The percolation mechanism of conductivity in nanocomposite a-C:H<Ag+Ti> films

Abstract

The presented work is about percolation mechanism of electrical conductivity of composite a-C:H<Ag+Ti>
films. The a-C:H<Ag+Ti> thin films were deposited onto quartz substrates by ion-plasma magnetron sputtering
method. High purity argon (Ar) and methane (CH4) gases mixture and combined target of polycrystalline
graphite with the purity of 99.99%, silver (99.99%) and titanium (99.99%) were used to produce а-
С:Н<Ag+Ti> films. Resistance of the produced films has been measured using «two probe» method to obtain
concentration dependence of electrical conductivity. Conductivity of a-C:H<Ag+Ti> films was described
theoretically in two ways: using the classical theory of percolation and a general effective medium (GEM)
theory. Staircase percolation can be seen from the experimental results. The first percolation threshold occurs at
the concentration xc = 0.015 and the second one - at xc = 0.07. This could take place due to the fact that a-
C:H<Ag+Ti> composite material consist of two different inclusions, silver and titanium dioxide nanoparticles.
The percolation mechanism of a-C:H<Ag+Ti> film conductivity could be described by classical percolation
theory and by effective medium model as well.