Optical and crystallographic analysis of thin films of GeC deposited using a unique hollow cathode sputtering technique

Experimental results on thin films of the new material GexC1−x, deposited by a unique dual plasma hollow cathode sputtering technique, are presented. The GeC films, grown on etched Si(1 0 0), exhibited remarkable crystallinity with a lattice spacing which has shifted from that of pure Ge toward that of Si. This order has been characterized using X-ray diffraction (XRD) and Raman spectroscopy. The substrate temperature, which yielded the best results to date, was 350 °C. The deposition rate of the Ge and the deposition rate ratio of Ge to C did not have a great effect on the crystallinity. However, the substrate type had a great influence as did the presence of Al as an added impurity.Thin films were grown on etched Si, naturally oxidized Si, and onto glass substrates. The absorption coefficient was much higher for GeC than either Si or Ge. To verify that absorption was greater than Si or Ge for the more crystalline form of GeC, ellipsometry measurements were made. The photon absorption inferred from these ellipsometry measurements confirmed the fact that GeC has a quantum efficiency much greater than crystalline Si or Ge and even more than amorphous Si.