Electronic properties of CsSn

Thin films of Cs-Sn intermetallic compounds formed by the reaction of evaporated Sn layers with Cs vapors were studied by x-ray photoelectron spectroscopy. The stable end product was identified as equiatomic CsSn. It was produced as a $p$-type semiconductor. Core electron binding energies give evidence of substantial charge transfer from Cs to Sn. The Mössbauer-effect isomer shift shows a $5s$ configuration between those of grey and white tin, indicating that the transferred charge dominantly enters $5p$ states. Oxidation of CsSn yields a surface covered with cesium suboxide which has good photoemissive properties. A new compound tentatively identified as Cs${\mathrm{Sn}}_4$ was found.