Electronic and atomic structures of the Si-C-N thin film by x-ray-absorption spectroscopy and theoretical calculations

Abstract

This study measures the x-ray-absorption spectra of a crystalline (c)-Si-C-N thin film at the C and Si K edge using the sample drain current mode and at the N K edge using the fluorescence mode. A resonance peak resembling the C 1s core exciton in the chemical-vapor-deposition-diamond/Si is observed. In addition, a broad feature is found in the energy range between ∼290 and 305 eV, which can be assigned to the antibonding C 2p-Si 3sp hybridized states and the C 2p-N 2sp hybridized states as well. The fact that the resonance peak is located ∼1.5 eV below the C 1s ionization energy suggests that the Frenkel-type exciton model can appropriately describe the core exciton of carbon atoms in c-Si-C-N. Closely examining the N K edge near edge absorption spectra reveals similar features in both c-Si-C-N and $\alpha -{\mathrm{Si}}_3{\mathrm{N}}_4,$ indicating that nitrogen atoms generally have a similar local environment in these two materials. Moreover, results obtained from Si K-edge absorption spectra of c-Si-C-N demonstrate a proportional combination of local Si-N and Si-C bonds associated with the local tetrahedral ${\mathrm{C}-\mathrm{S}\mathrm{i}-\mathrm{N}}_3$ arrangement as well as the long-range ordered atomic structure around Si atoms. Theoretical calculations using the first-principles pseudofunction method are also presented and compared with experimental data.