In situ surface characterization of SrTiO3(100) substrates and homoepitaxial SrTiO3 thin films grown by molecular beam epitaxy and pulsed laser deposition

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(4)F-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(2)Cu(3)O(x) (YBCO) ultra-thin films. (C) 1998 Elsevier Science B.V. All rights reserved.