| Resistive random access memory(RRAM)with simple structure,fast read/write speed,small size,and long data retention time,has attracted great attention and has become the most promising non-volatile memory of the new generation.In order to improve the storage densities of RRAM devices,the resistive switching and magnetic properties controlled by electric field simultaneously was studied intensely.Recently,due to the potential application in spintronics,the study of graphene has attracted much attention.Different from grapheme,graphene oxide(GO)contains carboxyl(-COOH),carbonyl(-C=O-),epoxy group(-CH(O)CH-),hydroxyl(-OH)and other oxygen-containing functional groups,thus,GO exhibits insulator/semiconductor properties.Until now,there have been few studies on the electrical control of the resistance and magnetic properties in GO.Therefore,in this work,GO monolayer and GO/Gd2O3 bilayers were used as the dielectric layers in the RRAM devices and the resistive switching and magnetic modulation in these films were studied.The mechanism was also discussed.The main conclusions are as follows:(1)A series of GO films were prepared on an ITO substrate using a spin coating.By studying the effect of different suspension concentration and spin coating speed on the resistance of GO monolayer membrane,the optimum suspension concentration and spin coating speed were found.Based on the above results,the influence of electric field on the magnetic properties of GO monolayer film was studied.This results show that the magnetic property of the Ti/GO/ITO device was changed with different resistance states,and the magnetization of the High Resistance State(HRS)is greater than that of the Low Resistance State(LRS).We propose that the migration of oxygen ions in GO dielectric layer under the electric field is the main reason for controlling the resistance and magnetic properties of Ti/GO/ITO devices.Under the electric field,oxygen ions in the GO film layer and ITO migrate toward the top electrode.In this process,with the gradual reduction of oxygen ions,SP2 cduster conductive filaments are formed in the GO layer,which switch the device from a high-resistance state to a low-resistance state,resulting in a decrease in the magnetization of the device.Under the the reverse electric field,with the migration and increase of oxygen ions,the SP2 cluster filaments of the GO thin film layer are broken,which lead the device return to high-resistance state,resulting in a strong magnetic property of the device.(2)Four different top electrodes were prepared by vapor plating on GO monolayers,and corresponding devices X/GO/ITO((X=Au,Ag,Cu,AI))were obtained.The effects of different top electrodes(XF=Au,Ag,Cu,Al)on the resistive switching of GO thin films were studied.When the forward bias is applied first,the four devices only exhibit a resistive hysteresis window under the negative voltage;but when the negative bias is applied first,the four devices exhibit bipolar resistive switching.The resistance ratio of Au/GO/ITO devices is the largest(13 times),the Al/GO/ITO device is the smallest(4 times),Ag/GO/ITO(9 times)and Cu/GO/ITO is among them(7 times).Oxygen ion migration is the main reason for the on-off switching in the GO thin film.Compared to the active Al and Cu electrodes,the inert Au,Ag electrodes are not able to absorb oxygen ions during the resistance change,thus increase the resistance of the GO film in the high resistance state and leading to the highe resistance ratio of the devices.(3)The resistive switching and magnetic properties of GO/Gd2O3 bilayer films were investigatedby depositing them on a Pt substrate.Compared to GO single-layer Ag/GO/Pt devices,Ag/GO/Gd2O3/Pt devices exhibit bipolar resistive switching under lower trigger voltages.The experimental results show that the magnetic property of the Ag/GO/Gd2O3/Pt device was changed with different resistance states,and the magnetization of the HRS is greater than that of the LRS.We propose that the oxygen-rich Gd2O3 film can be used as oxygen storage layer by providing a large amount of oxygen ions during the resistive switching process.When a negative bias is applied to the top electrode,oxygen ions which carry a negative charge migrate from the GO dielectric layer to the GO/Gd2O3 interface and combine with oxygen vacancies in the Gd2O3 film.As the oxygen content in the GO layer decreases,SP2 cluster conductive filaments are formed,which triggers the device to a low-resistance state;with the decrease of the number of oxygen-containing functional groups in the GO dielectric layer,the magnetic properties of the device are reduced.When the forward voltage is applied,not only the oxygen ions at the GO/Gd2O3 interface return to the GO dielectric layer,but also the oxygen ions contained in the Gd2O3 interior migrate to the GO dielectric layer,thus the oxygen-containing groups in the GO dielectric layer increase,and the SP2 cluster conductive filament breaks,the device returns to a high resistive state.At the same time,with the increase of oxygen groups in the GO dielectric layer,the magnetization of the GO film increased. |
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