Optical properties and scanning probe microscopy study of some Ag [sbnd]As [sbnd]S [sbnd]Se amorphous films

Abstract

Doping of As S Se amorphous films by silver photo-dissolution leads to a decrease of the optical gap and to an increase of the refractive index in forming Ag As S Se films. The difference of the optical gap and refractive index between undoped and doped films has been found in case of Ag 15As 26S 29Se 30 film up to 0.37 eV and 0.26, respectively. Transreflectance in far infrared spectral region indicates formation of AgAsS 2 and AgAsSe 2 entities in Ag 15As 26S 29Se 30 film. Scanning probe microscopy, namely atomic force microscopy, atomic force acoustic microscopy (AFAM) and Kelvin probe force microscopy (KPFM) was used for studying Ag As S Se films. It was found that silver growth is rather three dimensional and it is reminiscent of the Stranski–Krastanov growth mode. Observed silver protuberances represent silver reservoirs responsible for a local increase of silver content. Hence, the silver growth mode enhances formation of nano/meso inhomogeneities of the surface and near surface density/stiffness, seen in AFAM, and in the surface electric potential, seen in KPFM.