Effect of vacuum annealing on the structural and optical properties of sputtered Cu 4 O 3 thin films

Abstract

Cu₄O₃ thins films were deposited by the reactive magnetron sputtering process on glass and Si (100) wafers. In order to investigate the thermal stability of the Cu₄O₃ phase, the films were subjected to vacuum annealing treatment for one hour at various temperatures ranging from 200°C to 500°C. The samples were characterized by using EDS, XRD, SEM and UV–VIS. The phase transformation of Cu₄O₃ into Cu₂O was obtained from 300°C (critical temperature). Increasing annealing temperature leads to compact morphology and the grain shape changing from elongated towards spherical. Due to this annealing the film structure presentes coexistence of a Cu₄O₃ and Cu₂O mixture where O atoms are lost in the Cu–O system. The UV–VIS analysis reveals a gradual increase in the transmittances from 55 to 70% with the increasing annealing temperature, while the band gap shows a maximum value (Eg = 2 eV) at 500°C corresponding to the Cu₂O phase.