Radio Frequency Reactive Magnetron Sputtering Research Articles

Pseudo-capacitance of silver oxide thin film electrodes in ionic liquid for electrochemical energy applications

Abstract The energy storage potential of silver oxide (Ag2O) thin film electrodes, deposited via radio frequency reactive magnetron sputtering, was investigated in an ionic electrolyte (1-Ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide for supercapacitor applications. X-ray diffraction (XRD), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS) and Fourier Transform infrared spectroscopy (FTIR) tools were used to evaluate the structural and oxide phases present in the sputtered silver oxide thin film electrodes. The growth mode, morphology, surface area, wettability and surface energy of the deposited nano-structure silver oxide thin films were confirmed by scanning electron microscope (SEM) data, the Brunauer-Emmett-Teller (BET) analysis and by goniometer and tensiometer studies. Furthermore, the ion diffusion, the Faradaic redox reactions and the capacitance of the sputtered thin films exposed to 1-Ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ionic electrolyte, were monitored with electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV). The SEM micrographs depict that silver oxide thin films exhibit a columnar growth mode. The wettability analysis reveals that Ag2O thin films are hydrophilic, an indication for excellent electrochemical behaviour. Cyclic voltammetry measurements show that Ag2O thin films exhibit a specific capacitance of 650 F/g at higher sputtering power, demonstrating its promising potential as an active electrode for supercapacitor applications.

Iron-ion irradiation effects on microstructure of yttrium oxide coating fabricated by magnetron sputtering

Ceramic coatings have been investigated as tritium permeation barrier for several decades; however, there is little knowledge about irradiation effects on the coatings. In this study, yttrium oxide coatings were fabricated on reduced activation ferritic/martensitic steel substrates by radio frequency reactive magnetron sputtering, and their microstructures were investigated after iron-ion irradiation under various parameters with damage concentration of up to 20 displacement per atom. The formation of voids and an amorphous layer was confirmed in all the irradiated samples. In addition, it was found that irradiation-induced grain growth proceeded with damage concentration, and the increase of grain size was proportional to damage concentration. Furthermore, a layer with few voids formed between the crystallized and amorphous layers for the irradiated samples with higher incident energy or higher dose. Defect recovery and heat-driven grain growth and/or crystallization occurred for the sample irradiated at 500 °C, resulting in a larger average grain size than those irradiated at room temperature. Further consideration of irradiation effects to the coatings under fusion-relevant irradiation conditions is necessary.

Effects of helium implantation on mechanical properties of (Al0.31Cr0.20Fe0.14Ni0.35)O high entropy oxide films**Project supported by the National Natural Science Foundation of China (Grant Nos. 11775150 and 11505121).

It is widely accepted that helium (He) bubbles can prevent dislocations from moving and causing hardening and embrittlement of the material. However, He can affect the mechanical properties of materials in various ways. In this work, ultrafine nanocrystal high entropy oxide (HEO) films with He implantation are prepared by using a radio frequency (RF) reactive magnetron sputtering system to investigate the effects of He bubbles located at grain boundary on the mechanical properties of the films. The mechanical properties of the HEO films are investigated systematically via nanoindentation measurements. The results indicate that the grain boundary cavities induced by He implantation can degrade the hardness, the elastic modulus, and the creep resistance of the HEO films. The mechanical properties of the HEO films are sensitive to the interaction between the He bubbles and the dominating defects.

Formation mechanism and thermoelectric properties of CaMnO3 thin films synthesized by annealing of Ca0.5Mn0.5O films

A two-step synthesis approach was utilized to grow CaMnO3 on M-, R- and C-plane sapphire substrates. Radio-frequency reactive magnetron sputtering was used to grow rock-salt-structured (Ca, Mn)O followed by a 3-h annealing step at 800 °C in oxygen flow to form the distorted perovskite phase CaMnO3. The effect of temperature in the post-annealing step was investigated using x-ray diffraction. The phase transformation to CaMnO3 started at 450 °C and was completed at 550 °C. Films grown on R- and C-plane sapphire showed similar structure with a mixed orientation, whereas the film grown on M-plane sapphire was epitaxially grown with an out-of-plane orientation in the [202] direction. The thermoelectric characterization showed that the film grown on M-plane sapphire has about 3.5 times lower resistivity compared to the other films with a resistivity of 0.077 Ωcm at 500 °C. The difference in resistivity is a result from difference in crystal structure, single orientation for M-plane sapphire compared to mixed for R- and C-plane sapphire. The highest absolute Seebeck coefficient value is − 350 µV K−1 for all films and is decreasing with temperature.

Two dimensional α-MoO3 nanosheets decorated carbon cloth electrodes for high-performance supercapacitors

The production of two dimensional (2D) layers, especially nanosheet is of significant importance to develop supercapacitors. Herein, reactive radio-frequency magnetron sputtering method is employed to the 2D α-MoO3 nanosheet preparations on carbon cloth substrate. As-prepared 2D α-MoO3 nanosheet coated carbon cloth has been characterized by XRD, UV–vis, Raman, FE-SEM, EDX techniques. Supercapacitor performance of 2D α-MoO3 nanosheet coated carbon cloth is tested from cyclic voltammetry (CV) and galvanostatic charge discharge (GCD) techniques in 1.0 M aqueous Na2SO4 electrolyte. 2D α-MoO3 nanosheet coated carbon cloth delivers the specific capacitance 240 F g−1 at current density of 1.5 mA cm−2 with capacity retention of 78.8% for 5000 cycles at 2.5 mA cm−2. Compared to bare carbon cloth and α-MoO3 decorated carbon cloth at room temperature, 2D α-MoO3 nanosheet coated carbon cloth exhibits much higher specific capacity, superior cyclability, and good rate capability, highlighting the advantages of hierarchical nanosheet and high surface area in the MoO3 structure.

Well-defined (0001)-oriented aluminum nitride polycrystalline films on amorphous glass substrates deposited by ion plating with direct-current arc discharge

500-nm-thick aluminum nitride (AlN) polycrystalline films were deposited on amorphous glass substrates at a substrate temperature of 200 °C by ion plating (IP) with direct-current (DC) arc discharge, radio frequency (RF) and DC reactive magnetron sputtering (MS). The IP technique enables a very high deposition rate of 113 nm/min compared with that of MS techniques. The structural properties of AlN films were investigated by X-ray diffraction (XRD), Raman spectroscopy, and electron probe micro analyzer (EPMA) measurements. XRD results show that AlN films with a columnar grain structure deposited by IP have a texture with a well-defined (0001) orientation between grains normal to the substrate, whereas AlN films grown by MS have a mixture of (0001) planes and planes with other orientations. Raman spectroscopy and XRD measurement results revealed high residual compressive stress in AlN films deposited by IP compared with that in AlN films grown by MS. The analysis of the data obtained by EPMA measurement showed that IP produces AlN films with a small amount of remaining oxygen species, whereas MS produces AlN films with a large amount of residual oxygen species.

Fabrication of nanoporous thin films via radio-frequency magnetron sputtering and O2 plasma ashing

In this study, we report a new method for fabricating nanoporous thin films. In the first step, metal–carbon thin films were prepared by radio-frequency reactive magnetron sputtering, using Cu, Ni, and Ti targets as the metal sources and CH4 gas as the carbon source during the co-deposition process. In the second step, the metal–carbon films were then oxidized by an oxygen plasma generated with a flowing a gas mixture of Ar and O2, and nanoporous metal–oxide films were obtained by removing carbon atoms from the metal–carbon thin films. The pores in the films varied with the amount of carbon in the film surface, and mesopores grew to lager macropores as the flow rate of CH4 was increased. Depending on the film composition, the calculated porosity varied from 50% to 90%. With advantages such as a wide range of suitable raw materials and good reproducibility, this fabrication method is expected to offer a new approach to the commercial production of nanoporous materials.

The influence of Cr content on the phase structure of the Al-rich Al-Cr-O films deposited by magnetron sputtering at low temperature

The Al-rich Al-Cr-O films were directly deposited on Si(100) substrate by reactive radio frequency magnetron sputtering (RFMS) using Al-Cr alloy targets. The elemental composition and phase structure of the films deposited from alloy targets with different Cr content at low substrate temperature were analyzed by electron probe microanalysis (EPMA), grazing incident X-ray diffraction (GIXRD) and transmission electron microscopy (TEM). The results show that the single corundum structured (Al0.7Cr0.3)2O3 solid solution films could be successfully synthesized by sputtering the Al70Cr30 target at low substrate temperature of 550 ℃. The phase structures of the films deposited from Al80Cr20 target exhibit a mixture of Al-rich α-(AlxCr1-x)2O3, Cr-rich α-(AlxCr1-x)2O3, γ-Al2O3 and amorphous phases when the substrate temperature was lower than 550 ℃. The formation of γ phase could be suppressed at 600 ℃ while few amorphous alumina still remains in the film. In order to deposit single phase corundum-type Al-rich (AlxCr1-x)2O3 solid solution films at low temperature, the sufficient Cr content in the films is required.

Multifunctional monoclinic VO2 nanorod thin films for enhanced energy applications: Photoelectrochemical water splitting and supercapacitor

Monoclinic VO2 nanorod thin films were deposited on indium‑tin-oxide-coated glass substrates using radio-frequency reactive magnetron sputtering at a substrate temperature of 300°C and various O2 flow rates. The thin films were characterized via standard analysis techniques. The VO2 thin films exhibited a highly crystalline monoclinic phase with an indirect band gap of ~1.73eV. At optimized O2 flow rate (4sccm), the thin films was observed nanorod structures, exhibited a remarkable photocurrent of ~0.08mAcm−2 during photoelectrochemical water splitting in the visible region. Electrochemical performance tests of the nanorod films revealed a specific capacitance of ~486mFcm−2 at a scan rate of 10mVs−1. In addition, amperometric I–t curves showed that VO2 thin film electrodes were highly stable during the photo-oxidation process. The nanorod films also exhibited a good specific capacitance of ~120mFcm−2 after 5000cycles at a scan rate of 100mVs−1. The photocurrents during photoelectrochemical water splitting and the specific capacitance of VO2 thin films deposited at O2 flow rates of 2 and 6sccm were 0.06 and 0.07mAcm−2 and 398 and 37mFcm−2, respectively. The films deposited under Ar at 8sccm and O2 at 4sccm showed the highest photoelectrochemical water splitting performance and specific capacitance, owing mainly to their nanorod-like morphology.

Development of Microarc Oxidation/Sputter CeO₂ Duplex Ceramic Anti-Corrosion Coating for AZ31B Mg Alloy.

A duplex CeO₂/MAO coating was deposited on AZ31B magnesium alloy through microarc oxidation and reactive radio frequency magnetron sputtering. The microstructure and chemical composition of the proposed coating were investigated through scanning electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy. The CeO₂/MAO coating was approximately 580 nm in thickness and showed fewer micropores and defects than those the MAO coating presented. The properties of corrosion resistance were assessed using the polarization test, electrochemical impedance spectroscopy, and the neutral salt spray test. The CeO₂/MAO duplex coating had the lowest corrosion current density of 3.25×10-9 A/cm² and the highest polar resistance, approximately four orders of magnitude higher than that of the uncoated sample. Electrochemical measurements suggested that CeO₂ coating can serve as a strong physical barrier between the corrosion medium and the Mg alloy.

The Association Between Medication Adherence and Knowledge About Medication Wastage in The Community

Nitrogen doped ZnCdO films [ZCO:N] have been grown on quartz substrates by radio frequency (RF) reactive magnetron sputtering technique, and the effect of the ratio of nitrogen to argon gas flow [N2:Ar] on their electrical, microstructure and optical properties were investigated by Hall effect, energy dispersive X-ray spectroscopy (EDX), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), transmission electron microscope (TEM), optical absorbance and photoluminescence (PL) measurements. The results indicate that all the ZCO:N films are of hexagonal wurtzite structure with highly (002) preferential orientation. As the N2:Ar increases from 0:1 to 4:1, the absorption edge for the samples exhibits blue shift. Hall effect measurement results indicate that the N2:Ar exerts an immense influence on the p-type conduction conversion for ZCO:N film. It is found that ZCO:N film deposited at the N2:Ar of 1:2 shows the optimal p-type behavior, which has a carrier concentration of 1.10×1017 cm−3, a mobility of 3.28 cm2V−1s−1 and a resistivity of 17.3 Ω cm. Compared with the other samples, ZCO:N film fabricated at the relatively lower N2:Ar possesses the superior crystal quality, luminescent and electrical properties. Additionally, a possible mechanism of p-type conduction for ZCO:N film was discussed in this work.

Doubling the thermoelectric power factor of earth abundant tin nitride thin films through tuned (311) orientation by magnetron sputtering

Thermoelectricity has been considered a promising green energy source for mankind. This method of energy generation poses challenges due to scarcity of the constituent elements of the efficient thermoelectric materials. The development of high performance materials for thermoelectric generation is limited with the co-responsive nature of transport parameters. In this work, earth abundant tin nitride (Sn3N4) thin films were deposited by reactive radio frequency magnetron sputtering and investigated its thermoelectric response. The electron bands of the prepared thin films were actively aligned to optimize the trade-off between the Seebeck coefficient and electrical conductivity for the enhancement of power factor (S2σ). The reduction in nitrogen gas pressure of reactive sputtering reduced both working pressure and the amount of reactive nitrogen. This experimental approach of combined effect introduced preferred orientation (PO) and stoichiometric variations simultaneously in the fabricated thin films. The increased scattering associated with preferred orientation and increased carrier concentration associated with stoichiometric variations converged the conduction band along with shifting of Fermi energy toward the conduction band minimum. The engineered band structure of tin nitride thin film realized over 2-fold hike in power factor up to 390 μW/m-K2 at 250 °C with a Seebeck coefficient of −144 μV/K and resistivity of 53.11 μΩ-m. This study reveals the potential nature of the earth abundant nitrides in the field of renewable energy generation. The experimental strategy adopted in this study provides an alternative approach to engineer the band structure of a thin film for optimized transport parameters.

Substrate Temperature Dependent Properties of Sputtered AlN:Er Thin Film for In-Situ Luminescence Sensing of Al/AlN Multilayer Coating Health.

The integrity and reliability of surface protective coatings deposited on metal surface could be in-situ monitored via the attractive luminescence sensing technique. In this paper, we report the influence of substrate temperature on the properties of erbium (Er) doped aluminum nitride (AlN) film, which could be applied as a luminescent layer for monitoring the health of multilayered Al/AlN coating. The AlN:Er films were deposited via reactive radio-frequency magnetron sputtering, and the silicon substrate temperature was varied from non-intentional heating up to 400 °C. The composition, morphology, crystalline structure, and dielectric function of the AlN:Er films deposited under these different substrate temperature conditions were studied. These properties of the AlN:Er films show strong correlation with the substrate temperature maintained during film fabrication. The obtained AlN:Er films, without further annealing, exhibited photoluminescence peaks of the Er3+ ions in the visible wavelength range and the strongest photoluminescence intensity was observed for the AlN:Er film deposited with the temperature of substrate kept at 300 °C. The results demonstrated in this work offer guidance to optimize the substrate temperature for the deposition of AlN:Er film for future application of this sensing technique to thin metal components.

Non-uniform Excitation States in Photoinduced Deformation of Amorphous Carbon Nitride Films

Amorphous carbon nitride (a-CNx) films prepared via reactive radio frequency magnetron sputtering deform under on–off visible light illumination. We investigate the relationship between photoinduced deformation and surface electrical states via scanning electron microscopy with Ar+ laser irradiation (SEM-L). Two samples with different levels of photoinduced deformation are prepared. For the film with small photoinduced deformation, uniform secondary electron emission is observed on the film surface, regardless of whether the laser is on or off. On the a-CNx film, which has fifty times larger photoinduced deformation than the previous film, light and dark patches, similar to a speckle pattern, appear on the film surface in SEM-L images. This anomalous phenomenon indicates non-uniformity of the electrical states excited by laser light irradiation. A size of the patches is well correlated with an inhomogeneous distribution of sp3C and sp2C, Isp3C/Isp2C, obtained using soft X-ray emission spectroscopy (SXES). Simultaneously, temporal decrease in the sp3C component under illumination is obtained via SXES.

Orientation of AlN Grains Nucleated on Different Diamond Substrates by Magnetron Sputtering

For AlN/diamond structure, the crystal quality of diamond substrates is of great importance for the epitaxial growth of AlN. In this paper, c‐axis‐oriented AlN films are deposited on diamond with different crystal quality by radio frequency (RF) reactive magnetron sputtering. The effects of the microstructure of diamond substrates on the orientation of AlN are studied. The results show that the crystal quality of the diamond films greatly affects the growth behavior of AlN. The surface defects of diamond, such as the amorphous phase, will cause the growth direction of AlN to deviate from the c‐axis, resulting in the disorder of grain orientation. Meanwhile, diamond crystal orientation also has influence on the growth of AlN. The (111) oriented grains of diamond are beneficial to the c‐axis growth of AlN. The interface of AlN nucleation and initial growth plays a vital role in final performance of the films, where there is a transition zone from randomly oriented AlN grains to c‐axis‐oriented grains. The suitable diamond substrate can eliminate the transition zone, and can lead to AlN films with high‐degree c‐axis orientation.

Room temperature cathodoluminescence quenching of Er3+ in AlNOEr

This paper reports a cathodoluminescence (CL) spectroscopic study of nanogranular AlNOErx samples with erbium content, x, in the range 0.5–3.6 at%. A wide range of erbium concentration was studied with the aim of understanding the concentration quenching of CL. The composition of thin films, deposited by radiofrequency reactive magnetron sputtering, was accurately determined by Energy Dispersive X-ray Spectroscopy (EDS). CL emission was investigated in the extended visible spectral range from 350 nm to 850 nm. The critical concentration of luminescent activator Er3+ above which CL quenching occurs is 1%; the corresponding critical distance between Er3+ ions in AlNOErx is about 1.0 nm. The quenching mechanism is discussed. We discount an exchange-mediated interaction in favour of a multipole-multipole phonon-assisted interaction.

Fabrication of an all solid-state electrochromic device using zirconium dioxide as an ion-conducting layer

Zirconium dioxide (ZrO2) thin films were deposited onto glass substrates, indium tin oxide (ITO) coated glass substrates and nickel oxide (NiO) / ITO / glass structures by reactive radio frequency (RF) magnetron sputtering using a zirconium target at room temperature. The deposition power was held at 75 W and the influence of deposition pressure and film thickness on the properties of the ZrO2 films were investigated. Optical, electrochemical and electrochemical impedance spectroscopy measurements of the ZrO2 films were performed and the electrochromic behavior of a half-cell structure of ZrO2 / NiO / ITO / glass was investigated in a wide spectral range. The amount of inserted/extracted charges into/from each film during bleaching/coloring process were investigated in detail. The highest coloration efficiency (24.3 cm2/C) and optical modulation (42.8%) at a wavelength of 550 nm were found for a ZrO2 / NiO / ITO / glass structure having a ZrO2 film with a thickness of 100 nm, deposited at 4.00 Pa. Finally, a unique design of an all solid-state electrochromic device with a configuration of ITO / NiO / wet lithiated ZrO2 / dry lithiated tungsten oxide (WO3) / ITO / glass was fabricated. The optical modulation of the device was 53% at 550 nm for the applied potentials of ±3 V.

Glancing Angle Deposition Effect on Structure and Light-Induced Wettability of RF-Sputtered TiO₂ Thin Films.

Crystalline TiO2 films were prepared on unheated glass substrates by radio frequency (RF) reactive magnetron sputtering at normal angle of incidence (a = 0°) and at glancing angle (a = 87°). The effect of the glancing angle on the structure, microstructure, and wetting properties of the films was investigated. The inclination of the substrate led to phase transformation of the deposited films from rutile to either rutile/anatase or anatase, depending on the working pressure. Extreme shadowing at 87° results in a remarkable increase of the films’ porosity and surface roughness. The mechanism of the glancing-angle-induced crystalline phase formation is thoroughly discussed based on the thermodynamic, kinetic, and geometrical aspects of the nucleation and is related with the microstructural changes. Both crystalline phase and microstructure significantly affect the wetting properties of the TiO2 films. Glancing-angle-deposited anatase TiO2 exhibits a high degree of porosity and roughness, a high rate of UV-induced wettability conversion, and a long-term highly hydrophilic nature in dark. Therefore, anatase TiO2 is potentially a good candidate for applications as dye-sensitized solar cells (DSSC)/perovskite solar cells, microfluidic devices, and self-cleaning surfaces prepared on thermosensitive substrates.

Structural, Optical and Electrical Properties of Polycrystalline CuO Thin Films Prepared by Magnetron Sputtering

Cupric oxide thin films were deposited on silicon and sapphire substrates by reactive radio frequency magnetron sputtering at different substrate temperatures. The results showed that the CuO films were composed of different sizes of CuO nano-grains and the CuO films deposited on Si substrates showed a more dense and uniform surface than that deposited on Al2O3 substrates. It was noted that both the CuO films deposited on Si and Al2O3 substrates revealed only CuO related diffractions and the preferred orientation of the CuO films changed from (002) to (111) as the substrate temperature increased. Moreover, the carrier concentration was 1.141 × 1018 cm−3 and the mobility was 0.401 cm2/v s at 450°C substrate temperature. The controllable electrical properties of the films can be achieved by the variation of crystal quality arising from the substrate temperature.

Substrate and annealing temperature dependent electrical resistivity of sputtered titanium nitride thin films

We have studied the electrical resistivity and the temperature coefficient of resistance (TCR) of titanium nitride (TiNx) thin films deposited by radio-frequency (RF) reactive magnetron sputtering from a high purity titanium target in a nitrogen-argon gas mixture environment with high nitrogen-to-argon ratio (20:1). The electrical resistivity and TCR are measured from room temperature to 500 °C for films deposited with substrate temperatures of 25 °C, 350 °C and 600 °C. After deposition, some films are annealed at 600 °C for four hours either with or without breaking the vacuum. The structural stability of the films was examined by measuring electrical resistivity from room temperature to 500 °C repeatedly up to four cycles. Selected films were further characterized by Rutherford backscattering, X-Ray diffraction, and Raman spectroscopy. Our results show that RF sputtered TiNx films with good electrical resistivity and temperature-stable TCR for high-temperature applications of conductive diffusion barrier and temperature sensing can be produced. We conclude that high substrate temperature, high annealing temperature, and annealing without breaking the vacuum yield optimal structural stability and electrical resistivity. High mass density is also important to prevent oxidation and degradation of electrical performance.