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• AlCuNiTiZr high entropy alloy films deposited by magnetron sputtering • AlCuNiTiZr films showing excellent anti-corrosion properties • A scheme of a reasonable equivalent electrical circuit proposed In this study, corrosion-resistant AlCuNiTiZr high-entropy alloy (HEA) films were deposited by direct current magnetron sputtering. The films were found to be amorphous. Corrosion resistance of the films in 0.5 M H 2 SO 4 solution were investigated and compared with 316L stainless steel. The minimum corrosion current density of the HEA films was about one order of magnitude lower than that of 316L stainless steel. The inductively coupled plasma optical emission spectra showed that the concentrations of Cu, Ni, Ti and Zr ions in the corrosion solution were as low as 10−7 mol / L, while the concentration of Al ions was 7.5×10−6 mol / L. It is revealed that two passivation layers were formed on the surface from electrochemical impedance spectroscopy and equivalent electrical circuit, and the passivation layers resulted in protective effect on the AlCuNiTiZr HEA films in the sulfuric acid solution. [ABSTRACT FROM AUTHOR]

Solidly mounted resonators (SMRs) rely on high-quality Bragg reflectors, for which tungsten has been used as the high acoustic impedance layer. It is unclear about the effects of tungsten phases on the acoustic performance of SMRs. In this study, high-quality flat layers of different phase structures of W (α-W and β-W) are obtained by changing the post-growth annealing temperature and magnetron sputtering parameters. Our results show that the α-W has higher Young's modulus and acoustic impedance (205 GPa and 63 kg/m2s) than β-W (170 GPa and 57 kg/m2s). These small differences result in amplified difference in acoustic performance of Bragg reflectors using tungsten (W) as their high-impedance layer. Our tests show that the SMR of α-W Bragg reflector has a higher return loss (18.4 dB) at around 2.75 GHz and higher quality factor (687) than that of β-W Bragg reflector (9.2 dB and 228, respectively). • Different phase structures of W are obtained by changing the annealing temperature and magnetron sputtering parameters. • The acoustic impedance of α-W is 10% higher than that of β-W. • The influence of α- and β-W phases on performance of SMR devices is different. [ABSTRACT FROM AUTHOR]

Zirconium aluminum nitride thin films (Zr 0.11 Al 0.89 N) were prepared on different substrates using unbalanced DC reactive magnetron co-sputtering. The influence of sputtering atmosphere, including N 2 /Ar-flow ratio and their total pressure, on the crystalline structure and the electrical properties of the Zr 0.11 Al 0.89 N films has been investigated. In this work, the optimal N 2 /Ar-flow ratio is 1:1 and the optimal total pressure is 0.5 Pa. The resultant Zr 0.11 Al 0.89 N films have a wurtzite structure that is preferentially oriented along the c-axis and have uniform grains. The dielectric constant, dielectric loss, leakage current density and resistivity of the Zr 0.11 Al 0.89 N films reach ~ 16, ~ 0.01 (in a frequency range of 10 3 –10 6 Hz), 3.0 × 10 − 8 A/cm 2 and 1.92 × 10 12 Ω·cm, respectively, which are all superior to those under suboptimal conditions. Moreover, the Zr 0.11 Al 0.89 N films exhibit higher dielectric constants, as well as much lower dielectric loss and leakage current density compared to that of pure AlN films. [ABSTRACT FROM AUTHOR]

Highly c-axis oriented aluminum nitride films have been successfully grown by DC magnetron reactive sputtering with unbalanced magnetic fields at room temperature. It is shown that the application of unbalanced magnetic fields can improve the extent of preferential growth along the c-axis, and form AlN films with denser, larger grains and smaller surface roughness, compared to that grown with balanced magnetic fields. The AlN films prepared under optimized growth conditions have a dielectric constant of approximately 10.5 and a dielectric loss of 0.02 in the frequency range of 10 3 –10 6 Hz, and a leakage current of <1 × 10 −7 A/cm 2 at 5 V bias voltage, all the dielectric and insulating properties being superior to the films synthesized with balanced magnetic fields. In this work, the unbalanced magnetic fields are induced by adding an electromagnetic coil on the magnetron cathode. [ABSTRACT FROM AUTHOR]

AlCu x NiTiZr 0.75 high entropy alloy (HEA) films were deposited by magnetron sputtering with an alloy target in combination with a pure Cu metal target. The purpose of this study was to reduce electrical resistivity of the HEA films while maintaining mechanical properties and corrosion resistance by adjusting Cu content of the HEA. We found that the AlCu x NiTiZr 0.75 HEA films were amorphous and displayed a homogeneous or columnar microstructure along the cross sections. The increase of Cu content changed the electronic structure of the HEA films, so that the resistivity decreased sharply to 66 μΩ·cm at x = 1.4. The hardness-to-elastic modulus ration H/E, an indicator of a material's ductility, attained the maximum value at x = 1.4. Although the corrosion current densities increased with x , they were all below 10−6 A/cm2 in 3.5 wt% NaCl solution, indicating good corrosion resistance. These findings assumably help expand industrial application of HEA films, particularly when conductivity is required for the functionality of the films. • Amorphous AlCuxNiTiZr 0.75 high entropy alloy films were deposited by co-sputtering. • AlCuxNiTiZr 0.75 films maintained high hardness and good corrosion resistance. • The electronic structure of AlCuxNiTiZr 0.75 films were changed, and the lowest resistivity was 66 μΩ·cm. [ABSTRACT FROM AUTHOR]