Reactive Sputtering Technique Research Articles

Epitaxial growth and stoichiometry control of pyrochlore Nd2Ru2O7 thin films

We report on the epitaxial growth of pyrochlore NRO thin films utilizing a reactive off-axis sputtering technique. The growth process employed Ru and Nd metal targets with a repetitive substrate temperature sequence. X-ray diffraction, magnetic susceptibility, and spectroscopic ellipsometry measurements confirm that the structural, magnetic, and electronic properties of near-stoichiometric NRO films match those of the bulk material. Our spin-polarized density functional calculations based on Nd2Ru2O7 structural parameters accurately describe the optical spectra and assign Hubbard bands to the interband transitions observed above the optical band gap of 0.2 eV. By utilizing the technique's capability to adjust the degree of ruthenium deficiency, we investigated Nd2Ru2O7 films across a wide range of stoichiometric variations. Decreasing the Ru/Nd ratio results in lattice expansion, an increase in the optical band gap, and the suppression of Ru 4d intersite optical transitions. Additionally, this adjustment facilitates the elimination of minor inclusions of a ferromagnetic NdOx impurity phase, influencing the magnetic properties of stoichiometric films at low temperatures. The successful growth of Nd2Ru2O7 films opens up promising opportunities for designing and exploring strain- and light-induced states in pyrochlore ruthenates. Published by the American Physical Society 2024

Leveraging oxide reactive sputtering for thermal insulation in laser-heated diamond anvil cell

ABSTRACT We have developed an oxide reactive sputtering technique aiming at rapidly sputtering high-quality oxide films on a diamond surface, providing excellent thermal insulation in high-pressure and temperature experiments using a laser-heated diamond anvil cell (LH-DAC). We identified conditions for rapid deposition of an alumina layer on diamond anvils, showing deposition rates as high as 0.67 um/hr. We also investigated the deposition conditions of zirconia, which have lower thermal conductivity than alumina. Laser-heating tests were performed at high pressures and temperatures to evaluate the thermal insulation of the oxide film deposited on the diamond anvils. The heating efficiency of zirconia-deposited anvils was higher than that of the alumina-deposited ones. Our zirconia-sputtered anvils were capable of generating up to 2580 K at around megabar pressure without additional thermal insulation, demonstrating the potential of this technique for ultra-high temperature generation.

Realization of low specific-contact-resistance on N-polar GaN surfaces using heavily-Ge-doped n-type GaN films deposited by low-temperature reactive sputtering technique

We developed a low-temperature ohmic contact formation process for N-polar GaN surfaces. Specific-contact-resistances of 9.4 × 10−5 and 2.0 × 10−5 Ω cm2 were obtained using Ti/Al metal stacks on heavily-germanium-doped GaN films, which were deposited at 500 °C and 600 °C using a radical-assisted reactive sputtering method, respectively. The electrode sintering temperature was as low as 475 °C. Carrier concentrations for the 500 °C and 600 °C samples were 2.6 × 1020 and 1.8 × 1020 cm−3, respectively. These results suggest that this method is highly effective in reducing the contact resistance of GaN devices with low thermal budgets.

Exploring the Nb2O5 coating deposited on the Ti-6Al-4V alloy by a novel GE-XANES technique and nanoindentation load-depth

This research group has been demonstrating the significant advantages of using Nb2O5 coatings for functionalizing titanium, aluminium, and stainless steels. Regarding the biomedical sector and considering Ti-6Al-4V alloy, the reactive sputtering technique improved the cell viability, the osteogenic performance of cells involved in the osseointegration process as well as the ability to delay bacterial proliferation. The characteristics of the Nb2O5 coatings were assessed before by using standard methods, which provide information only a few tens of nanometers depth. Given that the Nb2O5 coating fabricated in this work exhibits a thickness of approximately 300 nm, the GE-XANES technique emerges as the most suitable method for this analysis. Additional information was provided with the aid of nanoindentation load-depth (P-h) curves. GE-XANES results indicated the formation of a homogeneous layer of Nb2O5 coating on the Ti-6Al-4V surfaces. The deposition process improved the surface hardness of the Ti-6Al-4V alloy (4.38 GPa versus 5.62 GPa) considering the 2 mN load.

Niobium and carbon nanostructured coatings for corrosion protection of the 316L stainless steel

This work aims to investigate the influence of niobium and carbon nanostructured coatings on the corrosion resistance of the 316L SS. The coated and uncoated specimens were morphologically and structurally characterized by using OM, SEM/EDX, DRX, FTIR, Raman spectroscopy and XPS techniques. The corrosion behaviour was assessed by OCP, PPc, EIS as well as immersion tests in 0.6 mol L−1 NaCl solution. In addition, the average contact angles were used to evaluate the surfaces free energy by the Van Oss interfacial tension component theory approach. Results showed that the surface treatments positively influenced the corrosion resistance of the 316L SS and the coatings act as a protective barrier against corrosion process. The reactive sputtering technique increased the wettability of the surfaces in relation to the base material. Considering applications in aggressive media, the 316L SS/Nb2O5 specimen exhibits superior performance when compared to the base material and 316L SS/carbon.

Benzene vapor sensing performance of different phases of copper oxide (CuxOy) thin films

Three different phases of copper oxide can be grown by thin-film deposition techniques, which differ in the oxidation state of copper. However, few studies have focused on comparing and considering sensing performance of these phases. The current study scrutinizes the benzene vapor sensing properties of various phases of copper oxide that can be used for the development of sensing device based on CuxOy thin films. RF reactive sputtering technique was employed, and different phases of copper oxide (CuO, Cu2O, and Cu4O3) were grown by tuning the sputtering power and reactive gas. The samples with phases of CuO, Cu2O, and CuO/Cu2O showed the response to benzene at different operating temperatures while the sample with the Cu4O3 phase was not sensitive to target vapor. The results demonstrated that the device based on CuO thin film can be a promising candidate to detect benzene vapor due to its remarkable sensitivity, selectivity, and stability.

Employment of Silicon Nitride Films Prepared by DC Reactive Sputtering Technique for Ion Release Applications

In this work, silicon nitride (Si3N4) thin films were deposited on metallic substrates (aluminium and titanium sheets) by the DC reactive sputtering technique using two different silicon targets (n-type and p-type Si wafers) as well as two Ar:N2 gas mixing ratios (50:50 and 70:30). The electrical conductivity of the metallic (aluminium and titanium) substrates was measured before and after the deposition of silicon nitride thin films on both surfaces of the substrates. The results obtained from this work showed that the deposited films, in general, reduced the electrical conductivity of the substrates, and the thin films prepared from n-type silicon targets using a 50:50 mixing ratio and deposited on both surfaces of a titanium substrate reduced the electrical conductivity of this substrate by 30%. This reduction in the release of ions from the coated metal substrate is attributed to the dielectric properties of the deposited silicon nitride thin films. This result is very important and applicable. This work represents the first attempt in Iraq to study such effects and may represent a good starting point for advanced studies in biomedical engineering.

Structural and Hardness Characteristics of Silicon Nitride Thin Films Deposited on Metallic Substrates by DC Reactive Sputtering Technique

Structural and Hardness Characteristics of Silicon Nitride Thin Films Deposited on Metallic Substrates by DC Reactive Sputtering Technique

Growth of Zn1−xNixO Thin Films and Their Structural, Optical and Magneto-Optical Properties

The radio frequency (RF) reactive sputtering technique has been used to prepare Zn1−xNixO thin films with 0 ≤ x ≤ 0.08. Composite targets were obtained by mixing and pressing NiO and ZnO powders. Sapphire, quartz and glass were used as substrates. X-ray diffraction analysis of Ni-doped ZnO films indicates that all samples are crystalised in a hexagonal wurtzite structure with a preferred orientation along the (002) plane. Any secondary phase, corresponding to metallic nickel clusters or nickel oxides was not observed. High-resolution transmission electron microscopy (HR-TEM) image observed for Zn1−xNixO thin film shows a strong preferred orientation (texture) of crystalline columns in the direction perpendicular to the substrate surface. Different surface morphology was revealed in AFM images depending on the film composition and growth condition. Optical absorption spectra suggest the substitution of Zn2+ ions in the ZnO lattice by Ni2+ ions. The energy bandgap value was also found a complex dependence with an increase in Ni dopant concentration. In photoluminescence spectra, two main peaks were revealed, which are ascribed to near band gap emission and vacancy or defect states. Faraday rotation demonstrates its enhancement and growth of ferromagnetism with the increase in Ni content of Zn1−xNixO thin films at room temperature.

X-ray Photoelectron Spectroscopy (XPS) Analysis of Ultrafine Au Nanoparticles Supported over Reactively Sputtered TiO2 Films.

The impact of a titania (TiO2) support film surface on the catalytic activity of gold nanoparticles (Au NP) was investigated. Using the reactive dc-magnetron sputtering technique, TiO2 films with an amorphous, anatase, and nitrogen-doped anatase crystal structure were produced for a subsequent role as a support material for Au NP. Raman spectra of these TiO2 films revealed that both vacuum and NH3 annealing treatments promoted amorphous to anatase phase transformation through the presence of a peak in the 513–519 cm−1 spectral regime. Furthermore, annealing under NH3 flux had an associated blue shift and broadening of the Raman active mode at 1430 cm−1, characteristic of an increase in the oxygen vacancies (VO). For a 3 to 15 s sputter deposition time, the Au NP over TiO2 support films were in the 6.7–17.1 nm size range. From X-ray photoelectron spectroscope (XPS) analysis, the absence of any shift in the Au 4f core level peak implied that there was no change in the electronic properties of Au NP. On the other hand, spontaneous hydroxyl (–OH) group adsorption to anatase TiO2 support was instantly detected, the magnitude of which was found to be enhanced upon increasing the Au NP loading. Nitrogen-doped anatase TiO2 supporting Au NP with ~21.8 nm exhibited a greater extent of molecular oxygen adsorption. The adsorption of both –OH and O2 species is believed to take place at the perimeter sites of the Au NP interfacing with the TiO2 film. XPS analyses and discussions about the tentative roles of O2 and –OH adsorbent species toward Au/TiO2 systems corroborate very well with interpretations of density functional theory simulations.

Reactively sputtered CdS:O buffer layers for substrate Sb2Se3 solar cells

Antimony selenide (Sb2Se3) is an emerging and promising photovoltaic material. High controllability for the energy level of buffer layers is greatly desirable for achieving higher performance Sb2Se3 solar cells due to the formation of heterojunction at the buffer/Sb2Se3 absorber interface. In this work, the CdS:O buffers were prepared by using a reactive sputtering technique including an Ar/O2 mixture gas and a CdS ceramic target, and a composite buffer were fabricated with a structure of CBD-CdS (∼10 nm)/CdS:O. The interface damage induced by sputtering is investigated, and untra-thin CBD-CdS is performed to recover the plasma induced damage at the CdS:O/Sb2Se3 heterojunction interface. By optimizing the S/(S+O) composition ratio and the phase component of the composite buffer, wide band-gap buffer layers were achieved, and the device spectra response and device parameters JSC and VOC were improved. It was found that the composite CdS:O buffer optimizes the heterojunction interface band alignment and further efficiently reduce the interface recombination, enhanced the transfer and collection of photogenerated carriers.

Synthesis of nanostructure Ta2O5 coatings using plasma reactive sputtering technique for optical filter application

Titanium bentoxide Ta2O5 deposited on glass substrates by were heated to 400 °C for 1, 2 and 6 hours. The as-deposited Ta2O5 films deposited by DC reactive sputtering show amorphous structure, the structure improved to crystalline after increasing annealing temperature. When the annealing time rises to 6 hours, Ta2O5 films with β-phase structure was obtained. The basic and optical properties of arranged films have been considered utilizing XRD and UV-Visible spectroscopy. The XRD comes about appeared that all films are polycrystalline in nature with orthorhombic structure and favored introduction along (0140) plane. The crystallite size was calculated using Scherrer formula and it is found that the 2 hrs sputtering time, 3Kv, 10Amp and 4×10-2mbar. Maximum crystallite size was (27.5nm). The absorbance and transmittance spectra have been recorded in the wavelength extend of (300-1000) nm in arrange to think about the optical properties. The optical energy gap for permitted direct electronic move was calculated using Tauc condition with regard to vitality of photon. It is found that the band gap increases with increasing annealing times and its ranges between 3.2 eV and 3.75 eV for the prepared Ta2O5 thin films.

Growth Mechanisms of TaN Thin Films Produced by DC Magnetron Sputtering on 304 Steel Substrates and Their Influence on the Corrosion Resistance

In this work, thin films of TaN were synthesized on 304 steel substrates using the reactive DC sputtering technique from a tantalum target in a nitrogen/argon atmosphere. All synthesis parameters such as gas ratio, pressure, gas flow, and substrate distance, among others, were fixed except the applied power of the source for different deposited coatings. The effect of the target power on the formation of the resulting phases and the microstructural and morphological characteristics was studied using XRD and AFM techniques, respectively, in order to understand the growth mechanisms. Phase, line profile, texture, and residual stress analysis were carried out from the X-ray diffraction patterns obtained. Atomic force microscopy analysis allowed us to obtain values for surface grain size and roughness which were related to growth mechanisms in accordance with XRD results. Results obtained showed a strong correlation between the growth energy with the crystallinity of the samples and the formation of the possible phases since the increase in the growth power caused the samples to evolve from an amorphous structure to a cubic monocrystalline structure. For all produced samples, the δ-TaN phase was observed despite the low N2 content used in the process (since for low N2 content it was expected to be possible to obtain films with α-Ta or hexagonal ε-TaN crystalline structure). In order to determine the corrosion resistance of the coatings, electrochemical impedance spectroscopy and polarization resistance were employed in the Tafel region. The results obtained through this evaluation showed a direct relationship between the power used and the improvement of the properties against corrosion for specific grain size values.

Noise behavior of tungsten oxide doped amorphous vanadium oxide thin films

Noise properties of a-VWOx thin films deposited by reactive DC sputtering technique for microbolometer applications have been investigated. It was found from measurements that there is no random telegraph switching (RTS) noise of deposited films. Electrode material effects on the contact resistance were measured thereby using electrode structure consisted of two different metals. Various currents and electrode structures effects on 1/f noise measurements were studied. As a result of calculations, 1/f noise parameter was found as 3.2 × 10−13. This situation shows that developed a-VWOx is notably a suitable material for microbolometer applications.

Heterostructure Silicon Solar Cells with Enhanced Power Conversion Efficiency Based on Si x /Ni3+ Self-Doped NiO x Passivating Contact.

Developing efficient crystalline silicon/wide-band gap metal-oxide thin-film heterostructure junction-based crystalline silicon (c-Si) solar cells has been an attractive alternative to the silicon thin film-based counterparts. Herein, nickel oxide thin films are introduced as the hole-selective layer for c-Si solar cells and prepared using the reactive sputtering technique with the target of metallic nickel. An optimal Ni3+ self-doped NiOx film is obtained by tuning the reactive oxygen atmosphere to construct the optimized c-Si/NiOx heterostructure band alignment. A thin SiOx interlayer was further introduced to reduce the defect of the c-Si/NiOx interface with the UV–ozone (UVO) treatment. The constructed p-type c-Si/SiOx/NiOx/Ag solar cell exhibits an increase in the open voltage from 586 to 611 mV and achieves a 19.2% conversion efficiency.

Effect of niobium oxide thin film on the long-term immersion corrosion of the 2198-T851 aluminium alloy

This work aims to study the effect of niobium oxide coating on the long-term immersion corrosion of the 2198-T851 aluminium alloy. The niobium oxide thin film was successful obtained on freshly plates of 2198-T851 alloy by reactive sputtering technique. Scanning vibrating electrode tests, electrochemical impedance spectroscopy and immersion tests measurements were used to reveal the insights of global and localised corrosion behaviour of the functionalised material in different concentrations of sodium chloride solution. The electrochemical impedance spectroscopy spectra showed that the coating significantly influenced on the corrosion resistance of the 2198-T851 alloy, since the functionalised alloy immersed in 0.6 mol L−1 NaCl solution during 720 h (30 days) displays the same result as the bare material for 3 h of immersion. The scanning vibrating electrode tests demonstrated the coated material was free of local corrosive attack by the electrolyte in the first 10 h of immersion, whilst the bare alloy exhibited active anodic and cathodic sites over the surface with increasing current density values for longer immersion times. The deposited coating was able to increase the corrosion resistance of the 2198-T851 aluminium alloy used as fuselage skin material by the aeronautical industry as verified by the immersion tests. Finally, experimental results confirm the extraordinary properties of niobium oxide as-deposited coating.

Self-powered transparent ultraviolet photo-sensors based on bilayer p-NiO/n-Zn(1−x) Sn(x)O heterojunction

A heterostructure using p-NiO/n-Zn(1−x)Sn(x)O (x = 0.14) (TZO) junction was successfully fabricated by DC-magnetron reactive sputtering technique for UV sensing. Under weak illumination of UV radiation (365 nm, 0.06 mW/cm2), the fabricated device had shown a photo responsivity of ~3.00 mA W−1 and quantum efficiencies about 1.01% even in zero bias condition. The device also exhibited impressive photo response about 19.70 mA W−1 and external quantum efficiencies nearly 6.69% at low reverse external bias of 3 V. The fabricated hybrid hetero structured UV photosensors had also shown great detectivity and transient speed of response about 8.6 × 1010 Jones, 2.3 s/1.4 s at zero bias respectively. Hence these observations suggest that p-NiO/n-TZO heterojunction could be used as novel, self-powered highly transparent photosensors for detecting UV radiation.

Corrosion behaviour of reactive sputtering deposition niobium oxide based coating on the 2198-T851 aluminium alloy

This work aims to improve the corrosion properties of the 2198-T851 aluminium alloy by coating with a set of niobium oxide thin films, using the reactive sputtering technique. The structural and morphological properties of the niobium oxide thin films were characterized by using SEM/EDX, AFM, FTIR and Raman spectroscopy. Global electrochemical tests (OCP, PPc, CV, and EIS) were performed in 0.6 mol L−1 NaCl solution. The results demonstrated that the reactive sputtering technique was advantageous for producing thin films on the 2198-T851 aluminium surface. Raman spectroscopy results revealed a band near 650 cm−1 related to NbO single bonds, whilst the band centred at 868 cm−1 may be attributed to NbO double bonds. The PPc results indicated that the niobium oxide acts as a protective barrier, since a difference of about 210 mV was observed between Epitting and Ecorr. The coated specimens displayed a superior breakdown potential when compared to the base material (−0.387 vs − 0.505 V/SCE). The impedance modulus has increased more than one order of magnitude and the phase angle is closer to - 90°, demonstrating a capacitive thin film was deposited on the 2198-T851 aluminium alloy surface.

Oxygen-deficient non-crystalline tungsten oxide thin films for solar-driven water oxidation

The preparation of metal oxide semiconductors in non-stoichiometric (oxygen-deficient) form can lead to significant change in their optical and electronic properties, and hence affect the photoelectrochemical performance. The controlled introduction of oxygen vacancy can improve the charge separation and increases the charge carrier density, which can significantly contribute to the enhancement of photoelectrocatalytic activity. Herein, we report fabrication of non-crystalline tungsten oxide films from metallic tungsten target using DC reactive sputtering technique. The oxygen flow rate was regulated to control the composition, structure and morphology of the films. The as-prepared films are amorphous in nature with distinct surface morphology and optical properties. The presence of oxygen vacancies were confirmed by the surface analysis. The non-stoichiometric films were evaluated for PEC performance by monitoring the water oxidation reaction under the UV–visible radiation. The findings reveal a correlation between photoelectrocatalytic activity, optical band gap, morphology, and, more importantly, oxygen content of the films.

STUDY OF THE EFFECT OF ANNEALING AND IRRADIATION OF HIGH ENERGY IONS ON VANADIUM OXIDE THIN FILMS

Vanadium due to multiple oxidation states (+2 to +5) has various oxides like vanadium dioxide, vanadium pentoxide, and hexavanadium tredecaoxide. Thin films of vanadium oxide have been fabricated using the reactive radio frequency sputtering technique. Deposited films are then annealed in Argon (Ar) environment at 500°C and then irradiated with 100 MeV Ag8+ high-energy ions. The vibrational properties of the thin films have been analyzed by Raman scattering and Fourier transform infrared spectroscopy (FTIR). Results (Raman and FTIR spectra) of the annealed film show that the V6O13 phase is converted into a mixed phase (V6O13, VO2, and V2O5). The annealed irradiated film shows no change in the Raman lines while a shift towards the lower wave number is noticed in FTIR spectra peaks. This shifting of peaks towards lower wave numbers in FTIR spectra is attributed to the weakening of vanadium oxygen bonds. It is considered that the weakening of bonds could occur when high-temperature cylindrical zones are created along the ion track.