尺寸调控SnO_(2)量子点的阻变性能及调控机理

Size-controlled resistive switching performance and regulation mechanism of SnO_(2)QDs

零维SnO_(2)量子点因具有优异的物理化学稳定性、高电子迁移率和能带结构可调等特性,是阻变存储器中阻变功能材料的良好选择,受到了研究者的广泛关注.本文采用溶剂热法制备了尺寸为2.51 nm,2.96 nm和3.53 nm的SnO_(2)量子点,在较小尺寸范围内证明了SnO_(2)量子点能带结构随尺寸离散化的量子尺寸效应;并基于其量子尺寸效应,实现了对SnO_(2)量子点阻变存储器开关电压的有效调控.研究表明,尺寸为3.53 nm的SnO_(2)量子点具有较低的开关电压(-2.02 V/3.08 V)与较大的阻变开关比(>10~4),器件在经过2×10~4次的耐久性测试后,阻变性能变化率小于5%,具有较好的稳定性与保持性.基于库仑阻塞效应,SnO_(2)量子点内部缺陷势阱作为俘获中心对电子的自俘获/脱俘作用,是其实现阻变效应的原因;此外,SnO_(2)量子点与ITO,Au界面肖特基势垒高度的有效控制则是精准调控其阻变开关电压的关键.以上工作揭示了SnO_(2)量子点在阻变存储领域的巨大应用潜力和商业化应用价值,为阻变存储器的发展提供了一项新的选择.

As a non-volatile memory,zero-dimensional quantum dot resistive random access memory(RRAM)has shown broad application prospects in the field of intelligent electronic devices due to its advantages of simple structure,low switching voltage,fast response speed,high storage density,and low power consumption.Tin dioxide quantum dots(SnO_(2)QDs)are a good option for resistive functional materials with excellent physical and chemical stabilities,high electron mobilities,and adjustable energy band structures.In this paper,the SnO_(2)QDs with sizes of 2.51 nm,2.96 nm and 3.53 nm are prepared by the solvothermal method,and the quantum size effect is observed in a small size range and the effective regulation of resistive switching voltage is achieved based on its quantum size effect,which is the unique advantage of quantum dot material in comparison with that of bulk material.Research result shows that as the size of SnO_(2)QD increases,the SET/RESET voltage gradually decreases from–3.18 V/4.35 V to–2.02 V/3.08 V.The 3.53 nm SnO_(2)QDs have lower SET/RESET voltage(–2.02 V/3.08 V)and larger resistive switching ratio(>10^(4)),and the resistive switching performance of the device has changed less than 5%after having experienced durability tests 2×10^(4)times,showing good stability and retention.Besides,according to the fitting of charge transport mechanism,SnO_(2)QD RRAM exhibits Ohmic conduction under LRS,while Ohmic conduction,thermionic emission and space charge limit current work together during HRS.The resistive switching effect of SnO_(2)QDs is controlled by trap filled limit current and interface Schottky Barrier modulation;the trapping/de-trapping behavior of internal defect potential well of SnO_(2)QDs on electrons dominates the HRS/LRS switching,while the effective control of ITO/SnO_(2)QDs and SnO_(2)QDs/Au interface Schottky barrier is the key to accurately regulating the switching voltage.The reason why SnO_(2)QD RRAM exhibits good size-switching voltage dependence is that the larger SnO_(2)QD has lower Fermi level and interface Schottky barrier height,so the junction resistance voltage division is reduced,and the SET/RESET voltage decrease accordingly.This work reveals the huge application potential and commercial application value of SnO_(2)QDs in the field of resistive switching memory,and provides a new option for the development of RRAM.