Effect of Sm doping and annealing on magnetic and structural properties of sputter deposited SnO2 thin films

Abstract

SmxSn1−xO2 thin films (with x = 0, 0.005, 0.02 and 0.04) were sputter deposited on Si (100) substrates and its physical properties were investigated. The as-deposited thin films were amorphous; however after electron beam rapid thermal annealing became polycrystalline tetragonal phase [JCPDS21-1250]. The preferred crystal growth orientation of the annealed thin films were along (101) plane, in contrast with its bulk where it is along (110) plane. However in both cases the crystallinity of SmxSn1−xO2 thin films reduced with increase in Sm dopant concentration. The annealed thin films showed continuous grain distribution, with linear increase in grain size from ∼12 to ∼52 nm with increase in Sm dopant concentration. Maximum magnetization of 0.031 emu was observed in annealed Sm0.04Sn0.96O2 thin film. The observed weak ferromagnetism in the thin films could have originated from the induced oxygen vacancies through Sm substitution and electron beam rapid thermal annealing in high vacuum. It was also observed that the optical absorption of doped SnO2 thin films (in 300 to 800 nm range) decreased by Sm doping. These observations suggest that Sm doped SnO2 thin films can be potentially used for dilute magnetic semiconductor and solar cell application.