Effect Of Bias Voltage Research Articles

Bias voltage effect on impedance, modulus and dielectric spectroscopies of HfO2-interlayered Si-based Schottky diodes at room temperature

In this study, Al/HfO2/p-Si metal-insulator-semiconductor (MIS) Schottky diode was fabricated by atomic layer deposition (ALD) technique with an adjusted HfO2 interlayer thickness of 3.3 nm. Using (I, V), (Z, θ) and (C, G) experimental data sets, the electric and dielectric properties of the fabricated diode were investigated in 1 kHz–10 MHz frequency range at different applied bias voltages at room temperature through complex functions like impedance, modulus, conductivity and dielectric. From the DC current-voltage (I–V) measurements, the ideality factor and the barrier height of the diode were estimated at room temperature as 2.22 and 0.86 eV, respectively. AC measurement results demonstrated the presence of two different polarization mechanisms (interfacial and orientational) in the investigated frequency range. The results also clearly showed that three relaxation phenomena exist within the diode bulk structure, and that both relaxation and conduction mechanisms are activated by the applied bias voltage. One of the relaxations was the Warburg relaxation spotted in the low frequency region in two different forms (semi-infinite Warburg in impedance Nyquist plots and finite-space Warburg in dielectric Nyquist plots) and both were explained by the slow diffusion of Al3+, O2− and Hf4+ ions across the interface layer. Equivalent circuit impedance fit analysis showed that the fabricated diode has a good MIS structure due to the demonstrated high resistivity and low-leakage of the interfacial HfO2 layer. The big values of the dielectric loss tangent (8.03 at 500 kHz and +2 V) as compared to the dielectric constant (0.13 at 500 kHz and +2 V) at room temperature and the independence of dielectric constant on temperature suggests the appropriate usage of the fabricated diode in thermal heating applications. The estimated four major parameters (ideality factor, barrier height, dielectric constant and dielectric loss tangent) were compared with other literature results based on different growth parameters and tabulated in conclusion.

Effect of Bias Voltage on Microstructure and Properties of Tantalum Nitride Coatings Deposited by RF Magnetron Sputtering

TaNx coatings were deposited by RF magnetron sputtering with different bias voltages. The growth morphology, crystalline structure, chemical bond structure, hardness and elastic modulus, adhesion strength and tribological performance of the coatings were studied as a function of the bias voltage. The results showed that an increasing bias voltage refines the coating grains and facilitates structure densification. Simultaneously, the structure of the TaNx coatings transfers from a composite structure consisting of TaN and Ta2N crystals, through a single composite mainly composed of the Ta2N crystal, to an amorphous structure as the bias voltage increases from low to high, indicating that the phase composition of the TaNx coatings can be varied by the bias voltage. The coating composed of Ta2N crystal showed a good overall performance including enhanced hardness, enhanced adhesive strength, and good tribological performance with enhanced wear resistance and a low friction coefficient of 0.18.

Measurement of Ion Energy Distribution and Deposition of Ti Thin Films Using ABPPS Technology on Glass Substrate

Ion energy distributions (IEDs) play an important role in material processes and thin film deposition. We developed a newly designed multistep pulsed power supply (modulator) for the asymmetric bipolar pulsed power sputtering (ABPPS) technology and studied the effect of reverse bias voltage in improving the properties of thin films through Ti deposition. Using an ion energy analyzer, we confirmed IEDs and relative ion intensity under a reverse bias voltage of the modulator at the substrate position. A dense plasma was generated near the sputter target at reverse bias voltages above 300 V. Experiments were conducted by varying the bias voltage applied to the sputter target and the duty cycle of the modulator. Our results demonstrate that the in-house-built ABPPS system can be used to clean the sample surfaces without requiring additional energy sources or substrate bias and that thin films prepared using this system have a smoother surface than those prepared by conventional sputtering.

Effect of Bias Voltage on Substrate for the Structure and Electrical Properties of Y:HfO2 Thin Films Deposited by Reactive Magnetron Co‐Sputtering

AbstractHfO2 thin film has been widely studied as the most promising candidate material for microelectronic devices. However, low leakage current density is the prerequisite for the excellent performance of devices. Therefore, effects of substrate bias duty ratio and frequency on the roughness and leakage current density are studied for the Y:HfO2 thin films deposited by reactive magnetron co‐sputtering method. The results illustrate that the substrate bias duty ratio and frequency influence the leakage current density through grain size and roughness of films. An appropriate substrate bias is beneficial to the densification of films and the reduction of leakage current. When the substrate bias duty cycle is 30.1% at the frequency of 19.7 kHz, the roughness and leakage current density of films are reduced to 0.4 nm and 8.8 × 10−8 A cm−2, respectively.

The Effect of Match between High Power Impulse and Bias Voltage: TiN Coating Deposited by High Power Impulse Magnetron Sputtering

Practical experience in the use of high power impulse magnetron sputtering (HiPIMS) technology has revealed that output bias current depends on the total energy output of the cathodes, which means that bias voltage settings do not necessarily match the actual output. In this study, we investigated the effects of bias current and voltage on the characteristics of titanium nitride thin films produced using high impulse magnetron sputtering. The bias current and voltage values were adjusted by varying the supplied cathode power and substrate bias under DC and pulsed-DC output models. Our results revealed that pulse delay (PD) and feed forward (FF) settings can be used to control bias current and voltage. Increasing the bias current from 0.56 to 0.84 was shown to alter the preferred orientation from (111) to (220), increase the deposition rate, and lead to a corresponding increase in film thickness. The surface morphology of all titanium nitride samples exhibited tapered planes attributable to the low bias current and voltage (−30 V). The maximum hardness values were as follows: DC mode (23 GPa) and pulsed-DC mode (19 GPa). The lower hardness values of pulsed-DC samples can be attributed to residual stress, preferred orientation, and surface morphology. The surface of the samples was shown to be hydrophobic, with contact angles of >100°.

Effect of bias voltage on the growth of super-hard (AlCrTiVZr)N high-entropy alloy nitride films synthesized by high power impulse magnetron sputtering

The purpose of this paper is to explore the effect of bias voltage on plasma discharge characteristics, element concentration, microstructure, morphology, and mechanical properties of super-hard (AlCrTiVZr)N high-entropy alloy nitride (HEAN) films synthesized by high power impulse magnetron sputtering (HiPIMS). Results show that all HiPIMS-deposited (AlCrTiVZr)N films and the DCMS reference sample present a single NaCl-type FCC structure. Compared with DCMS, HiPIMS can produce a higher ionization fraction of the HEA target elements, thereby improving the structure and mechanical properties, while reducing the deposition rate. With increasing bias voltage in HiPIMS, the ion bombardment is continuously enhanced due to the increasing flux and energy of ionized particles reaching the films. The altered plasma environment splits the growth of (AlCrTiVZr)N films into two regions: The bias voltages of 0 V to −150 V offer a moderate ion bombardment effect, while further increasing bias voltage up to −200 V makes the ion bombardment effect excessive. It is observed that the (AlCrTiVZr)N films deposited at −150 V have a compact and featureless structure with preferred orientation of (111), the smallest grain size of 11.3 nm, a high residual compressive stress of −1.67GPa, thereby exhibiting the highest hardness of 48.3 GPa which attains the super-hard grade.

Tuning structural, electrical and mechanical properties of diamond-like carbon films by substrate bias voltage

Diamond-like carbon (DLC) thin films are deposited by unbalanced RF magnetron sputtering at substrate bias voltages to tune the ratio of the sp3 to sp2 bonds and hydrogen composition in optimized Ar: CH4 ambient. The effect of substrate bias voltage on the sp2 and sp3 bonding ratios and hydrogen concentration is correlated to the physical and elastic properties for the optimized DLC film. Raman spectroscopy qualitatively established sp3/sp2 bonding ratios from the ID/IG ratio at various substrate bias voltages and the trend is in agreement with XPS data. High H content of at least 18.00 ± 2.00 at. % is evaluated from photoluminescence background for all substrate bias voltages. Applying an empirical approach to the ID/IG ratios, we derive the Tauc band gaps in the range between 1.51 and 1.57 eV. The highest band gap correlates to the highest resistivity values (131 × 102 Ω.cm) measured for DLC films deposited at the highest bias voltage of −100 V and with lowest H content. As DLC thin films deposited at −100 V exhibit optimal properties, the elastic constants are subsequently evaluated using the Surface Elastodynamic Greens functions to the discrete phonon dispersion obtained by surface Brillouin scattering. Enhancement in bulk, shear and elastic moduli is ascribed to higher sp3/sp2 ratio and predominantly to H content.

Effect of substrate bias voltage on the mechanical properties of AlTiN/CrTiSiN multilayer hard coatings

During physical vapor deposition (PVD), bias voltage is usually applied to the substrate for tuning the ion energies and tailoring the coating structure and mechanical properties of a protective hard coating for specific applications. In the present study, AlTiN/CrTiSiN multilayer coatings were deposited by a multisource cathodic arc ion deposition system with negative substrate bias voltages ranging from −20 to −180 V. During the coating process, graded CrN, CrN/AlTiN and CrTiSiN were deposited as interlayers to enhance adhesion strength of the coatings. Multisources of Cr, TiSi and AlTi alloy targets were used. Residual stresses and mechanical properties of AlTiN/CrTiSiN multilayer coatings deposited under various bias voltages were investigated. All the AlTiN/CrTiSiN multilayer coatings possessed higher hardness values (38.2–39.6 GPa) than AlTiN (32.5 GPa). As compared to the monolithic AlTiN, which had high residual stress of −9.8 GPa, the AlTiN/CrTiSiN multilayer coatings showed lower residual stresses of −2.4~ −9.1 GPa. The higher bias voltage was used the higher residual stress was observed. The AlTiN/CrTiSiN multilayer coating deposited at −20 V possessed the lowest residual stress (- 2.4 GPa). A cyclic impact test with high frequency were performed to evaluate the impact fatigue performance. The AlTiN/CrTiSiN multilayer coating deposited at −20 V showed the highest H/E (0.082) and H3/E2 (0.265) values to resist impact fatigue. The design of AlTiN/CrTiSiN multilayer coatings via low bias voltage can decrease residual stress and possessed good impact fatigue performance. Although the AlTiN/CrTiSiN coating deposited at high bias voltage of −180 V had similar hardness value to other AlTiN/CrTiSiN coatings under −20 V and −100 V, worse resistance to impact fatigue were found.

Effect of bias voltage and carrier gas on the hydrogen gas-sensing properties of tungsten oxide nanobeads

We investigated the effect of bias voltage and carrier gas on the hydrogen sensing performance of tungsten oxide nanobeads. The tungsten oxide nanobeads were prepared by a template-assisted method followed by calcination. The porous single walled carbon nanotube thin film was used as sacrificed template for the deposition of tungsten, followed by thermal calcination at high temperature to oxidize W into WO3 and to burn out the template. The crystal structures and morphology of the synthesized materials were characterized by X-ray diffraction, field-emission scanning electron microscopy, high-resolution transmission electron microscopy and Raman spectra. Hydrogen gas sensing properties were tested in air and in N2 as refence for comparison. Our results indicated that Schottky junction was formed at the interface of WO3 and Pt electrodes. The sensor operated under revered bias voltage processed excellent hydrogen sensing performance. In addition, the H2 sensing performance of the WO3 nanobeads is higher when measured in N2 gas as reference.

Multilayer graphene fundamental wave mixer under DC voltage bias

In this paper, a multilayer graphene mixer with inductor-capacitor resonators (LCR) and microstrip reflector stubs (MRS) loaded with direct-current (DC) voltage bias is presented. As a multifunctional material, multilayer graphene is especially suitable for mixer because of its nonlinearity. The experimental and simulation results show that the effect of bias voltage on multilayer graphene is significant. When the bias voltage is applied, the mixer is converted from subharmonic mixer to fundamental wave mixer. The measured minimum conversion loss with DC-load fundamental wave mixer is 18.9 dB at PLO = 16 dBm, fLO = 800 MHz, pRF = 0 dBm, fRF = 2 GHz which is about 1.2 dB lower than that DC-free subharmonic mixer. In addition, the nonlinear model of graphene is established by simplifying the approximate conductivity.

Application of a transmission line model to evaluate the influence of structural defects on the corrosion behavior of arc-PVD CrN coatings

The effect of bias voltages (40 V, 80 V, and 40/60/80 V) on microstructure and electrochemical properties of arc-PVD CrN coatings were evaluated. Increasing the bias voltage produced microstructural changes, from well-defined columns to columnar grains, and increased defect size. The electrochemical response proved susceptible to the defect type. Nano-droplets promoted the formation of oxides, while large pores allowed the migration of the electrolyte to the substrate/CrN interface. An impedance equivalent circuit based on the Bisquert transmission line was proposed to fit the experimentally obtained impedance spectra. The equivalent circuit allowed correlating the coating electrochemical response to the defect densities and sizes. Samples deposited with 40 V showed the lowest corrosion current (0.05 μA/cm2 ± 0.01), which was supported by the highest resistances to the transport of ions through the pores (Rp = 1047 ± 88 kΩꞏcm2). Films obtained with 80 V reduced Rp values by two magnitude orders compared to CrN 40 V. The increase of pore resistance in CrN 40 V was associated with the oxidation of nano-droplets (proposed auto-protection phenomenon), which blocks open pinholes due to the smallest average size of defects. Tailoring a gradual increase of the bias voltage (40/60/80 V) preserves the auto-protection mechanism of droplets and improves the surface finish of the coating.

Angular dependent magnetoresistance in organic spin valves

Vertical organic spin valve (OSV)-based organic spintronic devices with additional degree of freedom to utilize and control the magnetoresistance (MR) by spin of electrons, have attracted a lot of interests for both foundation science and future functional device applications. Herein the effects of temperature, bias voltage and direction of magnetic field on the MR of the OSV are investigated to disclose the mechanisms. Specifically, the MR shows angular dependence with the value tuned from negative to positive by rotating the field direction from in-plane to out-of-plane, corresponding to the angular dependent spin moment. A domain-switch model is proposed to simulate the resistance changes in OSV device. The research provides a new route to tune the MR in organic spintronic devices, which is significant for future functional device applications.

Experimental study of a string-based counterflow wet electrostatic precipitator for collection of fine and ultrafine particles

ABSTRACT Wet electrostatic precipitators (WESP) have been widely studied for collecting fine and ultrafine particles, such as diesel particulate matter (DPM), which have deleterious effects on human health. Here, we report an experimental and numerical simulation study on a novel string-based two-stage WESP. Our new design incorporates grounded vertically aligned polymer strings, along which thin films of water flow down. The water beads, generated by intrinsic flow instability, travel down the strings and collect charged particles in the counterflowing gas stream. We performed experiments using two different geometric configurations of WESP: rectangular and cylindrical. We examined the effects of the WESP electrode bias voltage, air stream velocity, and water flow rate on the number-based fractional collection efficiency for particles of diameters ranging from 10 nm to 2.5 μm. The collection efficiency improves with increasing bias voltages or decreasing airflow rates. At liquid-to-gas (L/G) as low as approximately 0.0066, our design delivers a collection efficiency over 70% even for fine and ultrafine particles. The rectangular and cylindrical configurations exhibit similar collection efficiencies under nominally identical experimental conditions. We also compare the water-to-air mass flow rate ratio, air flow rate per unit collector volume, and collection efficiency of our string-based design with those of previously reported WESPs. The present work demonstrates a promising design for a highly efficient, compact, and scalable two-stage WESPs with minimal water consumption. Implications: Wet Electrostatic Precipitators (WESPs) are highly effective for collecting fine particles in exhaust air streams from various sources such as diesel engines, power plants, and oil refineries. However, their large-scale adoption has been limited by high water usage and reduced collection efficiencies for ultrafine particles. We perform experimental and numerical investigation to characterize the collection efficiency and water flow rate-dependence of a new design of WESP. The string-based counterflow WESP reported in this study offers number-based collection efficiencies >70% at air flow rates per collector volume as high as 4.36 (m3/s)/m3 for particles of diameters ranging from 10 nm – 2.5 μm, while significantly reducing water usage. Our work provides a basis for the design of more compact and water-efficient WESPs.

Long Afterglow of a Nonporous Coordination Polymer with Tunable Room-Temperature Phosphorescence by the Doping of Dye Molecules.

Metal-organic frameworks (MOFs) or coordination polymers (CPs)-based phosphorescence materials may provide a powerful route for photoelectric and optical recording devices. Herein, two phosphorescence ligands, iso-phthalic acid (IPA) and 2-methylimidazole (MIM), were selected to construct an nonporous CP {Zn(IPA)(MIM)2} (1) with a long-lived phosphorescence lifetime up to 552 ms. By the doping of Eosin Y (EY) dye molecules under an in situ process, the phosphorescence emission color of 1 can be expressly tuned from green to red. The light-harvesting range can also be vastly broadened from the UV to the visible region (550 nm). Photoelectron measurements reveal that the synergistic effect of bias voltage and illumination can greatly restrain electron-hole recombination for the generation of additional free charges.

Design and simulation of Mg<sub>2</sub>Si/Si avalanche photodiode

InGaAs and HgCdTe materials are widely used in short wave infrared photodetectors, which contain heavy metal elements. The massive use of the heavy metal elements naturally results in their scarcity, and the nonnegligible environmental pollution. Searching for other suitable materials for infrared devices becomes a key to solving the above problems. As a kind of abundant and eco-friendly material, Mg<sub>2</sub>Si has a high absorption coefficient in the near-infrared band. Its application in infrared detector makes it possible to replace the infrared devices containing toxic elements on the market in the future. The Mg<sub>2</sub>Si/Si avalanche photodiode(APD) with separation structure of absorption layer, charge layer and multiplication layer, with Mg<sub>2</sub>Si serving as the absorption layer, is constructed by using the Atlas module in Silvaco software. The effects of the thickness and doping concentration of the charge layer and multiplier layer on the distribution of internal electric field, punch-through voltage, breakdown voltage (<i>V</i><sub>b</sub>), <i>C-</i><i>V</i> characteristics, and transient response of Mg<sub>2</sub>Si/Si SACM-APD are simulated. The effects of bias voltage on the <i>I-</i><i>V</i> characteristics and spectral response are analyzed. The punch-through voltage, breakdown voltage, dark current density, gain coefficient (<i>M</i><i><sub>n</sub></i>) and the current amplification factor (<i>M</i>) after avalanche effect of APD are obtained after the structure optimization. According to the simulation results, the spectral response wavelength of the device is extended to 1.6 μm, so the selection of Mg<sub>2</sub>Si as the absorption layer effectively extends the spectral response band of Si based APD. When the wavelength of incident light is 1.31 µm and the optical power is 10 mW/cm<sup>2</sup>, the obtained punch-through voltage is 17.5 V, and the breakdown voltage is 50 V. When the bias voltage is 47.5 V (0.95<i>V</i><sub>b</sub>), the peak value of spectral response is 25 A/W at a wavelength of 1.1 μm, a density of dark current is about 3.6 × 10<sup>–5</sup> A/cm<sup>2</sup>, a multiplication factor <i>M</i><i><sub>n</sub></i> is 19.6, and <i>M</i><i><sub>n</sub></i> achieves a maximum value of 102 when the device is broken down. Meanwhile, the current amplification factor <i>M</i> after avalanche effect is 75.4, and the current gain effect of the SACM structure is obvious. The peak value of spectral response for the pin-type photodiode in the previous study is only 0.742 A/W. Comparing with the pin-type photodiode, the spectral response of Mg<sub>2</sub>Si/Si SACM-APD is greatly improved. In this work, the structure parameters of the device are optimized, which lays a nice foundation for fabricating the high-performance devices.

Effect of Bias Voltage on Characteristics of Multilayer Si-DLC Film Coated on AA6061 Aluminum Alloy

The multilayer Si-DLC films have been deposited on AA6061 aluminum alloy using a mesh hollow cathode plasma-enhanced chemical vapor deposition technique from acetylene and silane precursor gas at temperature 373 K. Low magnification electron microscopes, Raman spectroscopy, and Fourier transform infrared spectroscopy were employed for characterizing the coating film structure. The MFT-4000 scratch tester, G200 nano-indentation tester, and MS-T3001 tribology tester were utilized to evaluate the adhesion strength, mechanical properties, and friction coefficient. Potentiodynamic polarization and potentiostatic techniques were used to study the multilayer Si-DLC films electrochemical behavior in harsh solution 3.5 wt.% NaCl. The findings revealed that the increase in bias voltage to − 300 V led to the adhesion strength, hardness, elastic modulus, and friction coefficient around 18N, 9.89 GPa, 85.57 GPa, and 0.17, respectively. The polarization results showed a decrease in corrosion current density, increased polarization resistance, and decreased passive current almost 1.28×10−10 A/cm−2, 5.26×109 Ω cm2, and 24.3 nA cm−2, respectively. The findings are ascribed to reduce the internal stress and increase the overall content of sp3 bonds in the film. Moreover, the Si-doped DLC film forms a passive layer from SiOx at the film/solution interface to impede the charge transfer.

Theoretical study on temperature-bias phase diagram of MgO-based magnetic tunnel junctions

MgO-based magnetic tunnel junction is a hot issue in the field of spin electronic devices, and its temperature and bias voltage play quite an important role in practical applications. Therefore, it is desiderated to obtain the temperature-bias phase diagram of MgO-based magnetic tunnel junction. This paper develops a theory which is suitable for magnetic tunnel junctions with single crystal barrier. In this theory, the single crystal barrier is regarded as a periodic grating, and the tunneling process is treated by optical diffraction theory, so the coherence of the tunneling electron can be well taken into account. Most importantly, the theory can handle both the temperature effect and bias effect of MgO-based magnetic tunnel junctions. According to the present theory, the temperature-bias phase diagram of MgO-based magnetic tunnel junctions is calculated under different half the exchange splittings, chemical potentials and periodic potentials. The theoretical results show that the extreme phase point of tunneling magnetoresistance (TMR) can move to high temperature region through regulating half the exchange splitting <i>Δ</i> of ferromagnetic electrode of MgO-based magnetic tunnel junction. This will be beneficial to the applications of magnetic tunnel junctions at room temperature. Moreover, the chemical potential <i>μ</i> can change the bias corresponding to the maximum phase point of TMR. As is well known, the chemical potential will vary with the material of ferromagnetic electrode. Therefore, if the material of ferromagnetic electrode is chosen with a proper chemical potential, we can obtain a large TMR under high bias voltage. In other words, the output voltage can be considerably increased. This will be favorable for the preparation of high power devices. In addition, it is found that the phase diagram of TMR is significantly dependent on periodic potential <i>v</i>(<i> <b>K</b> </i><sub><i>h</i></sub>). As a result, the effects of temperature and bias voltage in the MgO-based magnetic tunnel junctions can be optimized by regulating half the exchange splitting <i>Δ</i>, chemical potential <i>μ</i>, and periodic potential <i>v</i>(<i> <b>K</b> </i><sub><i>h</i></sub>). The present work provides a solid theoretical foundation for the applications of MgO-based magnetic tunnel junctions.

Design and analysis the operation of Schmitt trigger circuit in radiation environment

The object of research is the effect of gamma radiation on the characteristics of the operation amplifier, and consequently the behavior of the output voltage waveforms of Schmitt trigger circuit. One of the most problematic is the effect of the circuit elements, reference voltage, input frequency, input DC-voltage and bias voltage effects, on the operation of the proposed Schmitt trigger circuit. In the course of the research, the used Op Amp can be exposed to different types of radiation. As a result of the research it is shown that the threshold levels of Schmitt trigger circuit increased when operates in nuclear radiation environment.From the experimental work, computer simulation, and results analysis, the conclusions could be deduced, that Operation of operational amplifiers in gamma radiation environment show serious changes on their electrical characteristics. As a result, the Schmitt trigger circuit exposed to gamma radiation range from 3 kGy up to 20 kGy, at 10 Hz, where, its output voltage waveforms are shown to be independent on the gamma-dose. On the other hand, at frequency of 4.0 kHz, a severe effect are noticed, where the lower threshold level (VLTL) increase from –5.35 V up to –3.58 V, while the upper threshold voltage level (VUTL) is slightly increased from 4.21 V to 5 V, as a function of the same gamma doses. The obtained experimental results are shown to be in close agreement with those obtained from programming the Schmitt trigger equations to computer.In the future, the proposed approaches show that, whenever the Op Amp circuits are used in gamma radiation environment, it preferable to be operate at low frequency levels, where the output voltage waveform of Schmitt trigger circuit are shown to be independent on gamma dose but at high frequency the effect increased as a function of same gamma dose.

Analytical Study of Sputter-Grown ZnO-Based p-i-n Homojunction UV Photodetector

Here, an analytical model for dark current and photoresponsivity of ZnO-based thin film homojunction p-i-n ultraviolet (UV) photodetector (PD) is presented. This work provides a succinct insight about the effect of reverse bias voltage, thickness variation on the responsivity and dark current of homojunction p-i-n UV PDs based on ZnO-based layers grown by dual ion beam sputtering. The results affirm that with the increase in the thickness of top ${p}$ -type layer from 50 to 200 nm, the peak responsivity reduces by 41.9%, while with the increase in the ${i}$ -ZnO layer thickness from 20 to 80 nm responsivity increases by 108.6%. The obtained outcome, vindicates that by incorporating Sb:ZnO in lieu of Li-N:ZnO as p- type layer, a rise of ~7.6-fold and reduction of ~2.1-fold in the peak responsivity at 0 V and dark current at -15 V, respectively, at room temperature are attained. Hence, the developed model is indispensable for assessing the design optimization of high-performance ZnO-based p-i-n homojunction UV PDs.

Effect of bias voltage on the microstructure and properties of Nb-DLC films prepared by a hybrid sputtering system

Diamond-like carbon (DLC) films with Nb doping were fabricated by a hybrid sputtering system comprising a high power impulse magnetron sputtering unit and a pulse direct current magnetron sputtering source. The effect of bias voltage on the morphology and chemical bonding characteristic of the Nb-DLC films were investigated. Results showed that the bias voltage played a significant role on the microstructure of the films. The surface morphology revealed a granular microstructure and the average size of these granules decreased with increasing bias voltage. Accordingly, the cross-sectional morphology evolved from an apparent columnar structure to a compact and dense nanocomposite structure with NbC nanocrystallites embedding in the amorphous carbon matrix at a high bias voltage. The integrated area ratio of the D and G peaks (ID/IG) of the Raman spectra decreased with increasing bias voltage, indicating the sp3‒C bonding fraction was improved in the films. The mechanical properties including hardness and elastic modulus, internal stress and elastic recovery, as well as the wettability property of films with different bias voltages were also investigated. With increasing bias voltage, the high sp3‒C fraction, modulated stress and formed hard carbide phase were all conducive to the enhancement of the hardness. Furthermore, all the films exhibited hydrophobic behavior and this tendency weakened at relatively high bias voltage conditions.