LOCAL VARIATION OF ELECTRONIC-STRUCTURE IN BISRCACUO INVESTIGATED BY CRYOGENIC STM STS/

Local variation of electronic structure on the cleaved surface of BiSr CaCuO has been investigated by cryogenic STM/STS under magnetic fields up to 6T. Most of the cleaved surface showed a semiconducting nature, possibly due to the loss of oxygen from the surface in an inert atmos phere. However, it was found that the surface degraded layers can be r emoved by the STM scanning with appropriate bias conditions. On the fr esh surfaces as etched, a clear superconducting gap structure was repr oducibly observed. At 6T, the vortex lattice was not imaged by STM/STS , suggesting that the STM tip repels the vortex lines.