High On-current And Uniformity Realized In AgGeSe/Al₂O₃/Pt Threshold Switching Devices

Memristors have shown their great potential in high-density storage,in-memory computing and neuromorphic computing.However,the memristor array suffers from the limited on/off ratio of memristors.To exploit the scaling advantage of memristors,two-terminal devices with highly non-linear characteristics are demanded.Among those,conductive-filament(CF)based threshold switching devices stand out due to their ultra-low off-current,which is vital to suppress the sneak current.Nonetheless,due to the over-injected cations and the increasing stability as the filament size,CF-based threshold switching devices have a poor performance in on-current,uniformity,and endurance.Therefore,it's essential to study the realization of high-performance threshold switching devices.This paper is started with the device scaling,studying the fabrication of nanoscale devices.Then the threshold switching characteristics of nanoscale Ag/Al₂O₃/Pt devices are investigated.After that,the Ag active electrode is modified by the introduction of fast ion conductor(GeSe).The AgGeSe/Al₂O₃/Pt devices exhibit high on-current density(12.7MA/cm²),selectivity(10¹⁰),uniformity(2.18%),thermal stability(125?),and endurance(2×10⁵),serving as a good candidate for high-density storage.In addition,based on the density function theory(DFT)calculations,the formation of AgGeSe compound and the mechanism behind the performance improvement are explained.A filament formation model was also proposed.The main research contents are as follows:(1)According to the device structure,a via-hole structure and corresponding fabrication process are designed.The nanoscale structure is characterized.The effect of device scaling on the threshold switching characteristics is also investigated.(2)Based on DC and pulse measurements,the threshold switching characteristics of nanoscale Ag/Al₂O₃/Pt devices are investigated.(3)The fast ion conductor(GeSe)is introduced for performance improvement.The formation and bonding states of AgGeSe compound are analyzed in detail.Then,the threshold switching characteristics and thermal stability of AgGeSe/Al₂O₃/Pt devices are studied.Based on the comparison between Ag/Al₂O₃/Pt devices and AgGeSe/Al₂O₃/Pt devices,physical characterization results,and DFT calculations,the mechanism behind the performance improvement induced by AgGeSe is explained.A model is proposed to illustrate the filament formation process in the AgGeSe/Al₂O₃/Pt devices.Besides,the comparison between AgGeSe/Al₂O₃/Pt devices with different thickness of GeSe is provided to clarify the fabrication parameters.