Hopping conduction in SiO2 films containing C, Si, and Ge clusters

Temperature dependence of electrical characteristics of SiO2 films doped with C, Si, and Ge were studied. The conductivity sigma was found to vary with the temperature as ln sigma proportional to T--1/4 over a wide temperature range, indicative of the conduction by the variable range hopping (VRH) mechanism. Since the previous optical studies for the same films indicate the existence of clusters in the films, it is very likely that the VRH through localized states associated with clusters dominates the conduction process, irrespective of the kind of group IV elements. (C) 1996 American Institute of Physics.