Nitrogen doping on NiO by reactive magnetron sputtering: A new pathway to dynamically tune the optical and electrical properties

Abstract

N-doped nickel oxide (NiO:N) thin films were deposited on glass and silicon substrates by reactive DC magnetron sputtering in Ar/O2/N2 gas atmosphere with a series of N2/O2 gas ratio ranging from 0 to 80%. X-ray diffraction measurements have revealed that the films are constituted of Ni1-xO grains and showed enhanced polycrystalline features with increasing N-doping concentration. For the first time, we report here that N-doping in the Ni-deficient NiO (Ni1-xO) film leads to a band-gap narrowing from 3.6 to 2.3eV. X-ray photoelectron spectroscopy (XPS) measurements proved that up to 4 atomic percent (at.%) nitrogen can be incorporated at least at the surface of the NiO:N samples. In addition, XPS valence band spectra and UV–vis transmission measurements have demonstrated that the band-gap narrowing may originates from the contribution of an intermediate band (IB) ∼2.4eV just above the valence band maximum and the up-shifting of the valence band edge (∼0.3eV) due to the introduction of occupied N 2p states. Local I–V measurements, carried out by conductive AFM (C-AFM), have revealed that the extrinsic doping of N atoms within the oxide can be a good way to precisely control the electrical conductivity of such p-type materials.