Laser irradiation-induced α to δ phase transformation in Bi2O3 ceramics and nanowires

The alpha-Bi2O3 to delta-Bi2O3 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 alpha-Bi2O3, is tentatively attributed to delta-Bi2O3 near band gap transitions. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4747198]