Photoinduced interdiffusion was observed with above band gap light in nanolayered Se As2 S3 films. It is discussed in terms of the optical parameters such as band gap, Urbach edge (Ee) [F. Urbach, Phys. Rev. 92, 1324 (1953)], and B12 (Tauc's parameter) [J. Tauc, Phys. Status Solidi 15, 627 (1966)]. Experimental data of B12 and Ee for as-prepared samples do not show clear correlation implied by the Mott-Davis model [N. F. Mott and E. A. Davis, Electronic Process in Non-crystalline Materials (Clarendon, Oxford 1979), p. 287]. It is also shown that the optical parameters can be changed with a change in the Se sublayer thickness. Variations of these optical parameters as a function of modulation period and photoinduced interdiffusion were discussed in terms of the quantum confinement effect and changes in the valence and conduction bands. We proposed a model to explain the mechanism of Se diffusion in As2 S3, which suggests that diffusion takes place through the wrong bonds. X-ray photoelectron spectroscopy (XPS) is used to investigate the chemical alternations in the bonding. The proposed model was supported by the XPS data.
ASJC Scopus subject areas
- Physics and Astronomy(all)