Structural, optical and electrical properties of Sb doped and undoped AgIn_(1-x)Ga_xSe_2 and Ag(InGa)_5Se_8 thin films

摘要

Antimony doped and undoped nanostructured thin films of AgIn_(1-x)Ga_xSe_2 and Ag(InGa)_5Se_8 on optically flat soda lime glass substrates are prepared by a three stage co-evaporation process. Energy dispersive analysis of X-rays (EDAX) and X-ray photoelectron spectroscopy in conjunction with atomic force microscopic technique and scanning electron microscopic technique are used, respectively, for compositional and surface morphological analysis of the films. X-ray diffraction (XRD) data on the films are analysed to estimate the influence of antimony doping and indium replacement by gallium, on the structure of the films, by determining the anion-cation bond lengths and anion displacement in the thin films. The obvious dependence of band gap on the composition of the films establishes the possibility of band gap tailoring of the films. Low temperature optical absorbance measurements in the temperature regime 90-301K are used for investigating the effect of doping on the temperature coefficient of band gaps of the films. Rutherford scattering spectra quantify the thickness of the films for conductivity (σ) measurements. The films exhibit n-type conductivity with two linear regions in the ln(σ) versus temperature inverse graphs, which indicate a defect activated conduction and intrinsic conduction, respectively, in the near room temperature and high temperature regions.