Increase Of Negative Bias Voltage Research Articles

Effects of Bias Voltage and Substrate Temperature on the Mechanical Properties and Oxidation Behavior of CrWSiN Films

CrWSiN films were prepared through the co-sputtering technique, and the process variables were substrate bias voltage and temperature. The mechanical properties of hardness and elastic modulus of the CrWSiN films were dominantly affected by their average crystallite size and by substrate bias voltage and temperature. Moreover, the effect of substrate temperature was more evident than that of substrate bias. The highest hardness and elastic modulus of 42.6 and 459 GPa, respectively, were obtained for the Cr20W28Si9N43 film fabricated at a substrate temperature of 400 °C, which exhibits an evident advantage over the 25.0 and 323 GPa values for the Cr21W28Si9N42 film fabricated at room temperature. In contrast, an increase in negative bias voltage to −100 V on the substrate decreased the mechanical properties compared to one prepared using a similar process without applying the negative bias voltage. The oxidation resistance of the Cr-enriched Cr37W4Si10N49 and Cr37W5Si10N48 films was superior to that of the Cr20W28Si9N43 films with near-equal Cr and W contents annealed at 900 °C in air. The formation of a surficial Cr2O3 layer plays a vital role in restricting subsequent oxidation for CrWSiN films.

Residual stress and tribological behavior of hydrogen-free Al-DLC films prepared by HiPIMS under different bias voltages

Hydrogen-free Al-DLC films were prepared by HiPIMS technology under different bias voltages through an AlC composite target. Surface and cross-sectional morphologies, chemical composition, microphase structure and bonding state, residual stress, hardness and elastic modulus, friction coefficient and wear resistance of Al-DLC films were investigated to study the influences of substrate bias voltage. Results show that bias voltage decreased film roughness (Ra) from 3.83 nm to 1.16 nm through ion bombardment. The increase of negative bias voltage improved film disorder and altered the content of sp3 bonds. However, the existence of sp3 bonds should not be responsible for residual stress. Local distortions generated by film disorder together with the mismatch between film and substrate give rise to residual compressive stress in Al-DLC films. Film hardness is in the range of 10 GPa to 17 GPa which is affected by the content of sp3 bonds and film disorder. The lowest wear rate of Al-DLC film is 6.07 × 10−8 mm3/Nm. Besides graphitization, friction can also generate more sp3 bonds at wear interface between Al-DLC film and the counterpart ball.

Effect of Substrate Bias Voltage on the Structure and Properties of Mos2-Ti Composite Films on Titanium Alloy Surface

In order to discuss the effect of negative bias on the structure and properties of MoS2-Ti composite films on titanium alloy surface. In this paper, MoS2-Ti solid lubrication films were deposited on titanium alloy surface by unbalanced magnetron sputter. The effects of negative bias on the structure and properties of MoS2-Ti solid lubrication films were discussed. The morphology, phase, hardness, friction and wear resistance and wear mark morphology of solid lubricating film were analyzed and tested by scanning electron microscope, XRD, microhardness tester, friction and wear tester and surface profilometer. The results shows that wwhen the negative bias voltage was -150V and -200V, the structure of MoS2-Ti films is compact and the bonding with the substrate is compact. With the increase of negative bias voltage, the hardness of the film increases gradually. The wear rate of the films prepared at -150V bias voltage is the lowest, which is 2.2×10−17mm3/(N×m). The MoS2-Ti composite films deposited on the surface of titanium alloy exhibit excellent tribological properties with low friction and wear resistance, which effectively improves the surface friction and wear properties of titanium alloy.

Micro-stucture and Mechanical Properties of (NbAlSi)N Coatings by Arc Ion Plating with Different Negative Bias

Metastable (NbAlSi)N hard coatings were deposited on 1Cr11Ni2W2MoV steel sheetsby arc ion plating system at different negative pulse bias. The surface morphologies, fractured cross-sections, phase structure, hardness, friction coefficient were characterized using scanning electron microscopy,X-ray diffraction, microindentation and friction tester. All (NbAlSi)N coatings were mainly composed of δ-NbN with minorδ’-NbN. The applicating of negative bias gave rise to the change of preferred orientation, crystal refinement, decreased droplet number and improved structure density. With the increase of negative bias voltage, the hardness increased obviously and the friction coefficient decreased.

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.

Bias voltage dependence properties of Nb-doped indium tin oxide thin films by RF magnetron sputtering at room temperature

Niobium doped indium tin oxide (ITO:Nb) thin films were fabricated on glass substrates by RF magnetron sputtering from one piece of ceramic target material at room temperature. The bias voltage dependence of properties of the ITO:Nb films were investigated by adjusting the bias voltage. Structural, electrical and optical properties of the films were investigated using X-ray diffraction (XRD), atomic force microscopy (AFM), UV–visible spectroscopy, and electrical measurements. XRD patterns showed a change in the preferential orientations of polycrystalline crystalline structure from (222) to (400) crystal plane with the increase of negative bias voltage. AFM analysis revealed that the smooth film was obtained at a negative bias voltage of -120V. The root mean square (RMS) roughness and the average roughness are 1.37nm and 1.77nm, respectively. The films with the lowest resistivity as low as 1.45×10−4Ωcm and transmittance over 88% have been obtained at a negative bias voltage of −120V. Band gap energy of the films, depends on substrate temperature, varied from 3.56eV to 3.62eV.

Influence of Grinding Parameters and Substrate Bias Voltage in Dry Surface Grinding with TiN-Coated Single Layer Galvanic cBN Wheel

According to some patented literatures, grit pull-out in single layer galvanic wheels can be arrested by a physical vapor deposited (PVD) coating on the wheels. It has been assumed, therein, the uniform high energy bombardment of TiN caused a reinforcement of the bond as well as increased the stability of the cBN layer on the core. However, an in-depth study on the performance of PVD coated grinding wheel is still lacking. The present research deals with exploring the effect of grinding parameters and substrate bias voltage on the performance of TiN coated galvanic cBN wheels compared to their uncoated counterpart in dry surface grinding of AISI 52100 hardened bearing steel. TiN was deposited at the bias voltages of 0, −60, and −90 V in an in-house PVD coating system. The coating microstructure and post-grinding condition of the wheels were observed using scanning electron microscopy (SEM) and phase detection was carried out using grazing incidence X-ray diffraction (GIXRD). With the increase in negative bias voltage, highly dense and compact structure of TiN was observed along with a reduction in column size. GIXRD indicated the formation of nickel-titanium intermetallics at the interface of TiN and nickel bond. Amongst the grinding parameters, downfeed was found to be the most influential factor on the grinding forces and specific grinding energy. Both downfeed and wheel velocity exhibited significant percentage contributions to the maximum grit depth of cut. The uncoated wheel was found to undergo many grit fractures and some pull-out during grinding. TiN deposited at 0 V bias could not prevent the fracture. However, when TiN was deposited at the bias voltages of −60 V and −90 V, such failures were noticeably restricted due to the high energy ion-bombardment and diffusion of Ti and TiN within the nickel bond and the cBN grits.

Effects of Negative Bias Voltage on Structure and Mechanical Properties of DLC Films Synthesized by FCVA Deposition

Diamond-like carbon (DLC) films have been given great attention in the last twenty years and applied in many fields due to its super mechanical property. In this paper, DLC films were prepared by filter cathodic vacuum arc (FCVA) deposition under different negative bias voltage. No spalling was found in all of as-prepared DLC films. X-ray photoelectron spectroscopy (XPS), Raman spectra were employed to analyze composition and structure, the results showed that as-prepared DLC films had tendency of graphite with increase of negative bias voltage. Mechanical properties were characterized by micro-hardness and pin-on disc tests, the results showed that the hardness of DLC films decreased with bias voltage, but still kept good wear resistant.

Reduction of Gas Desorption in Graphite Anode Used in Lithium Ion Battery by Hydrogen Plasma Irradiation

In order to reduce amount of electrolyte solvent desorbed from anode material in lithium ion battery, hydrogen plasma irradiation for the anode material was conducted. During the irradiation, the sample was negatively biased. Natural graphite sample after the hydrogen plasma irradiation was soaked in propylene carbonate (PC) used as electrolyte solvent. Then, the gas desorption behavior was investigated by using a technique of thermal desorption spectroscopy (TDS). The amount of gasses in the sample irradiated by hydrogen plasma due to the PC was reduced compared with case in the non-irradiated sample. The reduction by the irradiation became large with the increase of negative bias voltage. The reduction also increased with the fluence and became roughly constant in the higher fluence regime. In order to discuss this mechanism, the sample without the soaking in PC was heated up to 1173 K. H2 desorption at high temperature region, around 1173 K, increased for the irradiated sample, compared with non-irradiated sample. This result suggests that implanted hydrogen ions form C-H bond with carbon of active sites and then the C-H bond might prevent the PC from adsorbing during the subsequent soaking.

Effect of pulsed DC CFUBM sputtered TiN coating on performance of nickel electroplated monolayer cBN wheel in grinding steel

The present research involves the deposition of pulsed DC CFUBM sputtered TiN on nickel plated steel discs and electroplated monolayer cBN wheels at seven different target frequencies and ten different bias voltages separately. The coating microstructures and the interaction between TiN and nickel were studied using scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX) and electron probe micro analysis (EPMA). Phase detection was carried out using grazing incidence X-ray diffraction (GIXRD) technique. The cohesive and adhesive strengths of nickel layer were assessed by scratch test. After grinding of low carbon steel (AISI 1020) and hardened bearing steel (AISI 52100), the conditions of the uncoated and coated cBN wheels were observed under Stereo Zoom Microscope and SEM. Average column size of TiN was found to decrease with increase in both target frequency and negative bias voltage. The structure of the coating gradually transformed from porous and open columnar (at 0 V bias) to very compact, dense and featureless (at − 80 V bias). EDX line scan and EPMA confirmed the cross-diffusion between TiN and nickel and GIXRD indicated the formation of nickel–titanium intermetallic phases at their interface. The cohesive strength of nickel layer was not effectively enhanced with increase in target frequency, whereas the same was significantly improved with increase in negative bias voltage. Seemingly, TiN coated wheel could not perform better than the uncoated wheel in grinding AISI 1020 steel due to high wheel loading. However, the uncoated wheel was found to undergo fracture wear, which was remarkably absent in the coated wheels. On the other hand, many fractured grits and some grit pull-out were observed in the uncoated wheel when grinding AISI 52100 steel, whereas almost no pull-out along with much less fractured grits were observed in the wheels coated at bias voltages like − 60 V and − 90 V.

Effect of target frequency, bias voltage and bias frequency on microstructure and mechanical properties of pulsed DC CFUBM sputtered TiN coating

Abstract Pulsed magnetron sputtering is well known since early 1990s for offering high process stability, improved coating quality, higher plasma density and high bias current. Target frequency, bias voltage and bias frequency are the three major influencing process parameters during deposition. In the present study, TiN was deposited on M2 grade high speed steel by pulsed DC closed-field unbalanced magnetron sputtering (CFUBMS) technique, over a wide range of above mentioned process parameters. The microstructure of the coating was analysed using field-emission scanning electron microscopy (FESEM) and high resolution transmission electron microscopy (HRTEM) and phases were detected using grazing incidence X-ray diffraction (GIXRD) technique. The mechanical properties, like adhesion and microhardness of the coating were assessed by scratch adhesion test and Vickers microhardness test respectively. The inter-diffusion phenomenon between the coating and the substrate was studied using depth profile secondary ion mass spectrometry (SIMS). The coating microstructure obtained from FESEM revealed that the deposition rate increased as well as column width reduced with increase of target frequency up to 150 kHz. The reduction in column width was more prominent with increase of negative bias voltage up to − 70 V. Scratch and hardness test indicated that adhesion and composite microhardness of the coating increased with increase of target frequency up to 200 kHz. However, both were at first increased and then decreased with increase of negative bias voltage. With increase of bias frequency, adhesion of the coating was found to improve with almost no edge spallation. However, no specific trend between coating microhardness and bias frequency could be obtained. Unlike some previous reports, with increase of bias frequency, average substrate ion current during pulse-on period was found to marginally decrease. However, the same during ion etching was noted to increase with increase of bias frequency.

Deposition of nano-scaled CrTiAlN multilayer coatings with different negative bias voltage on Mg alloy by unbalanced magnetron sputtering

In a magnetron sputtering system, the negative substrate bias voltage has been used as a basic process parameter to modify the deposition structure and properties of coatings. In this paper we report the effect of bias voltage ranging from −40 V to −90 V on nano-scaled CrN/TiN/CrN/AlN (CrTiAlN) multilayer coatings synthesized on a Mg alloy by a closed-field unbalanced magnetron sputtering ion plating system in a gas mixture of Ar + N 2. The technological temperature and atomic concentration in the multilayer coatings were controlled by adjusting the current density of different metal magnetron targets and the plasma optical emission monitor. The composition, crystallographic structure, deposition model and friction coefficient of multilayer coatings were characterized by X-ray photoelectron spectrometry (XPS), X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM) and ball-on-disc testing. The experimental results show that the deposition model and friction coefficient of nano-scaled CrTiAlN multilayer coatings were significantly affected by the negative bias voltage ( V b). The nitride species in multilayer coatings mainly involve CrN, AlN and TiN, and XRD analysis shows that the crystallographic structure was face-centered cubic. Under different bias voltage conditions, the multilayer coating composition shows a fluctuation, and the Al and Cr concentrations respond in the opposite sense to the bias voltage, attaining their greatest values at V b = −70 V. The surface and cross-sectional morphology shows deposition model change from a columnar model into non-columnar model with the increase in negative bias voltage. The friction coefficient of the nano-scaled multilayer coatings at V b = −55 V stabilize after 10 000 cycles.

Microstructural control of Cr–Si–N films by a hybrid arc ion plating and magnetron sputtering process

The microstructural evolution of Cr–Si–N films deposited by a hybrid arc ion plating and magnetron sputtering process was investigated by varying the sputtering power of Si target and substrate bias voltage. Detailed nanocomposite microstructures of the films were studied by high-resolution transmission electron microscopy. The results indicated that the incorporation of Si into the growing CrN films at 0 V led to the formation of a nanocomposite containing CrN nanocolumns embedded in amorphous SiN x matrix or near-amorphous microstructure. For the films having a Si content of ∼10 at.% and ∼15 at.%, a negative bias voltage of −50 V resulted in the aggregation of nanocolumns in the amorphous matrix. Further increase of negative bias voltage to −250 V led to the formation of a three-dimensional CrN/a-SiN x nanocomposite microstructure. The mechanism of microstructure evolution is discussed by considering the thermodynamic and kinetic factors.

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.

Deposition of TiN coatings on shape memory NiTi alloy by plasma immersion ion implantation and deposition

An investigation has been carried out to study the effect of pulse negative bias voltage on the morphology, microstructure, mechanical, adhesive and tribological properties of TiN coatings deposited on NiTi substrate by plasma immersion ion implantation and deposition. The surface morphologies were relatively smooth and uniform with lower root mean square values for the samples deposited at 15 kV and 20 kV negative bias voltages. X-ray diffraction results demonstrated that the pulse negative bias voltage can significantly change the microstructure of TiN coatings. The intensity of TiN(220) peak increased with the increase of negative bias voltage in the range of 5–20 kV. When the negative bias voltage increased to 30 kV, the preferred orientation was TiN(200). Nanoindentation test indicates that hardness and elastic modulus increased with the increase of the negative bias voltage (5 kV, 15 kV and 20 kV), and then dropped sharply at 30 kV. The adhesion between the TiN and NiTi alloy and tribological properties of TiN coated NiTi alloy depend strongly on the bias voltage parameter; the sample deposited at 20 kV possesses good adhesion strength and excellent tribological property.

Theoretical model of the mechanism study on the positive magnetoresistance in the heterostructure composed of two oxides

A positive colossal magnetoresistance (CMR) has been discovered at low applied magnetic field and in the temperature range from 130 to 290 K in the epitaxial p –n heterostructure fabricated with Sr-doped LaMnO 3 and Nb-doped SrTiO 3 by laser molecular-beam epitaxy. The mechanism causing the unusual positive CMR is proposed as an interface effect, i.e., creation of the region near the interface with electron filling in the t 2g spin-down band in La 0.9Sr 0.1MnO 3 plays a crucial role in spin-dependent carrier transport of the system. Self-consistent calculation has been carried out to obtain the band diagram around the interface of the heterostructure. Other puzzling CMR features, which exhibit values of positive CMR first increase and then decrease with increase of negative bias voltage and temperature, are well explained by the present scenario.

Indium tin oxide thin films by bias magnetron rf sputtering for heterojunction solar cells application

In this investigation ITO thin films were prepared by bias magnetron rf sputtering technique at substrate temperature of 180 °C and low substrate–target distance for future a-Si:H/c-Si heterojunction (HJ) solar cells application. Microstructure, surface morphology, electrical and optical properties of these films were characterized and analyzed. The effects of ion bombardments on growing ITO films are well discussed. XRD analysis revealed a change in preferential orientation of polycrystalline structure from (2 2 2) to (4 0 0) plane with the increase of negative bias voltage. Textured surface were observed on AFM graphs of samples prepared at high negative bias. Hall measurements showed that the carrier density and Hall mobility of these ITO films are sensitive to the bias voltage applied. We attributed these effects to the sensitivity of energy of Ar + ions bombarding on growing films to the applied bias voltage in our experiments. At last the figure of merit was calculated to evaluate the quality of ITO thin films, the results of which show that sample prepared at bias voltage of −75 V is good to be used in HJ cells application.

Grain size refinement of the diamond film deposited on the WC–Co cutting inserts using direct current biasing

The effect of negative direct current (DC) bias has been investigated in the deposited diamond on WC–Co insert. SPGN type of WC–Co was used as a substrate where diamond was deposited by hot filament chemical vapor deposition at 60 Torr with H2–3%CH4 gas. DC bias was applied to the insert with the range between 0 and −120 V. The grain size of diamond film deposited on WC–Co insert decreased with the increase in negative bias voltage. The grain size was more refined near the edge than the center of the insert. Compared to other processing parameters such as pressure, temperature and carbon concentration, the biasing is a very effective way to reduce the grain size of diamond film, especially at the edge region where workpiece contacts during machining process.

Synthesis and structure of nitrogenated tetrahedral amorphous carbon thin films prepared by a pulsed filtered vacuum arc deposition

Nitrogenated tetrahedral amorphous carbon (ta-C:N) thin films have been prepared by a pulsed filtered vacuum arc deposition system at various conditions. The chemical composition and structure of the ta-C:N films were investigated by Non-Rutherford backscattering spectroscopy, Auger electron spectroscopy, Raman, and Fourier transform infrared transmission measurements. It was observed that the amount of N atoms incorporated into the ta-C:N films, as well as the fraction and size of the sp 2 clusters, increased with increasing nitrogen pressure during deposition. On the other hand, the substrate negative bias voltage has different effects on the composition and structure of the films. The N content initially rises with increasing substrate negative bias voltage and then starts to decrease as it is further increased, while the sp 2 fraction increases monotonically with the increase of negative bias voltage. No or very few CN bond exists in the films. With increasing N content the components of the single CN and disorder activated CC diminish. The compressive stress in the films is found to decrease sharply with the increase of nitrogen content, and then keep almost constant when the N content is increased further.