Formation of β-Bi2O3 and δ-Bi2O3 during laser irradiation of Bi films studied in-situ by spatially resolved Raman spectroscopy

The formation of different phases of Bi2O3 induced by laser irradiation of Bi films has been assessed in situ by micro-Raman spectroscopy as a function of laser wavelength, power density and irradiation time. Raman mapping of the irradiated samples enabled a spatially-resolved study of the distribution of the formed Bi2O3 phases. Red laser (633 nm) irradiation was found to induce the appearance of β-Bi2O3, within a certain range of power densities, by diffusion-controlled processes. In contrast, ultraviolet (UV, 325 nm) laser irradiation, above a certain power density threshold, initially induces the formation of both β and δ-Bi2O3 phases. The amount of the produced δ-Bi2O3 phase increases by increasing the irradiation time, while that of the β phase follows the opposite trend. UV laser irradiation seems to be a suitable method to produce room temperature stable δ-Bi2O3 patterns on Bi films.