Planar intergrowth structures in the ZnO-In2O3 system

The accommodation of In2O3 in the ZnO wurtzite structure was investigated using a combination of atomistic simulation and HREM techniques. At low concentrations, indium ions are incorporated on zinc sites with creation of zinc vacancies to maintain charge neutrality; defect clustering involving two indium substitutional ions surrounding a zinc vacancy is energetically favourable. At higher concentrations, indium oxide is accommodated by a series of intergrowth phases, consisting of extended planar defects stacked along the c-axis of the hexagonal wurtzite structure. The proposed model for the In2O3-(ZnO)(m) phases consists of two indium oxide layers oriented along (0001) planes of ZnO separted by a ZnO wurtzite layer m/2 unit cells thick; each wurtzite region is displaced from the next by a translation of 1/3[01 (1) over bar 0]. The associated solution energies of these respective intergrowth phases are similar in magnitude, and are much lower than solution energies for both isolated defects and defect clusters.