Structural and electronic-structure investigations of defects in Cu-ion-implanted SnO2 thin films

Abstract

SnO2 thin films have been deposited on Si substrates using RF-magnetron sputtering and implanted by 200 keV Cu- ions with ion fluence of 2.79 x 10(16) ion/cm(2) and 4 x 10(16) ion/cm(2). Post annealing is done on the pristine and Cu- ion-implanted SnO2 thin films. Samples were characterized using the grazing-incidence X-ray diffraction (GIXRD), field-emission scanning electron microscopy (FESEM) and near-edge X-ray absorption fine structure (NEXAFS). After the annealing, amorphous to crystalline phase transition and growth of particles are seen. It is also evidenced that Cu ions do not make metallic/oxide phases up to the implantation dose of 2.79 x 10(16) ion/cm(2). Cu L-edge NEXAFS has confirmed the Cu2+ ions in the samples. The O K-edge NEXAFS spectra of annealed films have shown diminished peak intensity of O 2p to Sn 5s hybridized orbitals which signify the O vacancy formation. A pre-edge peak in the O K-edge NEXAFS of Cu implanted films has evolved and confirms the additional hybridization of unoccupied Cu d orbitals with O 2p orbitals. The improved intensity of Sn M-5,M-4-edge features is due to the enhanced crystallinity in annealed samples. Ion-solid interaction induced structural and electronic structure amendments are briefly discussed in the light of energy-loss mechanism.