Systematic investigation of the growth and structural properties of FeTiO3±δ epitaxial thin films

Abstract

An understanding of the thin film structure and properties of ilmenite is crucial for the future study of ilmenite-hematite solid solutions for spintronics applications. Here, we report a systematic study of the FeTiO3±δ thin film structure as a function of the deposition parameters during pulsed laser ablation. The films are found to be crystalline and epitaxial on α-Al2O3(0001) substrates for a wide range of substrate temperatures and oxygen pressures. Initial stages of the film growth and in-plane lattice relaxation were investigated. The increase in the a lattice parameter of up to 6% above its bulk value was observed and is most probably due to the buckling of a few ilmenite monolayers at the film/substrate interface because of a significant compressive stress induced on the film by sapphire substrate. In spite of the absence of a diffraction peak corresponding to the ordered R3¯ phase, these films consist of pure ilmenite phase with negligible net magnetization. Film conductivity is tuned over three orders of magnitude in the studied oxygen pressure range and is comparable to that of bulk ilmenite at pressures above 10 mTorr.