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 O 2 partial pressures. The electric resistivity (ρ) of NiO films continuously decreases from 0.45 to 0.01 Ω-cm as the O 2 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 O 2 partial pressure increases from 0 to 100%. The lattice parameter of NiO films increases with increasing the O 2 partial pressures, but the crystallinity of the films decreases significantly.