High-rate reactive high-power impulse magnetron sputtering of Ta–O–N films with tunable composition and properties

Abstract

High-power impulse magnetron sputtering of a planar Ta target in various Ar+O2+N2 gas mixtures was investigated at an average target power density close to 50Wcm−2 during a deposition. A strongly unbalanced magnetron was driven by a pulsed dc power supply operating at the repetition frequency of 500Hz and the average target power density of up to 2.4kWcm−2 in a pulse with a fixed 50μs duration. Si(100) and glass substrates were at a floating potential, and the substrate temperatures were less than 285°C. A pulsed reactive gas (O2 and N2) flow control made it possible to produce high-quality Ta–O–N films of various elemental compositions with high deposition rates of 97–190nm/min. The film compositions (in at.%) were varied gradually from Ta28O71 with less than 1at.% of H to Ta38O4N55 with 3at.% of H. The Ta27O40N31 films with 2at.% of H, which were produced at the 50% N2 fraction in the reactive gas flow with the highest deposition rate of 190nm/min achieved, were nanocrystalline with an optical band gap of 2.5eV and hardness of 8GPa. These films with a shift of the absorption edge to 500nm are potential candidates for application as visible-light driven photocatalysts.