Application Of Resistive Switching Effect In Spintronic Devices

In recent years,with the development of science and technology,there is a growing demand for information storage,such as:high capacity,high density,fast speed,nonvolatile and small size,etc..At present,the size of electronic storage is approaching the physical limit,so it is urgent to find a new technology to break through this bottleneck.Resistive random access memory(RRAM)has received much attention due to its simple structure,high density integration and nonvolatile memory performance.However,it is found that when the electronic devices are miniaturized to a certain extent,the influence of quantum effect on the devices cannot be ignored.Spintronics involves the interdisciplinary subjects of electronics,magnetism and information science,which can regulate the spin freedom of electrons.The combination of microelectronics technology and spin related effect provides a novel idea for the exploration of the new generation of electronic devices.Resistive switching(RS)has been widely reported,and various mechanisms have been proposed to explain this effect,but there is no unified conclusion,and it is still an unsolved problem.The Schottky emission,electron tunneling and conductive filament mechanisms have been widely accepted.RS not only shows the interesting physical phenomena,but also contains the rich physical mechanisms.We report the MoO_x with bipolar resistive switching(BRS)effect,and carried out corresponding research by applying external electric field on the reversible regulation of BRS in the device.Combining the RS and magnetoresistance(MR)effects,we reveal the mechanism of the RS in NiO.In addition,the application of RS to the photovoltaic effect provides a new way for the improvement of photovoltaic devices.1.Reversible voltage dependent transition of abnormal and normal bipolar resistive switchingPt/MoO_x/ITO device was prepared by pulsed laser deposition(PLD).Reversible transition of abnormal and normal BRS in dependence on the maximum voltage was observed.Below a critical maximum voltage of 2.6V,butterfly shaped I-V curves of abnormal BRS has been observed.Above 2.6V,normal BRS was observed.We believe that the mechanism of this phenomenon depends on the degree of displacement of oxygen vacancy from equilibrium position in the film under the applied voltage.In addition,in abnormal BRS,there is a dipole moment induced between the oxygen vacancy in the film and its original equilibrium position to generate a built-in electric field,the current minimum of the I-V curve of abnormal BRS is not in the position of theoretical zero field.2.Resistive switching of NiO film with various Al₂O₃ layer thicknessesWe have prepared NiFe/NiO/Pt and NiFe/Al₂O₃/NiO/Pt devices,and stable unipolar resistive switching(URS)behaviors have been observed after a forming process.The observation of MR effect confirmed that the metallic Ni conductive filaments formed in the NiO film,and the thickness of Al₂O₃ insulating layer affected the separation between the Ni filament and top electrode,thus making the device show transition from anisotropic magnetoresistance(AMR)to tunneling magnetoresistance(TMR).When the devices were switched to high resistance state(HRS),no MR can be observed.This confirms that the conduction filaments were totally broken.3.Effect of series circuit on magnetoresistance in different resistance states of Ni/Al₂O₃/Ni devices.Conductive filament is one of the main mechanisms for URS behavior,and can be manifested by the observation of MR effect.However,it was hard to control the conductive filaments in the device,sample always jumped to the low resistance state(LRS)in a short time.The inclusion of series resistance can effectively control the formation of conductive filaments.Increasing the series resistance can effectively increase the resistance of LRS for the device.The MR value decreases continuously with increasing resistance in LRS,which can be explained by that the diameter of Ni conductive filaments becomes smaller.4.Improving photovoltaic effect of inorganic perovskite by resistive switching using various electrode materials.We reported a half-cell planar structured RRAM based on CsPbBr₃ prepared by PLD,with generally used Ag or non-precious metallic Ni as electrode.Negative differential resistance(NDR)effect was observed in the device with Ag,due to the formation of Ag Br layer at interface and disappeared by replacing with Ni.The photovoltaic effect of the device is significantly improved in the HRS,which can be interpreted as the ion redistribution of the thin film under the action of an applied electric field,improving the hole-electron transferring efficiency.