First principles calculations of the electronic properties of bulk Cu2O, clean and doped with Ag, Ni, and Zn

Using first principles total energy calculations we have studied the electronic properties of bulk Cu2O, clean and doped with Ag, Ni and Zn. The calculated ground state structure of clean Co2O is cubic. Its lattice constant a = 4.30 Angstrom, and bulk modulus B-0 = 108 GPa are in excellent agreement with experimental values a = 4.27 Angstrom, and B-0 = 112 GPa. In its ground state, Cu2O is a semiconductor material with a small direct band gap at the Gamma point. Our calculated value of similar to0.5 eV is smaller than the experimental value of similar to2.0 eV, reflecting the problems of local density functional theory calculating the excited states. Doping with Ag, results in a reduction of the band gap. This result is important, since it implies that the band gap of Cu2O can be engineered by varying the amount of Ag in the crystal. Doping with Ni gives rise to a p-type semiconductor with the impurity levels above the valence band maximum, while doping with Zn results in a n-type semiconductor, with impurity levels above the conduction band minimum. (C) 2003 Editions scientifiques et medicales Elsevier SAS. All rights reserved.