Resistive switches, which are also known as memristors, are low-power, nanosecond-response devices that are used in a range of memory-centric technologies. Driven by an externally applied potential, the switching mechanism of valence change resistive memories involves the migration, accumulation and rearrangement of oxygen vacancies within a dielectric medium, leading to a change in electrical conductivity. The ability to look inside these devices and understand how morphological changes characterize their function has been vital in their development. However, current technologies are often destructive and invasive. Here, we report a non-destructive optical spectroscopy technique that can detect the motion of a few hundred oxygen vacancies with nanometre-scale sensitivity. Resistive switches are arranged in a nanoparticle-on-mirror geometry to exploit the high optical sensitivity to morphological changes occurring in tightly confined plasmonic hotspots within the switching material. Using this approach, we find that nanoscale oxygen bubbles form at the surface of a strontium titanate memristor film, leading ultimately to device breakdown on cycling.

电阻开关（也称为忆阻器）是一种低功耗，纳秒级响应的设备，已在一系列以存储器为中心的技术中使用。由外部施加的电势驱动的价变化电阻存储器的转换机制涉及介电介质中氧空位的迁移，积累和重排，从而导致电导率变化。观察这些设备内部并了解形态变化如何表征其功能的能力对于它们的开发至关重要。但是，当前的技术通常具有破坏性和侵入性。在这里，我们报告了一种非破坏性光谱技术，可以检测具有纳米级灵敏度的数百个氧空位的运动。电阻开关按纳米镜上几何形状排列，以利用高光学灵敏度来应对在开关材料内紧密限制的等离激子热点中发生的形态变化。使用这种方法，我们发现在钛酸锶忆阻膜的表面形成了纳米级的氧气泡，最终导致了器件在循环时发生故障。