Growth of ferromagnetic semiconducting cobalt-doped anatase titanium thin films

Heteroepitaxial and polycrystalline anatase ${\mathrm{Ti}}_{\text{1−x}}{\mathrm{Co}}_x{\mathrm{O}}_2$ $\text{(0.0⩽x⩽1.0)}$ thin films were prepared by soft chemical processing on ${\mathrm{LaAlO}}_3$ (001) and thermally oxidized silicon substrates and the crystallinity and magnetic properties were investigated. X-ray diffraction (XRD) spectrum of the ${\mathrm{Ti}}_{\text{1−x}}{\mathrm{Co}}_x{\mathrm{O}}_2$ films on ${\mathrm{LaAlO}}_3$ (001) substrate shows (004) and (008) peaks of heteroepitaxy anatase without any impurity phase. The full-width at half maximum of the (004) peak rocking curve is $\text{0.4°.}$ The XRD patterns of thin films deposited on the ${\mathrm{SiO}}_2/\mathrm{Si}\text{(001)}$ substrate are anatase type polyscrystalline structure. Microstructural characterization on ${\mathrm{Ti}}_{\text{1−x}}{\mathrm{Co}}_x{\mathrm{O}}_2$ thin film employing atomic force microscope showed island type grains in 20 nm in size and the surface roughness of typical thin films was 1.5 nm. Sharp hysteresis loops, indicating a well-ordered ferromagnetic structure, appeared in the magnetization versus magnetic field curves when the magnetic field was applied in the plane of the film. This result clearly indicates that the anatase ${\mathrm{Ti}}_{\text{1−x}}{\mathrm{Co}}_x{\mathrm{O}}_2$ thin films fabricated on ${\mathrm{LaAlO}}_3$ (001) by soft chemical process have crystal quality equivalent to high-vacuum technique.