Low temperature deposition of hexagonal BN films by chemical vapour deposition

Transparent hexagonal BN films were deposited onto copper substrates from the reactant gas BCl₃-NH₃-H₂ at temperatures in the range 250–700°C. The lowest deposition temperature of the films was about 250°C. The films deposited at temperatures below 450°C were unstable in moist atmosphere and devitrified; a 20%–30% decrease in weight was observed when these films were heated above 600°C in an argon atmosphere. In contrast, the films deposited at temperatures above 600°C were very stable, decreased in weight by 1%–2% on heating and were stable in air at temperatures below 750°C.     

Preparation of transparent water-repellent films by radio-frequency plasma-enhanced chemical vapour deposition

Preparation of transparent water-repellent films was carried out using three kinds of fluoroalkyl silanes (FASs) by radio-frequency plasma-enhanced chemical vapour deposition. The effects of the reaction conditions on the structures and properties of the films were studied. The films prepared showed high water repellency like poly(tetrafluoroethylene). The contact angles for water drops were about 107 °. The obtained contact angles depended on the length of perfluoroalkyl groups (C_nF_{2n + 1}-) in FASs. Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy were used to investigate the film properties. The existence of the fluorine-containing groups such as –CF₃, –CF₂– and > CF– was confirmed at the film surfaces. The contact angle decreased when oxygen was added to the plasma because of the decrease in the fluorine concentration in the deposited films by the decomposition of C–F bonds. The transmittance of the polycarbonate substrates coated using FASs was improved. The films also acted as an antireflective coating. This revised version was published online in November 2006 with corrections to the Cover Date.     

Preparation of cobalt oxide films by plasma-enhanced metalorganic chemical vapour deposition

Co oxide films were prepared on glass substrates at 150–400°C by plasma-enhanced metalorganic chemical vapour deposition using cobalt (II) acetylacetonate as a source material. NaCl-type CoO films were formed at low O₂ flow rate of 7cm³ min^–1 and at a substrate temperature of 150–400°C. The CoO films possessed (100) orientation, independent of substrate temperature. Deposition rates of the CoO films were 40–47 nm min^–1. The CoO film deposited at 400 °C was composed of closely packed columnar grains and average diameter size at film surface was 60 nm. At high O₂ flow rate of 20–50 cm³ min^–1, high crystalline spinel-type Co₃O₄ films were formed at a substrate temperature of 150–400°C. The Co₃O₄ film deposited at 400°C possessed (100) preferred orientation and the film deposited at 150°C possessed (111) preferred orientation. Deposition rates of the Co₃O₄ films were 20–41 nm min^–1. Both Co₃O₄ films with (100) and (111) orientation had columnar structure. The shape and average size of the columnar grains at the film surface were different; a square shape and 35 nm for (100)-oriented Co₃O₄ film and a hexagonal shape and 60 nm for (111)-oriented film, respectively.     

Crystalline carbon nitride films prepared by microwave plasma chemical vapour deposition

Crystalline carbon nitride films have been synthesized on Si (100) substrates by a microwave plasma chemical vapour deposition technique, using mixture of N₂, CH₄ and H₂ as precursor. Scanning electron microscopy shows that the films consisted of hexagonal bars, tetragonal bars, rhombohedral bars, in which the bigger bar is about 20 μm long and 6 μm wide. The X-ray photoelectron spectroscopy suggests that nitrogen and carbon in the films are bonded through hybridized sp² and sp³ configurations. The x-ray diffraction pattern indicates that the films are composed of α-, β-, pseudocubic and cubic C₃N₄ phase and an unidentified phase. Raman spectra also support the existence of α- and β-C₃N₄ phases. Vickers microhardness of about 41.9 GPa measured for the films.     

Preparation of VO2 films by organometallic chemical vapour deposition and dip-coating

Low-pressure organometallic chemical vapour deposition (OMCVD) and dip-coating of VO₂ films using vanadyl tri(isobutoxide) as the starting material were investigated. In OMCVD, discontinuous VO₂ films, which were composed of fine needle crystals, formed under very limited conditions, around 600° C with a flow rate of oxygen gas of 0.2 to 0.5 cm³ sec^–1. However, very uniform and tightly packed VO₂ films were grown by deposition at 300 to 700° C in the absence of oxygen gas and subsequent annealing in nitrogen at 500° C for 2 h. The films exhibited a sharp semiconductor to metal transition at 60 to 70° C, accompanied by a change in the resistivity by four to five orders of magnitude. In dip-coating with two-step heat-treatments (300° C for 1 h in nitrogen and subsequently 500° C for 2 h in nitrogen), of the gel films formed from VO(O-i-Bu)₃-H₂O-i-PrOH system, uniform (0 1 1) oriented VO₂ films were formed. A transition in the electrical conductivity by two to two and a half orders of the magnitude was found to occur around 60° C. Before and after the transition, no distinct variation in the XRD pattern was observed.     

Preparation of silicon oxide films by ultraviolet-assisted rf plasma-enhanced chemical vapour deposition

Abstracts are not published in this journal This revised version was published online in November 2006 with corrections to the Cover Date.     

High thermal conductivity diamond coated graphite by microwave plasma chemical vapour deposition

Diamond film was grown on high thermal conductivity graphite substrate using microwave plasma chemical vapour deposition method. Nanodiamond particles were uniformly seeded on the substrate to generate high nucleation density by a spray gun. The continuous and high purity diamond film was obtained, and growth rate was up to 2.7 μm h^??1. The thickness, surface morphology, quality and composite phase of the film were analysed by SEM, Raman and X-ray diffraction. It was shown that graphite coated with diamond presented a higher thermal conductivity (520?W?m^??1 k^??1) than copper. Furthermore, this coated material with high thermal conductivity, good strength and non-conductive surface will make it possible to be widely used in thermal management field.     

Preparation of ferroelectric BaTiO3 thin films by metal organic chemical vapour deposition

Polycrystalline BaTiO₃ thin films have been successfully prepared on (100) silicon substrates at temperatures under 600° C by metal organic chemical vapour deposition using barium acetylacetonate and diisopropoxy-titanium-bis-(acetylacetonate). To vaporize the barium acetylacetonate, which is nonvolatile under 300° C and thermally unstable, an ultrasonic spraying technique was used. The substrate temperature had a great influence on the structure and composition of films and the single-phase BaTiO₃ films could be prepared at 500° C. At temperatures above 550° C the reaction between the film and the silicon substrate occurred to a large extent. The polarization-electric field (P-E) hysteresis loops and counter-clockwise direction of hysteresis in the high-frequency (1 MHz)C-V characteristics indicate that the BaTiO₃ films deposited on silicon using the present method are ferroelectric.     

Preparation and properties of ZnS thin films by low-pressure metalorganic chemical vapour deposition

Low-pressure metalorganic chemical vapour deposition of ZnS thin films on silicon, oxidized silicon and glass substrates using Zn (C₂H₅)₂ and C₄H₄S as source chemicals was investigated. The growth process and the film properties were characterized as functions of process parameters including substrate temperature, reactant ratio and reaction pressure. In general, growth rates as a function of substrate temperature were found to reach a maximum at a much lower temperature than that for growth at atmospheric pressure. In addition, growth rates increased with reaction pressure and thiophene flow rate depending on the temperature condition. The microstructure indicated that growths above 250°C possess a cubic (zincblende) structure, while growths below 150°C are polycrystalline of wurtzite structure. The resistivity varies from 10⁴ cm to a maximum of about 3×10⁵ cm for growth at 250°C, depending on the reactant ratio. The details are discussed in the text.     

Growth of diamond thin films by chemical vapour deposition

Deposition of diamond thin films on non-diamond substrates at low pressures (<760 torr) and low temperatures (<2000°C) by chemical vapour deposition (CVD) has been the subject of intense research in the last few years. The structural and the electrical properties of CVD diamond films grown on p-type 〈111〉 and high-resistivity (>100 kΩ-cm) 〈100〉 oriented silicon substrates by hot filament chemical vapour deposition technique are described in this review paper.     

Formation of amine functionalized films by chemical vapour deposition

Thermally Activated Chemical Vapour Deposition (TA-CVD) has been used for the biofunctionalization of silicon substrates, among others. This technique uses 3-aminopropyltriethoxysilane as organometallic precursor. The deposited films show biofunctional properties, with reactive amines on the surface, as it was shown by FTIR and confocal microscopy. In this work, the influence of the deposition parameters in the microstructure and functionality of the films was investigated. Antibodies were immobilized on the films that had higher and more homogeneous distribution of amines. The confocal microscopy images show that the amines react with the antibodies and that these biomolecules keep their biological functionality.     

Thermal analysis of hydrogenated amorphous carbon films prepared by plasma enhanced chemical vapour deposition

Hydrogenated amorphous carbon (a-C∶H) films were produced from propane and argon by an inductively coupled radio frequency (r.f.) glow discharge process under a particular deposition condition. Thermal analysis for the deposit by GC, DSC, DTA, and TG gave information for the structural changes upon heating. Most C-H vibration spectra disappeared by heating up to 600 °C. The gas desorption began above 300 °C and reached maxima above 650 °C with several peaks. The desorption reaction was endothermic. Up to 600 °C the desorbed gases was not the hydrogen. The large weight change was observed without the thickness reduction. The weight change rate was maximum at 480 °C. Hydrocarbons are believed to desorb below 600 °C. A hydrocarbon desorption model is suggested. Hydrocarbons are formed in the inner surface of a microvoid and effuse out through the interconnected microvoids in the column boundaries. The proposed desorption reaction is also endothermic.     

Chemical stability of hydrogen-containing boron nitride films obtained by plasma enhanced chemical vapour deposition

The purpose of this paper is the investigation of the dehydrogenation kinetics of boron nitride films during thermal annealing. BN_x:H films on silicon substrates were prepared by remote plasma enhanced chemical vapour deposition at 473 K using a mixture of borazine and helium. IR spectroscopy and ellipsometry were used to characterize the film properties and composition. The films contain a certain amount of hydrogen in B---H and N---H bonds. The breakage kinetics of these bonds is different. The breakage of N---H bonds determines the hydrogen annealing kinetics at 973–1073 K. The low-temperature annealing (673–873 K) of B---H bonds is sensitive to the generation of hydrogen from N---H bonds. Heat treatment leads to ordering of the films.     

Preparation and characterization of Y-system superconducting thin films by mist microwave-plasma chemical vapour deposition

Superconducting thin films of Y-Ba-Cu-O were prepared on single-crystal MgO (100) substrates by the mist microwave-plasma chemical vapour deposition (MPCVD) using an aqueous solution of metal nitrate. The growth rate was observed to be controlled by the concentration of metal nitrate in the solution. The X-ray diffraction patterns showed that the prepared films consisted of 123 phase with c-axis orientation perpendicular to the substrates. The dependence of T _c-zero (zero resistance) of films on the microwave power was investigated. In addition, the effect of the ozone on the preparation of films was investigated. The maximum T _c-zero (84 K) of as-deposited films was obtained at a metal concentration in the solution of 0.50 moll^–1, a microwave power of 300 W and an ozone concentration in oxygen gas of 3.0%.     

Preparation of Fe-N films by r.f. sputtering

Fe-N films over a wide compositional range have been prepared by the reactive sputtering method. Fe-N sputtered films were composed of a single or two phases such as-Fe₂N,-Fe_3.02N,-Fe_3.82N,-Fe₄N and-Fe; however, an unknown phase was observed at a higher nitrogen pressure. A remarkable preferred orientation of the-Fe_3.02N (110) plane parallel to the film surface was observed. The Curie temperature of the sputtered -Fe_3.82N sample was 490° C, which was almost the same as that of-Fe₄N prepared by metal nitriding. The saturation magnetization, _s, of the sputtered Fe-N samples decreased from 151.8 to 42.4 e.m.u.g^–1 with increasing nitrogen content from 7.94 to 24.87 at%, and its coercive force,₁ H _c was found to lie in the range 150 to 600 Oe in the powder form at room temperature.     

Stress and crystallization of plasma enhanced chemical vapour deposition nanocrystalline silicon films

Nanocrystalline Si films were prepared with a RF-PECVD system using different SiH4/H2 ratios, plasma powers, substrate temperatures and annealing conditions. The film's intrinsic stress was characterized in relation to the crystallization fraction. Results show that an increasing H2 gas ratio, plasma power or substrate temperature can shift the growth mechanism across a transition point, past which nanocrystalline Si is dominant in the film structure. The film's intrinsic stress normally peaks during this transition region. Different mechanisms of stress formation and relaxation during film growth were discussed, including ion bombardment effects, hydrogen induced bond-reconstruction and nanocomposite effects (nanocrystals embedded in an amorphous Si matrix). A three-parameter schematic plot has been proposed which is based on the results obtained. The film structure and stress are presented in relation to SiH4 gas ratio, plasma power and temperature.