Cryogenic scanning tunneling microscopy/spectroscopy on the (110) surfaces of YBa2Cu3Oy epitaxial thin films

As-grown surfaces of (110) oriented laser-ablated YBa2Cu3Oy films have been investigated by scanning tunneling microscopy and spectroscopy, for the first time, at room temperature and 4.2 K. We found semi-macro scale surface structures along the c-axis, which were composed of (110) top planes and (100)/(010) lateral planes. The orthorhombic atomic lattice image, corresponding to Cu atom arrangement of both CuO2 double layers and CuO chain layers alternately, was observed on the (110) top plane at 4.2 K. Furthermore, broad swell-and-depression structures were observed as stripes perpendicular to the c-axis on the top plane. The STS results indicated superconducting nature on the swells and semiconducting nature on the depressions.