Core ionization energies of carbon-nitrogen molecules and solids

Core ionization energies have been calculated for various carbon-nitrogen m olecules and solids. The systems investigated contain many of the bonding p ossibilities which presumably arise in carbon nitride thin films prepared u nder varying conditions. The molecular core ionization energies are calcula ted by the Delta SCF self-consistent field method. Several singly, doubly, and triply bonded CxNyHz species have been considered. Core ionization ener gies of two C11N4 C sp(2) and C sp(3)solids have been calculated with the f ull-potential linearized augmented plane wave method. Molecular C 1s bindin g energies increase with approximately 1 eV for each singly or doubly bonde d nitrogen atom attached. The trend is similar in the solids although varia tions and saturation effects are obtained due to hybridization and nitrogen content. The 1s binding energies of two-coordinated nitrogen atoms in C sp (2) molecules and of pyramidal three-coordinated nitrogen atoms in C sp(3) molecules are close to each other. The differences depend on the size of th e systems and the number of CH3 groups attached. In the solid state compoun ds, where no CH3 groups are present, the energies of two-coordinated nitrog en in a C sp(2) environment are always lower than the energy of pyramidal t hree-coordinated nitrogen in the C sp(3) solid, by more than 1 eV. Concerni ng the micro structure in thin CNx films, comparisons of the computational results with experiment indicate that at low nitrogen concentrations the at omic configuration close to the N atoms are mostly of sp(3) character. At h igher N contents more two-coordinated nitrogen atoms are incorporated. The N 1s binding energy shifts observed at high substrate temperatures could be explained by either a gradual formation of three-coordinated N atoms in a graphitic-like C sp(2) environment or by local domains containing high N co ncentrations. (C) 1999 American Institute of Physics. [S0021-9606(99)30545- 6].