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 Co2+ 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
Co2+ emission. At last, the electrical conductivity reaches
values compatible with potential electroluminescent applications of the ZnO:Co
films.