Figure 3

Atomic force microscopy topography images of single (a) IGZO (1:1:1), (b) IGZO (2:2:7), and (c) ZnO films, and (d) a single IGZO memristor(IGZO(2:2:7)/IGZO(1:1:1)) and (e) a bi-layer IGZO/ZnO memristor. ZnO film can be observed by small grains of nanometric dimension.