Contribution of enhanced ionization to the optoelectronic properties of p-type NiO films deposited by high power impulse magnetron sputtering

Herein, intrinsic p-type conductivity of NiO films were enhanced by high power impulse magnetron sputtering (HiPIMS) technology, where more charged Ni3+ ions are created during the deposition process. The formation of Ni3+ ions are advantageous for strengthening the p-type conductivity of NiO films. As the pulse off-time increases from 0 mu s to 3000 mu s, Ni3+ concentration improves greatly, indicating the amount of Ni vacancies as well as the hole concentration significantly enhances. It confirms that HiPIMS is a preferential technology for preparing NiO films with high p-type conductivity. Especially, when pulse off-time reaches 3000 mu s, a high carrier concentration of 2.86 x 10(21) cm(-3) and a relatively low electrical resistivity about 0.07 Omega.cm are achieved.