Electronic properties of a grain boundary in Sb-doped ZnO

The electronic properties of a Sigma = 13 32.2 degrees [0001] tilt grain bo undary in ZnO have been investigated using first-principles calculations. T wo atomic models for the boundary have been considered, one of which contai ns structural units that are consistent with those observed for this orient ation using electron microscopy. Doping both the grain boundary models with antimony reveals a strong driving force for segregation. Analysis of the e lectronic densities of states, bond populations and Mulliken charges shows that antimony creates a localized impurity state in the grain boundary and acts as a donor dopant. The resulting charge accumulation at the grain boun dary together with the presence of local bonds that are metallic in charact er, will influence the mechanism for charge transport across the interface and this is discussed in relation to varistor applications.