INFRARED CHARACTERIZATION OF METHANOL ADSORBED ON CU(110)

The density of the first chemisorbed monolayer of CH3OH on a Cu(110) at 90 K is determined by thermal desorption spectroscopy (TDS), to be equal to 1 molecule/ 16(± 2) Å2. Photoelastic modulated infrared spectra of methanol submonolayers allow an accurate characterization of the adsorbate structure. At 90 K, the film formation is kinetically limited: a thermally activated reorganization occurs at 142 K. The methyl and hydroxyl group axes are inclined and quasiperpendicular to the surface normal, respectively. Both TDS and infrared results suggest that the first monolayer structure is similar to that of the reticular planes in the methanol crystal, except that all the methyl groups are puckered above the plane of the oxygens which are bonded to the substrate as previously observed for methanol on polycrystalline platinum. Films thicker than 2.5 monolayers are crystallizing into arbitrarily oriented small crystallites. © 1990, American Vacuum Society. All rights reserved.