  The adsorption of CO molecules at the Ca3Ru2O7(001) surface was studied using
low-temperature scanning tunneling microscopy (STM) and density functional
theory (DFT). Ca3Ru2O7 can be easily cleaved along the (001) plane, yielding a
smooth, CaO-terminated surface. The STM shows a characteristic pattern with
alternating dark and bright stripes, resulting from the tilting of the RuO$_6$
octahedra.
  At 78,K, CO adsorbs at an apical surface O at the channel edge with a
predicted binding energy of $E_{ads} = -0.85$eV. After annealing at room
temperature, the CO forms a strong bond ($E_{ads}= -2.04$eV) with the apical O
and the resulting carboxylate takes the place of the former surface O. This
carboxylate can be decomposed by scanning the surface with a high sample bias
voltage of +2.7V, restoring the original surface.
