Local spectroscopy and vortex-core imaging on chemically wet-etched surfaces of YBa2Cu3Oy by scanning tunneling microscopy/spectroscopy

Low-temperature scanning tunneling microscopy/spectroscopy has been performed on chemically wet-etched surfaces of YBa2Cu3Oy (YBCO) single crystals. Chemically wet-etched YBCO surfaces are stable in ultrahigh vacuum environments, and superconducting gap spectra are observed with high spatial uniformity up to the bulk superconducting transition temperature, Tc. When a magnetic field was applied, local electronic modulations due to vortices were detected up to 80 K, enabling the real-space imaging of vortices in YBCO at high temperatures (<Tc) and magnetic fields. Furthermore, local spectroscopy revealed spectra with a zero-bias anomaly due to weak impurities and the tendency of vortex pinning by these impurities.