SURFACE CHARACTERIZATION OF HTSC BY ATOMIC-SITE TUNNELING SPECTROSCOPY

A new mode of scanning tunneling spectroscopy (STM), the atomic-site t unneling(AST) spectroscopy which collects spectroscopic data simultane ously during a scan of the STM imaging, enables one to know how the or der parameter of superconductivity varies in the atomic scale on the s urface of high-T-c superconductor (HTSC). Perhaps due to the extremely short coherence length the order parameter in the HTSC has turned out to change drastically even across the terminating atomic layer on the HTSC surface. The observations seem to require us a specific precise control in the future device fabrication. This paper summarizes our re cent results obtained on Bi2212 crystals and YBCO as-prepared thin fil m surface.