Properties of Zn1−xCoxO thin films grown on silicon substrates prepared by pulsed laser deposition

Zn1−xCoxO (x = 0.05, 0.10) thin films are formed on silicon (100) substrates using pulsed laser deposition (PLD). The as-deposited films show ferromagnetic behaviors with Curie temperature higher than room temperature. Homogeneous film with a wurtzite structure has been formed when x = 0.05, whereas inhomogeneous film with a wurtzite phase mixed with cubic Co phase has been formed when x = 0.10. A significant increase in the magnetism is observed for the Zn0.90Co0.10O film because of the presence of Co clusters. After thermal annealing in O2, the carrier concentration of the Zn0.95Co0.05O film decreased three orders of magnitude from 1020 to 1017 cm− 3 and the film became paramagnetic. The electronic structure of Zn1−xCoxO (x = 0.125) was studied using full-potential linearized augmented plane-wave (FP-LAPW) method. Both the annealing experiments and calculation suggest that the double-exchange mechanism is the possible origin of the ferromagnetism in the Zn0.95Co0.05O film.