Modification of the Cu(110) Shockley surface state by an adsorbed pentacene monolayer

The modification of the Cu(110) Shockley-type surface state by an adsorbed pentacene layer was determined using high-resolution angle-resolved photoelectron spectroscopy. It was found that the surface state is shifted by 80-120 meV to higher binding energies, depending on the pentacene coverage. In addition, an increase in the surface-state population is measured for the sample adsorbed with one monolayer of pentacene. The modification of the surface state by the adsorption of pentacene is put into relation to a complex interplay of different phenomena such as the hybridization and mixing of electronic states, the polarization of the adsorbate in the surface dipole, and the Pauli repulsion. Thus, this observation of a molecular adlayer shifting a surface state away from the Fermi energy sheds more light on the adsorbate-adsorbent interactions.