AFM and STM investigations of a Bi2Sr2CaCu2O8 high-Tc superconductor

The results of the scanning tunneling microscopy and spectroscopy (STM/STS) as well as atomic force microscopy (AFM) measurements on the bismuth cuprate superconductors Bi2Sr2CaCu2O8(BSCCO) in the a-b plane are reported in this paper. emperature STM/AFM has been used to study the BSCCO single crystals. Their layered crystalline structure allows one to prepare them by cleaving the atomically flat surface. Experiments have shown quite a stability of the cleaved surface and it is possible to observe reproducible STM images of the fresh surface in the air. The micromorphology and step heights in the c direction corresponding to multiple values of the unit cell have been investigated. Initial tests in air have shown that the STM was able to etch the BSCCO surface in a layer-by-layer process of subsequent removal of non-metallic (BiO) and metallic (CuO2) planes. We have also observed large areas with very stable and reproducible tunneling spectra (I-V and dI/dV) as a function of position and tip-sample spacing. Contrary to STM, AFM imaging does not modify the examined surface and reveals the surface covered with uniformly corrugated (within 1 nm range) granules, arising due to the surface degradation of the BSCCO material.