Adsorption of CO on the Ca3Ru2O7(001) surface

TL;DR

This study investigates CO molecule adsorption on the Ca3Ru2O7(001) surface using STM and DFT, revealing adsorption sites, binding energies, and the ability to reversibly modify surface chemistry through annealing and scanning.

Contribution

It provides detailed atomic-scale insights into CO adsorption mechanisms and surface chemistry on Ca3Ru2O7(001), combining experimental STM data with theoretical DFT calculations.

Findings

CO adsorbs at apical surface O with -0.85 eV binding energy

Annealing forms a strong carboxylate bond with -2.04 eV energy

High bias scanning decomposes the carboxylate, restoring the surface

Abstract

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.