赝弹性银硫系化合物阻变行为的透射电镜研究

Investigation of the resistive switching behavior of pseudoelastic silver chalcogenides via TEM

银硫系化合物由于尺寸可缩减性好、擦写速度快、具有多值存储能力等优点,在阻变存储器介质材料研究中受到广泛关注。但随着介质材料尺寸的不断缩小,材料表/界面结构对器件的性能产生的影响尚不明确。因此从微观尺度上揭示阻变介质材料表/界面对性能影响的相关机理至关重要。本文利用脉冲激光沉积制备了Ag_(10)Ge_(15)Te_(75)薄膜,并在透射电子显微镜中构建了以其为介质的阻变存储器,研究了其阻变过程中微观形貌与物相的演化。实验发现,尺寸在20 nm以下的Ag_(10)Ge_(15)Te_(75)薄膜在被电压脉冲熔断后,能够用"冷焊"的方式重新连接并仍保持阻变特性。当给其施加正向电压时,薄膜中生成Ag_(2)Te多晶颗粒。当挤压拉伸薄膜时,Ag_(2)Te多晶颗粒不会消失。当施加反向电压时,Ag_(2)Te多晶颗粒消失。分析认为,Ag_(10)Ge_(15)Te_(75)薄膜的形变属于Coble赝弹性,Ag_(2)Te多晶的生成与电场诱导沉积有关。实验的结果对于构建新型柔性阻变存储器结构具有一定的指导意义。

Silver chalcogenide has been one of the most attractive dielectric materials in resistive random-access memory(RRAM)due to its excellent miniaturization potential,fast operation speed and multilevel data storage capacity.However,the influence of material surface/interface structure on device performance is ambiguous as the size of dielectric material decreases.Therefore,it is significant to reveal the corresponding mechanism of dielectric materials at atomic scale.In this paper,Ag_(10)Ge_(15)Te_(75) films were prepared by pulsed laser deposition,and a RRAM device based on the Ag_(10)Ge_(15)Te_(75) films was constructed in the transmission electron microscope(TEM).The evolution of morphology and phase during the resistive switching process was studied.It was found that the Ag_(10)Ge_(15)Te_(75) thin films with the size below 20 nm could be reconnected by cold welding after being fused by voltage pulse and still retain resistive switching characteristics.When the forward voltage is applied,Ag_(2)Te particles are formed in the film.Ag_(2)Te particles will not disappear until the reverse voltage is applied,even though the film is compressed or stretched.It can be concluded that the deformation of Ag_(10)Ge_(15)Te_(75) film belongs to Coble pseudoelasticity,and the formation of Ag_(2)Te is related to electrical field induced precipitation reaction.This work provides deep insights into mechanistic understanding of resistive switching in Ag_(10)Ge_(15)Te_(75) and a valuable strategy for producing flexible RRAM.