Correlation of some opto-electrical properties of Se–Te–Sn glassy semiconductors with the average single bond energy and the average electronegativity

Abstract

Studies of some electrical and optical properties of Se90Te10−xSnx (x = 2, 4, 6 and 8) glassy alloys, in bulk and thin film forms, were performed at room temperature. Pellets of a diameter ∼1.3 cm and different thicknesses ranging from 0.04 cm to 0.06 cm of these compositions were obtained. Measurements of I–V characteristics of these pellets have been carried out at room temperature. Ohmic behavior was observed in low voltage range (0–5 V) while a deviation from ohmic towards non-ohmic behavior was observed at higher voltage range (6–20 V). This deviation can be interpreted in terms of space charge limited conduction (SCLC) mechanism whereas the plots of ln (I/V) vs. V were found to be straight lines. The room temperature DC electrical conductivity σDC has been calculated from the linear region of the I–V characteristic curves. In addition, thin films of a thickness ∼1100 Å of the alloys under investigation were prepared and the optical band gap Eopt of these thin films is obtained from Tauc plot (αhν)2 = B (hν − Eopt) after the determination of the absorption coefficient α over a wavelengths range of 440–1100 nm. Analysis of the experimental data shows that σDC increases while Eopt decreases with increasing Sn content. These results are explained in terms of the decrease in the values of average single bond energy HS/<r> and average electronegativityχm.