Synthesis and characterization of Zn_100−xLi_xO and Zn_100−x−yLi_xCu_yO thin films for electronic and optoelectronic applications

p-type conductivity and the modulation of bandgap of ZnO are crucial aspects for realization of optoelectronic devices’ applications. The Li and Li-Cu could be suitable doping agents for achieving the p-type conductivity and the modulation of bandgap of ZnO. To this point of view, the Zn_100−xLi_xO (x = 0 to 40 at.%) and Zn_100−x−yLixCu_yO (fixed, x = 5 at.%, and y = 0:0 to 10 at.%) thin films were prepared on the microscopic glass substrates at a temperature of 350^◦C using cost effective chemical spray pyrolysis (CSP) technique. Field emission scanning electron microscope images show the coexistence of interconnected fibrous and flat grains on the films surface. The grain size changes as function of Li- and Li-Cu concentrations, and at a higher doping granular grains are observed. The successful incorporation of Li and Cu-Li into ZnO crystal is confirmed by X-ray photoelectron spectroscopy (XPS) measurements. The X-ray diffraction (XRD) patterns exhibit hexagonal polycrystalline structure of doped ZnO. However, the crystallinity is deteriorated at higher Li- and Li-Cu doping concentrations. The optical bandgap study exhibits direct transition type and it is red shifted from 3.21 to 2.61 eV and 2.84 to 3.56 eV for Li and Li-Cu doping in ZnO thin films, respectively. The optical conductivity enhances as a result of Li- and Li-Cu doping in ZnO. Therefore, Li- and Li-Cu can effectively be doped to tune bandgap and enhance optical properties of ZnO for electronic and optoelectronic device applications.