Cu-Cu interactions in the transparent p-type conductors:: CuAlO2 and SrCu2O2

Electronic structures of the p-type Transparent Conducting Oxides (TCO): CuAlO2 and SrCu2O2 are calculated using the Tight Binding Linearized Muffin Tin Orbital within the Atomic Sphere Approximation method (TB-LMTO-ASA). The band structures indicate two gaps for CuAlO2 (an indirect one with DeltaE approximate to 0.45 eV and a direct one with DeltaE approximate to 1.25 eV) and one direct gap for SrCu2O2 (with DeltaE approximate to 2 eV). In both oxides the Cu states are dominant at the top of the valence band, close to the Fermi level and the existence of weak Cu-Cu bonding interactions is revealed through the Integrated Crystal Orbital Hamiltonian Population (ICOHP). The presence of such interactions suggests that for the hole doped oxides the conduction may result from the direct overlapping of the orbitals of the Cu atoms within the Cu+ networks. (C) 2003 Editions scientitiques et medicales Elsevier SAS. All rights reserved.