Photoelectron spectromicroscopy as a microchemical probe of high temperature superconductors

Synchrotron-radiation photoemission spectroscopy at high lateral resolution is a fairly new branch of surface experimental science. Nevertheless, it has already emerged as one of the most powerful probes of local surface and interface chemical properties. We show that this approach can play a very important role in the research on high temperature superconductors (HTSCs). Experiments on these materials are becoming quite sophisticated and require extremely high-quality single crystals and films. The success of such experiments depends critically on the local chemical properties of the specimens, notably on their chemical homogeneity. We used synchrotron imaging spectromicroscopy to explore this issue for high-quality single crystals and films, and found that even these specimens sporadically exhibit inhomogeneities. Such inhomogeneities are quite critical, as they could simulate spurious effects and jeopardize the reliability of experiments, notably those on bandgap spectroscopy and on interface formation processes. (C) 1997 Elsevier Science B.V.