Influence Of Negative Bias Voltage Research Articles

Bias effects on AlMgB thin films prepared by magnetron sputtering

AlMgB thin films were deposited on silicon (100) substrate using a three-target magnetron sputtering system in argon atmosphere. The influence of negative bias voltage on the thickness, morphology, microstructure, local bonding and hardness of the deposited films was investigated. Experimental results show that all films are X-ray amorphous, and the properties of the deposited films have a strong dependence on the applied substrate's negative bias voltage. Deposited at high negative bias voltage, the AlMgB thin films are found to be generally dense, having a smooth surface and containing more well-formed B12 icosahedra, which consequently increase the hardness of the deposited films. However, deposited at low negative bias voltage, the AlMgB thin films exhibit loose structure, coarse surface and contain few B12 icosahedra. It is shown that the hardness of the dense and smooth AlMgB thin films can reach 22 GPa at the negative bias voltage of 400 V.

Correlation between the Interface Width and the Adhesion Strength of Copper Films Deposited on Ion-Etched Carbon Steel Substrates by Varying the Bias Voltage

The present study has been conducted in order to determine the influence of negative bias voltage applied to substrate on adhesion of copper films deposited on carbon steel substrates. The adhesion strength has been evaluated by the scratch test. Coatings were deposited by a DC magnetron sputtering system. The substrates were firstly mechanically polished and then ion-etched by argon ions prior to deposition. Adhesion was found to increase with the bias voltage. The critical load had a value of 9.5 g for an unbiased substrate and reached 18.5 g for a bias voltage of 600 V. Equally important, the interface width, measured using Auger electron spectroscopy, increased as a function of the bias voltage. The width of the interface is related to the time of ion milling in the Auger spectrometer. The size of this width is obtained from the Auger elemental depth profiles through measuring the depth of the interface coating/substrate. The width had a value of 335 min with a bias of 600 V whereas it didn't exceed 180 min when the substrate was unbiased. Therefore, the effect of the bias voltage was to expand the interface because of the diffusion phenomenon and physical mixing of materials at the interface. Moreover, the critical load increased with the increase of the interface width.

Influence of negative bias voltage on microstructure and property of Al-Ti-N films deposited by multi-arc ion plating

In this study, we systematically investigated the effects of negative bias voltage on the composition, deposition efficiency, microstructure, and mechanical properties of multi-arc ion plated (MAIP) AlTiN films. The films were deposited on high-speed steel substrates by MAIP at various negative bias voltages. The results indicated that the Al content [Al/(Al+Ti) ratio] and the deposition efficiency were significantly altered by the application of negative bias voltages. X-ray photoelectron spectroscopy analysis showed that the AlTiN films were composed of Ti–N and Al–N bonds. The macroparticles (MPs) on the film surface decreased with increasing negative bias voltage. We also discussed the different types of MPs found on the films and their influence on the process of determining the hardness of the films. The microhardness of the films depends on the negative bias voltages. The films deposited at −250V exhibited a maximum hardness of ~45GPa. The adhesion and frictional tests revealed that the film deposited at −150V demonstrated the highest cracking resistance, the best adhesion under a critical load of 78 N, highest adhesion strength, and the lowest and stablest coefficient of friction at 0.23.

Influence of negative bias voltage on structural and mechanical properties of nanocrystalline TiNx thin films treated in hot cathode arc discharge plasma system

Ti thin films were grown by DC sputtering on a glass substrate and then nitrided in a hot cathode arc discharge plasma system, which is an effective approach to independently monitoring the plasma and nitriding parameters. The hardness of pristine Ti thin film is found to be ~3.06GPa, which increases upto ~16.08GPa with an increase in negative bias voltage to −140V and then decreases to ~15.05GPa for higher of −240V bias voltage. Similar kind of variation has been observed in crystallite size and surface roughness. Crystallite size is found to increase from 11.1nm (pristine Ti) to 14.8nm (for −140V) and then reduces to 11.9nm for –240V. Surface roughness increases from 2.78nm (pristine) to 6.84nm (for –140V), which is found to be 4.14nm for –240V. Optical and electrical measurements also reveal the strong impact of negative bias voltage on the bandgap and resistivity of the films. Above results are understood on the basis of diffusion of nitrogen ions for lower voltages and saturation of nitrogen ions in the host lattice for high voltages.

Influence of negative bias voltage and deposition temperature on microstructure and properties of superhard TiB2 coatings deposited by high power impulse magnetron sputtering

It is critical to utilize the substrate bias voltage to attract the sputtered ions in high power impulse magnetron sputtering (HIPIMS) plasmas which contain a large amount of target ion species. In this work, superhard titanium diboride (TiB2) coatings were synthesized from TiB2 compound target by a HIPIMS technique at deposition temperatures of 200°C and 300°C, respectively. The substrate bias voltage was altered from 0V to −200V. The influence of the bias voltage at 200°C and 300°C on the chemical composition, phase structure, microstructure, surface morphology, mechanical and nanowear properties of the TiB2 coatings was investigated. The results indicated that the chemical composition and microstructure were significantly altered by increasing the bias voltage. At 200°C, the moderate bias voltage of −50V to −100V lead to enhanced ion energy and surface adatom mobility while the resputtering effect was induced as the bias voltage further increased from −100V to −200V. The TiB2 coating deposited at −100V exhibited the best mechanical and nanowear properties and lowest surface roughness. At 300°C, the continuous increase of the surface adatom mobility as the bias voltage increased from 0V to −200V acted as the dominant influence factor for the coating properties. The TiB2 coating with the best mechanical and nanowear properties and lowest surface roughness was obtained at −200V.

Influence of Negative Bias Voltage on the Microstructure and Tribological Properties of CrTiAlN Composite Films

By using the multi-ion plating,the CrAlTiN composite films were made on the suface of piston rings to improve its tribological properties and increase service life. The effects of negative bias voltage on morphology, hardness, adhesion strength, microstructure and tribological properties were studied. The results show that the morphology, phases, hardness, adhesion and wearability of the films were varied with negative bias voltage. When the negative bias voltage was at -200V, the hardness, adhesion strength of CrTiAlN coatings reaches maximum and the surface roughness, weightlessness for CrTiAlN composite coatings reaches minimum. And the conclusion can be obtained that the key factor which influences the wearability of the films are the function of the crystal size and adhesion strength together.

Influence of negative bias voltage on the mechanical and tribological properties of MoS2/Zr composite films

MoS2/Zr composite films were deposited on the cemented carbide YT14 (WC+14%TiC+6%Co) by medium-frequency magnetron sputtered and coupled with multi-arc ion plated techniques. The influence of negative bias voltage on the composite film properties, including adhesion strength, micro-hardness, thickness and tribological properties were investigated. The results showed that proper negative bias voltage could significantly improve the mechanical and tribological properties of composite films. The effects of negative bias voltage on film properties were also put forward. The optimal negative bias voltage was −200 V under this experiment conditions. The obtained composite films were dense, the adhesion strength was about 60 N, the thickness was about 2.4 μm, and the micro-hardness was about 9.0 GPa. The friction coefficient and wear rate was 0.12 and 2.1×10−7 cm3/N·m respectively after 60 m sliding operation against hardened steel under a load of 20 N and a sliding speed of 200 rev·min−1.

Ti–TiC–TiC/DLC gradient nano-composite film on a biomedical NiTi alloy

Ti–TiC–TiC/diamond-like carbon (DLC) gradient nano-composite films have been prepared on NiTi alloy substrates by the technique of plasma immersion ion implantation and deposition (PIIID) combined with plasma-enhanced chemical vapor deposition (PECVD). The influence of negative bias voltage applied to the substrate (from −100 V to −500 V) on the chemical structure, microstructure, mechanical properties and corrosion resistance was investigated by Raman spectrum, x-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), x-ray diffraction (XRD), friction coefficient test, scratch test, nano-indentation test and anodic polarization experiments. The Raman spectrum and XPS results showed that the doped films kept an amorphous DLC structure. TEM observation revealed that nanometer TiC particles were surrounded by the amorphous DLC. With the increase of bias voltage, the ratio of sp2/sp3 first decreased, reaching a minimum value at −200 V, and then increased. The nano-indentation results showed that the hardness of the Ti–TiC–TiC/DLC gradient films reached the maximum value at −200 V when TiC particles reached the maximum content in the films. The friction coefficient test and scratch test indicated that Ti–TiC–TiC/DLC gradient films had a low friction coefficient and high bonding strength with the NiTi substrates. Combined with anodic polarization curves and SEM observation, it was found that the corrosion resistance of the Ti–TiC–TiC/DLC gradient films was much better than that of the bare NiTi alloy.

Effect of negative bias voltage on CrN films deposited by arc ion plating. II. Film composition, structure, and properties

Chromium nitride (CrN) films were deposited on Si wafers by arc ion plating at various negative bias voltages and several groups of N2∕Ar gas flux ratios and chamber gas pressures. The authors systematically investigated the influence of negative bias voltage on the synthesis, composition, microstructure, and properties of the arc ion plating (AIP) CrN films. In this article, the authors investigated the influence of negative bias voltage on the chemical composition, structure, and mechanical properties of the CrN films. The results showed that the chemical composition and phase structure of the AIP CrN films were greatly altered by application of negative bias voltage. Due to the selective resputtering effect, substoichiometric CrN films were obtained. With increase in bias voltages, the main phases in the films transformed from Cr+CrN to Cr2N at low N2∕Ar flow ratios, whereas the films at high N2∕Ar flow ratios retained the CrN phase structure. The CrN films experienced texture transformation from CrN (200) to CrN (220), and Cr2N (300) to Cr2N(300)+Cr2N(110). Increase in negative bias voltage also resulted in microstructure evolution of coarse columnar grains→fine columnar grains→quasiamorphous microstructure→recrystallized structures. From the experimental results, the authors proposed a new structure zone model based on enhanced bombardment of incident ions by application of negative bias voltage. The influence of negative bias voltage on the microhardness and residual stresses of the films and the inherent mechanisms were also explored.

Effect of negative bias voltage on CrN films deposited by arc ion plating. I. Macroparticles filtration and film-growth characteristics

Chromium nitride (CrN) films were deposited on Si wafers by arc ion plating (AIP) at various negative bias voltages and several groups of N2∕Ar gas flux ratios and chamber gas pressures. The authors systematically investigated the influence of negative bias voltage on the synthesis, composition, microstructure, and properties of the AIP CrN films. In this part (Part I), the investigations were mainly focused on the macroparticle distributions and film-growth characteristics. The results showed that macroparticle densities on the film surfaces decreased greatly by applying negative bias voltage, which can be affected by partial pressure of N2 and Ar gases. From the statistical analysis of the experimental results, they proposed a new hybrid mechanism of ion bombardment and electrical repulsion. Also, the growth of the AIP CrN films was greatly altered by applying negative bias voltage. By increasing the bias voltage, the film surfaces became much smoother and the films evolved from apparent columnar microstructures to an equiaxed microstructure. The impinging high-energy Cr ions accelerated by negative bias voltages were deemed the inherent reason for the evolution of growth characteristics.

Effect of substrate bias voltage on the properties of diamond-like carbon thin films deposited by microwave surface wave plasma CVD

Diamond-like carbon (DLC) thin films were deposited on silicon and ITO substrates with applying different negative bias voltage by microwave surface wave plasma chemical vapor deposition (MW SWP-CVD) system. The influence of negative bias voltage on optical and structural properties of the DLC film were investigated using X-ray photoelectron spectroscopy, UV/VIS/NIR spectroscopy, Fourier transform infrared spectroscopy and Raman spectroscopy. Optical band gap of the films decreased from 2.4 to 1.7 with increasing negative bias voltage (0 to − 200 V). The absorption peaks of sp 3 C H and sp 2 C H bonding structure were observed in FT-IR spectra, showing that the sp 2/sp 3 ration increases with increasing negative bias voltage. The analysis of Raman spectra corresponds that the films were DLC in nature.