Growth of ferromagnetic semiconducting cobalt-doped anatase titanium thin films

Heteroepitaxial and polycrystalline anatase Ti1-xCoxO2 (0.0less than or equal toxless than or equal to1.0) thin films were prepared by soft chemical processing on LaAlO3 (001) and thermally oxidized silicon substrates and the crystallinity and magnetic properties were investigated. X-ray diffraction (XRD) spectrum of the Ti1-xCoxO2 films on LaAlO3 (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 0.4degrees. The XRD patterns of thin films deposited on the SiO2/Si(001) substrate are anatase type polyscrystalline structure. Microstructural characterization on Ti1-xCoxO2 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 Ti1-xCoxO2 thin films fabricated on LaAlO3 (001) by soft chemical process have crystal quality equivalent to high-vacuum technique. (C) 2002 American Institute of Physics.