Experimental comparison of N(1s) X-ray photoelectron spectroscopy binding energies of hard and elastic amorphous carbon nitride films with reference organic compounds

In this work, hard and elastic amorphous carbon nitride (a-CNx) films were deposited by DC magnetron sputtering on heated Si(001) substrates at 400degreesC. Nanoindentation results confirmed that the films were highly compliant and had high elastic recovery. X-ray photoelectron spectroscopy (XPS) was used to investigate nitrogen bonding by directly comparing the N(1s) spectra of a-CNx with the N(1s) peak positions of a variety of organic compounds that were characterized in the same XPS system. The N(Is) XPS spectra of hard and elastic a-CNx is resolved into two dominant intensity contributions at 398.5 and 400.6 eV. We show that the N(1s) spectra of a-CNx do not conclusively support a film-structure model with nitrogens bonded to sp(3) carbons. We offer an alternate interpretation based on the presented data and previous XPS, nuclear magnetic resonance (NMR), and computational work. Together, the data suggest that hard and elastic a-CNx consists of an sp(2) carbon network and that single-atom vacancy defects, as found in a graphite layer, may be present in the material. This implies that the low binding energy N(Is) component at 398.5 eV may be due to pyridine-like nitrogen bonded at the perimeter of a vacancy defect. (C) 2003 Elsevier Ltd. All rights reserved.