LOW-TEMPERATURE SPUTTER-DEPOSITION AND CHARACTERIZATION OF CARBON NITRIDE FILMS

Bombarding a carbon target with low-energy nitrogen ions causes the re lease of neutral carbon atoms (physical sputtering) and volatile carbo n nitride compounds (chemical sputtering) with relative yields depende nt on the energy of the nitrogen beam. The chemically sputtered specie s are volatile and can be condensed on the substrate by reducing its t emperature. Carbon nitride films have been deposited at varying nitrog en beam energies and substrate temperatures in a dual ion beam deposit ion chamber. Films were grown both with and without the presence of an additional assisting nitrogen beam. Reduction of the substrate temper ature in conjunction with low sputter beam voltages (<200 V) caused th e nitrogen concentration to attain a maximum value of 44%, the optical band gap to increase to 2.2 eV, the sheet conductivity to decrease to less than 10(-9) (Omega cm)(-1) and the density to be reduced to 1.6 g cm(-3). The chemical structure was investigated by Fourier transform infra-red, X-ray photoelectron and Auger electron spectroscopies. The increasing transparency is accompanied by structural changes indicati ng a transition from a predominantly sp(2)-bonded amorphous sp(2)/sp(3 ) C-N network to a more linear polymer-like structure consisting predo minantly of doubly and triply bonded C and N atoms. No evidence for th e formation of a beta P-C3N4 phase was found. (C) 1997 Elsevier Scienc e S.A.