Two-step treatment to obtain single-terminated SrTiO3 substrate and the related difference in both LaAlO3 film growth and electronic property

A two-step treatment, first chemical etching then thermal treatment, is proposed to achieve an atomically flat and thermally stable TiO2-terminated SrTiO3 substrate. LaAlO3 films were then grown on those TiO2-terminated and as-received substrates. LaAlO3 films on the TiO2-terminated SrTiO3 substrate maintained the layer-by-layer growth mode with a sharp interface, while films on the as-received substrates easily underwent reconstruction adverse to the sharp interface. Both LaAlO3/SrTiO3 interfaces displayed metallic conductive behavior, while the difference in magnetotransport properties indicated the difference in origin for interface conductivity. Large positive magnetoresistance implied that the LaAlO3/as-received substrate interface was a 3D conductive interface dominated by oxygen vacancies. However, the annealed-LaAlO3/treated-substrate interface preserved intrinsic quasi-2D interface magnetism as evidenced by large negative magnetoresistance.