Neutron-diffraction studies of amorphousCNxmaterials

Abstract

The results of neutron-diffraction experiments performed on two samples of amorphous ${\mathrm{CN}}_{x},$ with nitrogen concentrations of 5 and 30 at. %, prepared by a combination of filtered cathodic arc and Kaufman-type ion source, are presented. Increasing the N content of the samples is seen to cause a decrease of the average bond length and the first coordination number. An increase in the average bond angle from 113\ifmmode^\circ\else\textdegree\fi{} to 121\ifmmode^\circ\else\textdegree\fi{} is also observed. The pair-distribution functions indicate that N incorporation results in some transformation of ${\mathrm{sp}}^{3}$ C sites to ${\mathrm{sp}}^{2}$ sites, but there is no evidence for N inducing the formation of crystalline graphitic clusters, and the overall structure remains amorphous. A direct subtraction of the two data sets emphasizes the loss of ${\mathrm{sp}}^{3}$ bonds and the increasing ${\mathrm{sp}}^{2}$ character of the higher-N-content sample, and shows the occurrence of a variety of bonding environments for N. More limited information on second neighbor correlations involving N is also revealed.