The Resistance Switching Properties In Amorphous YFe_0.5Cr_0.5O_3-X Films

Resistance switching（RS） has been observed in metal/RS layer/metal structures, in which the resistance can be switched reversibly between a high resistance state（HRS） and a low resistance state（LRS） depending on the applied voltage. These two resistance states can be applied in resistance random access memory（ReRAM） devices, which have been investigated widely as promising candidates for commercial nonvolatile memory due to their low power consumption, fast switching speed, and scalability. Furthermore, some studies demonstrate that the actual active switching region occurs in a nano-scale region between metal electrodes and RS layers, which suggests great potential applications for nonvolatile memory device. Until now, a variety of materials had been investigated as RS layers in ReRAM devices, such as transition metal（TM） oxides, ferroelectric films, and perovskite oxides. Many models have been proposed to explain the RS behaviors, such as conductive filament（CF） model, Schottky barrier model, and space-charge limited current model. A common perspective is that the migration of oxygen vacancies（VOs） plays a dominant role on the RS for oxides. And, the formation or rupture of the CF is due to the interconnected or disconnected oxygendeficiencies at various applied voltages, respectively.More recently, some research proposed that large RS ratio and long retention could be achieved in amorphous-film-based ReRAM devices, and suggested that it is very attractive for future applications of nonvolatile ReRAM devices. In contrast to the polycrystalline material, amorphous material has a structural homogeneity on the atomic scale, which is beneficial to the ionic migration and then enhances the performance of ReRAM. However, each step must be carefully controlled to avoid any heating or chemical damaging/etching effect on the amorphous film to prevent crystallization during the entire fabrication process of the devices because the amorphous films was prepared at low temperature. Therefore, the amorphous film with high crystallization temperature is beneficial to the fabrication of the RS devices and thus its’ applications.YFe_0.5Cr_0.5O₃（YFCO） is a perovskite oxide with an orthorhombic structure. The Fe and Cr cations are randomly positioned instead of the 1:1 ordering in the B sublattice, and its crystallization temperature is very high. But the experimental results are still lacking due to the growth difficulty of the YFCO films. In this paper, we investigate for the first time the RS properties of amorphous-YFCO（a-YFCO） films prepared under various oxygen pressures. A bipolar RS with a large resistance ratio at room temperature was observed. The enhanced RS and long retention suggest its great potential for applications in nonvolatile memory devices. Herein, we demonstrate the contribution of the oxygen-deficiencies on the bipolar resistance switching（RS） properties of amorphous-YFe_0.5Cr_0.5O₃-x（a-YFCO） films. The a-YFCO films were prepared under various oxygen pressures to tune the concentration of oxygendeficiencies in the films. We confirm that the RS mechanism is related to the formation and rupture of a conductive filament consisting of interconnected oxygen-deficiencies. The enhanced RS and long retention in a-YFCO suggest a great potential for applications in nonvolatile memory devices.