X-ray Photoemission Spectroscopy (XPS) analysis of SBT was carried out using a monochromated A1 Ka\ X-ray source and with a hemispherical energy analyser (VG ESCALAB 220iXL) operated at 10 eV pass energy. The instrumental energy resolution is at least as small as the full-width at half-maximum (FWHM) of the Ag 3d5/2 peak, measured to be 0.47 eV at 10 eV pass energy. The binding energy (Eb) scale was calibrated by setting the adventitious C Is peak to 284.8 eV. For Electron Energy Loss Spectroscopy (EELS) an attached electron gun (primary energy 490 eV) was used and the analyser pass energy was set to 1 eV. Sample cleaning was performed by heating in UHV to 350°C after which no carbon signal, a measure for contamination, was detectable by XPS.