Novel plasma-assisted combustion route for NiOx thin film deposition

Abstract

The emerging field of flexible electronics demands low-temperature, high-throughput solution-processable thin films of oxide semiconductors. Towards this goal, we report a novel low-temperature synthesis route that is primarily in a combination of solution combustion synthesis and plasma irradiation to deposit p-type nonstoichiometric NiOx thin films at a relatively lower temperature range. The film morphology was studied by atomic force microscope (AFM) and scanning electron microscope (SEM) while the crystallographic information was obtained from X-ray diffraction (XRD) studies. The NiOx formation mechanism is extensively studied with X-ray photoelectron spectroscopy (XPS) measurements. Here we reveal the conditional analysis to optimize the Ni3+ concentration that essentially controls the net free carrier in the nonstoichiometric NiO thin films. Based on our understanding, the plasma treatment not only plays a deterministic role in the material and the defect formation but is also efficient in removal of chemical impurity to obtain crystalline NiO thin films. Temperature-dependent (130–303 K) electrical resistivity measurements revealed that variable-range hopping (VRH) is the dominant hole transport process in this material.