BARRIER PARAMETERS AND SUPERCONDUCTING GAP STRUCTURE OF THE ETCHED SURFACE OF Y-BA-CU-O BY SCANNING TUNNELING SPECTROSCOPY

Using a scanning tunnelling microscope, the tunnelling current vs. vol tage is measured between a gold tip and the chemically etched (001) su rface of YBa2Cu8Ox crystals at room temperature. The tunnelling barrie r height and thickness are derived by modelling the system in the norm al state as a conventional N-I-N junction. The I(V) and G(V) curves ar e computed for the same junction in the superconducting state (N-I-S j unction). The predicted gap structure for a single BCS-Dynes-like gap is simple and has low zero-bias conductance. The complex G(V) spectra measured below T(c) on the etched junctions with approximately 50% zer o-bias conductance suggest a possible multilayer contribution in the u nit cell.