Research And Applications Of Memristors Based On Two-dimensional Materials

Memristor has excellent characteristics such as high speed,low power consumption,high endurance,good retention characteristics and compatibility with CMOS technology,making it suitable for non-volatile storage,neuromorphic computing,non-volatile logic operations and other fields.It has great application prospects and has attracted widespread attention from academia circles and industry.However,there are still some urgent problems in memristors need to be solve.First of all,in terms of power consumption,traditional memristors based on oxides,chalcogenides,and two-dimensional materials have relatively large operating currents,which will generate large power consumption during the operation,which is not conducive to its use in low-power scenarios such as high-density memory or in-memory computing.Secondly,the formation and rupture of the conductive filament are random and difficult to control,resulting in poor consistency of memristors based on the mechanism of conductive filaments.To the above problems,we exploit two-dimensional materials to optimize the performance of memristors,and seek for some ways to reduce the power consumption of the devices and improve the controllability of the conductive filament growth.The main results are summarized as follows:（1）With the goal of reducing power consumption,we studied ultra-low power consumption memristors based on two-dimensional Hf Se₂ materials.The Ti/Hf Se_xO_y/Hf Se₂/Au device with crossbar structure was designed and prepared.The mechanically exfoliated two-dimensional Hf Se₂ material and the ultra-thin high"k"Hf Se_xO_yoxide layer obtained by oxygen plasma treatment on its surface were used as the resistive switching functional layer.We used XPS,AFM,EDS,Raman,SEM,etc.to fully characterize the devices and materials,and to screen the appropriate oxygen plasma treatment parameters and the thickness of the materials used.The prepared device exhibits excellent forming-free resistive switching performance with high switching speed（<50 ns）,low operating voltage（<3 V）,high switching ratio（>10³）,good retention characteristics（>15 ks）and high thermal stability（>400 K）.More importantly,the operation current and the power consumption reach100 p A and 0.1 f J-0.1 p J,much lower than other Hf-O based memristors.Through TEM analysis and I-V curve fitting,it is proposed that the mechanism of the device is the formation and rupture of oxygen vacancy conductive filaments in the 2 nm Hf Se_xO_y oxide layer.Finally,A functionally complete low-power Boolean logic is experimentally demonstrated using our memristive device,allowing it in the application of energy-efficient in-memory computing.（2）With the goal of exploring the way to control the growth and rupture of conductive filaments,we studied planar memristors based on two-dimensional GeSe materials.A planar Ag/GeSe/Au device was designed and fabricated.The mechanically exfoliated two-dimensional GeSe material was used as the lateral resistive switching functional layer to change the growth of metal conductive filament from a three-dimensional disordered structure to a one-dimensional channel.The VASP calculation results show that the potential barrier is the smallest when Ag migrates in the Zigzag direction of the GeSe surface,which provides theoretical support for the design of the device.Polarized Raman analysis can determine the crystal orientation of GeSe,which provides the realization conditions for the preparation of the device.Electrical characterization shows that the device has ultra-low operating voltage(V_SET=0.27 V,V_RESET=-0.11 V),small operating current,excellent consistency,good retention characteristics（>10³ s）and switching speed（<100 ns）,and compared with devices without design and devices with vertical structure,the uniformity of the designed planar device has been significantly improved,indicating that this method of controlling the growth of metal conductive filament is feasible.Through TEM,AFM analysis and I-V curve fitting,we believe that the resistive switching mechanism of the device is the formation and rupture of Ag conductive filaments formed on the GeSe surface.Finally,according to the characteristics of the device,the possibility of its application in resistive random access memory,logic devices,memristive transistors and selector is analyzed.