Low temperature CEMS of Sn-implanted SiO2

Conversion electron Mössbauer spectroscopy (CEMS) at room and low temperature has been used to study thin SiO2 films implanted with Sn atoms and annealed at 900°C. This work focuses on the determination of the Debye temperature (?D) and Debye-Waller factors ( f ) of the Sn oxidized phases formed in this system. The Sn2+ oxidation state is the predominant one, even if a small percentage of the Sn atoms is in the Sn4+ oxidation state. The real Sn-oxides fractions are calculated by normalizing the resonant areas to the f values, as calculated from the temperature dependence of the related resonant areas within a Debye model. The Sn4+ oxidation state, possibly related to Sn atoms close to the SiO2 surface, represents less than 20% of the Sn atoms. For the Sn2+ oxidation state, two different electronics configurations a and b, having different Debye temperature and hyperfine parameters are identified. The component a, with a lower ?D (137 K), is the predominant one and might be related to small (2-3 nm) amorphous SnOx clusters in the SiO2 matrix. The component b could be related to substitutional Sn atoms in the SiO2 network forming a local Sn environment similar to the SnO amorphous compound.