Electrical properties of reactively sputtered carbon nitride films

Abstract

Hydrogen-free carbon nitride films have been deposited with an opposed-target Penning-type sputtering source, as described by Murphy et al. [M.J. Murphy, J. Monaghan, D.C. Cameron, A.K.M.S. Chowdury, R. Walsh, M.Tyrrell, M.A Monclus, M.S.J. Hashmi, J. Vac. Sci. Technol. A., 17 (1999) 62], using graphite targets in an Ar/N2 atmosphere. The resistivity and optical band gap of the films have previously been investigated as a function of nitrogen content [M.A. Monclus, D.C. Cameron, A.K.M.S. Chowdhury, Thin Solid Films, 341 (1999) 94]. The C≡N bond structure was found to be the controlling factor for the resistivity, and increased concentrations of the C≡N bond led to the reduced resistivity. Nitrogen atoms bond to the carbon backbone in a non-doping configuration. The changes in bonding structure caused by varying the nitrogen partial pressure during growth were found to be the cause of the increase in resistivity, and these changes are discussed in terms of the optical gap and activation energy of the films. The relation between the density of states at the conduction band edge as indicated by electrical resistivity measurements and the unpaired electron concentration obtained by electron spin resonance spectroscopy is examined as a function of the amount of nitrogen incorporation. Finally, a proposed electronic band structure for nitrogen-free films and nitrogen-containing films is given.