Effect of rapid thermal treatments on the physical properties of Cobalt Doped ZnO Films

Cobalt doped ZnO (ZnO:Co) films with a 1 at% doping rate have been successfully grown on (100) oriented p type Si substrates by radiofrequency magnetron sputtering. Post annealing treatments at 973 K for various short periods have been carried out and structural, optical and electrical properties of the films have been investigated. Upon rapid annealing, the dopant distribution in the film has been found homogeneous. The annealing improves the (002) texture of the film and the mean column width increases with the annealing duration from 60 nm up to 95 nm. The lattice parameter of the ZnO:Co films decreases upon annealing and approaches that of bulk ZnO. The photoluminescence (PL) study reveals that the Co 2+ ions can be excited directly or through a transfer mechanism from the matrix. The PL intensity decreases with the annealing time suggesting a diffusion process of the dopant impeding the Co 2+ emission. At last, the electrical conductivity reaches values compatible with potential electroluminescent applications of the ZnO:Co films.