Study on amorphous carbon nitride film prepared by facing target sputtering

Amorphous carbon nitride films were prepared by facing target sputtering at different N2/Ar gas flow rate ratios. The films were characterized using X-ray photoelectron spectroscopy (XPS), atomic force microscopy, Raman scattering, ellipsometric spectroscopy and temperature dependent resistance tests. As the N2/Ar ratio varies from 0 to 40%, the nitrogen to carbon ratio in the deposited films increases from 0 to 0.28. Curve fitting of the C 1s and N 1s XPS spectra shows that the C-C sp3 fraction decreases with an increase in nitrogen content and that the nitrogen atoms are mainly bonded in sp2 C-N bonds. All films exhibit a clean and smooth surface morphology with a root mean square roughness less than 0.25 nm over an area of 1 μm2. The Raman spectra show a G peak ranging from 1555 to 1565 cm−1 and a D peak from 1390 to 1425 cm−1 for sp2 C-C bonds, a weak peak for sp1 C-N bond at approximately 2210 cm−1. As the N/C ratio increases, both G-peak and D-peak positions shift to low wave number, the ID/IG intensity ratio increases from 1.75 to 1.95, and the Tauc optical band gap decreases from 2.1 to 1.4 eV.