Experimental studies of Ge1-xCx and Ge1-x-yCxAly thin films

Experimental results on thin films of the materials GexC1-x, and Ge1-x-yCxAly deposited by a unique multiplasma hollow cathode sputtering technique, are presented. These films have been characterized by several techniques, the most important being in situ and ex situ spectroscopic ellipsometry, Auger electron spectroscopy (AES), and x-ray diffraction (XRD). The spectroscopic ellipsometry measurements of the films indicate that this material is a very strong absorber of photons. The XRD measurements reveal that the carbon is entering the lattice in substitutional sites, to a certain extent, and the AES depth profiling measurements determine the concentration and location of the different constituents. The materials appear to grow such that the concentration of the different elements is uniform throughout the films. The photon absorption inferred from the ellipsometry measurements corroborated the fact that GeC has a photon absorption efficiency much greater than crystalline Si or Ge and even more than amorphous Si in the wavelength range most useful for photovoltaic applications. In fact, the addition of aluminum increased this absorption efficiency substantially. (C) 2008 American Vacuum Society.