Microstructures, electrical and optical properties of non-stoichiometric p-type nickel oxide films by radio frequency reactive sputtering

The NiO films were sputtered by radio frequency (rf) reactive magnetron sputtering with different O2 partial pressures. The electric resistivity (ρ) of NiO films continuously decreases from 0.45 to 0.01 Ω-cm as the O2 partial pressure is increased from 10 to 100%. On the other hand, the transmittance also decreases continuously from 96.33% to 32.93% as the O2 partial pressure increases from 0 to 100%. The lattice parameter of NiO films increases with increasing the O2 partial pressures, but the crystallinity of the films decreases significantly.