Oxygen vacancy assisted multiferroic property of Cu doped ZnO films.

Exploring multi-functional properties in a single material is the focus for future material design and applications. In this work, we investigated the multiferroic property of Cu doped ZnO films using a combination of X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray absorption spectroscopy (XAS), classical magnetometry and electric measurements. The results show that the texture of Cu doped ZnO films is deteriorated with an increase in Cu contents, whereas the dielectric property is improved due to the introduction of Cu ions. The XAS result reveals that the Cu atoms occupy the substitutional Zn sites in the ZnO host, and thus induce local electric dipoles owing to the displacement of the Cu-O bond. The presence of oxygen vacancies together with Cu ions facilitates the movement of the ferroelectric domain boundary, and contributes to the ferromagnetism due to the indirect exchange between Cu atoms and large-sized vacancy orbitals. The Cu doped ZnO film is a feasible promising candidate for applications in multiferroic devices.