Boron-Silicon Thin Film Formation Using a Slim Vertical Chemical Vapor Deposition Reactor

A boron-silicon film was formed from boron trichloride gas and dichlorosilane gas at about 900℃in ambient hydrogen at atmospheric pressure utilizing a slim vertical cold wall chemical vapor deposition reactor designed for the Minimal Fab system. The gas flow rates were 80, 20 and 0.1 - 20 sccm for the hydrogen, dichlorosilane and boron trichloride gases, respectively. The gas transport condition in the reactor was shown to quickly become stable when evaluated by quartz crystal microbalances at the inlet and outlet. The boron-silicon thin film was formed by achieving the various boron concentrations of 0.16% - 80%, the depth profile of which was flat. By observing the cross-sectional TEM image, the obtained film was dense. The boron trichloride gas is expected to be useful for the quick fabrication of various materials containing boron at significantly low and high concentrations.

<100> Textured Diamond Film on Silicon Grown by Hot Filament Chemical Vapor Deposition

The <100> textured growth of diamond film on HF eroded silicon wafer has been studied by HFCVD. The evolution of grain size and sudece morphology vs deposition time is presented and the <100> textured thick diamond film (80μm) with smooth surface, desirable for practical application in many fields is obtained

Numerical simulation of chemical vapor deposition reaction in polysilicon reduction furnace

Three-dimensional model of chemical vapor deposition reaction in polysilicon reduction furnace was established by considering mass, momentum and energy transfer simultaneously. Then, CFD software was used to simulate the flow, heat transfer and chemical reaction process in reduction furnace and to analyze the change law of deposition characteristic along with the H_2 mole fraction, silicon rod height and silicon rod diameter. The results show that with the increase of H_2 mole fraction, silicon growth rate increases firstly and then decreases. On the contrary, SiHCl_3 conversion rate and unit energy consumption decrease firstly and then increase. Silicon production rate increases constantly. The optimal H_2 mole fraction is 0.8-0.85. With the growth of silicon rod height, Si HCl3 conversion rate, silicon production rate and silicon growth rate increase, while unit energy consumption decreases. In terms of chemical reaction, the higher the silicon rod is, the better the performance is. In the view of the top-heavy situation, the actual silicon rod height is limited to be below 3 m. With the increase of silicon rod diameter, silicon growth rate decreases firstly and then increases. Besides, SiHCl_3 conversion rate and silicon production rate increase, while unit energy consumption first decreases sharply, then becomes steady. In practice, the bigger silicon rod diameter is more suitable. The optimal silicon rod diameter must be over 120 mm.

Chemical Vapor Deposition Mechanism of Copper Films on Silicon Substrates

一个万用的金属器官的化学蒸汽免职(MOCVD ) 系统被设计并且构造。铜电影在硅(100 ) 上被扔由用 Cu (hfac )2 的化学蒸汽免职(CVD ) 的底层作为一位先锋。由 Cu (hfac )2 的 H 2 减小的硅底层上的 Cu 原子核的生长被原子力量显微镜学和扫描电子显微镜学学习。Cu 原子核的生长模式是开始 Volmer 网模式(岛) ，然后到 Stranski-Rastanov 模式(加岛的 layer-by-layer ) 的变换。硅(100 ) 上的 Cu 成核的机制底层被 X 光检查光电子进一步调查光谱学。从 Cu2p， O1s， F1s， Si2p 模式，观察 C=O，哦并且 CF 3/CF2 应该属于 Cu (hfac )2 的热分离形成的 Cu (hfac ) 。H 2 在表面上与 hfac 反应，生产哦。与它的累积，哦与 hfac 反应，形成 HO-hfac，并且同时，使放出铜氧化物被减少，并且因此，在 Cu (hafc )2 之间的氧化还原作用反应和 H 2 发生。

Room Temperature and Reduced Pressure Chemical Vapor Deposition of Silicon Carbide on Various Materials Surface

At room temperature, 300 K, silicon carbide film was formed using monomethylsilane gas on the reactive surface prepared using argon plasma. Entire process was performed at reduced pressure of 10 Pa in the argon plasma etcher, without a substrate transfer operation. By this process, the several-nanometer-thick amorphous thin film containing silicon-carbon bonds was obtained on various substrates, such as semiconductor silicon, aluminum and stainless steel. It is concluded that the room temperature silicon carbide thin film formation is possible even at significantly low pressure, when the substrate surface is reactive.

Quartz Crystal Microbalances for Evaluating Gas Motion Differences between Dichlorosilane and Trichlorosilane in Ambient Hydrogen in a Slim Vertical Cold Wall Chemical Vapor Deposition Reactor

A dichlorosilane gas and a trichlorosilane gas in ambient hydrogen were evaluated to show their different gas flow motions in a slim vertical cold wall chemical vapor deposition reactor for the Minimal Fab system. This evaluation was performed for improving and controlling the film qualities and the productivities, using two quartz crystal microbalances (QCM) installed at the inlet and exhaust of the chamber by taking into account that the QCM frequency corresponds to the real time changes in the gas properties. Typically, the time period approaching from the inlet to the exhaust was shorter for the trichlorosilane gas than that for the dichlorosilane gas. The trichlorosilane gas was shown to move like plug flow, while the dichlorosilane gas seemed to be well mixed in the entire chamber.

Characteristics and Electrical Properties of SiNx:H Films Fabricated by Plasma-Enhanced Chemical Vapor Deposition

SiNx：H films with different N/Si ratios are synthesized by plasma-enhanced chemical vapor deposition （PECVD）. Composition and structure characteristics are detected by Fourier transform infrared spectroscopy （FTIR） and X-ray photoelectron spectroscopy （XPS）. It indicates that Si-N bonds increase with increased NH3/SiH4 ratio. Electrical property investigations by I-V measurements show that the prepared films offer higher resistivity and less leakage current with increased N/Si ratio and exhibit entirely insulating properties when N/Si ratio reaches 0.9, which is ascribed to increased Si-N bonds achieved.

Thermodynamic Analysis of Chemical Vapor Deposition of BCl_3-NH_3-SiCl_4-H_2-Ar System

The thermodynamic phase stability area diagrams of BCl3-NH3-Si Cl4-H2-Ar system were plotted via Factsage software to predict the kinetic experimental results. The effects of parameters(i e, partial pressure of reactants, deposition temperature and total pressure) on the distribution regions of solid phase products were analyzed based on the diagrams. The results show that:(a) Solid phase products are mainly affected by deposition temperature. The area of BN+Si3N4 phase increases with the temperature rising from 650 to 900 ℃, and decreases with the temperature rising from 900 to 1 200 ℃;(b) When temperature and total pressure are constants, BN+Si3N4 phase exists at a high partial pressure of NH3;(c) The effect of total system pressure is correlated to deposition temperature. The temperature ranging from 700 to 900 ℃ under low total pressure is the optimum condition for the deposition.(d) Appropriate kinetic parameters can be determined based on the results of thermodynamic calculation. Si–B–N coating is obtained via low pressure chemical vapor deposition. The analysis by X-ray photoelectron spectroscopy indicates that B–N and Si–N are the main chemical bonds of the coating.

Structural evolution and optical characterization in argon diluted Si:H thin films obtained by plasma enhanced chemical vapor deposition

The structural evolution and optical characterization of hydrogenated silicon(Si:H) thin films obtained by conventional radio frequency(RF) plasma enhanced chemical vapor deposition(PECVD) through decomposition of silane diluted with argon were studied by X-ray diffractometry(XRD),Fourier transform infrared(FTIR) spectroscopy,Raman spectroscopy,transmission electron microscopy(TEM),and ultraviolet and visible(UV-vis) spectroscopy,respectively.The influence of argon dilution on the optical properties of the thin films was also studied.It is found that argon as dilution gas plays a significant role in the growth of nano-crystal grains and amorphous network in Si:H thin films.The structural evolution of the thin films with different argon dilution ratios is observed and it is suggested that argon plasma leads to the nanocrystallization in the thin films during the deposition process.The nanocrystallization initiating at a relatively low dilution ratio is also observed.With the increase of argon portion in the mixed precursor gases,nano-crystal grains in the thin films evolve regularly.The structural evolution is explained by a proposed model based on the energy exchange between the argon plasma constituted with Ar* and Ar+ radicals and the growth regions of the thin films.It is observed that both the absorption of UV-vis light and the optical gap decrease with the increase of dilution ratio.

Large-area chemical vapor deposition-grown monolayer graphene-wrapped silver nanowires for broad-spectrum and robust antimicrobial coating

New types of antimicrobial systems are urgently needed owing to the emergence of pathogenic microbial strains that gain resistance to antibiotics commonly used in daily life and medical care. In this study we developed for the first time a broad-spectrum and robust antimicrobial thin film coating based on large-area chemical vapor deposition （CVD）-grown graphene-wrapped silver nanowires （AgNWs）. The antimicrobial graphene/AgNW hybrid coating can be applied on commerdal flexible transparent ethylene vinyl acetate/polyethylene terephthalate （EVA/PET） plastic films by a full roll-to-roll process. The graphene/AgNW hybrid coating showed broad-spectrum antimicrobial activity against Gram-negative （Escherichia coli） and Gram-positive bacteria （Staphylococcus aureus）, and fungi （Candida albicans）. This effect was attributed to a weaker microbial attachment to the ultra-smooth graphene film and the sterilization capacity of Ag＋, which is sustainably released from the AgNWs and presumably enhanced by the electrochemical corrosion of AgNWs. Moreover, the robust antimicrobial activity of the graphene/AgNW coating was reinforced by AgNW encapsulation by graphene. Furthermore, the antimicrobial efficiency could be enhanced to -100% by water electrolysis by using the conductive graphene/AgNW coating as a cathode. We developed a transparent and flexible antimicrobial cover made of graphene/AgNW/EVA/PET and an antimicrobial denture coated by graphene/ AgNW, to show the potential applications of the antimicrobial materials.

Friction and Cutting Properties of Hot-Filament Chemical Vapor Deposition Micro-and Fine-grained Diamond Coated Silicon Nitride Inserts

The micro-crystalline diamond (MCD) and fine-grained diamond (FGD) films are deposited on commercial silicon nitride inserts by the hot-filament chemical vapor deposition (HFCVD) method. The friction andcutting properties of as-deposited MCD and FGD films coated silicon nitride (Si3N4) inserts are comparatively investigated in this study. The scanning electron microscopy (SEM) and Raman spectroscopy are adopted to studythe characterization of the deposited diamond films. The friction tests are conducted on a ball-on-plate typereciprocating friction tester in ambient air using Co-cemented tungsten carbide (WC-Co), Si3N4 and ball-bearing steel (BBS) balls as the mating materials of the diamond films. For sliding against WC-Co, Si3N4 and BBS,the FGD film presents lower friction coeffcients than the MCD film. However, after sliding against Si3N4, the FGD film is subject to more severe wear than the MCD film. The cutting performance of as-deposited MCD and FGD coated Si3N4 inserts is examined in dry turning glass fiber reinforced plastics (GFRP) composite materials,comparing with the uncoated Si3N4 insert. The results indicate that the lifetime of Si3N4 inserts can be prolonged by depositing the MCD or FGD film on them and the FGD coated insert shows longer cutting lifetime than the MCD coated one.

Broadband photodetector of high quality SbS nanowire grown by chemical vapor deposition

Low dimensional semiconductors can be used for various electronic and optoelectronic devices because of their unique structure and property.In this work,one-dimensional Sb2 S3 nanowires(NWs)with high crystallinity were grown via chemical vapor deposition(CVD)technique on SiO2/Si substrates.The Sb2 S3 NWs exhibited needle-like structures with inclined cross-sections.The lengths of Sb2S3 nanowires changed from 7 to 13μm.The photodetection properties of Sb2 S3 nanowires were comprehensively and systematically characterized.The Sb2S3 photodetectors show a broadband photoresponse ranging from ultraviolet(360 nm)to near-infrared(785 nm).An excellent specific detectivity of 2.1×10^(14)Jones,high external quantum efficiency of 1.5×10^(4)%,sensitivity of 2.2×10^(4)cm^(2)W^(-1)and short response time of less than 100 ms was achieved for the Sb2 S3 NW photodetectors.Moreover,the Sb2S3 NWs showed outstanding switch cycling stability that was beneficial to the practical applications.The high-quality Sb2S3 nanowires fabricated by CVD have great application potential in semiconductor and optoelectronic fields.

Effect of hydrogen on low temperature epitaxial growth of polycrystalline silicon by hot wire chemical vapor deposition

Polycrystalline silicon （poly-Si） films were prepared by hot-wire chemical vapor deposition （HWCVD） at a low substrate temperature of 525 ℃. The influence of hydrogen on the epitaxial growth of ploy-Si films was investigated. Raman spectra show that the poly-Si films are fully crystallized at 525 ℃ with a different hydrogen dilution ratio （50%-91.7%）. X-ray diffraction, grazing incidence X-ray diffraction and SEM images show that the poly-Si thin films present （100） preferred orientation on （100） c-Si substrate in the high hydrogen dilution condition. The P-type poly-Si film prepared with a hydrogen dilution ratio of 91.7% shows a hall mobility of 8.78 cm2/（V-s） with a carrier concentration of 1.3 × 10^20 cm^-3, which indicates that the epitaxial poly-Si film prepared by HWCVD has the possibility to be used in photovoltaic and TFT devices.

Kinetically-Induced Hexagonality in Chemically Grown Silicon Nanowires

Various silicon crystal structures with different atomic arrangements from that of diamond have been observed in chemically synthesized nanowires.The structures are typified by mixed stacking mismatches of closely packed Si dimers.Instead of viewing them as defects,we define the concept of hexagonality and describe these structures as Si polymorphs.The small transverse dimensions of a nanowire make this approach meaningful.Unique among the polymorphs are cubic symmetry diamond and hexagonal symmetry wurtzite structures.Electron diffraction studies conducted with Au as an internal reference unambiguously confirm the existence of the hexagonal symmetry Si nanowires.Cohesive energy calculations suggest that the wurtzite polymorph is the least stable and the diamond polymorph is the most stable.Cohesive energies of intermediate polymorphs follow a linear trend with respect to their structural hexagonality.We identify the driving force in the polymorph formations as the growth kinetics.Fast longitudinal elongation during the growth freezes stacking mismatches and thus leads to a variety of Si polymorphs.The results are expected to shed new light on the importance of growth kinetics in nanomaterial syntheses and may open up ways to produce structures that are uncommon in bulk materials.

Self-organization of various“phase-separated”nanostructures in a single chemical vapor deposition

Chemical vapor deposition(CVD)is one of the most versatile techniques for the controlled synthesis of functional nanomaterials.When multiple precursors are induced,the CVD process often gives rise to the growth of doped or alloy compounds.In this work,we demonstrate the self-assembly of a variety of‘phase-separated’functional nanostructures from a single CVD in the presence of various precursors.In specific,with silicon substrate and powder of Mn and SnTe as precursors,we achieved self-organized nanostructures including Si/SiOx core-shell nanowire heterostructures both with and without embedded manganese silicide particles,Mn11Si19 nanowires,and SnTe nanoplates.The Si/SiOx core-shell nanowires embedded with manganese silicide particles were grown along the<111>direction of the crystalline Si via an Au-catalyzed vapor-liquid-solid process,in which the Si and Mn vapors were supplied from the heated silicon substrates and Mn powder,respectively.In contrast,direct vapor-solid deposition led to particle-free<110>-oriented Si/SiOx core-shell nanowires and<100>-oriented Mn11Si19 nanowires,a promising thermoelectric material.No Sn or Te impurities were detected in these nanostructures down to the experimental limit.Topological crystalline insulator SnTe nanoplates with dominant{100}and{111}facets were found to be free of Mn(and Si)impurities,although nanoparticles and nanowires containing Mn were found in the vicinity of the nanoplates.While multiple-channel transport was observed in the SnTe nanoplates,it may not be related to the topological surface states due to surface oxidation.Finally,we carried out thermodynamic analysis and density functional theory calculations to understand the‘phase-separation’phenomenon and further discuss general approaches to grow phase-pure samples when the precursors contain residual impurities.

High rate deposition of microcrystalline silicon films by high-pressure radio frequency plasma enhanced chemical vapor deposition (PECVD)

Hydrogenated microcrystalline silicon (μc-Si:H) thin films were prepared by high- pressure radio-frequency (13.56 MHz) plasma enhanced chemical vapor deposition (rf-PECVD) with a screened plasma. The deposition rate and crystallinity varying with the deposition pressure, rf power, hydrogen dilution ratio and electrodes distance were systematically studied. By optimizing the deposition parameters the device quality μc-Si:H films have been achieved with a high deposition rate of 7.8 /s at a high pressure. The Voc of 560 mV and the FF of 0.70 have been achieved for a single-junction μc-Si:H p-i-n solar cell at a deposition rate of 7.8 /s.

Preparation of ZrC-SiC composite coatings by chemical vapor deposition and study of co-deposition mechanism

In this work, the Zr C-SiC composite coatings were co-deposited by chemical vapor deposition(CVD)using ZrCl4, MTS, CH4 and H2 as raw materials. The morphologies, compositions and phases of the composite coatings were characterized by scanning electron microscopy(SEM), energy dispersive X-ray spectroscopy(EDS) and X-ray diffraction(XRD). The results indicated that the morphologies, compositions and phases of the composite coatings were related to the deposition temperature, the flow rate of the carrier H2 gas, and the ratio of C/Zr. Moreover, the co-deposition mechanism of the composite coatings was also studied. It was found that different deposition temperatures resulted in different deposition mechanisms. At temperatures in the range of 1150–1250℃, the Zr C-SiC co-deposition was controlled by the surface kinetic process. At temperatures in the range of 1250–1400℃, the Zr C-SiC co-deposition was controlled by the mass transport process.

Multi-time scale photoelectric behavior in facile fabricated transparent and flexible silicon nanowires aerogel membrane

In recent years,transparent and flexible materials have been widely pursued in electronics and optoelectronics fields for usage as planar electrodes,energy conversion components and sensing units.As the most widely applied semiconductor material,the related progress in silicon is of great significance although with large difficulty.Herein,we report a one-step method to achieve flexible and transparent silicon nanowires aerogel membrane.A competitive carrier kinetics involving interfacial trapped carriers and the valence electrons transition is demonstrated,according to the photoelectric performance of a sandwiched graphene/silicon nanowires membrane/AI device,i.e.,rapidly positive photoresponse dominated by laser excited^ee-carriers generation(〜500 ms)and subsequent slow negative photocurrent evolution due to laser heating involved multi-levels process(>10 s).These results contribute to fabrication of silicon nanowire self-assembly structures and also the exploration of their optoelectrical properties in flexible and transparent devices.

Preparation of well-aligned carbon nanotubes/silicon nanowires core-sheath composite structure arrays in porous anodic aluminum oxide templates

The well-aligned carbon nanotubes (CNTs) arrays with opened ends were prepared in ordered pores of anodic aluminum oxide (AAO) template by the chemical vapor deposition (CVD) method. After then, silicon nanowires (SiNWs) were deposited in the hollow cavities of CNTs. By using this method, CNTs/SiNWs core-sheath composite structure arrays were synthesized successfully. Growing structures and physical properties of the CNTs/SiNWs composite structure arrays were analyzed and researched by the scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray diffraction spectrum (XRD), respectively. The field emission (FE) behavior of the CNTs/SiNWs composite structure arrays was studied based on Fowler-Nordheim tunneling mechanism and current-voltage (/-V) curve. And the photoluminescence (PL) was also characterized. Significantly, the CNTs/SiNWs core-sheath composite structure nanowire fabricated by AAO template method is characteristic of a metal/semiconductor (M/S) behavior and can

Synthesis and Diameter-dependent Thermal Conductivity of InAs Nanowires

In this work, we synthesized high-quality In As nanowires by a convenient chemical vapor deposition method,and developed a simple laser heating method to measure the thermal conductivity of a single In As nanowire in air. During the measurement, a focused laser was used to heat one end of a freely suspended nanowire, with its other end embedded into a carbon conductive adhesive. In order to obtain the thermal conductivity of In As nanowires, the heat loss in the heat transfer process was estimated, which includes the heat loss through air conduction, the heat convection, and the radiation loss. The absorption ratio of the laser power in the In As nanowire was calculated. The result shows that the thermal conductivity of In As nanowires monotonically increases from 6.4 W m-1K-1to 10.5 W m-1K-1with diameters increasing from 100 nm to 190 nm, which is ascribed to the enhanced phonon-boundary scattering.