  We report on the synthesis of high-quality Co-doped ZnO thin films using the
pulsed laser deposition technique on (0001)-Al$_2$O$_3$ substrates performed in
an oxidizing atmosphere, using Zn and Co metallic targets. We firstly optimized
the growth of ZnO in order to obtain the less strained film. Highly
crystallized Co:ZnO thin films are obtained by an alternative deposition from
Zn and Co metal targets. This procedure allows an homogenous repartition of the
Co in the ZnO wurzite structure which is confirmed by the linear dependance of
the out-of-plane lattice parameter as a function of the Co dopant. In the case
of 5% Co doped, the film exhibits ferromagnetism with a Curie temperature close
to the room temperature.
