Effect of temperature on carbon nitride films synthesized by ion-beam-assisted pulsed laser deposition

Carbon nitride thin films were deposited by pulsed laser deposition with nitrogen ion beam assistance at a substrate temperature varying from room temperature to 800 degreesC. The effect of the substrate temperature on the nitrogen content, surface morphology, structure, and electrical property of the carbon nitride films was investigated. The deposited films were characterized by atomic force microscopy (AFM), Fourier transform infrared (FTIR) spectroscopy, x-ray photoelectron spectroscopy (XPS), Raman spectroscopy, and four-probe resistance. The nitrogen content of the deposited films reached its maximum value of 25% at a substrate temperature of 400 degreesC. AFM images revealed that an island structure occurred and developed on the surface of the films deposited at the high substrate temperature. FTIR and XPS spectra showed the existence of sp(3)C-N and sp(2)C=N bonds in the deposited films. The deposited carbon nitride films had an amorphous structure with two carbon nitride phases inclusions, which had a stoichiometry near C3N4 and a variable stoichiometry from C5N to C2N, respectively. With the increase in substrate temperature, the relative content of the sp(3)C-N bonds, i.e., the C3N4 phase, increased and the crystallization degree of the deposited films enhanced, which were confirmed by the Raman analysis. Very few C=N bonds in the films were found as compared to other carbon-nitrogen bonds. Electrical resistivity exhibited the highest value for the film deposited at 400 degreesC. Investigation results indicated that the high substrate temperature could promote the formation of C3N4 phase. (C) 2000 American Institute of Physics. [S0021-8979(01)03601-5].