Evidence of nanostructure formation in Ge oxide by crystallization induced by swift heavy ion irradiation

Ge oxide films were irradiated with 150 MeV Ag ions at fluences varying between 1012 and 1014 ions/cm2. The irradiation-induced changes were monitored by FT-IR spectroscopy, atomic force microscopy, X-ray diffraction and photoluminescence spectroscopy. The FT-IR spectra indicate stoichiometric changes and an increase in Ge content on irradiation. X-ray diffraction shows a crystallization of the irradiated films and presence of both Ge and GeO2 phases. The Ge nanocrystal size, as calculated from Scherrer's formula, was around 30 nm. The morphological changes, observed in atomic force microscopy, also indicate formation of nanostructures upon ion irradiation and a uniform growth is observed for a fluence of 1 x 1014 ions/cm2