Rf Plasma-assisted Chemical Vapor Deposition Research Articles

Effect of Si-incorporation on wear–corrosion properties of diamond-like carbon films

Si incorporated diamond-like carbon (Si-DLC) films ranging from 0 to 2 at.% contents were deposited on STS 316L substrates for orthopedic implants by means of rf plasma-assisted chemical vapor deposition (rf PACVD) technique, using mixtures of benzene (C 6H 6) and silane (SiH 4) as the precursor gases. This study provides the reliable and quantitative data for assessment of the effect of Si incorporation on wear–corrosion properties in the simulated body fluid environment through the tribological and electrochemical test. It was found that wear and corrosion to resistance of Si-DLC coatings with increasing Si content were improved owing to high sp 3 bonding.

Preparation and characterization of ultra-thin ferroelectric PZT films grown by plasma-assisted CVD

The preparation and characterization of ultra-thin ferroelectric PZT films were done using the RF plasma-assisted chemical vapor deposition (CVD) system. The ZrO 2 phase was observed at an early stage of the growth of PZT film (film thickness <430 nm). The PZT film, including ZrO 2 phase, was observed to have poor ferroelectric properties. It was found that the ZrO 2 phase could be suppressed by delaying the supply of the Zr source. Even when the thickness was only 46 nm, monolayer PZT films with good ferroelectric properties were successfully grown. The reason for this result is thought to be because the optimum interface was prepared between the substrate and the film before the growth of the monolayer PZT by delaying the supply of Zr and thus suppressing the formation of ZrO 2.

Electrochemical behavior of diamond-like carbon films for biomedical applications

Diamond-like carbon (DLC) films have several advantages in biomedical applications such as high hardness, chemical inertness, low friction and electrical insulation. Furthermore, DLC-coated STS 316L films have been reported to have a good biocompatibility. In addition, corrosion resistance is the first consideration for the biomaterials to be used in the body. DLC films have been deposited onto substrates of STS 316L using rf plasma-assisted chemical vapor deposition (PACVD) with benzene (C6H6) or a mixture of C6H6 and silane (SiH4) as process gas. Three kinds of DLC films were prepared as a function of bias voltage and Si incorporation. Corrosion behavior of DLC films was investigated by electrochemical techniques (potentiodynamic polarization test and electrochemical impedance spectroscopy (EIS)) and surface analytical techniques (atomic force microscopy (AFM) and scanning electron microscopy (SEM)). The electrolyte used in this test was a 0.89% NaCl of pH 7.4 at temperature of 37 °C. Electrochemical measurements showed that DLC films with higher bias voltage and Si incorporation could improve corrosion resistance in the simulated body fluid environment.

Carburizing of tantalum by radio-frequency plasma assisted chemical vapor deposition

Tantalum carbide (TaC) has great potential as an alternative to tantalum and tantalum oxide for applications requiring thermal stability and corrosion resistance. In this study TaC layers were produced by inductive rf plasma-assisted chemical vapor deposition that combines diffusion with chemical vapor deposition. The maximum temperature of the tantalum substrates measured during a 6 h processing time was 900 °C using Ar–CH4 or Ar–CH4–H2 gas mixtures. The microstructure of the layers was characterized by X-ray diffraction and Auger electron spectroscopy, and the mechanical properties were studied by micro- and nanoindentation and by microscratch techniques. A close correlation among the carburizing parameters, the microstructure, the mechanical behavior of the layers, and the corrosion resistance was found. The best performing films, several μm thick, consisting of TaC phase with the highest hardness (∼25 GPa), were obtained under the following conditions: input power of 1400 W, pressure of 40–60 mbar, and substrate located at the center of the rf coil. The effect of gas composition, gas pressure, and substrate temperature on the layer composition, the TaC/Ta2C phase ratio, and the mechanical characteristics and chemical stability is presented and discussed. A mechanism of carburizing of tantalum in an inductive rf plasma is proposed.

Characterization of diamond-like carbon films before and after pulsed laser irradiation

In this work, we correlate the structural properties of DLC films with their photoelectric properties. DLC layers are deposited on silicon wafers by RF plasma-assisted chemical vapor deposition (RF PACVD). The films are irradiated with picosecond Nd 3+-YAG laser pulses at different wavelengths (213 and 266 nm) and energies (few μJ to mJ). Photoelectric sensitivity values are reported and compared with those of metals. The DLC coatings are characterized before and after irradiation by IR spectroscopy, micro-Raman spectroscopy and ellipsometry in order to observe laser-induced structural modifications of the layers. In situ measurements of work function variations at the surface induced by laser pulses are also reported.

Structure and optical properties of Si incorporated diamond-like carbon films deposited by r.f. plasma-assisted chemical vapor deposition

Silicon incorporated diamond-like carbon (Si-DLC) films were deposited by 13.56 MHz r.f. plasma assisted chemical vapor deposition (RF-PACVD), and the optical properties of the films were examined by spectroscopic ellipsometry analysis. In particular, the dispersion model developed by Jellison and Modine was used to determine the optical constants by fitting the measured ellipsometric spectra in the 300–1200 nm range. Various mixtures of benzene and diluted silane (SiH 4:H 2=10:90) were used as reaction gases, and the Si concentration in the film was found to increase monotonically up to 17 at.% as the diluted silane fraction in the reaction gas was increased from 0 to 95%. However, the variation of the optical gap exhibited distinctive silicon-concentration dependence; the minimum optical gap was found from the film with 5 at.% silicon concentration. The observed changes of the optical properties were attributed to the modification of the atomic bonding structures induced by silicon incorporation. In particular, the change in SP 2-bonded carbon cluster sizes and the interlinking between SP 2 clusters are discussed.

Wear-resistant fluorinated diamondlike carbon films

Fluorinated diamondlike carbon (FDLC) films have been deposited on Si wafers by rf plasma-assisted chemical vapor deposition, under a variety of conditions. The films have been characterized by FTIR and index of refraction measurements, RBS and FRES analysis for determination of film composition, and stress measurements from the bending of the wafers by the deposited films. Friction and wear measurements have been performed using pin-on-flat and pin-on-disk testers in ambient air, at maximum Hertzian contact pressures ranging from 320 to 1100 MPa. By adjusting the deposition parameters, the properties of the FDLC films could be changed from soft films, with no significant wear resistance, to films containing more than 20% F and having wear resistance comparable to unfluorinated DLC. The tribological properties of the FDLC films are discussed in relation to their physical properties, as determined by the deposition conditions.

Tribology of diamond-like carbon sliding against itself, silicon nitride, and steel

Diamond-like carbon (DLC) films were deposited on (100) silicon wafers and silicon nitride balls by RF plasma-assisted chemical vapor deposition at a pressure of 700 mTorr and a substrate temperature of 360 K. The friction coefficient and the wear rates were measured using a pin-on-disk tribometer in 40% humid and dry air. Friction coefficients are near 0.05 in all cases measured. In dry air, the wear of silicon nitride and steel against DLC is below measurement capability because of a protecting DLC transfer layer, and wear of DLC is 2.5 ± 10−8 mm3/Nm against silicon nitride and 6.5 ± 10−9 mm3/Nm against steel. In humid air, the DLC transfer layer does not adhere to the solids, and wear of both bodies is larger. Unmeasurable wear is obtained when DLC slides against itself in humid air; the wear rate is 5 ± 10−9 mm3/Nm in dry air. These results are interpreted in terms of the properties of a friction-induced transformation of the surface layer of DLC.

Adhesion of Titanium Nitride Films Deposited on High Speed Steel Substrates by RF Plasma Assisted Chemical Vapor Deposition

Abstract Effects of growth condition of titanium interlayer and sputter-etching before its deposition on adhesion of titanium nitride films grown onto high speed steel substrates by RF (13.56 MHz) plasma-assisted chemical vapor deposition were investigated. Adhesion of TiN film increased with sputtering pressure for deposition of the interlayer. Preferred orientation (002) of the interlayer resulted in poor adhesion of TiN film. Proper sputter-preetching gave rise to adhesion up to 45 N and the film demonstrated a cohesive flaking mode during scratch test.

Process Study of Silicon Carbide Coatings Deposited on Steel by Plasma-Assisted Chemical Vapor Deposition from Tetramethylsilane-Argon Gas System

Silicon carbide coatings were prepared in an RF plasma-assisted chemical vapor deposition (CVD) device from the tetramethylsilane-argon gas system. The present paper is devoted to investigation of the plasma process and determination of the deposition rate with the experimental parameters. By employing the general convective diffusion equation, we obtain a simple analytical expression of the deposition rate. Calculated results are compared with experimental data. The agreement between calculated and measured results as functions of total pressure, total flow rate, reactant composition, and plasma geometry is fairly good. The kinetic parameters selected are found to have a reasonable order of magnitude in comparison to those of other studies.

A study on synthesis of diamond by capacitively coupled RF plasma-assisted chemical vapor deposition

A capacitively coupled RF plasma-assisted chemical vapor deposition reactor was used to synthesize diamond. A diamond phase (sp 3C-C bonds) was detected in the deposits by Raman scattering spectroscopy. Its concentration, measured by core electron energy loss spectroscopy (CEELS), was estimated to be about 40%. The amount of hydrogen in the deposits measured by hydrogen profiling by helium ions was of the order of 1% regardless of the growth conditions. These results suggested a possibility of diamond synthesis by a capacitively coupled RF PACVD technique.

Diamondlike carbon films by rf plasma-assisted chemical vapor deposition from acetylene

Diamondlike carbon films by rf plasma-assisted chemical vapor deposition from acetylene

Growth of diamond by rf plasma-assisted chemical vapor deposition

A system has been designed and constructed to produce diamond particles by inductively coupled radio-frequency, plasma-assisted chemical vapor deposition. This is a low-pressure, low-temperature process used in an attempt to deposit diamond on substrates of glass, quartz, silicon, nickel, and boron nitride. Several deposition parameters have been varied including substrate temperature, gas concentration, gas pressure, total gas flow rate, rf input power, and deposition time. Analytical methods employed to determine composition and structure of the deposits include scanning electron microscopy, absorption spectroscopy, scanning Auger microprobe spectroscopy, and Raman spectroscopy. Analysis indicates that particles having a thin graphite surface, as well as diamond particles with no surface coatings, have been deposited. Deposits on quartz have exhibited optical bandgaps as high as 4 5 eV. Scanning electron microscopy analysis shows that particles are deposited on a pedestal which Auger spectroscopy indicates to be graphite. This is a phenomenon that has not been previously reported in the literature.