Study of the nanoscale electrical performance of NiO thin films by C-AFM and KPFM techniques: The effect of grain boundary barrier

Abstract

Conductive atomic force microscopy (C-AFM) and Kelvin probe force microscopy (KPFM) are applied to visualize the nanoscale current imaging and potential imaging of the NiO thin film on fluorine tin oxide (FTO) substrate. The results show that the grain boundary (GB) has a significant impact on the nanoscale current and potential of NiO film. The electronic conductivity and work function of NiO in grain face is higher than that of the NiO film on GB. The width of the conductive zone in the NiO film over GBs is ∼60 nm. The higher nanoscale current and work function in grain face is probably attributed to the presence of nickel vacancy (VNi) defects and excess oxygen (O2−) defects. The GB barrier in single-layer and bilayer NiO film was ∼0.0169 eV and ∼0.0226 eV, respectively. The nanoscale current is consistent to Schottky thermionic emission model.