Charge Transition of Oxygen Vacancies during Resistive Switching in Oxide-Based RRAM
Charge Transition of Oxygen Vacancies during Resistive Switching in Oxide-Based RRAM
复制标题
DOI：
10.1021/acsami.8b18386
复制
发表时间：
2019-03-27
影响因子：
9.5
通讯作者：
Lu, Wei D.
中科院分区：
文献类型：
--
作者：
Lee, Jihang;Schell, William;Lu, Wei D.
电阻随机存取存储器(RRAM)器件作为高密度非易失性存储器和神经形态计算应用的潜在构建块，已经引起了人们的广泛兴趣。对电阻开关(RS)过程的原子级热力学和动力学描述对于持续的器件设计和优化是必不可少的，但对于基于氧化物的RRAM来说则相对缺乏。通常认为，RS是由于外加电场驱动的带电氧空位的重新分布而发生的。然而，这一假设与实验观察到的稳定细丝相矛盾，即高空位浓度应该导致强烈的库仑排斥和细丝不稳定性。在这项工作中，通过预测原子计算和实验测量相结合，我们试图了解氧空位之间的相互作用，以及在Ta2O5基RRAM中稳定RS所需的微观过程。我们提出了一个基于一系列电荷跃迁过程的模型来解释RS过程中空位的漂移和聚集。该模型通过实验测量得到了验证，被照明的器件在设置和重置过程中表现出加速的RS行为。通过对暂态电流的测量，进一步实验确定了离子迁移和电荷跃迁的活化能，与模拟结果一致。我们的结果有助于全面了解RS的内部动力学，并将有助于器件的优化和应用。
Resistive random-access memory (RRAM) devices have attracted broad interest as promising building blocks for high-density nonvolatile memory and neuromorphic computing applications. Atomic level thermodynamic and kinetic descriptions of resistive switching (RS) processes are essential for continued device design and optimization but are relatively lacking for oxide-based RRAMs. It is generally accepted that RS occurs due to the redistribution of charged oxygen vacancies driven by an external electric field. However, this assumption contradicts the experimentally observed stable filaments, where the high vacancy concentration should lead to a strong Coulomb repulsion and filament instability. In this work, through predictive atomistic calculations in combination with experimental measurements, we attempt to understand the interactions between oxygen vacancies and the microscopic processes that are required for stable RS in a Ta2O5-based RRAM. We propose a model based on a series of charge transition processes that explains the drift and aggregation of vacancies during RS. The model was validated by experimental measurements where illuminated devices exhibit accelerated RS behaviors during SET and RESET. The activation energies of ion migration and charge transition were further experimentally determined through a transient current measurement, consistent with the modeling results. Our results help provide comprehensive understanding on the internal dynamics of RS and will benefit device optimization and applications.