(Zn + Co) co-doped CdO thin films with improved figure of merit values and ferromagnetic orderings with low squareness ratio well suited for optoelectronic devices and soft magnetic materials applications

Abstract

The present study focuses on the suitability of CdO thin films towards optoelectronic and spintronic devices through (Zn + Co) co-doping. Para to ferromagnetic transition mediated by oxygen vacancies takes place in the CdO:Zn thin films through Co doping which was acknowledged from the photoluminescence studies. Defect level peaks observed in the PL spectra at 411, 460 and 494 nm are associated with metal interstitials (Cdi, Zni, Coi), singly ionized oxygen vacancies (Vo+) and oxygen vacancies (Vo), respectively. The deep-level or trap state emission due to the ionized oxygen vacancies is observed at 521 nm. XRD analysis indicate that the undoped, Zn-doped (CdO:Zn) and (Zn + Co) co-doped CdO thin films have cubic structure with (1 1 1) plane being the preferential one. The crystallite size of pure CdO decreases with Zn-doping and with Co co-doping it increases. Cauliflower shaped nanostructures are evinced for the (Zn + Co) co-doped films. Increased optical transparency and decreased sheet resistance were observed for the (Zn + Co) co-doped films. Increased Haacke’s quality factor observed for the (Zn + Co) co-doped films confirmed their potential for optoelectronic devices.