Surface properties of SmB6 from x-ray photoelectron spectroscopy

We have investigated the properties of cleaved SmB\(_6\) single crystals by x-ray photoelectron spectroscopy. At low temperatures and freshly cleaved samples a surface core level shift is observed which vanishes when the temperature is increased. A Sm valence between 2.5 - 2.6 is derived from the relative intensities of the Sm\(^{2+}\) and Sm\(^{3+}\) multiplets. The B/Sm intensity ratio obtained from the core levels is always larger than the stoichiometric value. Possible reasons for this deviation are discussed. The B \(1s\) signal shows an unexpected complexity: an anomalous low energy component appears with increasing temperature and is assigned to the formation of a suboxide at the surface. While several interesting intrinsic and extrinsic properties of the SmB\(_6\) surface are elucidated in this manuscript no clear indication of a trivial mechanism for the prominent surface conductivity is found.