Fig. 3

STM images (86 nm × 86 nm, sample bias voltage 1.0 V, tunneling current 1 nA) of the RuO₂(110)/Ru(0001) sample before (a, c, e) and after (b, d, f) being chemically reduced: b, d after exposure to 10 L (1 × 10⁻⁷ mbar for 100 s) of CO, while the sample was held at 600 K; f after exposure to 100 L (1 × 10⁻⁶ mbar for 100 s) of CO, while the sample was held at 600 K. All images share the same gray scale ruler given to the left. The height–distance cross-sections along the dashed lines are presented in the rightmost column of the figure