In situ surface characterization of SrTiO 3(100) substrates and homoepitaxial SrTiO 3 thin films grown by molecular beam epitaxy and pulsed laser deposition

Abstract

The topmost atomic layer of SrTiO 3 (STO) substrates was investigated by in situ low-energy ion scattering spectroscopy (LEISS). After mechanochemical polishing, the topmost layer of the STO substrate consisted of SrO and TiO 2 planes. It was dominantly stabilized with TiO 2 planes after the STO substrate was treated with a pH-controlled NH 4F–HF(BHF) solution. STO thin films were deposited on the BHF-treated STO substrates by the molecular beam epitaxy (MBE) and pulsed laser deposition (PLD) methods. STO films were confirmed to have topmost layers with TiO 2 planes by the MBE method, and SrO planes by the PLD method. We also investigated the effects of the deposition conditions and surface treatments, and confirmed that the TiO 2 plane was more stable on the STO homoepitaxial film surface. Furthermore, the BHF-treated STO substrates greatly improved the thickness dependence of Tc of heteroepitaxial YBa 2Cu 3O x (YBCO) ultra-thin films.