Fabrication by Mist CVD Method and Evaluation of Corundum Structured Oxide Semiconductor Thin Films

Abstract

We propose a novel corundum-structured oxide semiconductor alloy system of α-(Ga₂O₃)-(Fe₂O₃)-(Cr₂O₃) thin films as a potential material with multifunctional properties contributing to future unique devices. In this paper the focus is given on the detailed characterization of α-Fe₂O₃ thin films grown on c-plane sapphire substrates. α-Fe₂O₃ is an oxide semiconductor with the optical band gap of 2.2eV, exhibiting a weak ferromagnetic property, and is alloyed with α-Ga₂O₃ to develop promising potentials toward spintronic applications. The growth has been carried out by the mist chemical vapor deposition (CVD) method which has been developed by our group. In the experiment, we used water solution of iron acetylacetonate [(C₅H₈O₂)₃Fe] as a Fe source and air as carrier gas. The growth temperature was set at 500°C. X-ray diffraction measurements revealed the successful formation of corundum-structured α-Fe₂O₃ thin films. The full-width at half maximum of X-ray diffraction rocking curve was as small as 41arcsec. In-plane pole figure measurements indicated that α-Fe₂O₃ thin films were epitaxially grown on the substrate, but that rotational domains were contained with the volume ratio of about 0.7%. The atomic force microscope surface image showed many grains and the root mean square roughness was 1.26nm. These results showed the successful fabrication of highly-crystalline epitaxial α-Fe₂O₃ thin films on c-plane sapphire substrates, though further efforts to improve the surface morphology were suggested.