Surface bulk differences in a conventional superconductor, ZrB12

We studied the electronic structure of a conventional superconductor, ZrB12, using high resolution x-ray photoemission spectroscopy and single crystalline samples. Experimental results with different bulk sensitivity reveal boron deficiency at the surface while the bulk is stoichiometric and different valence states of Zr at the surface relative to those in the bulk. Signature of satellite features is observed in the Zr core level spectra corresponding to the bulk of the material suggesting importance of electron correlation among the conduction electrons in the bulk while the surface appears to be uncorrelated. These results provide an insight on surface-bulk differences, which is important for fabrication of devices based on such superconductors. (C) 2013 AIP Publishing LLC.