH4; RC) ratio. The chemical bonding, microstructural, and electro-optical properties of the films were investigated in detail. With increasing RC, the silicon-carbon bond density in the films increased gradually and the overall microstructure became amorphous. Through sophisticated control of the carbon content of the films during high hydrogen dilution deposition, p-type hydrogenated nanocrystalline SiC:H (p-nc-SiC:H) films with nanometer-scale Si crystallites embedded in an amorphous SiC:H matrix were obtained. The p-nc-SiC:H films had wide bandgaps larger than 2 eV and reduced parasitic light absorption at wavelengths below 550 nm. When using wide-bandgap p-nc-SiC:H films with superior electro-optical properties as window layers in n-i-p flexible and p-i-n semi-transparent nc-Si:H solar cells, in place of conventional p-nc-Si:H layers with narrow bandgaps, enhanced cell performance was achieved because of both high open circuit voltage (VOC) and high quantum efficiency values at short wavelengths of 350–550 nm. The conversion efficiencies of the flexible nc-Si:H solar cells increased from 6.37% (VOC = 0.41 V, JSC = 22.81 mA/cm2, and FF = 68.10%, where JSC is the short-circuit current density and FF is the fill factor, respectively) to 7.89% (VOC = 0.51 V, JSC = 24.04 mA/cm2, and FF = 64.37%). A further increase in the conversion efficiency to 9.18% was obtained by inserting a very thin, highly-doped p-nc-SiC:H buffer layer between a low-doped p-nc-SiC:H window layer and an indium tin oxide front contact. A significant increase in the conversion efficiency from 3.66% (VOC = 0.42 V, JSC = 14.83 mA/cm2, and FF = 58.69%) to 4.33% (VOC = 0.45 V, JSC = 17.74 mA/cm2, and FF = 54.18%) was achieved with the semi-transparent nc-Si:H solar cell, with an average optical transmittance of 17.29% in the visible wavelength region of 500–800 nm.

Impacts of substrate bias and dilution gas on the properties of Si-incorporated diamond-like carbon films by plasma deposition using organosilane as a Si source

We have deposited silicon-incorporated diamond-like carbon (Si-DLC) films by plasma-enhanced chemical vapor deposition using monomethylsilane (CH3SiH3; MMS) as a Si source, and systematically investigated the impacts of substrate bias and dilution gas on the mechanical and tribological properties of the Si-DLC films. The use of a pulse bias and hydrogen dilution is very effective in suppressing the generation of particles during the deposition. The internal stress of the Si-DLC films deposited using the pulse bias tended to be lower than that of the Si-DLC films deposited using a DC bias, while the hydrogen dilution resulted in the increase in the internal stress. On the other hand, the Si-DLC film deposited with H2 using the pulse bias showed the highest adhesion strength and the lowest friction coefficient. The use of the pulse bias resulted in the increase in the wear resistance.

Poole-Frenkel emission and defect density in a-Si:H/nc-Si:H multilayer films for “all silicon” third generation photovoltaics

A layered structure of nanocrystalline Silicon (nc-Si) and Si compound dielectric (SiO2, Si3N4, SiC) is becoming popular for the third generation photovoltaics because of its tunable optical bandgap. However, this structure makes poor current conduction, as the barrier potential between Si and Si dielectric is very high. An excellent current conduction can be obtained by replacing the Si dielectric with amorphous Si (a-Si:H), as the barrier potential between a-Si and nc-Si is very low compared to nc-Si/Si dielectric structure. This paper presents the electrical properties of an a-Si:H/nc-Si:H multilayer film fabricated using hot-wire chemical vapour deposition. Hydrogen (H2) dilution in the nc-Si:H layers was considered as a variable parameter in different multilayer films. Formation of a nc-Si:H layer sandwiched between two a-Si:H layers was confirmed by Raman spectroscopy and X-ray diffraction. The current-voltage measurements performed in low temperature reveal different vertical charge transport mechanisms, such as Poole-Frenkel (PF) emission, phonon assisted tunnelling and direct tunnelling. Below room temperature, the PF emission rate increases the current with increase in H2 dilution in the multilayer films. The capacitance-voltage measurement performed near the room temperature explains the increased defects in the multilayer films with an increase in H2 dilution.

Low temperature plasma enhanced deposition approach for fabrication of microcrystalline GaP/Si superlattice

A plasma technology approach to grow microcrystalline GaP/Si superlattices was explored. The layers of GaP were grown using time modulated plasma enhanced deposition (atomic layer deposition approach), while Si layers were grown using the conventional plasma enhanced chemical vapor deposition mode with high hydrogen dilution. The (3 nm)GaP/(2 nm)Si superlattices were formed on Si and GaP substrates either by the growth of an amorphous GaP/Si multilayer structure followed by thermal annealing at 450–900 °C or by growth of a microcrystalline GaP/Si superlattice at temperatures not exceeding 400 °C. A quantum confinement effect of thin 2 nm Si layers was demonstrated by the appearance of a peak at 500 cm−1 in Raman spectra. The crucial role of hydrogen behavior in Si crystallization and void formation during the annealing of amorphous and growth of microcrystalline GaP/Si structures was demonstrated.

A review and comparative assessment of direct ammonia fuel cells

In this study, we present a comparative assessment of direct ammonia fuel cells and a discussion of these from various perspectives by considering the effective criteria. The effect of electrolyte and electrode materials, electrolyte thicknesses and operating temperatures on the performance of direct ammonia fuel cells are studied and discussed comparatively for evaluation purposes. A comparison of which cell types and configurations provide the optimum performance is conducted by utilizing the experimental results reported in the literature. The results of this study are expedient to provide important inferences about the performances of direct ammonia fuel cells. Ammonia fed oxygen ion conducting Samarium doped ceria electrolyte based solid oxide fuel cells have comparatively the highest peak power density of 1190 mW/cm2 when operated at 650 °C with a 10 µm thick electrolyte. Direct ammonia proton conducting electrolyte based solid oxide fuel cells have lower cell performance than oxygen ion conducting fuel cells due to the dilution of hydrogen at the anode by undecomposed ammonia as well as formed nitrogen gas. The operating temperature of the fuel cell and electrolyte thickness affect the cell performance considerably. A 200 °C increase in operating temperature increases the peak power density by nearly three to four times for ammonia fed solid oxide fuel cells. The molten alkaline electrolyte based fuel cells can be a promising technology. Further research is required for these type of fuel cells to investigate their performance with low electrode separation distance and more conductive alkaline electrolytes.

A gas management strategy for anode recirculation in a proton exchange membrane fuel cell

The anode configuration and gas management strategy are two of factors that affect the energy efficiency of a proton exchange membrane fuel cell. In order to improve the hydrogen utilization, unused hydrogen can be recirculated to the inlet using a pump. However, impurities diffusing from the cathode to the anode may cause the dilution of hydrogen in the anode. As a result, a gas management strategy is required for the anode recirculation configuration. In this preliminary study, a novel configuration for anode recirculation and a gas management strategy are proposed and verified by experiments. Two valves are installed in the recirculation line. The anode is operated in four modes (dead-end, recirculation, compression, and purge), and the real-time local current density (LCD) is monitored for gas management purposes. The results show that the LCD distribution is uniform during the recirculation mode and nonuniform during the dead-end and compression modes. With this configuration and gas management strategy, the cycle duration is increased by a factor of 6.5.

Biocompatibility of Hydrogen-Diluted Amorphous Silicon Carbide Thin Films for Artificial Heart Valve Coating

Amorphous silicon carbide (a-SiC:H) thin films were synthesized using trichloromethylsilane by a hot wire chemical vapor deposition process. The deposited films were characterized by Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, x-ray diffraction and x-ray photoelectron spectroscopy to confirm its chemical bonding, structural network and composition of the a-SiC:H films. The optical microscopy images reveal that hydrogen dilution increased the surface roughness and pore density of a-SiC:H thin film. The Raman spectroscopy and FTIR spectra reveal chemical network consisting of Si-Si, C-C and Si-C bonds, respectively. The XRD spectroscopy and Raman spectroscopy indicate a-SiC:H still has short-range order. In addition, in vitro cytotoxicity test ensures the behavior of cell–semiconductor hybrid to monitor the proper coordination. The live–dead assays and MTT assay reveal an increase in green nucleus cell, and cell viability is greater than 88%, respectively, showing non-toxic nature of prepared a-SiC:H film. Moreover, the result indicated by direct contact assay, and cell prefers to adhere and proliferate on a-SiC:H thin films having a positive effect as artificial heart valve coating material.