Arkaprava Das
Inter University Accelerator Centre, India
Title: Interconnection of charge neutrality level with electronic structure and p-d hybridization and its modification upon electronic excitation
Biography
Biography: Arkaprava Das
Abstract
Undoped and tin doped cadmium oxide (CdO) based thin films are irradiated by 84 MeV Si6+ and 120 MeV Ag9+ ions. In the present work the charge nutrality level (CNL) in highly conducting CdO thin films is demonstarted by the observed variation in the band gap upon annealing and doping. The increase in crystallite size with tin doping is a signature of decrease of CdO stoichiometry by substitutional replacement of Cd with Sn. Each Cd2+ ions are substituted by Sn2+ ions with reduction of Sn4+ via creating oxygen vacancies in the lattice which also enhnaces the carrier concentration in the tin doped thin film. The band gap enhancement cannot be explained by Burstein Moss Shift (BMS) only but can be explained by formation of charge neutrality level (CNL). The level of local CNL resides at the branch point of virtual gap states (ViGS) generation of which is the consequence of tin doping in CdO lattice. Further investigations using soft X-ray absorption spectroscopy (SXAS) at oxygen K and cadmium M edge and the analysis of the spectral features has revealed an evidence of p-d interaction between O 2p and Cd 4d orbitals. After irradiation, the thin films exhibit an unusual band gap enhancement via generation of oxygen vacancies due to huge electronic energy deposition inside the lattice by Ag and Si ions. The observed band gap enhancement has been substantiated by a schematic block diagram.