Interactions of hydride species and their roles in carbon nitride growth

The relative reactivity among neutral radicals, cations, and anions of various carbon and nitrogen hydride species, as well as the reactivity of these species with substrates of pseudocubic- and β-phase carbon nitrides, have been studied by analyzing their frontier orbitals calculated at Hartree-Fock and configuration interaction levels of theory using 6-31G** and 6-31 ++G** basis sets. For small species, the relative reactivity obtained in this study agrees well with the trend deduced from the available experimental rate constants. Our results show that both neutral carbon hydrides and nitrogen hydrides are less reactive than their cations and anions with the surfaces of carbon nitride substrates, and the cations are the most reactive species. The reaction of neutral and positive hydride radicals with carbon nitride substrates might be preferably accomplished through the formation of N-N bonds. Nevertheless, the negative hydride radicals may favor C-N bond formation with the substrate. Species containing C-N bonds were found to be preferable as precursors for chemical vapor deposition due to their high reactivity. The reactivity between gas-phase species and the carbon nitride clusters shows an increasing trend with the cluster size, indicating the ease of carbon nitride formation after its nucleation. Our results also show that CN radical possesses higher reactivity than C and N atoms and thus might be a good precursor for physical vapor deposition of carbon nitride films.