Investigation of the cobalt distribution in TiO2:Co thin films

We report a detailed study of the morphology of ${\mathrm{TiO}}_{\mathrm{2}}\mathrm{:Co}$ films grown on both ${\mathrm{LaAlO}}_3$ (001) and ${\mathrm{SrTiO}}_3$ (001) substrates by pulsed laser deposition. The films are optically transparent and ferromagnetic at room temperature with a magnetic moment of ${\text{1.7±0.4\hspace{0.17em}μ}}_B/\mathrm{Co}.$ Plan view transmission electron microscope studies show clear evidence of cobalt segregation with the clustering more pronounced for higher cobalt concentrations. Films grown on ${\mathrm{SrTiO}}_3$ substrates show the presence of a thin surface rutile (111) layer, into which the cobalt appears to migrate. These results are supported by x-ray structure determination and resistivity measurements.