Hybrid density functional calculations of the defect properties of ZnO:Rh and ZnO:Ir
Muñoz, Ramo David
Bristowe, Paul D
Thin Solid Films
MetadataShow full item record
Muñoz, R. D., & Bristowe, P. D. (2014). Hybrid density functional calculations of the defect properties of ZnO:Rh and ZnO:Ir. Thin Solid Films, 555 112-116. https://doi.org/10.1016/j.tsf.2013.08.013
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 (∼3 eV) and lattice parameters (∼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 larger than 2 eV, which helps maintain transparency in 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 concentration hole conduction occurs mainly by the band conduction mechanism at room temperature. We also develop models of the amorphous spinels by means of classical molecular dynamics simulations, and observe a marked reduction in the coordination number of Rh/Ir, from 6 to 4, in the amorphous phase, which may reduce transparency in these materials.
Financial support for this work is provided by the European Commission through contract No. NMP3-LA-2010-246334 (ORAMA).
External DOI: https://doi.org/10.1016/j.tsf.2013.08.013
This record's URL: https://www.repository.cam.ac.uk/handle/1810/245209