Electrical Properties of Thin In2O3/C Films

We have studied the structure and electrical properties of thin films based on the In2O3 semiconductor and carbon, grown by atomic layer deposition using ion-beam sputtering. The structure of the resultant materials, formed during layer-by-layer growth of island layers, is made up of nanocrystalline In2O3 granules distributed at random over amorphous carbon. The electrical transport properties of the In2O3/C thin films depend on their thickness. In the temperature range 80–300 K, the dominant electrical transport mechanism in the In2O3/C thin films of thickness h < 70 nm sequentially changes from variable range hopping between localized states in a narrow energy band near the Fermi level (between 80 and 120 K) to nearest neighbor hopping (between 120 and 250 K) and then to variable range hopping between localized states in the conduction band tail (between 250 and 300 K). The films of thickness h > 70 nm undergo a change from conduction associated with strong carrier localization to that due to the presence of percolation clusters formed by In2O3 nanocrystals, which shows up as a linear temperature dependence of conductivity, with a negative temperature coefficient.