Defect mediated modification of structural, optical and magnetic properties of Xe~(3+) ions irradiated GaN/sapphire films

摘要

We report tailoring of structural, optical and magnetic properties of PLD grown GaN films by 500 keV Xe~(3+) ions at irradiation fluences of 1 × 10~(16) and 5 × 10~(16) ions-cm~(-2). Deterioration in the crystallinity is observed after irradiation; however, average apparent crystallite size is increased at fluence of 5 × 10~(16) compared to 1 × 10~(16) ions-cm~(-2). In pristine film, broad yellow luminescence peak at —2.2 eV along with characteristic peak at —3.4 eV has been observed by photoluminescence spectroscopy. Appearance of peaks at 2.06, 2.65 and 3.06 eV after irradiation suggests defect states generation within the band-gap. Origin of yellow luminescence in GaN films is attributed to Ga vacancy related defects, point defect complexes with unintentional impurities (C and O) on the surface. Lattice disorder examined by RBS/C supports the structural and optical measurements/observations. Films remain diamagnetic as investigated by SQUID magnetometer for all fluences as the concentration of defects is not sufficient to trigger ferromagnetism.