Structural interpretation of the infrared sepctrum of a Sb_0.05As_0.45Se_0.50 glassy semiconductor

摘要

The infrared (IR) absorption spectrum for glassy Sb_0.05As_0.45Se_0.50 was measured in the wave number region 500-90 cm~-1 at room temperature and in a continuously purged sample compartment, following the polyethlene pellet method. Main structural units in the glassy are considered to be AsSe_3 and SbSe_3 pyramids, Se_8 rings and Se_n chains. By using X-ray diffraction data it was found a structural model with the assumption of tricoordinated As, tricoordinated Sb and dicoordinated Se[C. Corredor, J. Vazquez, R.A. Ligero, P. Villares, R. Jimenez-Garay, Materials Letters 36, 1998, 271; I. Quiroga, J. Vazquez, P. Villares, R. Jimenez-Garay, Materials Letters 17, 1993, 333.] which confirms the information obtained by means of far-infrared transmission (FIT). From the "Valence Force Field" (VFF) we can determine the vibrational frequencies, ω_i, of possible structural units of alloy in this study by using the expressions derived by Herzberg. The results for this alloy are the following: 85, 110 and 230 cm~-1, for AsSe_3, and 112, 215 and 315 cm~-1, for SbSe_3. The comparison between the frequencies obtained in the far-IR spectrum and the values calculated of the normal frequencies let us assign bands to structural units.