Role of multivalent Cu, oxygen vacancies and CuO nanophase in the ferromagnetic properties of ZnO:Cu thin films

Abstract

Room temperature ferromagnetism (FM) of these thin film samples are highly tuneable by the simultaneous presence of CuO nanophases and multivalent Cu and Vö concentrations.

Role of defects in one-step synthesis of Cu-doped ZnO nano-coatings by electrodeposition method with enhanced magnetic and electrical properties

“…Further contribution to RTFM can come from the point defects (Zinc interstitial 'Zn i ' or vacancy of oxygen 'V O ') or the secondary phases of Cu dopants in the host lattice [49]. Hence, the observed moment is not only from a single origin, but also from V O , mixed oxidation states of Cu and CuO secondary phases [26,48]. V O cannot solely induce ferromagnetism but when it is coupled with Cu, it can incorporate ferromagnetism ordering.…”

“…3a) Observed RTFM in the CZO is due to the interaction among the dopant Cu impurities as well as the native defect states present in ZnO [2]. Since delocalized electrons in Cu ions mediated the RTFM [26,47], it suggests that the ferromagnetism is originated from carrier-induced exchange couplings in the Cu dopants. Xia et al [44] reported that the exchange interaction among the conductive electrons and the local spin-polarized electrons induces RTFM as proposed in Ruderman-Kittel-Kasuya-Yosida (RKKY) theory.…”

“…The ionic radii of Zn 2+ and Cu 2+ are 0.074 and 0.054 nm, respectively, so the slight size mismatch results in the low formation of Cu Zn . High ionization energy of Cu and low formation energy of Cu Zn suggest that higher doping concentration can be achieved and in turn band gap can be engineered [26,31]. In addition, the substitution of Cu induces lattice distortion and morphological changes due to the size mismatch.…”

“…There are different synthesis processes to develop TMdoped ZnO nanostructures such as electron beam evaporation [32], metal organic CVD (MOCVD) [33], pulsed laser deposition (PLD) [26], molecular beam epitaxy [34], and electrodeposition [35]. Among these, electrodeposition is simple with a direct approach by adding an appropriate proportion of dopant into the electrolyte solution.…”

“…Some of the literature claims that the FM nature in TM-doped ZnO is due to the presence of external impurities like magnetic clustering and precipitations of metal ions [13][14][15][16][17][18][19][20]. To nullify the external effects, non-magnetic materials like metal Cu, metal Zn, ZnO, Cu 2 O, and bulk CuO were doped to produce intrinsic DMS materials [24][25][26]. Theoretical and Abstract We report the growth of flower-like ferromagnetic Cu-doped ZnO (CZO) nanostructures using electrochemical deposition on FTO-coated glass substrates.…”