Influence of oxygen partial pressure on properties of N-doped ZnO films deposited by magnetron sputtering

N-doped ZnO films were radio frequency (RF) sputtered on glass substrates and studied as a function of oxygen partial pressure (OPP) ranging from 3.0×10^-4 to 9.5×10^-3 Pa. X-ray diffraction patters confirmed the polycrystalline nature of the deposited films. The crystalline structure is influenced by the variation of OPP. Atomic force microscopy analysis confirmed the agglomeration of the neighboring spherical grains with a sharp increase of root mean square (RMS) roughness when the OPP is increased above 1.4×10^-3 Pa. X-ray photoelectron spectroscopy analysis revealed that the incorporation of N content into the film is decreased with the increase of OPP, noticeably N 1s XPS peaks are hardly identified at 9.5×10^-3 Pa. The average visible transmittance (380-700 nm) is increased with the increase of OPP (from ∼17 to 70), and the optical absorption edge shifts towards the shorter wavelength. The films deposited with low OPP (≤ 3.0×10^-4 Pa) show n-type conductivity and those deposited with high OPP (≥ 9.0×10^-4 Pa) are highly resistive (>10⁵ ·cm)