Structural properties of femtosecond laser irradiation induced bismuth oxide based nano-objects in Bi12SiO20 (BSO) single crystal

Single crystal of Bi12SiO20 was grown from the melt by Czochralski technique. The crystal growth was in the [111] direction. The surface of the polished sample was irradiated by a femtosecond pulsed laser beam of various power. The influence of laser power on structural properties of Bi12SiO20 crystal, as well as on its phase composition, was studied. The surface morphology of our samples was investigated by AFM. The surface of unirradiated sample is rather smooth with no cracks observed. In sample modified by pulsed femtosecond beam, we registered the presence of small spherical islands on the surface. The dimensions of the islands and their density depend on the applied power. There were also significant changes in far-infrared spectra of irradiated sample in comparation to non-irradiated sample. Based on these results, the material obtained after femtosecond pulsed laser irradiation consisting of bismuth oxide based nano-objects, formed as nanocrystals (dimensions below 20 nm in diameter), which are arranged in a matrix of Bi12SiO20.