Photochemical solution deposition of β-Bi2O3 thin films

Abstract

The non-equilibrium β-Bi2O3 polymorph is stabilized in thin films by a photochemical synthesis method. A strong ultraviolet-absorbing bismuth(III)-N-methyldiethanolamine complex is synthesized in solution as an ideal precursor for the β-Bi2O3 phase. Ultraviolet-light induces the formation of an amorphous —Bi—O—Bi— continuous network in the films deposited from the former solution that easily converts into the β-Bi2O3 polymorph at a temperature as low as 250 °C. The room temperature stabilization of the β-Bi2O3 phase is confirmed by their structural characterization using four-circle X-ray diffractometry. This study unequivocally identified the tetragonal crystal structure of the β-Bi2O3 polymorph in the films. The high phase purity of these β-Bi2O3 films is responsible for their exceptional visible-light photocatalytic activity, thus enabling the applications of the films of this metastable phase at room-temperature conditions. Photosensitive precursor solutions containing a photosensitive Bi(III)-N-methyldiethanolamine complex lead to the stabilization of the high-temperature β-Bi2O3polymorph in films on Pt-coated silicon substrates prepared at a low temperature of 250 °C using UV-irradiation.