Fabrication of NiO film by sparking method under a magnetic field for application in NiO/ZnO Heterojunction

Abstract

Nickel oxide (NiO) films cover numerous electronic applications, including transparent conducting oxides, heterojunction and hole transport layer due to its high transparency and wide band gap. A sparking discharge is a new and unique method for the deposition of NiO films because of non-complex operation and non-requirement of a vacuum atmosphere. However, NiO films fabricated by this method display a porous surface with inferior crystallinity and poor electrical properties as well. To reduce the porousness and enhance the crystallinity of NiO films, the assistance of a permanent magnet in the sparking apparatus is introduced. Furthermore, a substitutional of Ni ions by Co ions are considered for the improvement of the electrical properties of NiO films. Herein, we report the investigation of the NiO film and the p-NiO/n-ZnO heterojunction deposited by the sparking method under a uniform magnetic field. Moreover, we also report an influence of Co concentration on the properties of NiO films made by this method. Our results indicate that the increase in the magnitude of the magnetic field from 0 mT to 375 mT reduces the porousness and enhances the crystallinity of NiO films. Meanwhile, by the incorporation of cobalt ion until 0.1 M, a carrier concentration of NiO is increased, resulting in a reduction of the resistivity. This consequence is in agreement with the increase in a number of higher-valence Ni3+ because of the Co2+ substituted Ni2+. For heterojunction, the best device shows the rectification ratio of 95 and the ideality factor of 4.92. This work provides an alternative method for the deposition of the NiO film with promising applications in optoelectronic devices.