|Michael Sullivan Online|
Defects in codoped NiO with gigantic dielectric response
Ping Wu, Valeri Ligatchev, Zhi Gen Yu, Jianwei Zheng, Michael B. Sullivan, and Yingzhi Zeng
Institute of High Performance Computing, 1 Fusionopolis Way, #16-16 Connexis, Singapore 138632 Singapore
(Received 10 May 2009; published 16 June 2009)
Phys. Rev. B, 2009, 79, 235122.
We combine first-principles, statistical, and phenomenological methods to investigate the electronic and dielectric properties of NiO and clarify the nature of the gigantic dielectric response in codoped NiO. Unlike previous models which are dependent on grain-boundary effects, our model based on small polaron hopping in homogeneous material predicts the dielectric permittivity (104–5) for heavily Li- and MD-codoped NiO (MD=Ti,Al,Si). Furthermore, we reproduce the experimental trends in dielectric properties as a function of the dopants nature and their concentrations, as well as the reported activation energies for the relaxation in Li- and Ti-codoped NiO (0.308 eV or 0.153 eV depending on the Fermi-level position). In this study, we demonstrate that small polaron hopping on dopant levels is the dominant mechanism for the gigantic dielectric response in these codoped NiO.