Deposition of nanoporous BiVO4 thin-film photocatalyst by reactive magnetron sputtering: Effect of total pressure and substrate
Résumé
Nanoporous BiVO4 thin 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 films
was investigated. The crystallization of monoclinic scheelite
structure deposited on fused silica substrate starts at 250 °C and
the films are stable up 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) and it 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.
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