Electronic structure of C_2N_2X (X = O, NH, CH_2)∶ Wide band gap semiconductors

摘要

The electronic structure of Ⅳ_2Ⅴ_2Ⅵ class semiconductors, C_2N_2X (X = O, NH, CH_2), was investigated using first principles calculations. The crystal structures of C_2N_2X are isostructural with the Si_2N_2O compound, sinoite. The valence of the X atom is virtually two, and thus the substitution of X (X = O, NH, CH_2) is isoelectronic. From the calculated density of states, the carbon 2p orbital does not participate in the upper valence band (VB) (0 to -5eV). 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 CH_2 group. The calculated absorption edge is 7.76, 7.07, and 6.66 eV for C_2N_2O, C_2N_2(NH), and C_2Nv2(CH_2), respectively.