The affinity of Si–N and Si–C bonding in amorphous silicon carbon nitride (a-SiCN) thin film

The bonding sensitivities of Si–N and Si–C bonds in the a-SiCN thin films were investigated experimentally and theoretically. It was found that a sharp phase transition from the predominantly Si–C bonded structure to the Si–N bonded structure occurs during the deposition of SiCN thin films without and with N incorporation. The stronger affinity of silicon to bond with nitrogen than to bond with carbon results in the complete absence of Si–C bonds in a-SiCN thin films. These were further verified by the analyses of crystal structures and local bonding configurations, morphology, and optical properties. Finally, the relative stabilities of Si–C and Si–N bonds in the a-SiCN network were studied by the ab initio calculations for the simple SiCN clusters. The local atomic structure with Si–N–C (or Si–N C) bonding exhibits a considerably lower total energy of 0.65 (0.52) eV than that with Si–C–N (Si–C N) bonding, providing the explanation of the stronger affinity of Si–N bonds than Si–C bonds in a-SiCN thin films.