Strong asymmetrical doping properties of spinel CoAl 2O 4

Abstract

Using first-principles density-functional theory, we have investigated the intrinsic and extrinsic doping properties of CoAl 2O 4 by calculating the transition energies and formation energies of intrinsic and extrinsic defects. We find that CoAl 2O 4 exhibits strong asymmetrical doping properties: Although excellent p-type conductivity can be achieved by Li or Na doping at O-rich growth condition, n-type conductivity cannot be achieved by any intrinsic or extrinsic dopants at any growth conditions. These asymmetrical doping properties are attributed to the formation of intrinsic defects, particularly Al Co, which has very low formation energy at all growth conditions. Our results suggest that for better use of CoAl 2O 4, the electronic devices should require CoAl 2O 4 to exhibit p-type conductivity. © 2012 American Institute of Physics.