Growth of the magnetic semiconductor Fe2−x Ti x O3±δ thin films by pulsed laser deposition

Abstract

The understanding and control of the ilmenite–hematite solid solutions (Fe2−xTixO3±δ or IH) thin film structure and properties are crucial for spintronics applications. Good quality films of Fe2−xTixO3±δ on Al2O3(0001) substrates were obtained by pulsed laser deposition. For the studied compositions (x=1, 0.7, 0.5) in a wide oxygen pressure range all the films were epitaxial, with flat interfaces, and without secondary phases. Unconventional lattice strain relaxation with the increase of in-plane lattice parameter above its relaxed bulk value was observed for different film compositions, oxygen pressures, substrate temperatures, and film growth rates. This phenomenon is most likely explained by the buckling of a few first film monolayers because of a significant compressive stress induced on the film by the sapphire substrate. The IH thin films with x=0.7 and 0.5 exhibited the properties of a room temperature magnetic semiconductor. The resistivity changed over three orders of magnitude in the studied pressure range, thus clearly demonstrating the important role of oxygen stoichiometry in the creation of carriers.