Hybrid density functional calculations of the defect properties of ZnO:Rh and ZnO:Ir

作者：Ramo David Munoz^*; Bristowe Paul D

来源：Thin Solid Films, 2014, 555: 112-116.

DOI：10.1016/j.tsf.2013.08.013

• ZnO
• ZnRh2O4
• ZnIr2O4
• DFT
• Polaron
• Diffusion barrier

We report density functional calculations of the atomic and electronic structure of the spinel phases ZnRh2O4 and ZnIr2O4 as well as crystalline ZnO lightly doped (1 at.%) with Rh and Ir ions using the B3LYP hybrid functional. Calculations for the spinels show band gaps (similar to 3 eV) and lattice parameters (similar to 2% difference) in reasonable agreement with experimental data. Incorporation of the transition metals into ZnO induces local distortions in the lattice and the appearance of metal d levels in the low gap region and near the conduction band minimum, with a d-d splitting of about 2 eV, which reduces the effective transparency of the material. Addition of a hole to the simulation cell of both spinels and doped ZnO leads to charge localization in the neighbourhood of Rh/Ir accompanied by local lattice deformations to form a small polaron which may lead to low hole mobility. We calculate polaron diffusion barriers in the spinels and obtain values around 0.02-0.03 eV. These very low barrier energies suggest that at high Rh/Ir concentrations polaron hopping is not going to be detected at room temperature.

• 出版日期2014-3-31