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Grain-size effect on the optical properties of vacuum deposited nanocrystalline As2S3 thin films

TZ. BABEVA1, J. DIKOVA1,* , V. RASHKOVA1

Affiliation

  1. Central Laboratory of Photoprocesses, Bulgarian Academy of Sciences, “Acad. G. Bonchev” Str., Bl. 109, 1113 Sofia, Bulgaria

Abstract

The microstructure and optical properties of nanocrystalline and amorphous As2S3 films with thicknesses in the range 15-70 nm are followed. It is found that within the spectral interval 200-600 nm, the thickness dependencies of the refractive indices n and extinction coefficients k have different trends for both kinds of sample. It is established that the optical band gap energy, Eg, for indirect transitions is almost independent of the thickness of the amorphous films, while a strong reduction of this parameter is observed for the thickest nanocrystalline samples. Also, a fairly strong grain-size effect on the values of Eg for direct optical transitions in crystalline films is found. On the basis of the results obtained, the impact of a nanocrystalline structure on the optical behaviour of vacuum deposited As2S3 films is discussed..

Keywords

Chalcogenide glasses, Thin films, Nanocrystalline structure, Optical properties.

Submitted at: Nov. 1, 2006
Accepted at: Jan. 15, 2007

Citation

TZ. BABEVA, J. DIKOVA, V. RASHKOVA, Grain-size effect on the optical properties of vacuum deposited nanocrystalline As2S3 thin films, Journal of Optoelectronics and Advanced Materials Vol. 9, Iss. 1, pp. 170-173 (2007)