Enlargement of the diamond deposition area in combustion flame method by traversing substrate

In this study, diamond deposition on traversing substrate was carried out in order to get useful information for utilizing combustion flame method. In the case of stationary substrate, diamond particles were obtained on the condition that C₂H₂/O₂ flow ratio was from 1.00 to 1.15, while no particles could be obtained in oxygen rich environment. However, in the case of traversing substrate, dense diamond belt was deposited without oxidizing of the diamond particles due to oxidative flame. From these results, it was proved that large area deposition by substrate traversing was available even in the case of combustion flame CVD.     

Surface transformations of carbon (graphene, graphite, diamond, carbide), deposited on polycrystalline nickel by hot filaments chemical vapour deposition

The deposition of carbon has been studied at high temperature on polycrystalline nickel by hot filaments activated chemical vapor deposition (HFCVD). The sequences of carbon deposition are studied by surface analyses: Auger electron spectroscopy (AES), electron loss spectroscopy (ELS), X-ray photoelectron spectroscopy (XPS) in a chamber directly connected to the growth chamber. A general scale law of the (C/Ni) intensity lines is obtained with a reduced time. Both, shape analysis of the AES C KVV line and the C1s relative intensity suggest a three-step process: first formation of graphene and a highly graphitic layer, then multiphase formation with graphitic, carbidic and diamond-like carbon and finally at a critical temperature that strongly depends on the pretreatment of the polycrystalline nickel surface, a rapid transition to diamond island formation. Whatever the substrate diamond is always the final product and some graphene layers the initial product. Moreover it is possible to stabilize a few graphene layers at the initial sequences of carbon deposition. The duration of this stabilization step is strongly depending however on the pre-treatment of the Ni surface.     

Electrochemical behaviour of molybdenum coated with flame CVD polycrystalline diamond film

Although natural diamond is a complete chemically-inert material for a wide range of aggressive environments, its comparative scarcity and problems for coating design have hampered its utility as a corrosion protective coating. The recent discovery and development of chemical vapour deposition methods for growing diamond crystals and polycrystalline diamond films has opened up a wide range of applications thanks to their excellent tribological, electronic and optical properties. Various applications are in progress for corrosion and combined wear and corrosion protection. This paper presents the first study of the corrosion behaviour of continuous polycrystalline diamond films using electrochemical impedance electroscopy. Diamond films have been deposited on molybdenum substrates by means of the acetylene flame combustion method (FCVD). Electrochemical behaviour has been studied in a 0.6 M NaCl solution, it being seen that despite the inert character and apparent continuity of the film, there are areas of the base material which are exposed to the electrolyte. This behaviour has been modelled by means of an equivalent circuit which allows for the corroboration of the proposed mechanism.     

Preparation of high quality polycrystalline silicon thin films by aluminum-induced crystallization

High quality polycrystalline silicon (poly-Si) thin films without Si islands were prepared by using aluminum-induced crystallization on glass substrates. Al and amorphous silicon films were deposited by vacuum thermal evaporation and radio frequency magnetron sputtering, respectively. The samples were annealed at 500 °C for 7 h and then Al was removed by wet etching. Scanning electron microscopy shows that there are two layers in the thin films. After the upper layer was peeled off, the lower poly-Si thin film was found to be of high crystalline quality. It presented a Raman peak at 521 cm^− 1 with full width at a half maximum of 5.23 cm^− 1, which is similar to c-Si wafer.     

fabrication of diamond membranes for MEMS using reactive ion etching of silicon

Polycrystalline diamond thin film has been grown on a silicon substrate using high pressure microwave plasma-assisted chemical vapor deposition from a gas mixture of methane and hydrogen at a substrate temperature of 950°C. A simple process flow has been developed to fabricate optically transparent polycrystalline synthetic diamond membranes/windows employing reactive ion etching (RIE) of a single crystal silicon substrate using an electron beam evaporated aluminum thin film mask pattern formed by photolithography. Scanning electron microscopy has been used to study the morphology of as-grown diamond thin films.     

Hot-wire chemical vapor deposition and characterization of polycrystalline silicon thin films using a two-step growth method

A two-step growth method was proposed to reduce the amorphous incubation layer in the initial growth of polycrystalline silicon (poly-Si) films prepared by hot-wire chemical vapor deposition (HWCVD). In the two-step growth process, a thin seed layer was first grown on the glass substrate under high hydrogen dilution ratios (φ ≥ 0.9), and then a thick overlayer was subsequently deposited upon the seed layer at a lower φ value. The effect of various deposition parameters on the structural properties of poly-Si films was investigated by Raman spectroscopy and transmission electron microscopy. Moreover, the electrical properties, such as dark and photo conductivities, of poly-Si films were also measured. It was found that the Si incubation layer could be suppressed greatly in the initial growth of poly-Si with the two-step growth method. In the subsequent poly-Si film thickening, a lower φ value of the reactant gases can be applied to enhance the deposition rate. Therefore, a high-quality poly-Si film can be fabricated via a two-step growth method with a sufficient growth rate using HWCVD.     

The effect of temperature on the growth of carbon nanotubes on copper foil using a nickel thin film as catalyst

Growth of carbon nanotubes (CNTs) on bulk copper foil substrates has been achieved by sputtering a nickel thin film on Cu substrates followed by thermal chemical vapor deposition. The characteristics of the nanotubes are strongly dependent on the Ni film thickness and reaction temperature. Specifically, a correlation between the thin film nickel catalyst thickness and the CNT diameter was found. Two hydrocarbon sources investigated were methane and acetylene to determine the best conditions for growth of CNTs on copper. These results demonstrate the effectiveness of this simple method of directly integrating CNTs with highly conductive substrates for use in applications where a conductive CNT network is desirable.     

Finestructures study of the diamond/titanium interface by transmission electron microscopy

It is well known that a TiC layer can be formed and should act as a buffer layer in diamond films deposited on Ti alloy. Through our cross-sectional investigation in HRTEM, a thin layer (20–30 nm) was first identified between the outermost diamond film and the inner reactive TiC layer adjacent to the substrate. This layer consists of numerous crystalline nanoparticles with grain sizes of 5–20 nm. Through electron nanodiffraction patterns combined with EDS and EELS analysis, these nanoparticles can be identified as a TiC_1−xO_x phase with a similar structure to cubic TiC. Besides, C atoms and O atoms in TiC_1−xO_x randomly occupy the vacancies of C in TiC. The thickness of this TiC_1−xO_x layer does not change significantly with increasing deposition time, and the diamond phase directly nucleates and grows on it.     

两段成长法改善微波电浆辅助化学气相沉积多晶金刚石之品质

以化学气相沉积法成长多晶金刚石薄膜时,薄膜的品质会受到成长时间、成长压力、反应气体比例、偏压与否及成核的机制等因素影响.研究采用微波电浆辅助化学气相沉积(MPECVD)法,以甲烷(CH4)和氢气(H2)作为反应气体原料,在P型(111)硅基板沉积多晶金刚石薄膜.典型沉积多晶金刚石薄膜的制程可分为四个阶段:抛蚀表面阶段、渗碳阶段、偏压增强成核(BEN)阶段及成长阶段.研究将成长阶段划分为两个阶段,第一阶段压力较低(成长Ⅰ阶段),第二阶段压力较高(成长Ⅱ阶段).结果表明:第一阶段可大大改善金刚石薄膜的品质,所获多晶金刚石薄膜的晶粒具有明确的颗粒边界、较低的碳化物或缺陷,电导率急剧降低,显现出本徵金刚石半绝缘的性质.可以认为金刚石薄膜品质的改善完全为低压成长所致.实验发现在成长Ⅰ阶段或成长Ⅱ阶段施加偏压时,只会降低多晶金刚石薄膜的品质.     

Structure and magnetic properties of Ni0.11ZnxCo0.03Fe2.86-xO4 ferrite films deposited on Ag-coated glass substrates by wet chemical method

Ni_0.11Zn_xCo_0.03Fe_2.86-xO₄ spinel ferrite films with x = 0.00, 0.23, 0.34, 0.43 and 0.51 were prepared on Ag-coated glass substrates from nitrate and dimethylamine borane solution at 80 °C. The Ni_0.11Zn_xCo_0.03Fe_2.86-xO₄ ferrite films are singe-phased spinel ferrite. With the Zn content x increasing from 0 to 0.51, the lattice constant of the ferrite films increases from 0.8383 to 0.8425 nm. The Ni_0.11Zn_0.51Co_0.03Fe_2.35O₄ film is about 500 nm thick and composed of uniform equiaxed granules of about 40–50 nm. The Raman spectrum analysis indicates that the Zn²⁺ ions occupy the A sites. Saturation magnetization increases with x increasing from 0 to 0.35, reaches a maximum value of 460 kA/m at x = 0.35, and then decreases with further increase of x. Coercivity decreases monotonically from 12.3 to 1.7 kA/m with x increasing from 0 to 0.51. The change in magnetic properties may be explained by the decrease of A–B interactions and the anisotropy constant due to the incorporation of non-magnetic Zn²⁺ ions.     

Surface morphology and preferential orientation growth of TaC crystals formed by chemical vapor deposition

TaC film was deposited on (002) graphite sheet by isothermal chemical vapor deposition using TaCl₅-Ar-C₃H₆ mixtures, with deposition temperature 1200 °C and pressure about 200 Pa. The influence of deposition position (or deposition rate) on preferential orientation and surface morphology of TaC crystals were investigated by X-ray diffraction and scanning electron microscopy methods. The deposits are TaC plus trace of C. The crystals are large individual columns with pyramidal-shape at deposition rate of 32.4-37.3 μm/h, complex columnar at 37.3-45.6 μm/h, lenticular-like at 45.6-54.6 μm/h and cauliflower-like at 54.6-77.3 μm/h, with <001>, near <001>, <110> and no clear preferential orientation, respectively. These results agree in part with the preditions of the Pangarov's model of the relationship between deposition rate and preferential growth orientation. The growth mechanism of TaC crystals in <001>, near <001>, <111> and no clear preferential orientation can be fairly explained by the growth parameter α with Van der Drift's model, deterioration model and Meakin model. Furthermore, a nucleation and coalescence model is also proposed to explain the formation mechanism of <110> lenticular-like crystals.     

Microstructural and frictional control of diamond-like carbon films deposited on acrylic rubber by plasma assisted chemical vapor deposition

In this paper we concentrate on the microstructure of diamond-like carbon films prepared by plasma assisted chemical vapor deposition on acrylic rubber. The temperature variation produced by the ion impingement during plasma cleaning and subsequent film deposition was monitored and controlled as a function of bias voltage and treatment time. Its influence during film growth on the appearance of patterns of cracks and wrinkles, caused by the thermal stresses is evaluated. Different growth modes are proposed in order to explain the smaller patch sizes observed at negative variations of temperature. The coefficient of friction (CoF) of the samples is measured using a pin-on-disk tribometer in non-lubricated conditions. Much lower CoF values than unprotected rubber are seen, which can be correlated with the observed patch size.     

Study on W/SiC interface of SiC fiber fabricated by chemical vapor deposition on tungsten filament

SiC fiber was fabricated by chemical vapor deposition on tungsten filament heated by direct current in a CH₃SiCl₃-H₂ gas system. Microstructure of W/SiC interfacial reaction zone in the fiber was identified by means of scanning electron microscope and transmission electron microscope. Results showed that the thickness of the interfacial reaction zone is between 350 and 390 nm, and two reaction products of W₅Si₃ and WC were formed during fabricating SiC fiber. Electron diffraction analysis and composition detection indicated that W₅Si₃ is adjacent to tungsten core and WC is adjacent to SiC sheath, and the W/SiC interface can be described as W/W₅Si₃/WC/SiC. Furthermore, the formation mechanism of the interfacial reaction zone is discussed.     

Stability increase of fuel clad with zirconium oxynitride thin film by metalorganic chemical vapor deposition

A zirconium oxynitride (ZON) thin film was deposited onto HT9 steel as a cladding material by a metalorganic chemical vapor deposition (MOCVD) in order to prevent a fuel-clad chemical interaction (FCCI) between a U-10 wt% Zr metal fuel and a clad material. X-ray diffraction spectrums indicated that the mixture of structures of zirconium nitride, oxide and carbide in the MOCVD grown ZON thin films. Also, typical equiaxial grain structures were found in plane and cross sectional images of the as-deposited ZON thin films with a thickness range of 250-500 nm. A depth profile using auger electron microscopy revealed that carbon and oxygen atoms were decreased in the ZON thin film deposited with hydrogen gas flow. Diffusion couple tests at 800 °C for 25 hours showed that the as-deposited ZON thin films had low carbon and oxygen content, confirmed by the Energy Dispersive X-ray Spectroscopy, which showed a barrier behavior for FCCI between the metal fuel and the clad. This result suggested that ZON thin film cladding by MOCVD, even with the thickness below the micro-meter level, has a high possibility as an effective FCCI barrier.     

Structure and Electrical Characteristics of Zinc Oxide Thin Films Grown on Si (111) by Metal-organic Chemical Vapor Deposition

ZnO thin films were grown on Si(111) substrates by low-pressure metal-organic chemical vapor deposition.The crystal structures and electrical properties of as-grown sample were investigated by scanning electron microscopy(SEM) and conductive atomic force microscopy(C-AFM).It can be seen that with increasing growth temperature,the surface morphology of ZnO thin films changed from flake-like to cobblestones-like structure.The current maps were simultaneously recorded with the topography,which was gained by C-AFM contact mode.Conductivity for the off-axis facet planes presented on ZnO grains enhanced.Measurement results indicate that the off-axis facet planes were more electrically active than the c-plane of ZnO flakes or particles probably due to lower Schottky barrier height of the off-axis facet planes.     

Growth of carbon nanotubes using a thermal insulator investigated by in-situ mass spectroscopy

The low-temperature synthesis (500-560 °C) of carbon nanotubes (CNTs) on a triple-layered catalyst, Al/Fe/Mo was performed using complex hydrocarbon radicals which were produced from pyrolysis of C₂H₂. These radicals were produced using a high-temperature heater (~ 830 °C), but the substrate where the CNTs were grown was placed on a thermal insulator. This then enabled the substrate to be at a much lower temperature (500-560 °C). A simulated temperature distribution inside the chamber was also used to describe this low-temperature configuration. The synthesis of CNTs relies on the thermal dissociation and dissociative recombination of C₂H₂ for the formation of complex high-order radicals (i.e. C₆H₉, C₅H₉, and C₆H₁₃), and their presence was confirmed by in-situ mass spectroscopy. To explain this, a simple gas-phase radical chain process and a growth model are presented.     

Effects of annealing temperature on crystallisation kinetics and properties of polycrystalline Si thin films and solar cells on glass fabricated by plasma enhanced chemical vapour deposition

Solid-phase crystallisation of Si thin films on glass fabricated by plasma enhanced chemical vapour deposition is compared at different annealing temperatures. Four independent techniques, optical transmission microscopy, Raman and UV reflectance spectroscopy, and X-ray diffraction, are used to characterise the crystallisation kinetics and film properties. The 1.5 μm thick films with the n+/p−/p+ solar cell structure have incubation times of about 300, 53, and 14 min and full crystallisation times of about 855, 128, and 30 min at 600 °C, 640 °C, and 680 °C respectively. Estimated activation energies for incubation and crystal growth are 2.7 and 3.2 eV respectively. The average grain size in the resulting polycrystalline Si films measured from scanning electron microscopy images gradually decreases with a higher annealing temperature and the crystal quality becomes poorer according to the Raman, UV reflection, and X-ray diffraction results. The dopant activation and majority carrier mobilities in heavily doped n+ and p+ layers are similar for all crystallisation temperatures. Both the open-circuit voltage and the spectral response are lower for the cells crystallised at higher temperatures and the minority carrier diffusion lengths are shorter accordingly although they are still longer than the cell thickness for all annealing temperatures. The results indicate that shortening the crystallisation time by merely increasing the crystallisation temperature offers little or no merits for PECVD polycrystalline Si thin-film solar cells on glass.     

Homoleptic single molecular precursors for the deposition of platinum and palladium chalcogenide thin films

Platinum and palladium dithio/diselenoimidodiphosphinato complexes have been synthesized and used as single source precursors for the deposition of platinum and palladium chalcogenide thin films by the Low Pressure Chemical Vapour Deposition technique. Pure PtSe₂ thin films were deposited at varying temperatures from the [Pt{N(SePⁱPr₂)₂}₂] complex. However, only Pt films were obtained from the sulfur analogue. The palladium diselenoimidodiphosphinato complex gave palladium selenide films with different stochiometries depending on the growth temperature. The corresponding sulfur complex gave PdS₂ films with a regular platelet-like morphology.