Doping and thickness variation influence on the structural and sensing properties of NiO film prepared by RF-magnetron sputtering

Abstract

The NiO and NiO–Cu doped films with various Cu contents of 5.68, 10.34, and 14.64 at%. Were deposited on a glass substrate with various thickness 50, 100, and 150 nm by RF-reactive magnetron sputtering technique. The effect of the thickness and the doping on the structural, electrical, and sensory properties of the films was mainly investigated. The X-ray diffraction studies revealed that all the deposited films were of single crystalline nature and exhibited cubic structure with preferential growth along 200 and only NiO peaks appear in the NiO–Cu films and when the thickness increased from 50 to 150 nm, the grain size increases from 24.38 to 25.036 nm. Compositional analysis indicated that Cu content increased in the film as the bonded chips increase in the target surface. The electrical resistivity of the NiO film showed a high electrical resistivity 280 K Ω detected by a four point probe measurement and when the Cu content in the films is 5.68 at%. The ρ value is reduced significantly to 45.9 K Ω as Cu content is increased to 10.34 at%, and it further decreases to 25.3 K Ω when the Cu content further increases to 14.64 at% the resistivity value decrease to 10.45 K Ω. The Hall measurement for all NiO and Cu-doped NiO films shows p-type conduction and reduction in the mobility of charge carrier from 9.67 × 102 to 8.46 × 10 cm2/V s, when the concentrations of the charge carriers increase from 4.30 × 1010 to 4.23 × 1013 cm−3. The sensory measurements for NiO and Cu-doped NiO films, show that the 50 nm thickness has the highest sensitivity and response time for the NO2 gas at the operating temperature 150 °C.