Surface optimization of RBa2Cu3O7-delta (R = Y, Nd) epitaxial high T-c films for in situ photoemission studies

One of the intrinsic difficulties for in situ photoemission studies of high T-c oxide films is the surface volatility, especially the oxygen loss. In order to solve this problem, we have constructed a dedicated system for hig h T-c film surface studies, in particular for ARPES measurements. Here we b riefly describe our pulsed laser deposition (PLD) system that is linked to the photoemission chamber at the Synchrotron Radiation Center (SRC) in Wisc onsin, and discuss crystallographic and electronic properties measured on e pitaxial YBa2Cu3O7-delta (YBCO) and NdBa2Cu3O7-delta (NBCO) films. Resistiv ity and XRD studies show that the best c axis epitaxial films, with T-c (on set) = 92 K (T-c0 = 90.5 K), are monophase and single crystalline with crys tal coherence up to almost 1 mum. Initial core level photoemission study in dicates that, for YBCO on SrTiO3 (without any buffer layer), the Ba oxide l ayer tends to be the dominant surface layer. Further experiments are underw ay to reproducibly detect sharp Fermi edge and perform ARPES study on optim ally doped film surfaces.