Direct Current Sputtering Technique Research Articles

The effect of energy of Ar recoil particles on the interfaces and micro-structure in Ni/Ti multilayer fabricated by direct current magnetron sputtering technique

Ni/Ti multilayers have been therefore widely used in neutron optics devices because of their excellent reflective properties for neutrons, which is strongly dependent to their interfaces and microstructure. Hence, there have been many attempts to improve the interfaces and microstructure of Ni/Ti multilayers, for example reactive sputtering, interlayers and so on. In this paper, the influence of energy of Ar recoil particles on the interface and micro-structure of Ni/Ti multilayers were completed, through varying the sputtering pressure. Firstly, the Simulation present that the decreasing of sputtering pressure would enlarge the number recoil particle proportion. Secondly, three Ni/Ti multilayers were fabricated by direct current sputtering technique with variable sputtering pressures (0.080Pa, 0.120Pa, 0.199Pa). Thirdly, the grazing incidence X-ray reflectometry (GIXRR), diffusing scattering, X-Ray Diffraction (XRD), Transmission Electron Microscope (TEM) were used to characterize the interfaces and micro-structure of these films. The measured results present that their interfacial width and roughness were variable as diseasing the sputtering pressure, and the micro-structure of Ni layers transform from (111) only to both (111) and (100). These experimental results could result from the effects of energy of both Ar recoil particles and the Ni, Ti depositing atoms.

Sensing of heavy metal Pb2+ ions in water utilizing the photonic structure of highly controlled hexagonal TiON/TiO2 nanotubes

The detection of heavy metals in water, especially Pb2+ ions, is important due to their severe hazardous effects. To address this issue, a highly controlled hexagonal TiON/TiO2 heterostructure has been synthesized in this study. The fabrication process involved the utilization of atomic layer deposition and direct current sputtering techniques to deposit TiO2 and TiON layers onto a porous Al2O3 membrane used as a template. The resulting heterostructure exhibits a well-ordered hollow tube structure with a diameter of 345 nm and a length of 1.2 µm. The electrochemical sensing of Pb2+ ions in water is carried out using a cyclic voltammetry technique under both light and dark conditions. The concentration range for the Pb2+ ions ranges from 10–5 to 10–1 M. The sensitivity values obtained for the sensor are 1.0 × 10–6 in dark conditions and 1.0 × 10–4 in light conditions. The remarkable enhancement in sensitivity under light illumination can be attributed to the increased activity and electron transfer facilitated by the presence of light. The sensor demonstrates excellent reproducibility, highlighting its reliability and consistency. These findings suggest that the proposed sensor holds great promise for the detection of Pb2+ ions in water, thereby facilitating environmental monitoring, water quality assessment, and safety regulation across various industries. Furthermore, the eco-friendly and straightforward preparation techniques employed in its fabrication provide a significant advantage for practical and scalable implementation.

Fabrication of UV ZnO NRS photodetector based on seeded silicon substrate via the drop-casting technique

PurposeThe purpose of this study is to fabricate an ultraviolet (UV) metal-semiconductor-metal (MSM) photodetector based on zinc oxide nanorods (ZnO NRs) grown on seeded silicon (Si) substrate that was prepared by a low-cost method (drop-casting technique).Design/methodology/approachThe drop-casting method was used for the seed layer deposition, the hydrothermal method was used for the growth of ZnO NRs and subsequent fabrication of UV MSM photodetector was done using the direct current sputtering technique. The performance of the fabricated MSM devices was investigated by current–voltage (I–V) measurements. The photodetection mechanism of the fabricated device was discussed.FindingsSemi-vertically high-density ZnO (NRs) were effectively produced with a preferential orientation along the (002) direction, and increased crystallinity is confirmed by X-ray diffraction analysis. Photoluminescence results show a high UV region. The fabricated MSM UV photodetector showed that the ZnO (NRs) MSM device has great stability over time, high photocurrent, good sensitivity and high responsivity under 365 nm wavelength illumination and 0 V, 1 V, 2 V and 3 V applied bias. The responsivity and sensitivity for the fabricated ZnO NRs UV photodetector are 0.015 A W-1, 0.383 A W-1, 1.290 A W-1 and 1.982 A W-1 and 15,030, 42.639, 100.173 and 334.029, respectively, under UV light (365 nm) illumination at (0 V, 1 V, 2 V and 3 V).Originality/valueThis paper uses the drop-casting technique and the hydrothermal method as simple and low-cost methods to fabricate and improve the ZnO NRs photodetector.

Surface and Electrical Characterization of Bilayers Based on BiFeO3 and VO2.

Thin films of BiFeO3, VO2, and BiFeO3/VO2 were grown on SrTiO3(100) and Al2O3(0001) monocrystalline substrates using radio frequency and direct current sputtering techniques. To observe the effect of the coupling between these materials, the surface of the films was characterized by profilometry, atomic force microscopy, and X-ray photoelectron spectroscopy. The heterostructures, monolayers, and bilayers based on BiFeO3 and VO2 grew with good adhesion and without delamination or signs of incompatibility between the layers. A good granular arrangement and RMS roughness between 1 and 5 nm for the individual layers (VO2 and BiFeO3) and between 6 and 18 nm for the bilayers (BiFeO3/VO2) were observed. Their grain size is between 20 nm and 26 nm for the individual layers and between 63 nm and 67 nm for the bilayers. X-ray photoelectron spectroscopy measurements show a higher proportion of V4+, Bi3+, and Fe3+ in the films obtained. The homogeneous ordering, low roughness, and oxidation states on the obtained surface show a good coupling in these films. The I-V curves show ohmic behavior at room temperature and change with increasing temperature. The effect of coupling these materials in a thin film shows the appearance of hysteresis cycles, I-V and R-T, which is typical of materials with high potential in applications, such as resistive memories and solar cells.

Magnetic properties of (Bi1\u2212xLax)(Fe,Co)O3 films fabricated by a pulsed DC reactive sputtering and demonstration of magnetization reversal by electric field

(Bi1−xLax)(Fe,Co)O3 multiferroic magnetic film were fabricated using pulsed DC (direct current) sputtering technique and demonstrated magnetization reversal by applied electric field. The fabricated (Bi0.41La0.59)(Fe0.75Co0.25)O3 films exhibited hysteresis curves of both ferromagnetic and ferroelectric behavior. The saturated magnetization (Ms) of the multiferroic film was about 70 emu/cm3. The squareness (S) (= remanent magnetization (Mr)/Ms) and coercivity (Hc) of perpendicular to film plane are 0.64 and 4.2 kOe which are larger compared with films in parallel to film plane of 0.5 and 2.5 kOe. The electric and magnetic domain structures of the (Bi0.41La0.59)(Fe0.75Co0.25)O3 film analyzed by electric force microscopy (EFM) and magnetic force microscopy (MFM) were clearly induced with submicron scale by applying a local electric field. This magnetization reversal indicates the future realization of high performance magnetic device with low power consumption.

The effect of content and thickness of chitosan thin films on resistive switching characteristics

Introduction: Nowadays, a resistive switching memory using biological, transparent, and environmentally friendly materials is appreciated as the tendency of science and technology, especially in the field of electronic devices. Chitosan (CS), having dominant characteristics such as non-toxic, biocompatible and large capacity, plays as a switching medium in resistive random access memory devices (RRAM).
 Methods: In our study, CS film was fabricated onto a commercial substrate (FTO) using a simple spin coating method, and the top electrode (Ag) was deposited by a direct-current sputtering technique.
 Results: The Ag/CS/FTO devices shown the bipolar switching behavior when applying sequence voltage from -1.5 to 2V with the set process in the negative bias and the reset process in the positive bias. The content (0.2, 0.5, and 0.8 wt%) and thickness (100, 300, 500 nm) of chitosan film significantly affect the resistive switching performance. The devices with 0.5 wt%/v concentration and 300 nm-thickness of CS have shown better efficiency than the others with endurance over 100 sweeping cycles and ON/OFF ratio at ca. 2x10 times.
 Conclusions: It is found that the chitosan material has a large potential candidate for applications in optoelectronic devices.

High-Performance Ni/Pt Composite Catalytic Anode with Ultra-Low Pt Loading for Low-Temperature Solid Oxide Fuel Cells

In this study, we developed a Ni/Pt bilayer catalytic anode that has high electrochemical activity and significantly reduced Pt loading amount, for low-temperature solid oxide fuel cells (LT-SOFCs). The Ni/Pt bilayer anodes with various thicknesses of the Pt catalytic active layer were fabricated on yttria-stabilized zirconia substrates via the direct current sputtering technique, and their performances were evaluated for the LT-SOFCs. The optimal thickness of the Pt catalytic layer for the Ni/Pt bilayer was found to be 10 nm based on the results for the fuel cell performance and electrochemical impedance spectroscopy (EIS) analysis. The optimal Pt10/Ni140 anode showed a cell performance and polarization resistance very similar to those of a reference single-phase Pt anode, while having only 7% of the Pt loading amount of the reference Pt anode. For the detailed morphological analysis of the bilayer structure anode, we employed the pull-off delamination process to analyze both the surface and interface morphologies of the bilayer anodes and the interface morphology of the Ni/Pt bilayer anodes after the operating test was analyzed. The results presented herein indicate the suitability of the methodology for the morphological analysis of thin-film bilayer structures and contribute to reduce the cost of membrane electrode assembly fabrication for LT-SOFCs, thus facilitating the commercialization of these systems.

Rapid antibiotic susceptibility testing by resazurin using thin film platinum as a bio-electrode

Traditional antibiotic susceptibility testing methods take several days to confirm and start disease treatment. The lack of new antibiotics or drugs warrants a need for optimization of current diagnostic tools for immediate antibiotic susceptibility testing. We present a rapid screening method to evaluate the response of bacteria to antibiotics based upon the electrochemical measurement of live bacterial cell metabolic activity using an electroactive redox dye, resazurin. A thin film of Pt deposited over a glass substrate using the direct current sputtering technique was used as a working bio-electrode for electrochemical readouts. X-ray diffraction and scanning electron microscopy was carried out to characterize the Pt thin film. We tested the efficacy of the method using two different strains, Klebsiella pneumoniae (ATCC-700603) and Escherichia coli (ATCC-25922), against ampicillin, kanamycin and tetracycline. The dye, on incubation with viable bacteria, undergoes reduction and lowers the corresponding peak current value. However, in the presence of an effective antibacterial agent, reduction did not occur due to bacterial cell death and absence of a reducing environment. The electrochemical changes in peak current values were monitored using the differential pulse voltammetry technique and interpretation of the results obtained was based upon changes in peak current values. Our results depict a new methodology where a concentration of 104 cells/mL cells can be detected in less than 4 h. The results were also compared with the conventional disc diffusion method for susceptibility testing which has a bacterial incubation time of 18–24 h. The method can potentially be used for monitoring the susceptibility of bacterial strains towards existing antibacterial agents in an easy, rapid, reliable and inexpensive manner without any pre-cultivation of bacteria.

Microstructure, optical and electrical properties of thin films of gallium-phosphorus-titanium alloys synthesized by asymmetric bipolar pulsed direct current magnetron sputtering

Thin films of gallium-phosphorus-titanium (Ga-P-Ti) alloys were prepared on glass substrates at 573 K by an asymmetric bipolar pulsed direct current sputtering technique using an argon atmosphere and targets made from gallium phosphide (GaP) powder and metallic titanium (Ti), at the surface ratios of 8:1, 5:1, 2:1 and 1:1 GaP to Ti (GaP:Ti) on the sputtered area. Examination by X-ray diffraction, transmission electron microscopy, and field emission scanning electron microscope indicated that the as-deposited films from the sputtering targets having GaP:Ti ratios of 8:1, 5:1, and 2:1 were polycrystalline with the cubic zinc-blende crystal structure having GaP as the host material, i.e., Ti-doped GaP. Elemental compositions of the film obtained from the target at a GaP:Ti ratio of 5:1 closely resembled the theoretically predicted intermediate band compound Ga4P3Ti. It was projected that the Ga4P3Ti compound could be fabricated by co-sputtering of GaP and Ti from a single target having the surface area ratio GaP:Ti of 3.5:1. Optical transmission and reflection spectra, temperature dependence of electrical resistivity, and light response of the electrical resistivity showed semiconductor-like behavior for the films obtained from the targets with the GaP:Ti of 8:1 and 5:1, and were metal-like for those deposited from the other targets. Optical band gaps determined from the transmission spectrum of the semiconducting films by Tauc's expression for indirect transition were 1.2–1.5 eV. The results of the study could provide an alternative route for fabricating the intermediate band material based on the Ga-P-Ti system.

Plasma emission spectroscopy and its relation to the refractive index of silicon nitride thin films deposited by reactive magnetron sputtering

In this work, we present a thorough study on the relation between the plasma emission and the change of the silicon nitride thin films refractive index. Thin films were grown by reactive magnetron direct current sputtering technique and deposited onto silicon wafers at different fluxes of Ar and N2 and at different working pressures. This procedure, at certain deposition parameters, produced poor quality films, i.e. films with refractive index other than pure Si3N4 films. The emission of the plasma was interrogated in real time by means of optical emission spectroscopy (OES) observing at the vicinity of the trget location. In addition, optical properties of the films were measured by in situ ellipsometric-spectroscopy and then correlated with OES observations. Changes in the film refractive index could be deduced from changes in plasma emission applying a principal component analysis.

Role of sputtering power on the microstructural and electro‐optical properties of ITO thin films deposited using DC sputtering technique

The effects of sputtering power on the deposition rate as well as the microstructural, electrical, and optical properties of indium tin oxide (ITO) thin films are investigated in this paper. ITO thin films were deposited on glass substrates using direct current (DC) magnetron sputtering of different DC powers, ranging from 60 to 140 W, onto externally unheated glass substrates. All samples were grown at the minimum sustainable plasma pressure to reduce the destructive role of pressure. The microstructural, electrical, and optical properties of the sputtered ITO films were systematically characterized by X‐ray diffraction (XRD), atomic force microscopy (AFM), four‐probe electrical conductivity, and optical spectroscopy. XRD studies confirmed the cubic bixbyite ITO structure, and the main preferred orientations of the prepared thin films were (222), (400), (440), and (622). AFM analysis showed a minimum surface roughness of 1.37 nm for the films deposited at 140 W, while the average size of the grains was 65 ± 5 nm. The deposition time was fixed at 10 min for all samples, and the AFM characterization of the films showed 170, 230, and 250 nm thickness for the samples deposited at 60, 100 and 140 W, respectively. From the variations of the sheet resistance and the XRD patterns of the ITO thin films, it was concluded that, as the ratio I222/I400 of a sample approaches unity, the sheet resistance of the layer reduces. A minimum sheet resistance 16 Ω/square, transmittance 85% with the thickness of 230 nm, and optical bandgap 4.09 eV were found for the thin film grown on the externally unheated substrates at 100 W DC power and 32 mTorr working pressure. © 2017 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.

IMPURITY INDUCED WRINKLING PATTERNS IN METAL FILMS DEPOSITED ON SOFT ELASTIC SUBSTRATES

Metal (iron and nickel) films have been deposited on soft elastic polydimethylsiloxane (PDMS) substrates by direct current sputtering technique and the impurity induced wrinkling patterns are investigated by using optical microscopy and atomic force microscopy. It is found that the metal films can spontaneously form disordered wrinkles due to the isotropic compressive stress. In the vicinity of film impurities such as extraneous particles, linear defects, cracks and thickness-gradient film edges, the stress field becomes anisotropic owing to symmetry breaking and thus complex wrinkling patterns including straight stripes, herringbones, crossings, labyrinths and their transitions can be observed. The morphological evolutions, structural characteristics and physical mechanisms of the impurity induced wrinkles have been discussed and analyzed based on the continuum elastic theory.

ZnO Films Deposited on Porous Silicon by DC Sputtering

ZnO is now a fascinating semiconductor oxide material for light emission or transparent electronic conductors. We deposited ZnO films on porous silicon, which is known as a light emitting material based on silicon, by means of a direct current sputtering technique. The deposition was performed at room temperature, and the samples were annealed afterwards to improve the ZnO crystalline quality. The discussion to compare our results with that formed on Si wafer, reveals that the ZnO on porous silicon has the better crystalline quality in the scope of an X-ray diffraction measurement.

P-type ZnO films deposited by DC reactive magnetron sputtering using codoping process

P-type ZnO:Al:N thin films have been successfully deposited on Corning glass substrates using an industrial compatible, direct current sputtering technique. Effects of the nitrogen flow rate on the film structure and optoelectronic properties are investigated using X-ray diffraction measurement (XRD) and scanning electron microscopy. The XRD patterns suggest that all of the samples exhibit a preferential growth direction along the c-axis orientation and the change of film stress as the nitrogen flow increases. The Hall-effect measurements reveal that our samples are hole conduction (p-type), with high carrier concentration and low film resistivity. The UV–Vis spectroscopy measurements indicate that, as the nitrogen doping increases, the surface roughness increases, which significantly reduces the optical transmittance. For the purpose of demonstration, ZnO-based pn junctions have been fabricated and characterized by current–voltage measurements. It is shown that these fabricated devices exhibit a rectifying behaviour and, as a result, confirm the p-type conductivity.

Effect of layer thickness on electrical characterization of Ag/Si schottky diode fabricated by thermal evaporation technique

In this study, three Ag/Si schottky diode have been fabricated by depositing of Silver (Ag) layer with three different thickness 300, 360 and 400nm on p-Si substrate with (100) orientation by thermal evaporation technique and depositing of Aluminum (Al) layer with 120nm thickness on back of substrates by direct current sputtering technique. The main parameters of diode like ideality factor (n), series resistance (Rs) and potential barrier (Φb) are calculated by using two methods of current-voltage measurements and cheung functions. The ideality factor and potential barrier for three thickness 300, 360 and 400nm obtained by using I-V measurements respectively 3.8, 0.63eV, 2.058, 0.70eV and 1.01, 0.73eV. Also these calculated by using cheung functions respectively 3.46, 0.63eV, 2.42, 0.70eV and 0.73, 0.82eV. The series resistance values obtained by using cheung functions for three thickness 300, 360 and 400nm respectively 97, 53 and 10.2Ω. The results obtained from cheung functions and analysis of I-V measurements showed that by increasing layer thickness, the potential barrier of schottky diode increase and the series resistance decrease that leads to the formation of more ideal diode.

Electronic Transport of an Ni/n-GaAs Diode Analysed Over a Wide Temperature Range

We have reported a study on current–voltage (I–V) characteristics and capacitance–voltage (C–V) of an Ni/n-GaAs Schottky barrier diode in a wide temperature (T) range of 100–320 K in steps of 20 K, which is prepared by a magnetron direct current sputtering technique. The ideality factor decreases and barrier height (BH) increases with an increase in the temperature. The variation of the diode parameters with the sample temperature has been attributed to the presence of the lateral inhomogeneities in the BH. It has been seen that the junction current is dominated by thermionic field emission. The carrier concentration, diffusion potential, BH, Fermi energy level and the temperature coefficient of the BH have been calculated from the temperature-dependent C–V–T characteristics.

Low resistivity molybdenum thin film towards the back contact of dye-sensitized solar cell

This paper reports the optimization of the molybdenum thin film electrode as the back contact of dye-sensitized solar cell (DSSC). The molybdenum thin film was grown on the glass substrate by direct current sputtering techniques of which the sputtering power was 150 W at 18 sccm flow rate of Ar. At such sputtering parameters, the Mo film can reach the lowest resistivity of 1.28E −6 Ω cm at 400 nm thick. And the reflection of Mo membrane was 82%. This value is considered as a very good result for preparation of the back contact of DSSC.

Three-dimensional nanoporous and nanopillar composite Cu-Sn electrode for lithium-ion battery

A novel three-dimensional nanostructured, namely nanoporous and irregular nanopillar, composite Cu-Sn anode material for lithium-ion batteries was synthesized by directly oxidizing copper foil slightly in air and deoxidizing under H2/Ar atmosphere. Following that, Sn layer was deposited on as-prepared Cu substrate by the direct current sputtering technique. The morphology, constituent, and electrochemical performance of the obtained samples were characterized by field emission scanning electron microscope, X-ray diffraction, energy-dispersive X-ray spectrometer, and galvanostatic cycling test. The as-prepared Cu-Sn electrode (deposition time 10 min) exhibits a stable coulombic efficiency around 95 % over 50 cycles. The 50th specific capacity is 590 mA h/g at the current of 0.3 C, and at the high rate of 12 C, it exhibits 376 mA h/g which shows a high specific capacity and remarkable rate performance as an anode for lithium-ion batteries. The special 3D nanostructure, herein, can not only effectively offer enough space to accommodate large volume change but also act as structural reinforcement during electrochemical reaction. The simple fabrication approach of this novel nanostructure can be further extended to other anode materials with remarkable electrochemical property.

Quantum size effect in the photoluminescence properties of p-type semiconducting transparent CuAlO2 nanoparticles

Photoluminescence properties of CuAlO2 nanoparticles, deposited by a cost-effective direct current sputtering technique, have been studied. The nanoparticles show room-temperature photoluminescence peaks of near-band-edge emission due to recombination of free excitons. A blue-shift in the emission peaks as a decreasing function of the nanoparticle sizes is observed, which is attributed to the quantum confinement effect within the CuAlO2 nanoparticles. Theoretical calculations of bandgap enhancement values are found to be matching fairly well with that of the experimentally obtained values, confirming the existence of the quantum size effect within the nanomaterial. Approximate calculations show that the confinement effect falls within moderate-to-weak confinement regime. X-ray diffraction and electron microscopic measurements confirm the proper phase formation and nanocrystalline structure of the as-deposited nanoparticles. The room-temperature and size-dependent photoluminescence properties of this nanomaterial will be very useful for light emitting diode and similar optoelectronic applications.

Effect of Sputtering Parameters on Structural and Photocatalytic Properties of N-Doped TiO<sub>2</sub> Films

Nitrogen-doped titanium oxide (N-TiO2) films deposited on unheated glass slides at various flow rates of N2 in an atmosphere of Ar and O2 gas mixture by direct current sputtering technique were investigated. The Ti2p, O1s and N1s spectra by X-ray photoelectron spectroscopy (XPS) verified N-substitution into TiO2 lattice which is responsible for the band gap narrowing. The oxygen total ratio (rOT) in the gas mixture had profound influence on the photocatalytic properties of the N-doped films. At a ratio of rOT≦0.18, heterogeneous phases, such as titanium oxynitride (TiNxOy) and titanium nitride (TiN), with low crystallinity were formed in the TiO2 lattice, showing low photocatalytic activity. On the other hand, the N-TiO2 films prepared at rOT≧0.20 were found to have improved photocatalytic activity on methylene blue degradation under visible-light irradiation at wavelengths longer than 500 nm, due to the substitutional N ions in the TiO2 lattice.