Modifications in micro-structural, optical, and electrical properties of polycrystalline α-Al2O3 by 100 MeV Ag9+ ion beam irradiation

Abstract

We report the modifications of lattice structure, optical and electrical properties of α-Al2O3 by 100 MeV Ag9+ ion beam irradiation with fluences in the range of 1 × 1011 -1 × 1013 ions/cm2. X-ray diffraction patterns have confirmed the polycrystalline form of rhombohedral structure (space group R-3c) for both pristine and irradiated samples. The Raman active phonon-modes of the pristine sample gradually disappeared with the increase of fluence. The Field Emission Scanning Electron Microscopic images indicated a transformation of the surface morphology from a distinct and layered-type grain structure in pristine sample to a soft layered-type grain structure in the irradiated sample of highest infuence. The Energy Dispersive X-Ray Analysis confirmed elemental composition of the irradiated samples close to nominal value of pristine sample. The X-ray Photoelectron spectroscopy confirmed chemical state modification at the surface of irradiated samples, where a fraction of the Al–O bonds has reduced into metallic Al state. The electrical conductivity in irradiated samples has been enhanced and showed thermal irreversibility where the conductivity in the cooling mode is smaller than that in the warming mode. The optical band gap and activation energy for the electronic transition from valence band to conduction band of α-Al2O3 have been affected by Ag9+ ion beam irradiation.