D. Muñoz Ramo and P.D. Bristowe

Sponsors: European Commission (FP7)

• Oxide materials towards a matured post-silicon electronics era (ORAMA).
• Density functional calculations of band stuctures, doping mechanism, extended and point defects. Transport, dielectric and optical properties of crystalline or amorphous TCO and ASO materials.

Research Highlight

Density functional theory study of stoichiometric and nonstoichiometric ZnO grain boundaries

W. Korner, P. D. Bristowe and C. Elsasser, Phys. Rev. B 84, 045305 (2011)

We present a density–functional theory (DFT) analysis of stoichiometric and non-stoichiometric ZnO tilt grain boundaries (GBs) that reveals under which conditions such extrinsically undoped GBs may become electrically active. In the case of ZnO the self-interaction correction (SIC) scheme used allows a more accurate description of the formation energies as well as the electronic levels than the local density approximation (LDA). The results obtained with the SIC scheme deviate in some crucial ways from the LDA results of recent years. First, stoichiometric and non-stoichiometric ZnO GBs can show occupied deep levels whenever oxygen atoms are under-coordinated. Second, ZnO GBs with an oxygen excess at the boundary plane can exhibit unoccupied deep levels which may account for an experimentally observed weak varistor effect found in undoped polycrystalline ZnO.

View along [0001] of Σ = 7 (1230)  38.2° tilt grain boundary in stoichiometric ZnO. Two supercells are shown. The grain boundaries are located along the vertical dotted lines.