Optical and Structural Properties of Nanostructured CuIn_(0.7)Ga_(0.3)(Se_(1-x)Te_x)_2 Chalcopyrite Thin Films - Effect of Stoichiometry and Annealing

摘要

The aim of this work was to study the dependence of the optical, structural and morphological properties of CuIn_(0.7)Ga_(0.3)(Se_(1-x)Te_x)_2 (briefly CIGSeTe) thin films for two different stoichiometries (for x = 0.2 and 0.8). The films have been deposited onto soda lime glass (SLG) substrates by the e-beam evaporation technique. The films showed high absorption and revealed optical band gaps ranging from 1.17 eV to 1.06 eV for x = 0 with highest annealing temperatute at 525℃ and 1.12 eV to 1.02 eV for x = 0.8 and with highest annealed temperature at 600℃ These results were correlated with the microstructural analysis by Atomic Force Microscopy (AFM), Scanning Electron Microscopy (SEM) and X-ray diffractometry (XRD). The linear dependence of the lattice parameters as a function of Se and Te contents was examined. X-ray diffraction analyses showed that the films had the single phase chalcopyrite structure. The lattice parameters (a and c) varied linearly with the increase in Te content x from x = 0.2 to x = 0.8. The peak corresponding to the (1 1 2) plane orientation of the films increased with annealing process. Also, SEM images showed that both the grains size and the RMS (root mean square) values increased with annealing and higher Te amount that caused grains aggregation. The relative 600℃ elemental composition present in the deposited CIGS films have been measured by using energy dispersive X-ray analysis (EDX).