First-principles study of CO adsorption on 4H-SiC (001) surface

Using the first-principles method, the authors investigated the adsorption of carbon monoxide (CO) on a 4H-silicon carbide (SiC) (001) surface. The structure parameters and adsorption energy at different adsorption sites (top, bridge, hollow) of carbon monoxide on the 4H-silicon carbide (001) surface are calculated. By comparing the adsorption energies, it was deduced that the bridge site is the most favored site because its adsorption energy is larger than those at the top and hollow sites. The transfer trend of the charge in the progress of the adsorption is revealed by the density of states of the adsorbate, the orbital charge population change of the carbon monoxide molecule and the atomic orbital charge population change of the 4H-silicon carbide (001) surface. The conclusion shows that the main interaction in the process of adsorption comes from the 2p orbital of the carbon (C) atom and the 3s and 3p orbitals of the silicon (Si) atom. An interesting characteristic in electron transfer is that the π orbital of carbon takes a bridge role between silicon and oxygen (O).