Oxygen vacancy assisted multiferroic property of Cu doped ZnO films

Abstract

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.

Unveiling the dual role of chemically synthesized copper doped zinc oxide for resistive switching applications

“…1 The working principle of RS devices depends on the change in currents between the high resistance state (HRS) and low resistance state (LRS) in accordance with the external bias. It was found from the literature that perovskite oxides, 3 ferromagnetic materials, 4 ferroelectric materials, 5 polymers, 6 organic semiconductors, 7 and transition-metal oxides 1 (TMOs) were used as an interlayer or active material in these devices. Among these materials, TMO and ferroelectric materials are mostly preferred due to their high scalability, low cost, easy fabrication process, low power, fast switching speed, low operating voltage, and their high density integration with the existing CMOS process technologies.…”

“…Among these dopants, Cu has the similar electron shell structure as that of zinc (Zn) making it comfortably fit into the ZnO lattice structure. 4 On the other side, Cu atoms also act as electron traps in ZnO and conquer the recombination process. 22 Furthermore, the electrons move within the Cu and oxygen bonds because of their strong covalence, which may lead to electron deficiency in the nearby Zn and oxygen bonds.…”

Piezoelectricity and charge trapping in ZnO and Co-doped ZnO thin films

“…17 The control of ZnO conductivity by means of extrinsic doping can thus lead to a fine tuning of the piezoelectricity, which may also provide it with ferroelectric responses, whereas the ferroelectricity of undoped ZnO has never been reported from experiments on a macroscopic scale. 17 By contrast, local ferroelectricity can be induced by the presence of Li and Cu doping [18][19][20][21] as well as polar defects such as O vacancies at the surface, [22][23][24] and can be probed by performing experiments at the nanoscale.…”

Effects of Copper Dopants on the Magnetic Property of Lightly Cu-Doped ZnO Nanocrystals

“…As the Cu-doped level is very low, only the peak of Cu 2 p 3/2 is well-shaped. The asymmetrical peak of Cu 2 p 3/2 was also fitted by two Gaussian curves centered at 932.45 eV for Cu 1+ ( d 10 ) and 934.22 eV for Cu 2+ ( d 9 ), respectively [ 16 , 42 ]. This obviously shows that the Cu ions are of two valent states, and the nonmagnetic Cu 1+ ( d 10 ) ions account for 86% of all the Cu ions.…”

“…More recently, more meaningful phenomena were discovered upon Cu-doped ZnO. For example, Liu et al reported that RT polarization-applied electric field (P-E) loops can be observed directly, demonstrating the existence of multiferroic properties of the ZnO:Cu films [16]. Muhammad Younas found that the resistance can be switched from high resistance (HRS) to low resistance (LRS) through reversible tuning of the ferromagnetism of Cu-doped ZnO thin films [17].…”