Sputtering Power Research Articles

Effects of Oxygen Defects in Zr Oxide-Based Thin Films on Oxygen Reduction Reaction in Acidic Media

The use of carbon-supported platinum as cathode catalysts of polymer electrolyte fuel cells has some problems such as high cost and low amount of resources of platinum. Therefore, we have attempted to develop substitute of platinum based on group 4 metal oxides. In the case of Zr oxide-based powder catalysts, we found that zirconium oxide-based compounds with oxygen defects and deposited carbon derived from organometallic precursors had definite activity of oxygen reduction reaction (ORR) [1][2]. However, the ORR activities of these catalysts still remain low. In order to increase the ORR activity drastically, it is necessary to clarify the catalyst design. This requires an understanding of the active sites and the electron conduction path separately, which were not separated in powder catalysts. On the other hand, Sugino et al. investigated the effect of oxygen vacancies and nitrogen doping on the active site based on first-principles calculations [3]. Defects by oxygen vacancies and nitrogen dopants were introduced into the tetragonal ZrO2(101) slab. It was found that the energy barrier of the rate-determining step, or the removal of adsorbed OH, was comparable to (or only slightly lower than) that of the pristine surfaces, indicating that defects play only a minor role in enhancing the ORR activity. In other words, it was suggested that oxygen vacancies and nitrogen dopants contributed to the emergence of ORR activity by enhancing the electrical conductivity of ZrO2 rather than by forming high quality active sites. Simple models are suitable for experimentally confirming the results of theoretical calculations and for understanding the active sites and the electron conduction paths separately. Therefore, we attempted to prepare nitrogen doped ZrOx nanofilms by RF magnetron sputtering method with different targets and atmospheres and to investigate their potential as model electrodes.ZrOx thin films of ca. 3-5 nm thickness were prepared by RF magnetron sputtering method using glassy carbon (GC) plates as substrates and ZrN or Zr metal plates as targets under Ar, Ar+O2 and Ar+N2. The sputtering power, the deposition time, and the substrate heating temperature were 100 W, 10 min, and 300 ℃, respectively. The flow rates of Ar, O2, and N2 gas were controlled to keep the total chamber pressure at approximately 0.6 Pa. When the gases were mixed, the partial pressure ratio was set to 1:1. Electrode prepared with a ZrN target in Ar was denoted as "ZrN_Ar", and electrodes prepared with a Zr target in Ar:O2 and Ar:N2 were denoted as "Zr_Ar+N2" and "Zr_Ar+O2", respectively. A conventional three-electrode cell was used for electrochemical measurements with Reversible Hydrogen Electrode (RHE) as a reference and a GC plate as a counter electrode in 0.5 M sulfuric acid at 30 ℃. The oxygen reduction current density i ORR (geometric area standard) was calculated by subtracting the current in N2 from the current in O2.Figure 1 shows the effect of sputtering condition on potential-ORR current curves of the ZrOx thin film electrodes. For comparison, the result of the GC substrate only is also plotted as "GC only." The ORR activity of the ZrN_Ar was lower than that of the GC only. In addition, the current of the steady-state cyclic voltammogram of the ZrN_Ar was smaller than that of the GC only. This may be due to the electrochemical oxidation of ZrN surface and the formation of an insulating layer without active sites, presumably Zr hydroxide. On the other hand, the onset potential of the Zr_Ar+N2 and the Zr_Ar+O2 for the ORR were higher than that of the GC only and the Zr_Ar+N2 showed highest ORR activity. The steady-state cyclic voltammograms of the Zr_Ar+N2 and the Zr_Ar+O2 were larger than that of GC only, revealing that these electrodes might have high conductivities. In addition, XPS measurements suggest that the Zr_Ar+N2 contains nitrogen and the Zr_Ar+N2 and the Zr_Ar+O2 have oxygen vacancies. These results suggested that their high ORR activities were caused by nitrogen doping and oxygen defects. Therefore, the electrodes prepared by RF magnetron sputtering method may be able to separate the active sites from the electron conduction by changing the sputtering conditions such as film thickness.AcknowledgementThe authors thank the financial support of the New Energy and Industrial Technology Development Organization (NEDO).References(1) A. Ishihara et al., J. Phys. Chem. C, 123, 18150 (2019).(2) M. Chisaka et al., ACS Omega, 2, 678 (2017).(3) S. Muhammady et al., J. Phys. Chem. C, 126, 15662 (2022). Figure 1

Corrosion Properties of a Novel FeCrMoNbB Thin Film Metallic Glass Deposited by DC Magnetron Sputtering

The application of amorphous alloys as thin-film coatings with good corrosion properties has drawn attention in the last years since overcoming the typical limitations of these materials, such as the critical size and brittleness. Techniques based on Physical Vapor Deposition, like DC magnetron sputtering, are interesting once it allows parameter optimization to achieve the desired microstructure [1,2,3]. This study aims to characterize the electrochemical properties of a novel FeCrMoNbB (low Cr content – 11at%) alloy as a coating.Thin-film coatings were produced in a DC magnetron sputtering PVD system with 0.5 Pa Ar working pressure, 92 W of sputtering power, and 200°C deposition temperature. The substrate was 316L stainless steel. Corrosion tests were performed in a three-electrode cell in a Gamry 600+ potentiostat using the following sequence: two hours of open circuit potential (OCP), electrochemical impedance spectroscopy (EIS) from 100kHz to 0,02 Hz, 20 minutes of OCP, and potentiodynamic polarization test from -0,03 to 1,2V (vs. OCP). The solution was a 0,6M NaCl (Cl- content equivalent to seawater), natural pH of 5.5. Measurement Model software, developed by Orazem et al. [4], was used for data regression. X-ray photoelectron microscopy (XPS) was performed to obtain complementary information about the passive film. An XR3E2 apparatus from Vacuum Generator with an Mg-Kα source was used. The analysis was performed after stabilization in an open circuit for two hours.Fully amorphous thin films of about 400 nm were obtained. Outstanding corrosion behavior was observed for the coating, which presented a corrosion current (icorr) around 5 x10-9 Acm-2 and a corrosion potential of 127 mV. The icorr value is more than two decades lower when compared to the 316L of the substrate, indicating a higher corrosion resistance after applying the coating. EIS results showed a high impedance modulus at low frequency was |Z|LF = 3.7 MΩ.cm2. XPS analysis showed that all the alloying elements were in the oxidized form on the surface. Metallic species from the underlying surface could also be detected, meaning the oxide layer has less than 10 nm. Regression with Measurement Model software found a global capacitance C = 5.7 μF.cm2, a typical value for a compact passive layer. From the value of C, the film thickness was estimated to be around 2 nm, corroborating with the XPS analysis. A compact, thin layer of oxide composed of Cr, Nb, and Mo can be associated with high protectiveness of the passive film, hence, good corrosion resistance. Furthermore, the pitting phenomenon typical of 316L near 500mV was not observed in the coating. In summary, the results are promising for using these alloys as coatings for marine applications, potentially replacing conventional stainless steels.[1] M. Panayotova, Y. Garbatov, C. Guedes Soares, Corrosion of Steels in Marine Environment, Monitoring and Standards, Safety and Reliability of Industrial Products, Systems and Structures, Taylor & Francis Group, 2008.p.370.[2] WOOD Maureen; VETERE ARELLANO Ana Lisa; VAN WIJK Lorenzo. Publications Office of the European Union; 2013. JRC84661[3] Chu, J. P. et al. Thin film metallic glasses: Unique properties and potential applications. Thin Solid Films 520, 5097–5122 (2012).[4] M.E.O. W. Watson, EIS: Measurement Model Program., ECSarXiv. (2020). https://doi.org/10.1149/osf.io/kze9x.

Investigation of Antibacterial Efficacy of CuCrO2 Delafossite Thin Films Against E. coli

Terminals used in hospitals, information systems displaying patient information, and smartphones use touch panels that incorporate n and p transparent conducting oxide (TCO) layers [1]. There are a lot of pre-existing research present on n-type TCO while at the same time similar research interest related to p-type TCOs has been lacking. This is due to the inherently high electrical resistivity or low optical transparency of p-type TCOs. Recently, there has been a spike in research related to p-type delafossite thin films, owing to their excellent electrical and optical properties as compared to the other p-type counterparts. Cu-based p-type delafossite materials exhibit low resistivity and at the same time good optical transparency in the visible region. Among the Cu-based delafossites, copper chromium oxide (CuCrO2) exhibits the lowest electrical resistivity reported yet. Use of CuCrO2 as the p-type TCO along with a suitable n-type TCO might demonstrates significant potential to be used for optoelectronic applications.In this work, CuCrO2 thin films have been deposited on quartz substrates using dual target RF magnetron sputtering technique. This involved dual sputtering of 3- inch Cu2O and Cr2O3 targets. The substrate temperature was maintained at 400 °C during the deposition with Ar used as the sputtering gas. This was followed by post deposition annealing. Previous research carried out by our group has indicated that single-phase CuCrO2 was obtained at an annealing temperature of 650 °C in N2 ambiance for 4 hours [2, 3]. Successful synthesis of single-phase CuCrO2 has been confirmed using XPS and XRD study. The resistivity of CuCrO2 was obtained as 0.652 Ω-cm, which is the lowest reported so far. The optical study denoted an average optical transmission of > 60% in the visible wavelength spectrum and a high optical bandgap of 3.2 eV. The antibacterial efficacy of different thickness of CuCrO2 thin films was tested against E. coli bacterial strain and compared against the efficacy of plain quartz in this research work. Results showed that with an increase in the thickness of CuCrO2 thin films, the efficacy against E. coli increases. The highest antibacterial efficacy of 78.07 % was shown by 2000 A° CuCrO2 thin film.[1] Chiu T-W, Yang Y-C, Yeh A-C, Wang Y-P, Feng Y-W. Antibacterial property of CuCrO2 thin films prepared by RF magnetron sputtering deposition. Vacuum. 2013;87:174-177.[2] Sundaresh S, Bharath AH, Sundaram KB. Effect of Annealing Temperature on Radio Frequency Sputtered p-Type Delafossite Copper Chromium Oxide (CuCrO2) Thin Films and Investigation of Diode Characteristics Forming Transparent pn-Heterojunction. Coatings2023.[3] Sundaresh S, Bharath AH, Sundaram KB. Effect of Cu2O Sputtering Power Variation on the Characteristics of Radio Frequency Sputtered p-Type Delafossite CuCrO2 Thin Films. Coatings2023.

Effect of sputtering power on the physical properties of amorphous SiO2-doped InZnO transparent conductive oxide.

In order to control the optical and electrical properties of the transparent conductive oxide, the radio frequency (RF) sputtering power was changed from 30 to 40, 50, and 60W. To optimize the power condition of the SiInZnO (SIZO) layer, we changed the sputtering power from 30 to 60W, systematically. The chemical properties of the SIZO layer were analyzed using X-ray photoelectron spectroscopy (XPS). XPS proved that this change is dominant in thickness. In order to fabricate the SIZO transparent conducting oxide (TCO) with the optimized power of 50W, the transmittance of 99.1% at 550nm and the figure of merit of 12.4×10-3 Ω -1 were obtained.

Sputter-grown two-dimensional α-MoO3 thin films: Microstructure dependence on growth conditions

Van der Waals epitaxy is an emerging technology for transferring freestanding films grown at high temperatures onto arbitrary substrates using two-dimensional epitaxial layers. This study investigates the microstructure and growth of α-MoO3 thin films prepared via sputtering. Under a narrow deposition temperature range, epitaxial α-MoO3 thin films were successfully grown on SrTiO3 substrates. The films were characterized by a flat surface morphology, corresponding to (0k0) planes, without undergoing reaction with the substrates. To examine the growth behavior and surface morphological variation of the α-MoO3 thin films under various process parameters, we modified the Ar:O2 ratio, working pressure, sputtering power, and crystal structure of the substrates. Transmittance electron microscopy confirmed the epitaxial growth of the α-MoO3 thin films on (001)-oriented SrTiO3 substrates with a two-dimensional layer structure. Finally, we demonstrate the morphological evolution of the α-MoO3 thin films etched in heated water as a function of soaking time. The etching results suggest that the α-MoO3 thin films are promising sacrificial layers for the transfer of large-scale epitaxial thin films onto flexible substrates. External control of the strain states of transferred freestanding thin films by bending or stretching provides new perspectives for the design of flexible or wearable electronic devices.

Deposition and photoluminescence of zinc gallium oxide thin films with varied stoichiometry made by reactive magnetron co-sputtering

This paper reports on the deposition and photoluminescence of amorphous and crystalline thin films of zinc gallium oxide with Ga:Zn atomic ratio varied between 0.3 and 5.7. The films are prepared by reactive direct current magnetron co-sputtering from liquid/solid gallium/zinc targets onto fused quartz substrates; the temperature of the substrate is varied from room temperature (RT) to 800 °C. The sputtering process is effectively controlled by fixing the sputtering power of one of the targets and controlling the power of the other target by plasma optical emission spectroscopy. The method, in conjunction with oxygen flow adjustment, enables the production of near-stoichiometric films at any temperature used. The composition analysis suggests a few at% oxygen deficiency in the films. The resulting deposition rate is at least an order of magnitude higher compared to the commonly used radio-frequency sputtering from a ceramic ZnO:Ga2O3 target. Deposited onto unheated substrates, the films with Ga:Zn ≈ 2 are X-ray amorphous. Well-defined X-ray diffraction peaks of spinel ZnGa2O4 start to appear at a substrate temperature of 300 °C. The surface of the as-deposited films is dense and exhibits a fine-featured structure observed in electron microscopy images. Increasing the deposition temperature from RT to 800 °C eliminates defects and improves crystallinity, which for the films with Ga:Zn ratio close to 2 results in an increase in the optical band gap from 4.6 eV to 5.1 eV. Room temperature photoluminescence established the main peak at 3.1 eV (400 nm); a similar peak in Ga2O3 is ascribed to oxygen-vacancy related transitions. A prominent feature around 2.9 eV (428 nm) is attributed to self-activation center of the octahedral Ga-O groups in the spinel lattice of ZnGa2O4. It was found that photoluminescence from ZnGa2O4 depends significantly on the stoichiometric ratio between Ga and Zn and the deposition/annealing temperature.

Surface Modification of NiTi Alloy with Sputtered Tantalum Coatings to Improve its Hardness, Corrosion Resistance and Biocompatibility

In this research, titanium alloys including smart nitinol (NiTi) were studied. The (NiTi) alloy tends to emitting (Ni) toxic ions due to its low resistance to corrosion within the body conditions over time. For (NiTi) coating process, the magnetron plasma sputtering (DC) technique was used with Aragon gas ratio of (90%) and Oxygen of (10%) in order to coat the alloy with Tantalum and its Oxide (Ta2O[Formula: see text] thin films. This is one of the methods used to improve the biocompatibility and better adhesion stability of the membrane on the (NiTi) surface, since Tantalum and its oxides are biocompatible and are not affected by the body fluids. Hardness, corrosion and biocompatibility were tested. The results showed improvement in the nominated properties using this coating technique. The hardness for the non-coated sample was (630 Kgf/mm[Formula: see text], meanwhile, the coated sample recorded (762 Kgf/mm[Formula: see text] using sputtering power of (25 W) with a thickness of (226 nm). Tantalum and its precipitated oxides on a pillar of thickness (90.4–226 nm) also exhibited a biocorrosion enhancement, when it was immersed in a Simulated Body Fluid (SBF). The corrosion rate for the non-coated sample was (1.204 × 10[Formula: see text], meanwhile for the coated sample, its value was (3.453 × 10[Formula: see text] at sputtering power of (15 W), considered as the lower corrosion rate. The scanning electron micrographs also showed an increase in the biocompatibility for the coated nitinol alloys (NiTi) in comparison with the non-coated, ones since it showed a clear formation of Hydroxyapatite (HA) on the sample surface after immersion in the SBF. This behavior was confirmed by the XRD measurements, which presented higher HA peaks on the coated samples surface in comparison with the non-coated samples.

Effect of substrate temperature and annealing on the growth of TiO2‐x thin films deposited by using DC‐magnetron sputtering technique

In this study, the effect of annealing on the structural, surface morphology and chemical structure of titanium suboxide (TiO2‐x) thin films has been investigated. TiO2‐x films had been grown on Si substrates by DC‐magnetron sputtering with different sputter powers (75 and 100 W) at room temperature (RT) and 200°C substrate temperature (ST). The films were subsequently annealed for 1 h at 300, 400 and 500°C in vacuum. The impact of ST, post‐annealing and sputter power on crystallinity, surface morphology and chemical state of the films were studied. Grazing incidence X‐ray diffraction (GIXRD) data revealed that the films were amorphous or exhibited a very low crystalline structure while deposited at RT and even after annealing. Moreover, the films showed crystallinity while deposited at ST and exhibited an anatase‐rutile (A‐R) mix phase from anatase (A) annealed at 300°C (75 W at ST). X‐ray reflectivity (XRR) data showed that the mass density of the films increased with the annealing temperature. Images obtained using atomic force microscopy (AFM) and field emission scanning electron microscopy (FESEM) revealed that post‐annealing increased the surface roughness of the films. X‐ray photoelectron spectroscopy (XPS) analysis indicated the films were sub stoichiometric. It was also indicated that Ti was in the form of Ti4+ and Ti3+ states in all films, and the proportion of Ti4+ slightly increased after post‐annealing at 500°C. The findings showed that post‐annealing, ST and sputtering power can all affect the growth of TiO2‐x films.

Structural, optical and mechanical properties of Ti-doped Ta2O5 films for PV glass covers

Ti doped Ta2O5 thin films (TTO) with uniform thickness were prepared on photovoltaic glass substrates by DC and RF magnetron co-sputtering with different target powers. The surface morphology and microstructure of the films were characterised by scanning electron microscopy (SEM), transmission electron microscopy (TEM), atomic force microscopy (AFM). The composition of the films was analyzed by X-ray photoelectron spectroscopy. The optical parameters of the films were measured by UV–visible spectrophotometer. The hardness and Young 's modulus of the coating were tested by nanoindentation. XPS analysis shows that the main components of TTO films are TiO2 and Ta2O5. SEM and AFM results show that the surface of the TTO film is smooth and flat, with uniform elemental distribution and nanometer roughness. The SEM cross-sectional morphology shows that the TTO film presents a dense columnar structure growth. The TEM results show that the TTO films do not show bright diffraction rings and mainly exhibit an amorphous phase structure dominated by Ta2O5. The optical test results show that the maximum transmittance of TTO film can reach 94.59 %. The transmittance of TTO films shows a decreasing trend with increasing sputtering power of the target, while the opposite is true for reflectance and refractive index. The optical band gap of the TTO films is between 4.12 eV and 4.42 eV. The mechanical test results show that the hardness of the TTO film can reach up to 9.53 Gpa. The hardness of TTO film increases with the increase of target power. The H/E and H3/E2 values indicate that Ti doped Ta2O5 films are favourable for improving the resistance to plastic deformation of the films. Comprehensive analyses show that Ti doped Ta2O5 films can have both excellent optical and mechanical properties. TTO films can provide a valuable reference for the study of PV glass protective layer.

Influence of the RF magnetron sputtering power on the optical and electrical properties of AZO films

Influence of the RF magnetron sputtering power on the optical and electrical properties of AZO films

The effect of DC power and annealing on the structural, optical, and electrical characteristics of sputtered amorphous WOX thin films

Tungsten oxide (WOX) is considered as one of the promising materials due to its unique properties in widespread optoelectronic and photonic applications. This study reports on the deposition of WOX thin films via reactive magnetron sputtering technique with various low DC power and constant sputtering pressure at room temperature. XRD results reveal that an amorphous state for all the as-deposited films, while annealed films at 650 °C have WO3 monoclinic structure. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) studies indicate all as-deposited films have a dense, homogeneous, and quite smooth surface with a root-mean-square roughness (σRMS) below 1 nm. Annealing significantly affects film morphology, the formation of large grains and increasing the surface roughness. Optical parameters were examined by ultraviolet–visible (UV–Vis) spectrophotometer. Increasing sputtering power leads to a decrease in transparency value, an increase in absorbance, a reduction in penetration depth, a red shift of the fundamental absorption edge, and a reduction in the band gap energy from 3.06 eV to 2.61 eV. The annealed films exhibit a smaller optical band gap compared to as-deposited films in the range of 2.44 eV–2.93 eV. The temperature dependence of the sheet resistance corresponds to the Arrhenius law for as-deposited films with DC power of 10 W–30 W, indicating semiconducting nature. A decreasing trend in activation energy (0.283–0.055 eV) was observed with increasing DC power. All the annealed films exhibit insulator nature with a resistance of more than 100 MΩ. Analysis of these results suggests that the desired structural, optical, and electrical properties can be achieved by controlling deposition conditions.

Regulation of static and dynamic magnetic properties of amorphous FeCoZr composition gradient films by Zr doping

A series of amorphous FeCoZr composition gradient monolayer films with varying Zr contents was prepared on the Si(100) substrate using RF magnetron sputtering. The effects of the Zr sputtering power PZr on the static and dynamic magnetic properties of FeCoZr films were systematically investigated. The results demonstrate that the introduction of the Zr element as a composition gradient into FeCo films not only improves the soft magnetic properties of the films but also enhances their in-plane uniaxial magnetic anisotropy. In particular, the doping of Zr elements leads to the destruction of FeCo lattice, inducing a transformation of the films from polycrystalline to amorphous state, resulting in a significant decrease in coercivity (Hc reduced by 82%) and surface roughness (Ra reduced by 78%). In addition, as PZr increases from 30 to 70 W, the anisotropy fields Hk of the films increase from 128 to 340 Oe, and the resonance frequency fr increases from 4.24 to 5.23 GHz. By fitting the permeability spectrum using the LLG equation, it is found that FeCoZr composition gradient films exhibit a lower damping coefficient α of around 0.011–0.014, indicating the reduction of energy loss during magnetization dynamics. These findings highlight the potential applications of FeCoZr composition gradient films in the field of high-frequency microwaves.

Correlation of sputtering power with microstructure and ionic conductivity in lithium aluminum oxide thin films prepared by reactive co-sputtering

Li–Al–O thin films synthesized via the reactive magnetron co-sputtering have the potential to act as solid-state electrolytes in micro-batteries. In this paper, the constant RF power (155 W) and variable DC power (20–50 W) were applied to lithium (Li) and aluminum (Al) metal targets, respectively, in Ar/O2 atmosphere to produce films with adequate ionic conductivity. The influence of DC sputtering power on the composition, microstructure, band gap energy, ionic conductivity, and dielectric loss of films were studied in detail. X-ray photoelectron spectroscopy (XPS) showed a shift of the Li 1s peak towards higher binding energy with increasing DC power. X-ray diffraction (XRD) spectra confirmed the amorphous state for all as-deposited films, while the post-annealed films at 950 °C contain the γ-LiAlO2 phase. Field emission scanning electron microscopy (FESEM) and atomic force microscopy (AFM) images revealed that the increasing DC power had a significant impact on the film morphology, enlarging grain size and increasing surface roughness. Energy dispersive X-ray (EDX) spectroscopy showed that increasing the DC power increased the Al content. The optical properties were examined by ultraviolet–visible (UV–vis) spectroscopy, which indicated that increasing the Al content led to a blue shift of the absorption edge and an increase in the band gap energy (5.40–5.68 eV). Increasing the DC power resulted in an improvement of room-temperature conductivity by two orders of magnitude (∼2.85 × 10−9 S cm−1) and a decrease in the activation energy from 0.54 eV to 0.32 eV. These results suggest that composition and microstructure significantly affect the ionic transport in co-sputtered Li–Al–O films.

A Co-Sputtering Process Optimization for the Preparation of FeGaB Alloy Magnetostrictive Thin Films.

A co-sputtering process for the deposition of Fe0.8Ga0.2B alloy magnetostrictive thin films is studied in this paper. The soft magnetic performance of Fe0.8Ga0.2B thin films is modulated by the direct-current (DC) sputtering power of an FeGa target and the radio-frequency (RF) sputtering power of a B target. Characterization results show that the prepared Fe0.8Ga0.2B films are amorphous with uniform thickness and low coercivity. With increasing FeGa DC sputtering power, coercivity raises, resulting from the enhancement of magnetism and grain growth. On the other hand, when the RF sputtering power of the B target increases, the coercivity decreases first and then increases because of the conversion of the films from a crystalline to an amorphous state. The lowest coercivity of 7.51 Oe is finally obtained with the sputtering power of 20 W for the FeGa target and 60 W for the B target. Potentially, this optimization provides a simple way for improving the magnetoelectric coefficient of magnetoelectric composite materials and the sensitivity of magnetoelectric sensors.

Nb2O5 deposited by ion-assisted reactive magnetron sputtering for near-infrared optical coating: Power modulation and performance degradation

Nb2O5 exhibits outstanding optical properties within the near-infrared spectra, suggesting considerable potential for application in optical coatings. In this work, Nb2O5 was deposited by ion-assisted reactive magnetron sputtering. The potential of sputtering power modulated various properties of Nb2O5 was revealed. The results showed that the deposition rate rose up to 2.05 Å/s with increasing power. Optimal deposition of amorphous Nb2O5 was achieved at 450–600 W, exhibiting a defect-free surface and cross-section, accompanied by a minimal roughness of 0.36 nm and a consistent refractive index range of 2.10 to 2.35. These Nb2O5 demonstrated excellent optical performance in the near-infrared band. The reflectance of high-reflective coatings achieved 99.8 %, and the reflectance of antireflective coatings achieved 0.06 %. NbO2 was successfully deposited at 900 W, presenting a promising method for large-scale NbO2 deposition, independent of precise oxygen control. The high-temperature performance of Nb2O5 was evaluated, and the results showed significant crystallization at 750 °C, inducing a substantial rise in defects and surface roughness, exceeding 6 nm. The optical properties of Nb2O5 were affected, resulting in high-temperature performance degradation in optical coatings. Specifically, the reflection spectra of anti-reflective coatings experienced a 48 nm shift. The reflectance of high-reflective coatings decreased from 99.8 % to 41.2 %, and was accompanied by a blue shift exceeding 80 nm in the near-infrared band. The critical temperature of this dramatic change was identified to be within 450–550 °C. Typical catastrophic optical damage on the laser facet was observed. These findings provide valuable insights for the application of Nb2O5 optical coatings in near-infrared lasers.

A comprehensive calibration of integrated magnetron sputtering and plasma enhanced chemical vapor deposition for rare-earth doped thin films

A new integrated deposition system taking advantage of magnetron sputtering and electron cyclotron-plasma enhanced chemical vapour deposition (IMS ECR-PECVD) is presented that mitigates the drawbacks of each fabrication system. This tailor-made system provides users with highly homogeneous and pure thin films with less undesired hydrogen and well-controlled rare-earth concentration compared to existing methods of rare-earth doping, such as metalorganic powders, sputtering, and ion implantation. We established the first comprehensive report on the deposition parameters of argon flow and sputtering power to achieve desired rare-earth concentrations in a wide composition range of terbium (Tb) doped-silicon oxide (Tb:SiOx) matrices including silicon-rich (x < 2), oxygen-rich (x > 2), and stoichiometric silicon oxide (x = 2). The deposition parameters to fabricate crystalline structure (Tb2Si2O7) in oxygen-rich samples are reported where Tb ions are optically active. IMS ECR-PECVD pushes the solubility limit of the rare-earth dopant in silicon films to 17 at.% for the desired future nanophotonic devices.Graphical

The microstructure and mechanical properties of He charged Al films fabricated by HiPIMS/DCMS co-sputtering

Although magnetron sputtering is an effective method to prepare helium (He) charged films, due to the shadowing effect and low plasma density, the films prepared by this method are high porosity and residual stress. In order to solve this problem, the microstructure and properties of He charged aluminum (Al) thin films deposited by the direct current magnetron sputtering (DCMS) and high power impulse magnetron sputtering (HiPIMS)/DCMS co-sputtering were investigated carefully. The results show that, even with the same concentration of He content, He charged film deposited by HiPIMS/DCMS show relatively lower hardness than that of He charged films by DCMS, which the difference is about 0.75 GPa. This is mainly because increased gain size and decreased the number of dislocation loops, due to strong migration ability on the growth surface in HiPIMS/DCMS process. A denser, less columnar structure of He charged film was prepared by the HiPIMS/DCMS co-sputtering, which might help to promote the research on the properties of metal materials containing He bubbles.

Effect of Si content on the microstructure and high temperature oxidation resistance of TiAlCrNiSi high-entropy alloy films synthesized by multi-target magnetron co-sputtering

In this study, we prepared TiAlCrNiSi high-entropy alloy films (HEFs) with different contents of four elements by multi-target magnetron co-sputtering with regulated sputtering power, and the elemental contents of the films all met the high-entropy range (5 at%−35 at%). Scanning electron microscopy (SEM) and atomic force microscopy (AFM) showed that the surface of the films was relatively smooth, the increase of sputtering power and Si element in the films reduced the roughness of the films. This demonstrates the effect of Si in refining the grains and reducing the roughness of the film. X-ray diffraction (XRD) showed that the average grain size of films decreases with the increase of Si content. This phenomenon proves that Si has the effect of refining grains and reducing the roughness of the film. The TC4 substrate and the films were treated at 700 ℃ for 50 h. It was found that TiAlCrNiSi HEFs could improve the high temperature oxidation resistance of TC4. The mechanism of oxidation resistance of the films was investigated by XRD, X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM), and it was found that the generation of dense oxides Al2O3, Cr2O3 and SiO2, the grain refining effect of Si and the appearance of amorphous structure were the main reasons for the increased oxidation resistance.

Hard and Highly Adhesive AlMgB14 Coatings RF Sputtered on Tungsten Carbide and High-Speed Steel

We report a new industrial application of aluminum magnesium boride AlMgB14 (BAM) coatings to enhance the hardness of tungsten carbide ceramic (WC-Co) and high-speed steel tools. BAM films were deposited by RF magnetron sputtering of a single dense stoichiometric ceramic target onto commercial WC-Co turning inserts and R6M5 steel drill bits. High target sputtering power and sufficiently short target-to-substrate distance were found to be critical processing conditions. Very smooth (6.6 nm RMS surface roughness onto Si wafers) and hard AlMgB14 coatings enhance the hardness of WC-Co inserts and high-speed R6M5 steel by a factor of two and three, respectively. Complete coating spallation failure occurred at a scratch adhesion strength of 18 N. High work of adhesion and low friction coefficient, estimated for BAM onto drill bits, was as high as 64 J/m2 and as low as 0.07, respectively, more than twice the surpass characteristics of N-doped diamond-like carbon (DLC) films deposited onto nitride high-speed W6Mo5Cr4V2 steel.

ZnO Deposition on Silicon and Porous Silicon Substrate via Radio Frequency Magnetron Sputtering

Nanostructured Zinc Oxide (ZnO) was deposited on silicon (c-Si) and macroporous silicon (m-PS) using a radio frequency (RF) reactive magnetron sputtering technique. Two RF powers of 60 and 80 W were selected for ZnO deposition on the substrates. Furthermore, the c-Si and m-PS substrate temperatures were kept at 500 and 800 °C, respectively. The morphological, structural, and optical characteristics of the samples were studied using scanning electron microscopy (SEM), an X-ray diffractometer (XRD), X-ray photoelectron spectroscopy (XPS), and photoluminescence spectroscopy (PL). The SEM images revealed the formation of ZnO nanorods on the c-Si and ZnO nanostructures constituted by the assembly of nanorods. It has been found that the increasing RF sputtering power caused the rise in the residual stress. In addition, the increase in the deposition temperature caused an improvement in the arrangement of the crystals, which was attributed to the decrease in crystal defects.