Effect Of Substrate Bias Research Articles

Effect of Substrate Bias on the Structure and Tribological Performance of (AlTiVCrNb)CxNy Coatings Deposited via Graphite Co-Sputtering

In the existing literature, there are few studies on the effect of deposition bias on the tribological properties of carbon-doped high-entropy alloy coatings. In order to further study the effect of the deposition bias on the properties of coatings, (AlTiVCrNb)CxNy coatings were deposited via unbalanced RF magnetron sputtering. The microstructure and tribological properties of carbon-doped high-entropy alloy ceramic coatings under different deposition biases were studied. The composition, morphology, crystal structure, and chemical morphology of each element of the coating were analyzed using scanning electron microscopy (SEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). The hardness, elastic modulus, friction, and wear properties of the coating were further characterized using a nanoindentation instrument, reciprocating sliding friction, a wear tester, and a white light interferometer. The coating density reached the optimal level when the deposition bias value was 90 V. The hardness and elastic modulus of the (AlTiVCrNb)CxNy coating increased first and then decreased with an increase in deposition bias, and the maximum hardness was 23.98 GPa. When the deposition bias was 90 V, the coating formed a good-quality carbon transfer film on the surface of the counterbody due to sp2 clusters during the friction and wear process. The average friction coefficient and wear rate of the (AlTiVCrNb)CxNy coating were the lowest, 0.185 and 1.6 × 10−7 mm3/N·m, respectively. The microstructure, mechanical properties, and tribological performance of the (AlTiVCrNb)CxNy coating were greatly affected by the change in deposition bias, and an (AlTiVCrNb)CxNy coating with excellent structure and friction properties could be prepared using graphite co-sputtering.

Design of CMOS Based LC-Voltage Control Oscillator Using Substrate Bias Effect and Current Mirror Technique

Design of CMOS Based LC-Voltage Control Oscillator Using Substrate Bias Effect and Current Mirror Technique

Ge quantum well channel P-MOSFET for 2.45 GHz wireless weak energy harvesting

Wireless energy harvesting is an important application of microwave wireless energy transmission system, but due to the weak energy of RF signals in the 2.45 GHz band, its rectification efficiency is not ideal. As one of the core rectifier components of wireless weak energy harvesting system, the performance of MOSFET determines the rectification efficiency of the system, and its optimized design to improve the rectification efficiency is an important direction of current research in the field. In view of this, this paper proposes and designs Ge quantum well channel PMOS for wireless weak energy harvesting at 2.45 GHz, aiming to improve the rectification efficiency of wireless weak energy harvesting systems. Starting from adjusting the structural physical parameters of the MOS tubes, the absolute value of the threshold voltage is reduced in the weak energy density region, which in turn improves the rectification efficiency of the device. Then, the novel diode connection with the introduction of substrate bias effect is compared with the conventional connection using an ADS simulation circuit, and the simulation results show that the leakage current is smaller and the rectification efficiency is higher under the novel connection. On this basis, a Ge quantum well channel PMOS device is proposed. Compared with the Ge surface channel, the hole mobility of the quantum well channel will be greatly improved, and its rectification efficiency can also be improved. The device is connected to the rectifier circuit with a novel connection and simulated using Silvaco's Mixedmode module. The results show that the rectification efficiencies of the Ge quantum well channel MOS reach 13.53 % and 32 % at low input powers of −20.34 dBm and −6.28 dBm, respectively, which are 3.3 and 1.14 times higher than those of the conventional surface channel MOS.

Effect of sputtering power and substrate bias on microstructure, mechanical properties and corrosion behavior of CoCrFeMnNi high entropy alloy thin films deposited by magnetron sputtering method

The CoCrFeMnNi high entropy alloy thin films with crystalline (solid solution) structure or amorphous state were fabricated by magnetron sputtering process at different target powers and different substrate bias. Effects of the target power and substrate bias on the characteristics of the CoCrFeMnNi thin films such as microstructures, morphology and surface topography, as well as mechanical properties and corrosion behavior were studied. Phase prediction was calculated by using thermodynamic and kinetic criteria under various deposition conditions. The enthalpy, entropy, δ and Ω parameters, and electronegativity differences influenced the solid solution stability of thin films. These parameters led to the formation of solid solutions with crystalline or amorphous structures under specific limits, which corresponded to the practical XRD and TEM analysis results. Using a substrate bias in the deposition of CoCrFeMnNi thin film changed the amorphous structure to a crystalline (solid solution (BCC + FCC)) at higher target powers (200 and 300 W). On the other hand, the film structure was entirely amorphous at all sputtering target powers without the substrate bias. The mechanical properties, such as hardness, Young's modulus, film strength, and fracture toughness of CoCrFeMnNi thin film, can be enhanced by using the substrate bias and increasing the sputtering power. The potentiodynamic polarization test in 3.5 wt% NaCl aqueous solution indicated that the deposition of CoCrFeMnNi thin films at different sputtering powers and without substrate bias could increase the corrosion resistance of 304 stainless steel substrate. Using the substrate bias of −100 V in the fabrication of CoCrFeMnNi thin film decreased the corrosion current density and increased its polarization resistance.

Effect of substrate bias on the formation of nanotwin and properties in Cu thin films for advanced packaging technology

Materials with nanotwinned structures have drawn much attention due to their unique properties. The high-density nanotwinned Cu films are generally deposited at room temperature with high deposition rate. In this study, we report nanotwins can be formed in the Cu films at 150 °C with the aid of the ion bombardment effect caused by applied substrate bias. Cu thin films were deposited on Si (100) substrate by the unbalanced magnetron sputtering system using different applied substrate biases ranging from 0 V to −160 V. The results show that, with a suitable applied substrate bias of −120 V, the twinning density of the Cu films can reach over 80 % and exhibit a high hardness of 3.1 GPa. This study provides a concept to tailor the microstructure of the sputtered Cu films by tuning applied substrate biases and realizing the mechanism of substrate bias on the twin formation during deposition.

Synergistic effect of deposition temperature and substrate bias on structural, mechanical, stability and adhesion of TiN thin film prepared by reactive HiPIMS

Titanium nitride (TiN) thin films continue to attract unprecedented attention due to their favourable mechanical, thermal, electrical and chemical properties. These properties depend, among others, on the morphology and the architecture of the thin film, which can be tuned with different configurations of the deposition parameters. This study presents an experimental investigation to tune the properties of TiN thin film deposited using reactive High-power impulse magnetron sputtering (HiPIMS) at different deposition temperatures (without heating (RT) and 400 °C) and substrate bias potentials (of floating, ground, −20 V, −40 V and −60 V). It is demonstrated that the morphological, structural, and mechanical properties of TiN can be tailored by controlling the deposition temperature and substrate potential bias to deposit dense thin films. A maximum hardness of 30 GPa was achieved for the thin film deposited at RT with a bias voltage of −60 V. The failure mechanism of the fracture toughness exhibited an isotropic behaviour at an applied load of 1 and 2 N respectively, for thin films deposited at RT. In contrast, an anisotropic behaviour was observed in the thin film deposited at a temperature of 400 0C.Overall, the thin film deposited at a temperature of 4000C showed an improved fracture toughness resistance (KIC) than the thin films deposited at RT. The use of bias potential was also observed to be beneficial for improving the KIC of the TiN thin films.

Effect of Substrate Bias on the Microstructure and Properties of Non-Equimolar (AlCrSiTiZr)N Films with Different Cr/Zr Ratios Deposited Using Reactive Direct Current Magnetron Sputtering

To reduce the cost of tools operated in extreme environments, we developed films with excellent corrosion/oxidation resistance. Two high-entropy nitride films, (AlCrSi0.3TiZr)N and (AlCr1.5Si0.3TiZr0.5)N, were deposited using reactive DC magnetron sputtering under different substrate biases. The films exhibited a maximum hardness of 32.5 GPa ((AlCrSi0.3TiZr)N) and 35.3 GPa ((AlCr1.5Si0.3TiZr0.5)N) when deposited at −150 V, corresponding to 27 and 142% increases compared to those deposited at 0 V. This indicates that the bias strengthened (AlCr1.5Si0.3TiZr0.5)N (higher Cr/Zr ratio) more significantly. The enhancement of the mechanical properties was highly correlated with the interstitial point defects and densification of the film microstructures. The corrosion resistance of the films deposited on 6061 Al alloy substrate under different biases was tested in 0.1 M H2SO4. (AlCrSi0.3TiZr)N and (AlCr1.5Si0.3TiZr0.5)N displayed the lowest corrosion currents of 0.75 and 0.19 μA/cm2 when deposited at −100 and −150 V, respectively. These values are two orders of magnitude lower than that of the uncoated substrate. The (AlCr1.5Si0.3TiZr0.5)N film showed better oxidation resistance than the (AlCrSi0.3TiZr)N film and remained partially oxidized after heat treatment at 1000 °C. The (AlCr1.5Si0.3TiZr0.5)N film deposited at −150 V exhibits excellent mechanical properties and corrosion/oxidation resistances, making it suitable for protecting tools operating in harsh environments.

In-situ monitoring of stress evolution in high power impulse magnetron sputtering-deposited Ti-Al-N films: Effect of substrate bias and temperature

The origin of residual stress during film deposition is a topic of strong interest in the coating engineering community; it requires appropriate investigation tools to explain the different mechanisms acting on the evolution of stress concerning process conditions and material characteristics. In the present work, we used in-situ curvature stress probing combined with ex-situ techniques such as X-ray diffraction cos2α*sin2ѱ applied to the deposition of model Ti0.42Al0.58N coatings. The films were prepared at room temperature and 300 °C, and four substrate bias strategies were studied, namely two constant values of substrate bias (0 V and −75 V), and two systems with alternating high bias and no bias. At room temperature, the application of bias changed the stress from slightly tensile to compressive, while at 300 °C, the use of high bias increased the compressive intrinsic stress by 3 GPa along with hardness. Linking in-situ and ex-situ stress measurements permitted a direct assessment of thermal stress, which varied considerably with bias. The combined analysis revealed the presence of different contributors to stress generation, particularly at the grain boundaries. The relevance of each contributor to the final stress state was found to depend on the energetic growth conditions. Stress monitoring revealed significant differences between the growth of dense films on the porous ones compared to the opposite sequence, suggesting a straightforward pathway to stress mitigation. This is documented by films produced in the alternating −75/0/−75 V bias sequence that presented comparable mechanical properties as films deposited at a constant high (−75 V) bias, but with substantially lower residual stress.

Substrate bias effects on cathodic arc deposited Cr coatings

We investigate the effects of substrate bias on cathodic arc deposition of Cr coatings without external substrate heating at four different substrate bias levels, floating, −30, −50, and −70 V. After 10 min of deposition, the substrate temperature reaches 180, 210, 230, and 260 °C for floating potential, −30, −50, and −70 V, respectively. Time-of-flight energy elastic recoil detection analysis shows that all grown coatings are of high purity, with no coating containing more than 0.2 at.% of C and/or O. Increasing the substrate bias also reduces the number of macroparticles, steers the texture from preferred [110]- to [100]-orientation and induces a residual compressive stress of ∼450 MPa in the coatings. The hardness of the coatings remains at a constant 7.5 GPa irrespective of the substrate bias. The four-point probe resistivity of the grown coatings is 15–17 μΩcm regardless of substrate bias, close to the 12.9 μΩcm of bulk Cr.

Effect of substrate bias on structure and properties of (AlTiCrZrNb)N high-entropy alloy nitride coatings through arc ion plating

This study mainly focused on the effects of different substrate bias on the microstructure, elemental composition, mechanical and tribological properties of (AlTiCrZrNb)N coatings. (AlTiCrZrNb)N high-entropy nitride coatings with different substrate bias parameters were deposited on cemented carbide and silicon wafers using arc ion plating. The results showed that the bias voltage created a high-energy particle bombardment effect to reduce the number and volume of macroparticles brought by arc ion deposition technology; this optimized the surface quality of the coating. (AlTiCrZrNb)N coatings at different bias voltages exhibited a single-sided cubic solid solution structure. Substrate bias can significantly change the preferred orientation of coatings. As bias voltage increased from 0 V to −100 V, the preferred orientation of coatings changed from (111) to (200), and when negative voltage further increased to 200 V, the preferred orientation changed from (200) to (111). Appropriate substrate bias parameters can improve the residual stress, mechanical properties, and tribological properties of coatings. The highest hardness of the coating reached 34.85 ± 2.05 GPa. The lowest average friction coefficient was 0.26, and the lowest wear rate was 8.86 ± 1.05 × 10−6 mm3 ∙ N−1 ∙ m−1.

Effect of substrate bias on the properties of plasma deposited organosilicone (pp-HMDSN) thin films

Effect of substrate bias on the properties of plasma deposited organosilicone (pp-HMDSN) thin films

A TCAD-Based Analysis of Substrate Bias Effect on Asymmetric Lateral SiGe HBT for THz Applications

In this work, a new asymmetric lateral silicon germanium heterojunction bipolar transistor (SiGe HBT) is proposed. This asymmetric structure allows one to modulate the carrier densities in the collector region by the application of substrate bias, which causes significant improvements in device performance. The open base breakdown voltage can be tuned from 2.2 to 3.6 V and the transit frequency ( <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <inline-formula> <tex-math notation="LaTeX">$ \textit{f}_{{\sf T}} $</tex-math> </inline-formula> </i> ) is improved up to <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\sim$</tex-math> </inline-formula> 90% by varying the substrate bias. The bias-dependent variation in transit time is elaborately discussed using regional analysis. This work, for the first time, demonstrates an oscillation frequency ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$ \textit{f}_{\text{MAX}} $</tex-math> </inline-formula> ) of 2.7 THz achievable by tuning the substrate bias in an asymmetric silicon-on-insulator (SOI) lateral SiGe HBT.

Bilayer molybdenum contact prepared via high-power pulsed magnetron sputtering: Effects of substrate bias

Molybdenum (Mo) is widely used to fabricate the back contact of compound semiconductor thin film solar cells. Most of those contacts are deposited using direct current (DC) or radio frequency (RF) sputtering; however, those processes are ill-suited to achieving low resistance with good adhesion. In this study, we sought to overcome this issue using high-power pulsed magnetron sputtering (HiPIMS) with a focus on the effects of substrate bias on adhesion and resistance. When used with a HiPIMS power source, substrate bias was shown to promote the (110) preferred orientation of the top Mo contact, while reducing the (211) preferred orientation of the bottom Mo contact. This resulted in the lowest recorded resistivity (9.7 μΩ cm) when the bottom was deposited without bias and the top Mo contact was biased at −40 V.

Microstructure and Mechanical Properties of Co-Deposited Ti-Ni Films Prepared by Magnetron Sputtering

Ti-Ni films with various Ni contents (16.5, 22.0, 33.5 at. %) were deposited on Al alloy substrates using DC magnetron co-sputtering. The effects of Ni target power and substrate bias (−10, −70, −110 V) on morphologies, crystallography, nanomechanical properties and scratch behavior of films were studied. All the deposited Ti-Ni films exhibited a BCC structure of β-Ti (Ni). The Ti-Ni films grew with a normal columnar structure with good bonding to substrates. When increasing the Ni target power and substrate bias, the grain size grew larger and the surface became denser. The as-deposited Ti-Ni films significantly improved the hardness (&gt;4 GPa) of the Al alloy substrate. With the increase of bias voltage, the hardness and modulus of the film increased. The hardness and modulus of the Ti-22.0Ni film prepared at −70 V bias were 5.17 GPa and 97.6 GPa, respectively, and it had good adhesion to the substrate.

Effect of substrate bias on the microstructure and mechanical and tribological properties of ZrNbTiMo refractory high entropy alloy film

ZrNbTiMo refractory high entropy alloy (RHEA) films were deposited via direct current magnetron sputtering under different substrate biases (0 to −200 V). The phase structure, microstructure, surface roughness, mechanical, and tribological properties of the ZrNbTiMo RHEA films were investigated. Results show that the ZrNbTiMo RHEA films exhibit a single body-centered-cubic structure. As the substrate bias increases, the preferred orientation of the ZrNbTiMo RHEA films changes from (110) to (200). The surface roughness of the films decreases from 3.9 nm to 2.0 nm then increases to 4.1 nm. The growth mechanism can be understood as the result of the interaction of ion incident direction, ion bombardment effect, and atom diffusion ability which are controlled by the substrate biases. The hardness of the films increases from 6.8 GPa (0 V) to 21.3 GPa (−200 V). The maximum fracture toughness (0.968 MPa × m1/2) is obtained under −200 V. The wear resistance does not exhibit a monotonically increasing trend with the increase of substrate bias. The films deposited under −50 and − 100 V have lower values of H/E and H3/E2, but these films still possess better wear resistance. The wear mechanism of the ZrNbTiMo RHEA films is investigated in detail from the microstructure perspective.

Effects of Substrate Bias and Ar Pressure on Growth of α-phase in W Thin Films Deposited by RF Magnetron Sputtering

Effects of Substrate Bias and Ar Pressure on Growth of α-phase in W Thin Films Deposited by RF Magnetron Sputtering

Effects of substrate bias on the sputtering of high density (111)-nanotwinned Cu films on SiC chips

This article presents a study of the influence of the substrate bias on the microstructure, preferred orientation, and mechanical and electrical properties of nanotwinned Cu film. The formation of a nanotwinned structure and (111) surface orientation can be properly controlled by applied substrate bias. High density nanotwinned structures were introduced into Cu films sputtered on SiC substrates with over 90% of (111)-orientation at − 150 V. Densely packed Cu nanotwins were observed within the columnar grains stacked up on each other along the film growth direction, with an average twin spacing of 19.4 nm. The Cu films deposited on SiC substrate via bias sputtering had surface roughness of 8.6 to 15.8 nm. The resistivity of the copper nanotwinned films sputtered with various substrate biases varied. The optimal indentation, 2.3 GPa, was found in the nanotwinned Cu film sputtered with a bias voltage of − 150 V. The effects of Ar ion bombardment on microstructure, surface morphology and properties are further discussed.

Growth of diamond-like carbon films with significant nanocrystalline phases in a low-pressure high-density CH4 plasma in ICP-CVD: Effect of negative dc substrate bias

Working at relatively low-temperature and low-pressure, the development and optimization of diamond-like carbon (DLC) films with significant nanodiamond components on inexpensive glass substrates, without conventional pre-treatment by diamond powders, is the main objective of the present work. Using the most familiar CH4-precursors diluted by Ar in a high-density plasma triggered at high rf power (900 W) in a planar inductively-coupled plasma chemical vapour deposition (ICP-CVD) system, DLC thin-films are prepared via optimization in the flow rate of the precursor gas at 30 mTorr (∼4 Pa) pressure and 450 °C substrate temperature and, further by applying negative dc-bias to the substrates. The optimized samples obtained with negative substrate-bias possess good crystalline properties. From Raman results, the most crystalline sample is obtained with characteristic minimum ID/IG ratio reduced from 0.75 to 0.61, maximum IDia/ID enhanced from 0.94 to 1.09, and the sp3 hybridized CC bonds increased from 44% to ∼64% at a substrate-bias of –40 V. The residual stress, and the optical band gap were calculated from Raman analysis. The optimized DLC film exhibits a high optical band gap (3.71 eV) as calculated from Tauc’s plot analysis of the UV–Vis data. The well-identified 〈111〉 crystallographic planes in the TEM micrograph demonstrate a significant fraction of nanocrystalline diamond component in the optimum DLC film.

Electron transport in discontinuous metal thin films

The structure and basic experimental electrical properties of vacuum evaporated discontinuous (island) metal thin films of discrete metal nanoparticles on insulating substrates are briefly reviewed. Then the widely accepted Neugebauer and Webb (N&W) electrostatically activated electron tunneling conduction model is covered (with enhancements) before the numerous discrepancies between this model and experimental observations are identified, e.g. minimal substrate bias effect, non-linear field distribution, anomalous AC effects, asymmetrical contact effects, and switching. A modified model, based on contact electron injection and extraction, and computer simulations are introduced which explain these discrepancies at a qualitative level. However, quantitative experimental verification of the model is not possible without stable, reproducible films of known structures. The paper concludes with a review of possible preparation techniques which could yield satisfactory samples, especially self-assembly of organically protected metal nanoparticles. One of these has already demonstrated electrostatically activated conduction.

Research on the Effect of Substrate Bias on Properties of Sputtered AlCrNbSiTiV High Entropy Alloy Nitride Films

Research on the Effect of Substrate Bias on Properties of Sputtered AlCrNbSiTiV High Entropy Alloy Nitride Films