Localized deposition of hydrocarbon using plasma activated chemical vapour deposition

The new technique of micro-jet chemical vapor deposition was used to deposit hydrocarbon on a glass substrate kept at a short distance from a capillary injector. Acetylene gas was used as reactant and the decomposition was achieved via plasma excitation. Plasma was generated and sustained in a localized manner between two copper electrodes. This new technique is characterized by a high-deposition rate (hundreds of microns per second), a low spread (i.e. a high aspect ratio) and low-power input to the plasma (high efficiency).     

Fabrication of nanocrystalline silicon carbide thin film by helicon wave plasma enhanced chemical vapour deposition

Nanocrystalline cubic silicon carbide thin films have been fabricated by helicon wave plasma enhanced chemical vapour deposition on Si substrates using the mixture of SiH₄, CH₄, and H₂ at a low substrate temperature of 300 °C. The infrared absorption spectroscopy analyses and microstructural characteristics of the samples deposited at various magnetic fields indicate that the high plasma intensity in helicon wave mode is a key factor to the success of growing nanocrystalline silicon carbide thin films at a relative low substrate temperature. Transmission electron microscopy measurements reveal that the films consist of silicon carbide nanoparticles with an average grain size of several nanometers, and the light emission measurements show a strong blue photoluminescence at room temperature, which is considered to be caused by the quantum confine effect of small size silicon carbide nanoparticles.     

Diamond deposition using anX-Y stage in a d.c. plasma jet chemical vapour deposition

Diamond was deposited using the substrate scanning mode in a d.c. plasma jet of the Ar-H₂-CH₄ system. Film thickness profiles, SEM and Raman spectra of the diamonds obtained revealed that uniformity of film thickness, crystal size and crystal quality was improved, but the deposition rate decreased with the scanning speed and the crystal quality was worse than that made in the centre of the flame without scanning.     

The deposition of insulators onto InP using plasma-enhanced chemical vapour deposition

SiO₂ and Si₃N₄ films were deposited onto InP using plasma-enhanced chemical vapour deposition techniques. It was established that highly resistive non-dispersive films can be obtained from these processes. However, considerable differences were observed in the performance of InP transistor devices incorporating these two dielectrics. The superior device performance obtained with the SiO₂ was attributed to minimization of preferential loss of phosphorus from the surface of the semiconductor during the initial stages of dielectric deposition.     

Photonic metamaterials by direct laser writing and silver chemical vapour deposition

Metamaterials are artificial materials that--unlike natural substances--enable magnetism to be achieved at optical frequencies. The vast majority of photonic metamaterials has been fabricated by electron-beam lithography and evaporation of metal films, both of which are well-established two-dimensional (2D) technologies. Although stacking of three or four functional layers made using these methods has been reported, a truly 3D fabrication approach would be preferable for 3D photonic metamaterials. Here, we report first steps in this direction by using a combination of direct laser writing and silver chemical vapour deposition--the 3D analogues of electron-beam lithography and evaporation, respectively. The optical characterization of a planar test structure composed of elongated split-ring resonators is in good agreement with theory. Retrieval of the effective optical parameters reveals the importance of bi-anisotropy. Once suitable theoretical blueprints are available, our fabrication approach will enable rapid prototyping of truly 3D photonic metamaterials.     

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.     

Fabrication of selective-emitter silicon heterojunction solar cells using hot-wire chemical vapor deposition and laser doping

The Si heterojunction (HJ) solar cells were fabricated on the textured p-type mono-crystalline Si (c-Si) substrates using hot-wire chemical vapor deposition (HWCVD). In view of the potential for the bottom cell in a hybrid junction structure, the microcrystalline Si (μc-Si) film was used as the emitter with various PH₃ dilution ratios. Prior to the n-μc-Si emitter deposition, a 5 nm-thick intrinsic amorphous Si layer (i-a-Si) was grown to passivate the c-Si surface. In order to improve the indium-tin oxide (ITO)/emitter front contact without using the higher PH₃ doping concentration, a laser doping technique was employed to improve the ITO/n-μc-Si contact via the formation of the selective emitter structure. For a cell structure of Ag grid/ITO/n-μc-Si emitter/i-a-Si/textured p-c-Si/Al-electrode, the conversion efficiency (AM1.5) can be improved from 13.25% to 14.31% (cell area: 2 cm × 2 cm) via a suitable selective laser doping process.     

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.     

The fundamentals of chemical vapour deposition

Fundamentals of the chemical vapour deposition process are described and examples given of its application. The most important aspects of the process are reviewed; these include deposit structure (with its relation to process parameters), process control through application of the principles of thermodynamics and reaction kinetics (with emphasis on deposit thickness uniformity, deposit composition control and deposit-substrate adherence) and basic design features of the equipment used.     

Diamond deposition on cemented carbide by chemical vapour deposition using a tantalum filament

Diamond deposition on WC-Co cemented carbide was examined by chemical vapour deposition using a tantalum filament. The filament was much superior to conventional tungsten filament for high-temperature use. Diamond film was deposited at a filament temperature up to about 2600 °C for tantalum filament, which was much higher than the maximum filament temperature available for tungsten (2000 °C). The critical methane concentration in H₂-CH₄ gas for diamond deposition became higher with increasing filament temperature. A deposition rate about 20 times higher was obtained when using a tantalum filament compared with a tungsten filament. The origin of the improved deposition rate of diamond on WC-Co substrate using a tantalum filament is discussed.     

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.     

Ion irradiation-induced modifications of diamond nanorods synthesised by microwave plasma chemical vapour deposition

Diamond nanorods (DNRs) synthesised by the high methane content in argon rich microwave plasma chemical vapour deposition (MPCVD) have been implanted with nitrogen ions. The nanorods were characterised by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) techniques. The DNRs consist of single-crystalline diamond cores of 3–5?nm in diameter and several tens of nanometres in length. For purification from non-diamond contents, hydrogen plasma etching of DNRs was performed. Structural modifications of etched DNRs were studied after irradiating with 50?keV nitrogen ions under the fluence of 5?×?10¹⁴, 1?×?10¹⁵, 5?×?10¹⁵ and 1?×?10¹⁶?ions?cm^?2. Nitrogen-ion implantation changes the carbon–carbon bonding and structural state of the nanocrystalline diamond (NCD). Raman spectroscopy was used to study the structure before and after ion irradiation, indicating the coexistence of diamond and graphite in the samples. The results indicated the increase in graphitic and sp²-related content, at the expense of decrease in diamond crystallinity, for ion implantation dose of 5?×?10^15?cm^?2 and higher. The method proves valuable for the formation of hybrid nanostructures with controlled fractions of sp³–sp² bonding.     

Copper chemical vapour deposition using copper(I) hexafluoroacetylacetonate trimethylvinylsilane

The effects of the deposition temperature on the microstructure and the electrical resistivity of copper films prepared by chemical vapour deposition (CVD) were studied at the deposition temperatures between 160 C and 330 C. Copper films were prepared on titanium nitride (TiN) substrates in a low-pressure warm-wall reactor using copper(I) hexafluoroacetylacetonate trimethylvinylsilane, Cu (hfac)(TMVS), as the precursor. The activation energy for the deposition was found to be 45.4 kJ mol^–1 at the total pressure of 66.7 Pa. The films deposited at below 200 C, where the deposition is limited by surface reaction, were dense and had low resistivity of approximately 2 cm. Moreover, they exhibited excellent step coverage. However, the films deposited at above 200 C, where the mass transport processes become important, were composed of poorly connected globular grains, resulting in considerably high resistivities and rough surfaces. Effects of the deposition temperature on the grain size and the preferred orientation of the films were also investigated.     

Synthesis of carbon nanotubes by swirled floating catalyst chemical vapour deposition method

A series of developments have been made in synthesizing Carbon Nanotubes (CNTs) by Catalytic Vapour Deposition (CVD) methods since its discovery as a possible route to the large scale and high quality production of CNTs. In this study, CNTs were synthesized continuously in a swirled floating catalytic chemical vapour deposition reactor using acetylene as carbon source, ferrocene as catalyst, with argon and hydrogen as carrier gases within the temperature range of 900-1050 degrees C. The effects of pyrolysis temperature, acetylene flow rate, hydrogen flow rate, and ratio of flow of acetylene to hydrogen on the rate of production of CNTs were investigated. The CNTs produced were purified with dilute nitric acid and the nature and quality of the CNTs were analysed by TEM, Raman spectrometer, EDX, and TGA. Results obtained revealed that a mixture of single and multi wall carbon nanotubes were produced continuously with a maximum yield rate of 0.31 g/min at 1000 degrees C and a flow ratio of acetylene to hydrogen of one to five.     

Plasma assisted chemical vapour deposition of Cr coatings using chromium (III) acetylacetonate vapour source

We report here the synthesis and characterisation of Cr coatings by an environmental friendly Plasma Assisted Metal-Organic Chemical Vapour Deposition (PAMOCVD) process. The Cr coatings were developed using Cr(acac)₃ as the chemical vapour source at a substrate temperature and a power density of 550 °C and 70 mW/cm², respectively. The films were characterized using X-ray diffraction, scanning electron microscopy, X-ray photoelectron spectroscopy and Vicker's microhardness measurements. The investigations revealed that the Cr films are nanocrystalline, free from pores and cracks and have hardness of 1200 HV. The energy dispersive analysis of X-rays and XPS confirmed the presence of Cr in the films.