Figure 1: Observation of a reversible transition between a conductive and insulating state by exposure to water and light.
From: Giant conductivity switching of LaAlO3/SrTiO3 heterointerfaces governed by surface protonation

(a) Schematic showing the bulk electrical transport measurement of 4 unit cell (uc) LaAlO3 (LAO) on SrTiO3 (STO). (b) Sheet resistance R as determined by a van der Pauw measurement versus total time exposed to deionized water (twater, left) and total time exposed to broadband light (tlight, right). Measurement uncertainty is smaller than the data markers in all cases.