The bottom electrode was fully coated with a 20 nm insulating high-quality (uniform and devoid of pinholes; see details in section 3.3) alumina layer using atomic layer deposition (ALD) (details in SI, Sec. 1.4), as confirmed by AFM (Figure ). A second round of photolithography was then performed to create micropores at the center of the bottom electrodes, using the previously described protocol (SI, Sec. 1.1) with precise alignment using the micro-writer. After developing the micropattern, the photoresist exposed a ~20 µm 2