Sol–Gel Derived Epitaxial MgTiO3 Thin Films

Abstract

MgTiO3 thin flms have been successfully grown on a sapphire crystal by the sol–gel process. Epitaxial growth of MgTiO3 thin films was obtained using magnesium acetylacetonate and titanium isopropoxide in the sol–gel process. In nonhydrolytic conditions, the c-axis oriented ilmenite structure of MgTiO3 thin films developed at the crystallization temperatures 650–800°C with a 3-fold axis symmetry in the c-plane. These epitaxial MgTiO3 thin films had extremely fine features in morphology, i.e., a fine grain size of 10–20 nm and a very smooth surface of 0.9 nm rms roughness. The epitaxial MgTiO3 thin films exhibited a UV absorption edge at 280 nm and were transparent in the wavelength range of 400–1100 nm. The ordinary refractive index of the epitaxially grown MgTiO3 thin films was 2.305, very close to the value of single-crystal MgTiO3. This suggests that the epitaxially grown MgTiO3 thin films are well crystallized and sufficiently strain-relaxed due to the small lattice mismatch with Al2O3 substrate.