Optical properties and scanning probe microscopy study of some AgAsSSe amorphous films

Doping of AsSSe amorphous films by silver photo-dissolution leads to a decrease of the optical gap and to an increase of the refractive index in forming AgAsSSe films. The difference of the optical gap and refractive index between undoped and doped films has been found in case of Ag₁₅As₂₆S₂₉Se₃₀ film up to 0.37 eV and 0.26, respectively. Transreflectance in far infrared spectral region indicates formation of AgAsS₂ and AgAsSe₂ entities in Ag₁₅As₂₆S₂₉Se₃₀ film. Scanning probe microscopy, namely atomic force microscopy, atomic force acoustic microscopy (AFAM) and Kelvin probe force microscopy (KPFM) was used for studying AgAsSSe 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.