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Improved Threshold Switching and Endurance Characteristics Using Controlled Atomic‐Scale Switching in a 0.5 nm Thick Stoichiometric HfO2 Layer
Advanced Electronic Materials ( IF 5.3 ) Pub Date : 2021-01-06 , DOI: 10.1002/aelm.202000869
Seungwoo Lee 1 , Writam Banerjee 1 , Sangmin Lee 1 , Changhyuck Sung 1 , Hyunsang Hwang 1
Affiliation  

Electrochemical metallization cell–based threshold switching (TS) devices are promising candidates for selectors in high‐density cross‐point memory arrays. However, TS characteristics in density‐ and stoichiometry‐engineered solid electrolyte systems have not been studied. By adopting TS‐based stoichiometric and substoichiometric solid electrolyte HfO2 layers, the localized atomic scale movement of Ag ions can be effectively controlled in ultrathin bilayers. The stoichiometric HfO2 thickness is crucial to this. This study proposes defect‐ and density‐engineered bilayer TS with a 0.5 nm critical thickness of the stoichiometric HfO2 layer, which maximizes various switching characteristics. The unstable filament in the ultrathin stoichiometric HfO2 layer prevents the formation of stable Ag clusters owing to limited Ag injection into the dense and stoichiometric HfO2 layer. In addition, the substoichiometric HfO1.91 (1.5 nm) buffer layer prevents direct injection of Ag ions from the top electrode into the dense HfO2 layer. These factors enable the bilayer design to achieve a high turn‐off speed of 100 ns, excellent endurance above 107 cycles, low off current of ≈pA, and tight Vth distributions even for sub‐2 nm devices. These exceptional results demonstrate the possibility of designing density‐graded bilayer TS devices with high stability, fast switching, and high endurance.

中文翻译:

通过在0.5 nm厚的化学计量HfO2层中使用受控的原子尺度开关来改善阈值开关和耐力特性

基于电化学金属化单元的阈值开关(TS)器件有望成为高密度交叉点存储阵列中选择器的候选者。但是,尚未研究密度和化学计量设计的固体电解质系统中的TS特性。通过采用基于TS的化学计量和亚化学计量的固体电解质HfO 2层,可以有效地控制超薄双层中Ag离子的局部原子尺度运动。化学计量的HfO 2厚度对此至关重要。这项研究提出了缺陷和密度工程双层TS,其化学计量HfO 2层的临界厚度为0.5 nm ,这可以最大化各种开关特性。超薄化学计量HfO 2中的不稳定灯丝由于有限地向致密且化学计量的HfO 2层中注入了有限的Ag,因此该层阻止了稳定的Ag团簇的形成。此外,亚化学计量的HfO 1.91(1.5 nm)缓冲层可防止Ag离子从顶部电极直接注入致密HfO 2层。这些因素使双层设计可以实现100 ns的高关断速度,10 7个周期以上的出色耐久力,≈pA的低关断电流以及即使对于2 nm以下的器件也具有严格的V th分布。这些出色的结果证明了设计具有高稳定性,快速切换和高耐久性的密度分级双层TS器件的可能性。
更新日期:2021-02-15
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