Stabilization of Fermi level via electronic excitation in Sn doped CdO thin films

Abstract

Pure and Sn doped CdO sol-gel derived thin films were deposited on corning glass substrate and further irradiated by swift heavy ion (SHI) (Ag and O) with fluence upto 3×1013 ions/cm2. The observed tensile stress from X-ray diffraction pattern at higher fluence for Ag ions can be corroborated to the imbrications of cylindrical tracks due to multiple impacts. The anomalous band gap enhancement after irradiation may be attributed to the consolidated effect of Burstein–Moss shift (BMS) and impurity induced virtual gap states (ViGs). At higher excitation density as Fermi stabilization level (EFS) tends to coincide with charge neutrality level (CNL), band gap enhancement saturates as further creation of additional defects inside the lattice becomes unsustainable. Raman spectroscopy divulges an intensity enhancement of 478 cm−1 LO phonon mode with Sn doping and irradiation induces further asymmetric peak broadening due to damage and disordering inside the lattice. However for 3% Sn doped thin film irradiated with Ag ions having 3×1013 fluence shows a drastic change in structural properties and reduction in band gap which might be attributed to the generation of localized energy levels between conduction and valance band due to high density of defects.