L.V.Yashina, S.P.Kobeleva, V.S.Neudachina, T.B.Shatalova, V.P.Zlomanov. XPS study of fresh and oxidized (Pb,Ge)Te crystal surface. Surface and Interface Analysis, 2002, v.34, p.498-501.
The oxidation of (Pb,Ge)Te crystal surfaces at ambient temperature and humidity was studied by means of XPS in time range from minutes to months. Vacuum cleft crystal was used for the experiment. It was found that Ge in PbTe lattice occupies two different positions. At one of them donor behaviour is revealed, and the concentration of donor atoms increases at temperatures lower than those of cubic-rhombohedral phase transition. It was found that the oxidation takes place even after few minutes of air exposure. Germanium atoms oxidize entirely to oxidation state 4+, this being followed by slow oxidation of tellurium atoms from the oxidation state 2- to 4+. After long air exposure significant surface enrichment in Pb was observed.