Electronic structure of C2N2X (X = O, NH, CH2): Wide band gap semiconductors

The electronic structure of IV2V2VI class semiconductors, C2N2X (X = O, NH, CH2), was investigated using first principles calculations. The crystal structures of C2N2X are isostructural with the Si2N2O compound, sinoite. The valence of the X atom is virtually two, and thus the substitution of X (X = O, NH, CH2) is isoelectronic. From the calculated density of states, the carbon 2 p orbital does not participate in the upper valence band (VB) (0 to –5 eV). The upper valence band is dominated by the N 2 p and X 2 p orbitals. The calculated optical absorption edge shifts to a lower energy as the substitution progresses from the O atom to the CH2 group. The calculated absorption edge is 7.76, 7.07, and 6.66 eV for C2N2O, C2N2(NH), and C2N2(CH2), respectively.