Effect of O 2 /Ar value on the structure, optical and electrical properties of NiO:In 3+ films grown through dc magnetron sputtering

Abstract Indium-doped nickel oxide (NiO:In 3+ ) films were grown on the microscope slide through dc magnetron sputtering at different flow rate ratios of O 2 to Ar gases (O 2 /Ar). The dc discharge power of 180 W and high working pressure of 1.8 Pa were especially adopted for the better crystallization and surface morphology. The dependance of the structure, optical and electrical properties of the NiO:In 3+ films on O 2 /Ar value was studied using the data from x-ray diffraction, scanning electron microscopy, energy dispersive spectroscopy, Raman spectra, transmittance spectra and Hall effect. NiO:In 3+ films have the preferred orientation that is enhanced and then weakened with increasing the ratio O 2 /Ar. The near-violet absorption edge of the films varying in the range of 3.42 eV through 3.59 eV slightly blue shifts and then red shifts with increase of O 2 /Ar, which shows that the ratio O 2 /Ar does not have clear effect on the absorption edge of the films. A conducting transition from n to p type occurs at 2:1 O 2 /Ar. The n- and p-type conductions of the films are attributed to the incorporation of In 3+ into NiO lattice and to the enhanced oxygen-rich state, respectively. The electrical conductivity of the films is roughly improved with increase of O 2 /Ar.