Effect of NiOx’s film thickness on the electrical properties of Ni/p–NiOx/n-Si structures

In this study, non-stoichiometric NiO films were obtained by using radio frequency sputtering technique to fabricate a heterojunction p–n Schottky diode. The crystal structure and topographical features of nickel oxide (NiOx) films were evaluated by means of X-ray diffraction, scanning electron microscopy and atomic force microscopy. The X-ray diffraction analysis has shown that all films have cubic polycrystalline nature, and some microstructural properties such as lattice constant, average crystallite size, micro-strain, dislocation density were changed depending on film thickness. In addition, topography of the nickel oxide films deposited with different film thickness consisted of fine nanoscale grains, showing a consistency between scanning electron microscopy and atomic force microscopy measurements. To evaluate electrical performance of NiOx films, high-quality vacuum evaporated silver (Ag) (ohmic) layer and nickel (Ni) (measurement electrode) dots were used. The current–voltage (I–V) measurements of Ni/p–NiOx/n-Si device indicated that all devices exhibit rectifying properties and these improve with the increasing film thickness. All electrical properties were correlated with the structural properties of the films to better understand transport mechanism of Ni/p–NiOx/n-Si device.