Post-growth annealing effect of Li-doped NiO thin films grown by mist chemical vapor deposition

Nickel oxide (NiO) thin films were grown by mist chemical vapor deposition (mist CVD) with various amounts of Li dopant in the precursor (0-15%). As the Li dopant readily decomposed under the high temperature above 700 degrees C, the post-growth annealing was conducted at 600-800 degrees C. The crystal quality of the undoped and Li-doped NiO films was improved by thermal annealing due to the crystal reconstruction. The optical transmittance of NiO films was decreased with increasing the amounts of Li dopants, whereas it was increased with thermal annealing. The bandgap of the NiO films was slightly red-shifted with increased amounts of Li dopants, whereas it was blue-shifted with increasing annealing temperature. The resistivity of as-grown NiO films ranged from 25-75 Omega<middle dot>cm with Li doping. Electrical properties abruptly decreased under a high annealing temperature of 700 degrees C. Hence, an appropriate combination of Li doping and post-growth annealing might improve the structural properties of the NiO thin films while retaining the p-type conductivity.