IN-SITU SURFACE CHARACTERIZATION OF SRTIO3(100) SUBSTRATES FOR WELL-DEFINED SRTIO3 AND YBA2CU3O7-X THIN-FILM GROWTH

The topmost atomic layer of SrTiO3 (STO) substrates was investigated u sing in sit low-energy ion scattering spectroscopy (LEISS) for ultra-t hin YBa2Cu3O7-x (YBCO) film growth. The topmost layer of a STO substra te after mechanochemical polishing consisted of SrO and TiO2 planes. T he topmost layer was dominantly stabilized with a TiO2 plane after the STO substrate was treated with a pH-controlled NH4F-HF(BHF) solution. It was confirmed that the topmost layer of STO thin films deposited o n STO substrates was affected by the surface structure of the STO subs trates. Furthermore, the dependence of T-c of heteroepitaxial YBCO ult ra-thin films on thickness was better for BHF-treated STO substrates t han for other substrates.