Effect Of Substrate Bias Research Articles

Nanolayer (Ti,Cr)N coatings for hard particle erosion resistance

This paper discusses the synthesis and characterization of titanium chromium nitride ((Ti,Cr)N) thin films deposited onto AM355 stainless steel by multi-source cathodic arc physical vapor deposition (PVD) for improved erosion resistance. The effect of Cr evaporator current and substrate bias on the erosion resistance of the (Ti,Cr)N coating were investigated. The coatings were characterized using X-ray diffraction, scanning electron microscopy, electron probe microanalysis, scanning transmission electron microscopy, scratch adhesion testing and erosion testing. The (Ti,Cr)N coatings deposited using multisource mode were determined to be nanolayered structures consisting of TiN rich and CrN rich layers. EPMA showed that the atomic percentage of Cr within the coating increased (increased Cr:Ti ratio) with increasing Cr evaporator current and that the (Ti,Cr)N chemical composition did not appear to change with varying bias. Using XRD and STEM, it was determined that all nanolayer (Ti,Cr)N coatings were multi-phased consisting of a B1 NaCl crystal structure. XRD also revealed that as the Cr evaporator current was increased, there was an increase in the CrN phase volume. Macroparticle incorporation increased with an increase in Cr evaporator current and decreased with an increase in bias. The nanolayer (Ti,Cr)N coatings ranged in Vickers hardness from 1700 to 2800 VHN0.050. Coating adhesion increased as Cr:Ti ratio increased. In regards to erosion, (Ti,Cr)N coatings with a high number of TiN/CrN interfaces performed poorly against alumina media. As the Cr evaporator current was varied, the coating deposited with the highest Cr:Ti ratio (evaporator current of 85 A) and when bias was varied, the lowest substrate bias of -50V had the best erosion performance.

Modeling of Reduced Surface Field Laterally Diffused Metal Oxide Semiconductor for Accurate Prediction of Junction Condition on Device Characteristics

In this paper, an accurate model of resistive drift region in laterally diffused metal oxide semiconductor (LDMOS) is presented. We have improved the dynamically varying depletion width model at the drift/substrate junction, by considering both the drain and substrate bias effects. The both bias condition causes the resistance modification of the high resistive drift region for the reduced-surface-field structure (RESURF). In addition, new expansion-effect model is developed by considering the substrate bias effect. The developed models have been implemented into Hiroshima University starc insulated gate field effect transistor model for high voltage (HiSIM-HV) and it is proved that the models reproduce measured direct current (DC) characteristics for the wide variety of the substrate bias variation.

Bias effects on microstructure, mechanical properties and corrosion resistance of arc-evaporated CrTiAlN nanocomposite films on AISI 304 stainless steel

CrTiAlN films were deposited on AISI 304 stainless steel by cathodic arc evaporation under a systematic variation of the substrate bias voltage. The effects of substrate bias on the coating morphology and mechanical properties, such as structure, composition, adhesion, hardness and Young's modulus, were studied in details using field emission scanning electron microscopy, X-ray diffraction, electron probe microanalysis and indenter. Polarization test and immersion test were also carried out to evaluate the corrosion behavior of the various films. CrTiAlN films are nanocrystalline that exhibit a CrN/TiAlN multi-layered morphology. At the optimal value of substrate bias voltage (i.e., − 150 V), the CrTiAlN film showed an increased Cr content and improved properties, such as higher adhesion, higher hardness (38 ± 2 GPa), and greater Young's modulus (319 ± 16 GPa) vs. the films deposited at other substrate bias voltages. Moreover, the optimum film has better corrosion resistance in 3.5 wt.% NaCl and 20 vol.% HCl solutions.

Substrate bias effect on AlOx based magnetic tunnel junctions

The effect of substrate bias during deposition on the properties of magnetron sputtered aluminium oxide-based magnetic tunnel junctions (MTJ) is investigated. Ge buffer layers have been used for MTJs for the first time. Transmission electron microscope (TEM) images clearly indicate that application of substrate bias during the deposition of MTJ layers [IrMn/Co/AlOx/NiFe/Cu] provides extremely smooth layers and flat interfaces (without annealing) in comparison to the layers deposited without bias. But hysteresis loops (magnetization v/s magnetic field M-H) obtained from alternating gradient force magnetometer (AGFM) make it clear that IrMn deposited with a substrate bias is not effective in providing exchange bias. The reason is the change in composition of IrMn with bias as shown by Rutherford backscattering (RBS) experiments. RBS for AlOx shows a clear Ar peak with the application of substrate bias.

Propensity and geometrical distribution of surface nanobubbles: effect of electrolyte, roughness, pH, and substrate bias

Nanobubbles are believed to have surface charges at the gas–liquid interface. However, the effect of various factors on the formation mechanism and stability of these charged species is not well understood. Using atomic force microscopy (AFM) in tapping mode (TMAFM), the propensity of formation and geometrical distribution of nanobubbles on an ultra-thin polystyrene (PS) film immersed in deionized (DI) water and saline (sodium chloride) solution was investigated. The results reveal that in saline solution, nanobubbles form in larger number and size as compared to nanobubbles in DI water. This is attributed to the enhanced surface charge stabilization of the nanobubbles caused by the electrolyte ions in saline solution. A PS film of higher roughness causes the formation of larger nanobubbles due to the presence of more nucleation sites provided by surface asperities, causing numerous nanobubbles in close proximity to coalesce to form larger ones. The study of the effect of pH shows that nanobubbles are more stable in an alkaline solution than in an acidic solution. The results further reveal that the size of nanobubbles increases with increasing positive substrate bias, whereas there is no measurable change in size with increasing negative substrate bias, possibly due to differential charging at the interfaces across the non-conductive PS film.

Effect of Negative Substrate Bias on the Structure and Properties of Ta Coatings Deposited Using Modulated Pulse Power Magnetron Sputtering

Crystalline phase control is critical for obtaining desired structure and properties of Ta coatings deposited by magnetron sputtering. We have shown the approach to control the alpha and beta Ta phase formations by tuning the negative substrate bias voltage during modulated pulse power (MPP) magnetron sputtering, which generates a large fraction of target metallic ions in the plasma providing enhanced ion bombardment on the growing film. It was found that the peak and mean substrate ion current densities increased rapidly from 42 to 165 mAcm-2 and 16 to 55 mAcm-2, respectively, as the negative substrate bias voltage was increased from -20 to -50 V and became saturated with a further increase in the negative substrate bias voltage. As the negative substrate bias voltage was increased from 0 to -100 V, the MPP Ta phase changed from an all beta phase when the bias voltage was at 0 V and a floating bias, to a mixed alpha and beta phases when the bias voltage was in the range of -30 to -40 V, and finally to an all alpha phase when the negative bias voltage was -50 V or greater. In this paper, alpha Ta coating with thicknesses up to 100 μm were successfully deposited using the MPP technique with high deposition rate. The residual stress of the thick Ta coating was measured using an X-ray stress analyzer. The adhesion strength of the thick Ta coating was evaluated using Rockwell-C indentation and scratch tests. The possibility to coat complex-shaped substrates with good coating coverage on the substrate's surface placed orthogonal to the target has also been demonstrated.

Effect of copper content and substrate bias on structure and mechanical properties of reactive sputtered CrCuN films

The CrCuN films with various Cu contents were deposited under different substrate bias by DC magnetron sputtering. The influence of Cu content and substrate bias was examined with regard to the microstructure, morphology, and mechanical properties of these films. The CrCuN films containing low Cu content (3.4 at.%) present distinctive columnar growth. Their preferred orientations change from (1 1 1) (−50 V bias) to (2 0 0) (−200 V bias) and surface morphology changes from porous to granular structure with increasing bias. However, when the copper content is increased to 15 at.%, CrCuN films remain (2 0 0) preferred growth independent of bias, while the film maximum hardness is reduced from 32 GPa to 20 GPa because of excess soft metal.

A magnetron sputtering technique to prepare a-C:H films: Effect of substrate bias

Amorphous hydrogenated carbon (a-C:H) films were deposited by magnetron sputtering with a mixture gas of Ar and CH 4. The a-C:H films deposited by this method have relatively low internal stress (<1 GPa) compared to some films deposited by conventional deposition process. The effects of substrate bias voltage on microstructure, surface morphology and mechanical properties of the films were investigated by various techniques. It has been found that the polymer-like structure is dominated at low bias voltage (−100 V), while the diamond-like structure with the highest hardness and internal stress is the main feature of the a-C:H films deposited under high bias voltage (−300 V). With increasing the bias voltage further, the feature of diamond-like structure decreases associating with the increase of graphitization. The frictional test shows that the friction coefficient and wear rate of the a-C:H films are depended strongly on structure and mechanical properties, which were ultimately influenced by the deposition method and bias voltage.

Effect of substrate bias and temperature on magnetron sputtered CrSiN films

The combine influence of substrate temperature and bias on microstructure and mechanical properties of CrSiN film was examined. The silicon content and phase constitutions of the films are independent on substrate temperature and bias. The crystal preferred orientation is controlled by substrate bias but unrelated to substrate temperature. The influence of bias (0 V to −300 V) on hardness is more obvious than that of the substrate temperature (100–500 °C).

Effect of high substrate bias and hydrogen and nitrogen incorporation on spectroscopic ellipsometric and atomic force microscopic studies of tetrahedral amorphous carbon films

The influence of substrate bias and hydrogen/nitrogen incorporation on the optical properties [studied by spectroscopic ellipsometry (SE)] and surface morphology [studied by atomic force microscopy] of tetrahedral amorphous carbon (ta-C) films, deposited by S bend filtered cathodic vacuum arc (FCVA) process, is reported. SE spectra of the imaginary part of the dielectric constant are used to estimate carbon bonding ratios. In ta-C films, optical constants increase with substrate bias and hydrogen/nitrogen incorporation. The optical band gap (Eg) and sp3 content increase up to −200V substrate bias and then decrease. Eg increases with hydrogen incorporation but is unchanged by nitrogen incorporation.

X-ray photoelectron spectroscopic study of nitrogen incorporated amorphous carbon films embedded with nanoparticles

The effect of substrate bias on X-ray photoelectron spectroscopy (XPS) study of nitrogen incorporated amorphous carbon (a-C:N) films embedded with nanoparticles deposited by filtered cathodic jet carbon arc technique is discussed. High resolution transmission electron microscope exhibited initially the amorphous structure but on closer examination the film was constituted of amorphous phase with the nanoparticle embedded in the amorphous matrix. X-ray diffraction study reveals dominantly an amorphous nature of the film. A straight forward method of deconvolution of XPS spectra has been used to evaluate the sp 3 and sp 2 contents present in these a-C:N films. The carbon (C 1s) peaks have been deconvoluted into four different peaks and nitrogen (N 1s) peaks have been deconvoluted into three different peaks which attribute to different bonding state between C, N and O. The full width at half maxima (FWHM) of C 1s peak, sp 3 content and sp 3/sp 2 ratio of a-C:N films increase up to −150 V substrate bias and beyond −150 V substrate bias these parameters are found to decrease. Thus, the parameters evaluated are found to be dependent on the substrate bias which peaks at −150 V substrate bias.

Growth, characterization and effect of substrate bias on ZnO prepared by reactive capillaritron ion beam sputtering deposition

ZnO thin films have been deposited on Si substrates by reactive ion beam sputtering deposition utilizing a capillaritron ion source. All the as-deposited ZnO films exhibit a preferred (0 0 2) growth direction while the grain size increases as oxygen partial flow rate increases. An optimum photoluminescence result was achieved using oxygen partial flow rate of ∼40% that the ratio of integrated deep level emission to that of integrated near-band-edge emission is less than 1.5. The atomic percentage ratio of Zn:O remains at 55/45, regardless of oxygen partial flow rates. With the applied substrate bias, the atomic percentage ratio of Zn/O changes to 40/60, indicating that stoichiometric ZnO may be achieved by selecting appropriate substrate bias. With the substrate bias applied, increased amount of oxygen atoms were found located in oxygen deficient matrixes, likely due to the bombardment of secondary ions.

Effect of high substrate bias and hydrogen and nitrogen incorporation on density of states and field-emission threshold in tetrahedral amorphous carbon films

This article reports the influence of substrate bias during growth and of hydrogen and nitrogen incorporation on density of states [N (EF)] and field-emission threshold (Eturn-on) in tetrahedral amorphous carbon (ta-C) films, deposited using an S-bend filtered cathodic vacuum arc process. The variation in negative substrate bias from −20 to −200 V was found to initially lead to a small decrease in N (EF) and Eturn-on, and a small increase in the emission current density (J) at 12.5 V/μm in the case of as-grown ta-C films; beyond −200 V substrate bias there is a reversal in the trend. The values of N (EF)=1.3×1017 cm−3 eV−1, Eturn-on=8.3 V/μm, and J=6.19 mA/cm2 were observed at −200 V substrate bias. However at −300 V the properties were not very different from those at −200 V substrate bias and so with a view to use the higher energy, hydrogen and nitrogen incorporation studies were carried out in this condition. It was observed that there was further enhancement in properties with hydrogen and nitrogen incorporation. The best properties measured with in the range of hydrogen and nitrogen incorporation in the present study were N (EF)=8.0×1016 cm−3 eV−1, Eturn-on=7.6 V/μm, and J=23.7 mA/cm2, respectively.

Substrate Bias Effects on Amorphous Carbon Film Deposition Process during Acetylene Plasma, Investigated with Infrared Spectroscopy

Substrate Bias Effects on Amorphous Carbon Film Deposition Process during Acetylene Plasma, Investigated with Infrared Spectroscopy

Effect of Substrate Temperature, Biasing and Sputter Cleaning on the Structure and Properties of Nanostructured TiB&lt;SUB&gt;2&lt;/SUB&gt; Coatings on High Speed Steel

Fabrication and development of TiB2-based nanostructured coatings was investigated in the present work. By varying the sputter-target power density, substrate temperature, deposition time, substrate-to-target distance, substrate biasing and substrate sputter cleaning, the relationship between the sputtered structure, properties and sputtering conditions were established. The experimental results showed that the target-to-substrate distance played a major role in the coating structure and properties. Sputter cleaning of substrate helped to improve TiB2 coating hardness and adhesion. The deposition process could be controlled to produce a TiB2 coating with both high hardness and good adhesion strength. This was achieved by introducing substrate sputter-cleaning and then biasing for the early stage of deposition, followed by deposition without biasing. [doi:10.2320/matertrans.MC200906]

Grid and substrate bias effects on mechanical properties of diamond films prepared by HFCVD

Diamond films were prepared at different grid bias and substrate bias in hot filament chemical vapor deposition (HFCVD) system. The Raman and SEM results show that grain size decreases and non-diamond impurities increase for applying grid and substrate bias currents. The defects and impurities in the film increase with the decrease of grain size, which causes the decrease of hardness and elastic modulus of diamond films. The fracture toughness of film increases because of the grain size effects by applying bias. The grid bias and substrate bias make the friction coefficient smaller because of the smaller grain size and lubricating effect of graphite in the film. But the excessively high substrate bias current will lead to the dramatic decrease of mechanical properties of CVD diamond as a lot of non-diamond impurities appear in the film.

The effect of low frequency pulse-shaped substrate bias on the remote plasma deposition of a-Si : H thin films

We have applied both sinusoidal and pulse-shaped rf substrate biasing techniques to the expanding thermal plasma deposition of hydrogenated amorphous silicon. Spectroscopic ellipsometry and Fourier transform infrared spectroscopy data demonstrate that both methods of substrate biasing can result in improved film properties at deposition rates ranging from 1.4 to 16 nm s−1, at relatively low substrate temperatures (200 °C), as demonstrated by an increase in refractive index, and a decrease in the microstructure factor (R*). An extra plasma forms in front of the substrate upon the application of both bias techniques, but optical emission spectroscopy data show that the emission intensities are significantly greater with the sinusoidal rf bias. Although the application of sinusoidal rf bias results in an initial improvement of the materials, the H content and R* values both increase at higher rf-induced substrate bias voltages (−Vbias >∼ 70 V). The same bias conditions that result in increased H content and R* correspond to the conditions where the additional plasma in front of the substrate undergoes both a sharp increase in emission, and a decrease in measured ion current, suggesting an α to γ′ transition.

Effects of Deposition Conditions and Counter Bodies on the Tribological Properties of Pulsed DC Magnetron Sputtered TiN–MoS x Composite Coating

In the current study, TiN–MoS x composite coatings were deposited by co-sputtering of MoS2 and Ti targets under a mixture of Ar and N2 gas environment using pulsed DC closed-field unbalanced magnetron sputtering. The tribological response of TiN–MoS x composite coatings was studied against two different counter bodies: cemented carbide (WC–6% Co) ball and pin made of aluminium alloy (AlSiMg). First, the effect of substrate bias was studied on tribological properties using cemented carbide ball. Lowest coefficient of friction in the range of 0.03–0.04 was obtained for the specimen deposited at a substrate bias of −60 V. Wear coefficient was also found to be minimum for the same specimen. Coatings were further deposited at an optimum bias of −60 V in order to vary MoS x content of TiN–MoS x composite coating. Effect of variation of chemical composition of the coating was then studied on tribological performance of the coating against aluminium alloy counterface. Excellent anti-sticking property of MoS x was found to have enabled the TiN–MoS x composite coating to achieve considerably low coefficient of friction against aluminium alloy. It was shown that with optimum MoS x content of TiN–MoS x composite coating, it was possible to attain as low coefficient of friction as 0.09 against aluminium alloy even under normal atmospheric condition.

Effects of Silicon Source Gas and Substrate Bias on the Film Properties of Si-Incorporated Diamond-Like Carbon by Radio-Frequency Plasma-Enhanced Chemical Vapor Deposition

We have deposited Si-incorporated diamond-like carbon (DLC) films by radio-frequency plasma-enhanced chemical vapor deposition using methane, argon, and organosilanes, and investigated the effects of Si source gas (monomethylsilane, dimethylsilane) and substrate bias (negative dc bias, negative pulse bias) on the structure and the mechanical and tribological properties of the films. The Si-DLC films deposited using monomethylsilane as a Si source gas tended to have a higher Si atomic fraction ratio [Si/(Si+C)] than the films deposited using dimethylsilane. Friction coefficient and internal stress decreased by the incorporation of Si into the films. However, many particles composed mainly of Si were observed on the film surfaces when deposition using a dc bias was carried out at higher monomethylsilane or dimethylsilane flow ratios. It was found that for both the Si source gases, the use of a pulse bias was effective in suppressing the formation of particles and further decreasing friction coefficient and internal stress. Additionally, the pulse-biased Si-DLC films were found to have a higher wear resistance than the dc-biased Si-DLC films.

Nanocrystalline zirconium oxide thin films grown under low pulsed dc voltages

Zirconium oxide thin films were deposited at room temperature by an off-plane filtered cathodic vacuum arc under a pulsed substrate bias between 0 and −250 V. The film properties including structure, surface morphology, mechanical and optical properties on n-Si(1 0 0) and quartz were investigated in terms of substrate bias. The results show that a strong effect of substrate bias on the film properties on n-Si(1 0 0) has been observed. With increasing substrate bias, the film changes from an amorphous state at floating bias to a randomly oriented crystalline structure at −100 V, and then to a preferred orientation along the [2 0 0] direction at −250 V. The stoichiometric ratio is decreased with increasing substrate bias as well as deposition rate. The film surface remains smooth at floating bias while large roughness is found when biases were applied. Besides, it is also observed that both hardness and Young's modulus increase with the substrate bias. However, for the films on quartz substrate, nanocrystalline film was found only at −250 V. Optical properties including optical constants and optical band gap (Eg) were investigated. The mechanisms of changes in structure and related properties were discussed.