Magnetic and optical properties of epitaxial n-type Cu-doped ZnO thin films deposited on sapphire substrates

摘要

In this paper, we report on pulsed laser deposition of n-type Cu-doped ZnO thin films on c-plane sapphire substrates at 700℃. XRD and HRTEM were employed to study the epitaxial growth relationship between the Zn_(1-x)Cu_xO film and sapphire substrate. Absorption measurements showed excitonic nature of the thin films and a decrease in the bandgap energy with increased Cu concentration was observed. Such as-deposited films showed room temperature ferromagnetism with Curie temperature (T_c) at around 320 K. The moment per Cu atom decreases as the Cu concentration increases. The largest magnetic moment about 0.81μB/Cu atom was observed for Zn_(0.95)Cu_(0.05)O thin films. The presence of any magnetic second phase was ruled out and the ferromagnetism was attributed to Cu ions substituted directly into the ZnO lattice.