Comparable nuclear and electronic energy loss effect of Au2+ irradiation on structural, surface morphological, optical and phonon properties of Al:ZnO thin films

Abstract

Al-doped ZnO (Al:ZnO) thin films of average thickness ~400 nm were grown on silicon substrates. The annealed films were irradiated using 6 MeV Au2+ ions at varying ion fluence. The residual structural, morphological, phonon and optical properties due to the comparable elastic and inelastic collision have been studied. The pristine films stabilize in hexagonal wurtzite structure which remained invariant after irradiation. However, the crystalline size decreases with increasing ion fluence. The compressive microcrystalline stress for pristine films converts into tensile with increasing the ion beam fluence. AFM micrographs indicate a smooth and dense surface micromorphology. The irradiated films with increasing ion fluence become rough and cluster formation takes place after irradiation. The optical band gap estimated from absorption spectra decreases with increasing ion fluence. In the Raman spectra, two significant phonon modes E2High and E1(LO) have been observed at room temperature. The structural and optical properties of films almost remain invariant up to ion beam irradiation fluence (~1 × 1013 ions/cm2) and start declining at higher fluence.