Toward nano-technology of functional oxides: photoemission studies of in situ grown ultra-thin films of high-Tc cuprates and related oxides

The emerging oxide nano-technologies require a full understanding of the electronic structure and in particular E(k) dispersion relation of ultra-thin films (<50 nm). In order to achieve this we have constructed a special film growth facility directly linked to a photoemission chamber. Systematic measurements on in situ grown oxide films (100 nm → ∼1 nm), by using cylindrical mirror analyser (CMA) at the Synchrotron in Wisconsin, show that phases that contain `chainsʹ (RBCO-123 (R=Y, Nd), YBCO-124 and ruthanocuprates) do not exhibit clear evidence of the Fermi edge. The Fermi edge is clearly observed in LSCO-214, BSCCO-2201, BSCCO-2212 and BSCCO-2223 films. Combined photoemission and X-ray analysis of BSCCO-2212 films show that a structural phase transition occurs at nominal thickness of approximately one unit-cell, converting the precursor Bi2O2.33 highly coherent ultra-thin film into the Bi2Sr2CaCu2O8+x structure.