Hopping conduction of amorphous Carbon film modified by embedded Au nano-particles*

Insulated amorphous Carbon with sp3 orbital can be modified into sp2 graphene-like orbital by the interface effect when in contact with Au nanoparticles. When the density of the modified domains exceeds the percolation limit, a hopping conduction via percolation paths becomes possible. In this study, Au nanoparticles generated on the top of quartz or amorphous C film were grown by sputtering technique at liquid nitrogen temperature or dipping in Au nanoparticle solution at room temperature, while the amorphous C films were grown by DC sputtering method at room temperature from a graphite target. The morphology, crystal structure and electric transportation were investigated by using an AFM in a tapping mode, a high resolution TEM and a high resistance meter in a cryostat, respectively. The size of Au nanoparticles was found to vary in a wide range of 40 nm to 300 nm with a height of ~10 nm. TEM images show that the modification for sp2 regions are a very thin layer within adjacent Au nanoparticles. The resistivity as a function of temperature indicates that the film is purely conducting by hopping mechanism.