Electrical and Structural Properties of Carbon-Nitrogen Films

Abstract

To investigate the role of nitrogen in the structure formation and electrical properties of CN_x thin films, several carbon thin films containing variable concentrations of nitrogen were deposited using a magnetron sputtering in a reactive N₂/ Ar discharge. The chemical composition of the as-deposited films was investigated by means of Rutherford backscattering (RBS) and a [N]/[C] ratio up to 0.5 was obtained. TEM studies confirmed that the deposits are mainly amorphous and contain nanocrystalline CN_x compounds. Additional STM investigations reveal a cluster-like microstructure of the surface showing a maximum cluster size of 10 nm in thin films deposited at a N₂ / Ar pressure ratio of 30% in the plasma. The electrical resistivity ρ was studied as a function of temperature between 10 K and 320 K. All deposited films show semiconducting behaviour. The lowest ρ values were observed in films containing no nitrogen, whereas the films deposited with 30% N₂in the sputter plasma reveal strongest semiconducting properties. The temperature dependence of the measured resistivity will be discussed according to Mott’s law and the activation energy for the electrical transport estimated at room temperature will be given.