STRUCTURE OF AMORPHOUS-CARBON IN AMORPHOUS C/GE MULTILAYERS

Amorphous C-Ge multilayers have been produced with periods varying from 2.6 to 12.5 nm. We have studied the multilayers using Raman spectroscopy and dc conductivity measurements and found that their properties change significantly when the carbon sublayer thickness is smaller than 2.5 nm. This value corresponds to the proposed dimension of sp2 bonded carbon islands within a-C and we find that our results can be understood in terms of the carbon forming these islands, but the islands becoming disconnected as the nominal carbon layer thickness decreases. The conductivity shows a percolation behavior for the thinnest layers.