Kepič Peter, Horák Michal, Kabát Jiří, Hájek Martin, Konečná Andrea, Šikola Tomáš, Ligmajer Filip
Brno University of Technology, Central European Institute of Technology, Purkyňova 123, 612 00 Brno, Czech Republic.
Institute of Physical Engineering, Brno University of Technology, Faculty of Mechanical Engineering, Technická 2, 616 69 Brno, Czech Republic.
ACS Nano. 2025 Jan 14;19(1):1167-1176. doi: 10.1021/acsnano.4c13188. Epub 2025 Jan 2.
Vanadium dioxide (VO) has received significant interest in the context of nanophotonic metamaterials and memories owing to its reversible insulator-metal transition associated with significant changes in its optical and electronic properties. The phase transition of VO has been extensively studied for several decades, and the ways how to control its hysteresis characteristics relevant for memory applications have significantly improved. However, the hysteresis dynamics and stability of coexisting phases during the transition have not been studied on the level of individual single-crystal VO nanoparticles (NPs), although they represent the fundamental component of ordinary polycrystalline films and can also act like nanoscale memory units on their own. Here, employing transmission electron microscopy techniques, we investigate phase transitions of single VO NPs in real time. Our analysis reveals the statistical distribution of the transition temperature and steepness and how they differ during forward (heating) and backward (cooling) transitions. We evaluate the stability of coexisting phases in individual NPs and prove the persistent multilevel memory at near room temperatures using only a few VO NPs. Our findings unveil the physical mechanisms that govern the hysteresis of VO at the nanoscale and establish VO NPs as a promising component of optoelectronic and memory devices with enhanced functionalities.
由于二氧化钒（VO₂）具有可逆的绝缘体 - 金属转变，并伴随着其光学和电子性质的显著变化，因此在纳米光子超材料和存储器领域引起了广泛关注。几十年来，VO₂的相变已经得到了广泛研究，并且在如何控制其与存储器应用相关的滞后特性方面有了显著改进。然而，尽管单个单晶VO₂纳米颗粒（NPs）是普通多晶薄膜的基本组成部分，并且自身也可以像纳米级存储单元一样发挥作用，但在单个单晶VO₂纳米颗粒层面上，尚未对转变过程中共存相的滞后动力学和稳定性进行研究。在此，我们采用透射电子显微镜技术实时研究单个VO₂ NPs的相变。我们的分析揭示了转变温度和陡度的统计分布，以及它们在正向（加热）和反向（冷却）转变过程中的差异。我们评估了单个NPs中共存相的稳定性，并仅使用少数VO₂ NPs证明了在接近室温下的持久多级存储。我们的研究结果揭示了在纳米尺度上控制VO₂滞后现象的物理机制，并将VO₂ NPs确立为具有增强功能的光电器件和存储器件的有前途的组件。
