Laser irradiation-induced alpha to delta phase transformation in Bi_2O_3 ceramics and nanowires

Abstract

The α-Bi_2O_3 to σ- Bi_2O_3 phase transformation has been locally induced by laser irradiation in ceramic samples and single-crystal nanowires of this oxide. The threshold power densities necessary to induce this transformation, as well as the corresponding transformation kinetics and its temporal stability, have been investigated in both kinds of samples by micro-Raman spectroscopy. The appearance of the delta phase was also monitored by spatially resolved photoluminescence spectroscopy. An emission band peaked near 1.67 eV, not observed in α-Bi_2O_3, is tentatively attributed to to σ- Bi_2O_3 near band gap transitions.