Abstract: The dependence of chemisitry properties of elements Sn and O on the surface of oxidized Sn films on vacuum annealing was studied. By using in-situ
measurements of X-ray photoelectron spectroscopy (XPS), it was found that great number of negatively charged particles (such as O^- and O^-₂) were adsorbed on the
surface. The amount of the adsorbed oxygen particles increased with the annealing temperature (T_ann), and then the adsorbed oxygen particles became less charged. The
increase in the number of the adsorbed oxygen particles is attributed to the transition from SnO_2 to Sn₂O₃ as T_ann≤350℃. At 350≤T_ann≤400℃,
the relative content of Sn in metallic Sn phase increased suddenly with T_ann due to the transition from Sn³⁺ to Sn^0, which resulted in releasing and successively piling up of O particles adsorbed on
the surface. Moreover, SnO₂ became more stable than Sn₂O₃ in the case of higher annealing temperauters, as say T_ann≤350℃. The adsorbed states of the oxygen
particles on the surface and the correlation between the adsorbed states and annealing temperature were also discussed.

Key words: oxidized Sn film, vacuum annealing, in-situ XPS measurements