The electronic properties of Co-doped Σ=7[0001] grain boundaries in ZnO were investigated using first-principles calculations. Grain boundary segregation calculations show that for Σ=7 grain boundaries, the driving force of Co segregation at grain boundaries is strong, and the segregation energy of interstitial filling is lower than that of grain boundary substitution. We obtain negative segregation energies at the two grain boundary sites, indicating that Co aggregates at the grain boundaries. The analysis of the band structure, electronic density of states and plane-averaged charge density shows that the pure Σ=7 grain boundary will lead to the generation of shallow-level acceptor states due to the breaking of bonds at the grain boundary, but it will not cause nonlinear I-V characteristics. Calculations for doping Σ=7 grain boundaries show that Co produces local impurity states at the grain boundaries and acts as a donor dopant, the conduction band intersects with the Feimi level, enhancing the grain boundary conductivity.

DFT,Doped,PDOS,Varistor