化学气相沉积低温热解炭的微观组织结构与沉积模型

利用扫描电子显微镜(SEM),透射电子显微镜(TEM)结合选取电子衍射(SAED)研究了化学气相沉积低温热解炭的微观组织结构。结果表明:低温热解炭是由直径小于2μm的球形颗粒状炭组成,该球形颗粒状炭的核心是炭黑颗粒,外层为中织构热解炭。其沉积过程主要经历了:微小炭黑颗粒的萌生,炭黑颗粒外层的生长,炭颗粒表面热解炭的沉积和炭颗粒的聚集长大四个过程。     

Thermal barrier coatings produced by chemical vapor deposition

Yttria stabilized zirconia (YSZ) can be employed as thermal barrier coatings (TBCs) on Ni-based super alloys in gas turbines and aircraft engines. The YSZ coatings have been fabricated by atmospheric plasma spraying or electron-beam physical vapor deposition. The increase in operation temperature of gas turbines demands another fabrication process to obtain high quality TBCs. Chemical vapor deposition (CVD) can be an alternative route to prepare TBCs due to excellent conformal coverage and columnar microstructure. This paper reviews the fabrication of YSZ films by conventional thermal CVD and plasma CVD intended for TBCs. A new laser CVD developed by our group with a high deposition rate of 660 μm h⁻¹ was also briefly introduced.     

Synthesis of carbon nanofiber films and nanofiber composite coatings by laser-assisted catalytic chemical vapor deposition

Uniform carbon nanofiber films and nanofiber composite coatings were synthesized from ethylene on nickel coated alumina substrates by laser-assisted catalytic chemical vapor deposition. Laser annealing of a 50 nm thick nickel film produced the catalytic nanoparticles. Thermal decomposition of ethylene over nickel nanoparticles was initiated and maintained by an argon ion laser operated at 488 nm. The films were examined by scanning electron microscopy and by transmission electron microscopy. Overall film uniformity and structure were assessed using micro-Raman spectroscopy. Film quality was related to the experimental parameters such as incident laser power density and irradiation time. For long irradiation times, carbon can be deposited by a thermal process rather than by a catalytic reaction directly over the nanofiber films to form carbon nanocomposite coatings. The process parameters leading to high quality nanofiber films free of amorphous carbon by-products as well as those leading to nanofiber composite coatings are presented.     

Thin molybdenum oxide films produced by molybdenum pentacarbonyl 1-methylbutylisonitrile with plasma-assisted chemical vapor deposition

Molybdenum oxide thin films were prepared by plasma-enhanced chemical vapor deposition of molybdenum pentacarbonyl 1-methylbutylisonitrile. This precursor is an interesting alternative for the commonly used molybdenum hexacarbonyl, because the substance is liquid at room temperature, offers sufficient volatility and stability to air and water. The film growth was monitored in situ by a soft X-ray reflectivity measurement. The films were deposited with different plasma gases (hydrogen and oxygen) under different conditions and analysed by Auger electron spectroscopy, X-ray diffraction and spectral ellipsometry.     

Low pressure chemical vapor deposition of niobium coatings on graphite

Niobium coatings were prepared on graphite by low pressure chemical vapor deposition using niobium chloride and hydrogen as the reactant gases. The effects of deposition temperature on the morphology, phase, and deposition rate of niobium coatings were studied. The as-deposited niobium coatings were characterized by scanning electron microscopy and X-ray diffraction. The results indicate that the niobium coatings exhibit a granular hillock structure at 850-900 °C while a laminar structure at 950-1100 °C. The deposition is dominated by surface chemical kinetics with an apparent activation energy of 93.2 kJ/mol at 850-950 °C, while it is dominated by mass transport with an apparent activation energy of 7.9 kJ/mol at 950-1050 °C. At temperatures below 1100 °C, the deposited coatings mainly contain niobium. At temperatures above 1100 °C, the deposited coatings mainly contain niobium carbides. Considering the deposition kinetics and interfacial reactions, the deposition temperature should be controlled below 950 °C.     

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

In this work, the ZrC-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 °C, the ZrC-SiC co-deposition was controlled by the surface kinetic process. At temperatures in the range of 1250–1400 °C, the ZrC-SiC co-deposition was controlled by the mass transport process.     

以生物质为催化剂化学气相沉积制备碳纳米管

以富含过渡金属元素铁的天然生物质黑木耳、紫菜、香菇、黑芝麻的炭化粉末作为催化剂前驱体,天然气为碳源,采用化学气相沉积工艺制备了碳纳米管(CNTs)。所制CNTs阵列的管径较窄,排列整齐,归因于蘑菇、紫菜和黑芝蔴的碳含量高及铁基纳米颗粒分散均匀。采用黑木耳为催化剂所制CNTs的直径也较窄,但杂乱生长,可能是由于黑木耳的碳含量低及铁基纳米颗粒分布不均匀所致。     

Effects of argon and oxygen flow rate on water vapor barrier properties of silicon oxide coatings deposited on polyethylene terephthalate by plasma enhanced chemical vapor deposition

Plasma polymer coatings were deposited from hexamethyldisiloxane on polyethylene terephthalate (PET) substrates while varying the operating conditions, such as the Ar and O₂ flow rates, at a fixed radio frequency power of 300 W. The water vapor transmission rate (WVTR) of the untreated PET was 54.56 g/m²/day and was decreased after depositing the silicon oxide (SiO_x) coatings. The minimum WVTR, 0.47 g/m²/day, was observed at Ar and O₂ flow rates of 4 and 20 sccm, respectively, with a coating thickness of 415.44 nm. The intensity of the peaks for the Si-O-Si bending at 800-820 cm^− 1 and Si-O-Si stretching at 1000-1150 cm^− 1 varied depending on the Ar and O₂ flow rates. The contact angle of the SiO_x coated PET increased as the Ar flow rate was increased from 2 to 8 sccm at a fixed O₂ flow rate of 20 sccm. It decreased gradually as the oxygen flow rate increased from 12 to 28 sccm at a fixed Ar carrier gas flow rate. The examination by atomic force microscopy revealed a correlation of the SiO_x morphology and the water vapor barrier performance with the Ar and O₂ flow rates. The roughness of the deposited coatings increased when either the O₂ or Ar flow rate was increased.     

Silicon-carbon-oxynitrides grown by plasma-enhanced chemical vapor deposition technique

In this paper we report some preliminary results about the growth at low temperature (493 K) of hydrogenated silicon-carbon-oxygen-nitrogen amorphous thin-film alloys (a-SiC_xO_yN_z:H) by means of capacitively-coupled radio-frequency (13.56 MHz) plasma-enhanced chemical vapor deposition using a mixtures of silane (SiH₄), propane (C₃H₈), nitrous oxide (N₂O) and ammonia (NH₃) precursor gases. Thin films of a-SiC_xO_yN_z:H were grown at different deposition conditions, obtaining growth speeds varying from 0.22 to 0.44 nm/s. The films were characterized by means of Fourier transform infra-red spectroscopy in order to investigate the internal bonding structure, by UV-VIS transmittance spectroscopy to check the optical properties and by mechanical profilometry to measure the film thickness and estimate the growth rate. The comparison of structural and optical properties of samples grown with and without NH₃ presence in the gas mixture showed that the ammonia addition allows a better control of nitrogen incorporation in the film structure, while increasing film transparency and reducing the growth rate.     

Hybrid gas-to-particle conversion and chemical vapor deposition for the production of porous alumina films

Porous alumina films can be found in a wide variety of materials, including filters, thermal insulation components, dielectrics, biomedical and catalyst supports, coatings and adsorbents. Production methods for these films are as equally diverse as their applications. In this work, a hybrid process based upon chemical vapor deposition and gas-to-particle conversion is presented as an alternative technique for producing porous alumina films, with the main advantages of solvent-free, low substrate-temperature operation. In this process, nanoparticles were produced in the vapor phase by reaction of aluminum acetylacetonate in the presence of oxygen. Downstream of this reaction zone, these nanoparticles were collected via thermophoresis onto a cooled substrate, forming a porous film. Some deposited films were subjected to post-processing in the form of annealing in air. Fourier-transform infrared spectra and X-ray energy-dispersive spectroscopy analysis confirmed the production of alumina at processing temperatures above 973 K. X-Ray diffraction revealed that the films were amorphous. Film thickness, ranging from 30 to 250 μm, and the average deposition rate were determined from scanning electron microscopy results. From transmission electron microscopy, the average primary particle size was determined to be approximately 18 nm and the formation of nanoparticle aggregates was evident. Annealing of the films at temperatures ranging from 523 to 1173 K in the presence of air did not have an effect on particle size. The specific surface area of the powder composing the films ranged from 10 to 185 m² g⁻¹, as determined from nitrogen gas adsorption by the Brunauer–Emmett–Teller method.     

催化化学气相沉积过程中硫元素引发的炭形貌衍变

以甲苯为碳源,二茂铁为催化剂,噻吩为生长促进剂,通过化学气相沉积方法得到了多分叉结构的炭.借助SEM、XRD和EDX考察了硫元素对产物的形貌和微观结构的影响.结果表明,当甲苯中的噻吩体积分数在0.01%～1%变化时,产物形貌由树状逐渐衍变为分支状.树状炭南较长而笔直的多分叉炭纤维构成,而分支状炭则由较短且弯曲的炭纤维构成.XRD结果表明硫元素对产物的微观结构没有明显的影响.     

High-growth rate YSZ thermal barrier coatings deposited by MOCVD demonstrate high thermal cycling lifetime

Yttria-stabilized zirconia (YSZ) thermal barrier coatings (TBC) were prepared by metalorganic chemical vapor deposition (MOCVD) using Y(OButⁿ)₃, Zr(OButⁿ)₄ precursors and O₂ carrier gas. A thermodynamic analysis guided experiments by optimizing elemental molar (n) stoichiometric ratios for the (Zr-Y-O-C-H system). This analysis showed single-phase YSZ was favored at 950 °C, 1 kPa, n_O/(n_Y + n_Zr) > 30, n_Y/(n_Y + n_Zr) = 0.06-0.10 (fixed n_C, n_H). Experimental YSZ growth had multiple phases (fcc, monoclinic), had a relatively high growth rate (43 μm/h, 1005 °C), had an Arrhenius dependence (845-950 °C, E_a = 53.8 ± 7.9 kJ/mol), had columnar grains (SEM analysis), and had a coating through-thickness n_Y/(n_Y + n_Zr) = 0.04 (EPMA analysis). Doubling the inlet yttrium precursor mole fraction resulted in fcc YSZ growth with a coating through-thickness n_Y/(n_Y + n_Zr) = 0.07. Hot-insertion thermal cycling of YSZ coatings on FeCrAlY bond coats showed >1000 h lifetime, matching current standards for EB-PVD YSZ coatings.     

Initiated chemical vapor deposition of biopassivation coatings

Organosilicon polymers show great utility as both biocompatible and electrically insulating materials. In this work, thin films of a novel organosilicon polymer are synthesized by initiated CVD utilizing trivinyl-trimethyl cyclotrisiloxane as a monomer and terbutyl peroxide as a free radical generating initiator. Use of an initiator allows for formation of polymer films at filament temperatures as low as 250 °C which allows for retention of all siloxane ring moieties within the resulting polymer. The all-dry deposition process generates a highly crosslinked matrix material in which over 95% of the vinyl moieties present on the monomer units have been reacted out to form linear polymerized hydrocarbon chains. The material possesses an electrical resistivity of 4 × 10¹⁵ Ω cm. In addition, biased soak testing of material samples in a simulated biological environment demonstrates retention of electrical material properties for greater than 2 years.     

乙炔催化裂解制备碳纳米带及其结构表征

以乙炔（C2H2）为碳源,铁为催化剂,通过化学气相沉积技术在单晶硅衬底上制备了碳纳米带.采用场发射SEM、TEM、激光Raman光谱等先进分析手段对其形态和结构进行了表征.研究发现：碳纳米带是一种准二维材料,厚度约30nm,宽度在几百纳米,长度在100μm量级.碳纳米带的碳层沿着与其生长轴方向一致的（002）晶向排列,碳层的边缘都弯曲折叠成封闭结构.碳纳米带中碳层的排列不很平直,其中存在大量的层错.由此认为碳纳米带可用于能源等领域.     

Thin-film phases of organic charge-transfer complexes formed by chemical vapor deposition

Thin films of organic charge-transfer salts, (TTF)(TCNQ) and (TTF)(DMDCNQI), are prepared by the chemical vapor deposition method, where TTF is tetrathiafulvalene, TCNQ is tetracyanoquinodimethane, and DMDCNQI is dimethyldicyanoquinonediimine. Depending on the substrate temperatures, we have obtained randomly oriented polycrystalline phases composed of relatively large crystals and microcrystalline thin-film phases, which sometimes contain well-grown nanowires. The latter shows much different conducting properties from the bulk crystals, and particularly the (TTF)(DMDCNQI) film is nearly as conductive as the (TTF)(TCNQ) film in spite of the bulk insulating property coming from the mixed-stack crystal structure.     

Deposits obtained by photolysis of hexamethyldisilane by ArF excimer laser (SiC thin film preparation by ArF excimer laser chemical vapor deposition, Part 2)

Thin films have been prepared by decomposition of hexamethyldisilane (HMDS) by ArF excimer laser at the fixed laser fluence of 800 J m⁻² and the substrate temperatures from 300 to 673 K and have been characterized using X-ray diffraction (XRD), scanning electron microscope observation, IR reflection spectroscopy and X-ray photoelectron spectroscopy. The XRD patterns showed the formation of 3C-SiC films but it is suggested that the films obtained at lower substrate temperature include organic functional groups, which might be derived from gaseous reaction products. Hydrogen existing in the form of Si-CH₂-Si could be decreased by decreasing the partial pressures of HMDS.     

Tribological behavior at elevated temperature of multilayer TiCN/TiC/TiN hard coatings produced by chemical vapor deposition

Multilayer hard coatings of TiCN/TiC/TiN on high speed steel substrates were deposited using a chemical vapor deposition system. Evaluations of microstructure, wear morphology of coatings were characterized by scanning electron microscopy, and optical microscopy. Friction coefficient and wear rates of coatings were investigated using ball-on-disk tester sliding against a WC ball at a constant load of 20 N. Tribological behavior of the coatings at room and elevated temperature were discussed. Different changing tendency of friction coefficient were observed from ball-on-disc experiments. Results showed that the friction coefficient of coatings increased gradually to a highest value, then to a relatively constant value at room temperature dry sliding wear. The friction coefficient exhibited a reverse variation tendency at temperature of 550 °C. It got a higher value at the first sliding friction cycles. Then the value of friction coefficient decreased, suffered irregular oscillations and kept a relatively lower value with increasing sliding time. Reasons of the variation of friction coefficient with sliding time and wear mechanism were analyzed and discussed at room and elevated temperatures, respectively.     

Effects of different acetylene/nitrogen ratios on characteristics of carbon coatings on optical fibers prepared by thermal chemical vapor deposition

The effects of C₂H₂/(C₂H₂ + N₂) ratios on the characteristics of carbon coatings on optical fibers prepared by thermal chemical vapor deposition are investigated. The C₂H₂/(C₂H₂ + N₂) ratios are set to 60, 70, 80, 90, and 100%. Additionally, the deposition temperature, working pressure, and mass flow rate are 1003 K, 133 kPa, and 40 sccm, respectively. The deposition rate, microstructure, and electrical resistivity of carbon coatings are measured. The low-temperature surface morphology of carbon-coated optical fibers is elucidated. Experimental results indicate that the deposition rate increases with increasing the C₂H₂/(C₂H₂ + N₂) ratio, and the deposition process is located at a surface controlled regime. As the deposition rate increases, the electrical resistivity of carbon coatings increases, while the ordered degree, nano-crystallite size, and sp² carbon atoms of the carbon coatings decrease. Additionally, the low-temperature surface morphology of the carbon coatings shows that if the carbon coating thickness is not smaller than 289 nm, decreasing the deposition rate is good for producing hermetic optical fiber coatings.     

Graphite formation on Ni film by chemical vapor deposition

Thin film formation of graphite by chemical vapor deposition using 2-methyl-1,2′-naphthyl ketone as a starting material was carried out on Ni film substrates. On Ni films directly deposited on quartz glass, the graphite films were obtained when the Ni film thickness was above 1 000 Å and above 5 000 Å at 700 °C and 1 000 °C, respectively. Depositions on thinner Ni film substrates comprise amorphous carbon (a-C) or graphite tubes which was owing to the thermal coagulation of the Ni film into droplets. On the other hand, graphite film was obtained on the Ni film with thickness 10 Å when a-C was inserted between the Ni film and the quartz glass. The coagulation of the Ni film is considered to be avoided by inserting a-C layer.     

Crystallographic and electrical properties of platinum film grown by chemical vapor deposition using (methylcyclopentadienyl)trimethylplatinum

Platinum thin films grown by chemical vapor deposition (CVD) using a liquid precursor of (methylcyclopentadienyl)trimethylplatinum were characterized in terms of crystallographic nature, morphology, contaminants, and their influence on electrical properties. The lattice constant of these CVD films (3.91–3.92 Å) is smaller than that of bulk platinum. A high oxygen contaminant is observed, irrespective of the oxygen ratio during growth. A film grown at low oxygen content consists of randomly oriented micro-grains and contains a large amount of carbon contaminants. When the film is grown under oxidative conditions, it shows a 111-textured cylindrical morphology with increasing thickness. The electric resistivity is higher than the bulk standard, and it increases with decreasing oxygen ratio during the film growth. These results indicate that the carbon contaminant causes the randomly oriented micro-grains and contributes to the high residual resistivity.