ATOMICALLY RESOLVED STM/STS OBSERVATION ON THE EDGE OF CUO2 AND (BIO)2 LAYERS OF BI-SR-CA-CU-O

Atomic resolution STM observation of the layered structure of an oxide superconductor has been achieved for the first time. The relative contributions to the electronic states from the CuO2 and (BiO)2 layers were remarkably different depending on the tunneling bias voltage, reflecting the two-dimensional nature of the electronic structure of Bi2Sr2CaCu2Oy. STS on each layer indicated the (BiO)2 layer to be insulating with an energy gap of 0.1 eV while the CuO2 layer was found to be essentially metallic but with an anomalous low-lying excitation spectrum. The modulation structure was observed on the layer-edge surface as well as on the basal plane. © 1990 The Japan Society of Applied Physics.