Conductive properties of transparent Ni–In–Zn–O films deposited by combinatorial RF magnetron cosputtering

Abstract

The electrical, optical, and structural properties of cosputtered Ni–In–Zn–O films deposited on a flexible poly(ether sulfone) (PES) substrate were investigated by a combinatorial technique. The X-ray diffraction results showed that amorphous Ni–In–Zn–O films were deposited regardless of the Ni content [Ni/(Ni + In + Zn), at. %] in the range of 8.5–45.6 at. %. The surface of the amorphous Ni–In–Zn–O films was quite smooth. The obtained surface roughness (RRMS) values ranged from 0.7 to 1.5 nm. A high resistivity of 5.2 × 10−4 Ω cm and an average transmittance of 88% in the visible wavelength range were obtained for a Ni–In–Zn–O film with an elemental composition ratio of 10.5/73.8/15.7 at. % (Ni/In/Zn). The In content could be reduced by as much as −10 at. % compared with that of commercial indium tin oxide (ITO) while retaining a similar resistivity of −10−4 Ω cm. The measured work functions ranged from 4.84 to 5.02 eV, which are higher than those for ITO films. These findings indicated that Ni–In–Zn–O films grown by RF magnetron sputtering are promising for use as flexible transparent conducting electrodes owing to their low resistivity, high optical transmittance, and high work function.