Influence of electronic excitations on structural, optical and electrical properties of undoped and antimony doped tin oxide thin films

Study reports on the influence of swift heavy ion irradiation (SHII) induced electronic excitations (EEs) on structural, optical and electrical properties of undoped SnO2 (TO) and antimony doped SnO2 (ATO) thin films. EEs in the thin films were induced by 70 MeV Si ion irradiation. It is noticed from the structural analysis that the crystallinity of TO and ATO almost remains unchanged upon Si ion beam irradiation. However, morphological studies by atomic force microscopy and scanning electron microscopy show surface modification upon irradiation. Interestingly, transport measurements show that the pristine ATO film possesses high conductivity which further increases upon irradiation for a fluence of 1 × 1012 ions/cm2, followed with drastic decrease in conductivity and carrier concentration at higher fluences of irradiation. Band gap modification in TO and ATO films are also reported with irradiation fluence and found to be in agreement with quantum confinement (QC) model for TO; while with Burstein-Moss shift (BMS) model for ATO films. However, the modifications at higher fluence can be ascribed to the band tail states due to very high disorder in the lattice as revealed by very high value of Urbach energy in corroboration with transmittance investigations, which also exhibits a significant decrease in transmittance in both films at irradiation fluence ≥ 1 × 1013 ions/cm2.