Deposition of nanoporous BiVO4 thin-film photocatalyst by reactive magnetron sputtering: Effect of total pressure and substrate
(1. School of Metallurgy and Materials Engineering, College of Engineering, University of Tehran, Tehran, Iran;
2. Institut FEMTO-ST, UMR 6174, CNRS, Univ. Bourgogne Franche-Comté, 15B, Avenue des Montboucons, 25030 Besan？on, France)
2. Institut FEMTO-ST, UMR 6174, CNRS, Univ. Bourgogne Franche-Comté, 15B, Avenue des Montboucons, 25030 Besan？on, France)
Abstract: Nanoporous BiVO4thin films were deposited using reactive magnetron sputtering in Ar and O2 atmosphere, on various substrates, employing pulsed direct-current (DC) power supplies applied to metallic Bi and V targets for rapid deposition. The procedure was followed by a post-annealing treatment in air to crystallize the photoactive monoclinic scheelite structure. The influence of total pressure and substrate on the crystal structure, morphology, microstructure, optical and photocatalytic properties of the filmswas investigated. The crystallization of monoclinic scheelite structure deposited on fused silica substrate starts at 250 °C and the films are stableup to 600 °C. The morphology of the films is rather dense, despite at the high sputtering pressure (>2 Pa), with embedded nanopores. Among the thin films deposited on fused silica, the one deposited at 4.5 Pa exhibits the highest porosity (52%), with the lowest bandgap (2.44 eV) andit shows the highest photocatalytic activity in the degradation of Rhodamine-B (26% after 7 h) under visible light irradiation. The film deposited on the silicon substrate exhibits the highest photoactivity (53% after 7 h). Lack of hypsochromic shift in the UV-Vis temporal absorption spectra shows the dominance of the chromophore cleavage pathway in the photodecomposition.
Key words: photocatalysis; BiVO4; thin film; sputtering; nanoporous film