ELECTRONIC-STRUCTURE AND REACTIVITY OF ULTRA-THIN FE FILMS ON A RH(100) SURFACE

The electronic structure and reactivity of ultra-thin Fe films on a Rh(100) surface have been investigated by angle-resolved ultraviolet photoelectron spectroscopy (ARUPS) and thermal desorption spectroscopy (TDS). The dispersion of d-bands of a clean Rh surface is consistent with the projection of the bulk band structure. One monolayer of Fe film shows a systematic shift of d-bands toward large binding energy by 0.4 eV and a large reduction in the density of states just below the Fermi level, in particular, around the MBAR point. In accordance with the decrease in the density of states at the Fermi level, the bonding energy of hydrogen is greatly reduced to 245 kJ/mol on a 1 ML (ML = monolayer) Fe film, although the sticking coefficient is still in the range of 0.1-0.3. The successive increase in activation energy for the desorption of hydrogen with the increase of Fe film thickness from 1 to 3 ML is associated with a recovery of the density of states at the Fermi level.