Coexisting phases of individual VO₂ nanoparticles for multilevel nanoscale memory

Vanadium dioxide (VO₂) 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. While the VO₂ transition has been extensively studied for several decades, the hysteresis dynamics of individual single-crystal VO₂ nanoparticles (NPs) remains largely unexplored. Here, employing transmission electron microscopy techniques, we investigate phase transitions of single VO₂ 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 assess the stability of coexisting phases in individual NPs and prove the persistent multilevel memory at near-room temperatures using only a few VO₂ NPs. Our findings shed new light on the underlying physical mechanisms governing the hysteresis of VO₂ and establish VO₂ NPs as a promising component of optoelectronic and memory devices with enhanced functionalities.