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The effect of oxide/oxide interface for controlling the migration process of oxygen vacancies (or oxygen ions) on resistive switching behaviors has been investigated by fabricating the ZrO2/ZnO oxide heterostructures. Completely different resistive switching behaviors are observed in the heterostructures with a set process under a different bias polarity. It is demonstrated that the change of the oxide/oxide interface barrier height determining the migration of oxygen vacancies (or oxygen ions) leads to the current direction-dependent resistive switching. Furthermore, the ZnO/ZrO2 heterostructure with the homogeneous resistive switching behavior could be potentially applied as a controllable and stable multistate memory by controlling reset-stop voltages. Our method opens up an opportunity to explore the resistive switching mechanism and develop resistance switching devices with specific functions through engineering oxide/oxide interfaces in oxide heterostructures.

Oxygen nonstoichiometry plays a critical role in determining the physical and chemical functionalities of oxide materials. For widespread applications involving oxygen transport and exchange with the environment, fast, inexpensive, and reversible control of oxygen deficiency is highly desired. This article illustrates voltage-controlled oxygen nonstoichiometry in SrCoO3−δ (SCO) thin films, in which the oxygen deficiency (δ) can be tuned between 0 and 0.5 within tens of seconds by a small applied voltage (<1.7 V). Correspondingly, its magnetism as well as the electrical and optical properties can be tuned accordingly from one end to the other, making it a good candidate for a number of commercial applications, such as oxygen capacitors, catalysts, smart windows, and so forth. This approach can be used as an effective method in imaging the phase diagrams of transition-metal oxides, such as ternary ABO3−δ (A = Ln, Ca, Sr, Bi; B = Cr, Mn, Co, Fe, Ni) or binary TiO x , WO x , VO x and NiO x , and so forth, paving the way for the search for novel properties in redox materials.

The resistive switching behavior of Co-nanoparticle-dispersed polypyrrole (PPy) composite films is studied. A novel design method for resistive random access memory (ReRAM) is proposed. The conducting polymer films with metal nanocrystal (NC)-dispersed carbon chains induce the spontaneous oxidization of the conducting polymer at the surface. The resistive switching behavior is achieved by an electric field controlling the oxygen ion mobility between the metal electrode and the conducting polymer film to realize the mutual transition between intrinsic conduction (low resistive state) and oxidized layer conduction (high resistive state). Furthermore, the formation process of intrinsic conductive paths can be effectively controlled in the conducting polymer ReRAM using metal NCs in films because the inner metal NCs induce electric field lines converging around them and the intensity of the electric field at the tip of NCs can greatly exceed that of the other region. Metal NCs can also bring new characteristics for ReRAM, such as magnetism by dispersing magnetic metal NCs in polymer, to obtain multifunctional electronic devices or meet some special purpose in future applications. Our works will enrich the application fields of the electromagnetic PPy composite films and present a novel material for ReRAM devices.

Multiferroic materials with flexibility are expected to make great contributions to flexible electronic applications, such as sensors, memories, and wearable devices. In this work, super-flexible freestanding BiMnO 3 membranes with simultaneous ferroelectricity and ferromagnetism are synthesized using water-soluble Sr 3 Al 2 O 6 as the sacrificial buffer layer. The super-flexibility of BiMnO 3 membranes is demonstrated by undergoing an ≈180°folding during an in situ bending test, which is consistent with the results of first-principles calculations. The piezoelectric signal under a bending radius of ≈500 μm confirms the stable existence of electric polarization in freestanding BiMnO 3 membranes. Moreover, the stable ferromagnetism of freestanding BiMnO 3 membranes is demonstrated after 100 times bending cycles with a bending radius of ≈2 mm. 5.1% uniaxial tensile strain is achieved in freestanding BiMnO 3 membranes, and the piezoresponse force microscopy (PFM) phase retention behaviors confirm that the ferroelectricity of membranes can survive stably up to the strain of 1.7%. These super-flexible membranes with stable ferroelectricity and ferromagnetism pave ways to the realizations of multifunctional flexible electronics.