Development of intrinsic surfaces, and their electronic structures and stability of non-c-axis YBCO epitaxial films

Surface-cleaning using 100% ozone beams or atomic oxygen beams has been applied for the fabrication of high quality [110]- and (100)-axis oriented YBCO epitaxial films. The treatment recovers metallic surfaces in spite of the semiconducting properties of the as-received surfaces. High quality [110]- and (100)-oriented films with high T/sub c/ and high orientation were deposited by temperature-gradient self-template method. On both kinds of film clear photoelectron Fermi edges, evidence of a metallic feature, were observed at room temperature. For the [110] films, well-defined photoelectron Fermi edges are observed for the first time, For the (100) surface, the rather high electron density of states Fermi edge is as high as about 15% of Cu 3d signal in valence band, On the other hand, the edge-height of the [110] surface was less than 5% of the Cu 3d and it was reduced as a function of time. Detailed electronic structures and the origin of the difference of the surface-stabilities is discussed.