Stabilities and electronic properties of vacancy-doped Ti2CO2

Abstract

The stabilities and electronic properties of vacancy-doped Ti2CO2 have been investigated by a first-principles method. The formation energies of carbon (C) vacancies are relatively small. And they change from negative to positive as the defect concentration of C vacancies increases. Atomic-vacancy-induced defect states appear in the band structure of defective Ti2CO2. The Fermi energy of C vacancy (VC)-doped Ti2CO2 shifts upward compared with that of perfect Ti2CO2, making VC-doped Ti2CO2 exhibit metallic character. A localized defect state of oxygen vacancy (VO)-doped Ti2CO2 occurs in the midgap of pristine Ti2CO2. And as the defect concentration decreases, the VO-induced band becomes more localized with nearly flat band dispersion. The defective state of VO-doped Ti2CO2 acts as an electron donor state when Ti2CO2 is used as a semiconducting material. Further, the stabilities and electronic properties of different C and O divacancy configurations are explored. Investigation of the C divacancy (V2C) in a 4 × 4 × 1 Ti2CO2 supercell indicates that the C vacancy configuration distribution has little influence on the electronic conductivity of V2C-doped Ti2CO2. Hence it is possible to modulate the electrical conductivity of Ti2CO2 by adjusting the C vacancy concentration. Investigation of the O divacancy (V2O) suggests that the O vacancy configuration distribution changes the electronic band structure at the Fermi level of V2O-doped Ti2CO2.