Figure 1: Striking the correct bias.
Maurice et al. used an STM to image both the oxide surface and the buried interface3. At the first bias voltage (V1), the tunnelling current is generated by the conduction band of the oxide film, and the oxide surface can be observed. At V2 (<V1) the unoccupied electronic states of the metal are probed and the image produced corresponds to the metal surface underneath the oxide.
