Effect of reactive pressure on direct current-sputtered NiO films with improved p-type conduction ability

The NiO films with improved p-type conduction ability are direct current sputtered on glass substrates at different reactive pressures (Preact). For NiO films, Preact has a threshold value of 1.0 Pa for the continuous glow discharge. The NiO film at 1.0 Pa Preact has more point defects than other NiO films. That is related to the blue glow discharge of oxygen atoms at 1.0 Pa Preact that confirms the occurrence of the energy transfer between Ar+ and O atoms. Although the decrease in point defect concentration of the films with increase of Preact result in the improvement in crystallization and the reduction in p-type conduction ability, the p-type conduction of the films is still greatly improved compared with other reports. The p-type NiO films at different Preact all have a near -violet absorption edge of ca. 3.6 eV.