SURFACE OPTIMIZATION OFRBa2Cu3O7-δ(R=Y, Nd)EPITAXIAL HIGHTcFILMS FORIN SITUPHOTOEMISSION STUDIES

One of the intrinsic difficulties forin situphotoemission studies of highTcoxide films is the surface volatility, especially the oxygen loss. In order to solve this problem, we have constructed a dedicated system for highTcfilm surface studies, in particular for ARPES measurements. Here we briefly describe our pulsed laser deposition (PLD) system that is linked to the photoemission chamber at the Synchrotron Radiation Center (SRC) in Wisconsin, and discuss crystallographic and electronic properties measured on epitaxialYBa2Cu3O7-δ(YBCO) andNdBa2Cu3O7-δ(NBCO) films. Resistivity and XRD studies show that the bestcaxis epitaxial films, withTc(onset)=92 K (Tc0=90.5K), are monophase and single crystalline with crystal coherence up to almost 1 μm. Initial core level photoemission study indicates that, for YBCO onSrTiO3(without any buffer layer), the Ba oxide layer tends to be the dominant surface layer. Further experiments are underway to reproducibly detect sharp Fermi edge and perform ARPES study on optimally doped film surfaces.