Fig. 5

STM images (86 nm × 86 nm, sample bias voltage 1.0 V, tunneling current 1 nA) of the RuO₂(110)/Ru(0001) sample after being chemically reduced by exposure to 10 L (1 × 10⁻⁷ mbar for 100 s) of HCl, while the sample was held at 700 K. a An area which was covered by the oxide homogeneously before the reduction. b An area which partially contains the parallelogram-shaped metallic patch prior to reduction