Structural and optical investigations on amorphous SnSe[formula omitted] alloy

Abstract

The structural and optical properties of an amorphous SnSe9 alloy made using mechanical alloying were investigated through Extended X-ray Absorption Fine Structure and photoacoustic spectroscopy techniques. Average interatomic distances, average coordination numbers, disorder and asymmetry of the gij(r) functions, and also optical parameters such as Urbach and weak absorption tail energies and the optical gap were obtained. At 300 K, we found rSe–Se=2.388±0.002 Å and NSe–Se=1.96±0.04, for Se–Se pairs, and rSe–Sn=2.65±0.02 Å and NSe–Sn=0.35±0.04 for Se–Sn pairs. We determined a direct gap at Eg=1.51±0.02eV for SnSe9. Results indicated that the structure of SnSe9 is very different from those found in crystalline Sn–Se alloys, and the optical gap is the largest one considering amorphous alloys, being even larger than those found in some crystalline alloys of Sn–Se system.