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TY - THES AU - Chen, Ching-Jung TI - Modeling the spatio-temporal evolution of oxygen vacancies in valence change memory cells PB - Rheinisch-Westfälische Technische Hochschule Aachen VL - Dissertation CY - Aachen M1 - RWTH-2024-10672 SP - 1 Online-Ressource : Illustrationen PY - 2024 N1 - Veröffentlicht auf dem Publikationsserver der RWTH Aachen University 2025 N1 - Dissertation, Rheinisch-Westfälische Technische Hochschule Aachen, 2024 AB - Valence change memory is a promising type of non-volatile memory for next-generation applications. Compared to contemporary NAND Flash, valence change memory cells exhibit advantages such as lower power consumption and faster operating speeds. In addition, devices can be fabricated by existing semiconductor technologies. However, the underlying physical mechanisms intrinsically impose difficulties in manipulating the cell resistance precisely, leading to endurance and data retention issues. It has been observed that the variability of the electrical behavior can be reduced by adopting a large current compliance, which limits the maximum current flowing through the device, but theoretical interpretations are still incomplete. Specifically, most numerical models focus on devices with a large current compliance, while the impact of a small current compliance remains unclear. From a statistical perspective, different tendencies in a wide range of current compliances have been observed in measurements. Different theoretical models have been proposed based on a simple scheme, where one conductive path exists in the oxide layer. However, none of these can explain the observed tendency in a small current compliance regime. In addition, devices with a small current compliance consume less power, thus offering significant advantages for practical applications. The goal of this work is the theoretical investigation of the spatio-temporal evolution of oxygen vacancies resulting in a resistive change of the valence change memory cell. By treating oxygen vacancies as point defects, the same viewpoint as in the density functional theory, findings from ab initio calculations can be applied. This enriches the understanding of local structures and physical quantities during the oxygen migration. To this end, the measurements at a macroscopic level can be explained by the spatio-temporal evolution of oxygen vacancies at a microscopic level. The discussion sheds light on engineering devices for a specialized functionality. LB - PUB:(DE-HGF)11 DO - DOI:10.18154/RWTH-2024-10672 UR - https://publications.rwth-aachen.de/record/996548 ER -