Bias induced structural changes in tungsten nitride films deposited by unbalanced magnetron sputtering

Tungsten nitride thin films were deposited using unbalanced magnetron sputtering system. The effect of the ratio of nitrogen partial pressure to the total pressure during deposition and the substrate bias on the tungsten nitride formation has been studied. The glow discharge characteristics of the process have been studied in order to determine the deposition parameters. It is observed that nitrogen partial pressure ratio 0.4 and cathode current of 200mA favors the formation of the $W_2N$ films. The variation in the electrical resistivity of the films has been studied as a function of nitrogen partial pressure and substrates bias. A minimum resistivity of $406\mu\Omega$cm is observed for tungsten nitride films prepared at 70V bias. X-ray diffraction analysis of the films indicate the formation of $\beta-W_2N$ (1 0 0) phase at the partial pressure ratio of 0.4. The effects of the bias on the structural properties were also studied at this condition. The internal stress and the particle size of the deposited films were calculated and it was found that there is no appreciable change with the applied bias voltage

Characterization of bias magnetron-sputtered silicon nitride films

Influence of the deposition parameters and the substrate bias voltage on the optical, compositional and the surface properties of DC magnetron-sputtered silicon nitride thin films are studied. Silicon nitride thin films are deposited on silicon (100) and quartz substrates at different partial pressures of nitrogen and discharge currents. The variation in the refractive index and the optical band gap of these films is studied. Compositional variation has been studied using Rutherford backscattering spectroscopy (RBS). Silicon nitride thin films deposited at 3 \times 10^-^2 Pa partial pressure of nitrogen with $2.5 mA/cm^2$ cathode current density showed an optical band gap of 4.3 eV and refractive index of 2.04 (at 650 nm). Nitrogen to silicon ratio in the film is 1.31, and the roughness of the films is 2.3 nm. Substrate bias during deposition helped in changing the optical properties of the films. Substrate bias of -60V resulted in films having near stoichiometry with N/Si ratio 1.32, and the optical band gap, refractive index, and the roughness are 4.8 eV, 1.92 and 0.78 nm, respectively

Effect of C/Si Ratio on the Electrochemical Behavior of a-SiCx:H Coatings on SS301 Substrate Deposited by PECVD

Amorphous hydrogenated silicon carbide (a-SiCx:H) coatings were deposited on stainless steel 301 (SS301) using plasma enhanced chemical vapor deposition with the methane gas flow ranging from 30 to 90 sccm. XRD spectra confirmed the amorphous structure of these coatings. The as-deposited coatings all exhibited homogenous dense feature, and no porosities were observed in SEM and AFM analysis. The a-SiCx:H coatings remarkably increased the corrosion resistance of the SS301 substrate. With the increase of the C concentration, the a-SiCx:H coatings exhibited significantly enhanced electrochemical behavior. The a-SiCx:H coating with the highest carbon concentration acted as an excellent barrier to charge transfer, with a corrosion current of 3.5×10-12 A/cm2 and a breakdown voltage of 1.36 V, compared to 2.5×10-8 A/cm2 and 0.34 V for the SS301 substrate

Plasma surface modification of polystyrene and polyethylene

Polystyrene (PS) and polyethylene (PE) samples were treated with argon and oxygen plasmas. Microwave electron cyclotron resonance (ECR) was used to generate the argon and oxygen plasmas and these plasmas were used to modify the surface of the polymers. The samples were processed at different microwave powers and treatment time and the surface modification of the polymer was evaluated by measuring the water contact angle of the samples before and after the modification.Decrease in the contact angle was observed with the increase in the microwave power for both polystyrene and polyethylene. Plasma parameters were assessed using Langmuir probe measurements. Fourier transform infrared spectroscopy showed the evidence for the induction of oxygen-based functional groups in both polyethylene and polystyrenewhen treated with the oxygen plasma. Argon treatment of the polymers showed improvement in the wettability which is attributed to the process called as CASING, on the other hand the oxygen plasma treatment of the polymers showed surface functionalization. Correlation between the plasma parameters and the surface modification of the polymer is also discussed

Structural, mechanical, tribological, and corrosion properties of a-SiC:H coatings prepared by PECVD

ABSTRACT: Amorphous hydrogenated silicon-carbide (a-SiC:H) coatings appear very attractive due to their superior optical and mechanical properties and chemical inertness. In the present work a-SiC:H coatings were prepared by PECVD on stainless steel 301 (SS301) and Ti–6Al–4V (TiAlV) substrates at a temperature of 300 °C, using different SiH4/CH4 precursor ratios. We systematically studied such mechanical properties as hardness, reduced Young's modulus and elastic recovery using depth-sensing indentation, their tribological characteristics such as coefficient of friction and wear coefficient using the pin-on-disc method, as well as their corrosion and tribo-corrosion behaviors. a-SiC:H films (∼ 3 μm thick) prepared on SS301 and TiAlV at optimal deposition conditions exhibited a hardness of 23.5 GPa, reduced Young's modulus of 160 GPa, and elastic rebound of 73%. They showed a friction coefficient of ∼ 0.35, and a wear rate of 10 × 10−6 mm3/Nm. These values are low compared to ∼ 0.85 and ∼ 0.5, 240 × 10−6 mm3/Nm and 700 × 10−6 mm3/Nm for SS301 and TiAlV, respectively. The films exhibited a very high corrosion and tribo-corrosion resistance on both metallic substrates. The coating behavior is correlated with the microstructure and composition, determined by complementary characterization techniques including ERD, FTIR and Raman analyses

Wettability enhancement of polystyrene with electron cyclotron resonance plasma with argon

Polystyrene cell-culture substrates were treated with argon glow discharge to make their surfaces hydrophilic. The process was novel in that it used a microwave electron cyclotron resonance (ECR) source for polymer surface modification. The substrates were processed at different microwave powers and time periods, and the surface modification was assessed with by measurement of the water contact angle. A decrease in contact angle was observed with increasing microwave power and processing time. Beyond a certain limit of power and duration of exposure, however, surface deterioration occurred. The optimum conditions for making the surfaces hydrophilic without deterioration of the samples were identified. The plasma parameters were assessed by Langmuir probe measurement. Fourier transform infrared spectroscopy with attenuated total reflectance showed evidence for the induction of hydrophilicity on the surface. The surface micromorphology was examined with scanning electron microscopy. The results prove that the ECR glow discharge was an efficient method for enhancing the wettability of the polymer surfaces