Characterization of Ir and Os doped NIO films and heterojunction applications

In this study, undoped and Os and Ir doped NiO thin films at different volume ratios (1% and 3%) were deposited on glass and n-type Si substrates using the sol-gel spin coating method. The undoped films produced were named NO1 and NO3 according to their molarities, while the Os doped films were named ONO1 and ONO3, and the Ir doped films were named INO1 and INO3. The structural, optical, electrical, and morphological properties of the undoped, Os and Ir doped NiO films deposited on glass were investigated. XRD measurements to examine the structural properties revealed that Os and Ir doping disrupted the NiO crystal structure and reduced the crystallite size. Optical measurements indicated that as the doping ratio increased, the optical band gap decreased, and the Urbach energy values increased. Morphological measurements revealed that the surface of the NO1 film was homogeneous and that there was no significant change with Os doping; however, the defects were observed on the surface of the NO3 film, and a homogeneous surface was formed with Ir doping. To obtain the electrical properties of heterojunction structures, current-voltage (I-V) measurements were carried out for the undoped, Os and Ir doped NiO films deposited on n-Si substrate. The results showed that these heterostructures have a rectifiying behaviour and the calculated their idealite factors increased depending on the increasing doping ratios of Ir and Os. To examine the photosensor properties, photosensitivity and photoresponse values were calculated. It was observed that photosensitivity increased and photoresponse decreased with Os doping, while both photosensitivity and photoresponse decreased with Ir doping.