Adsorption structure of formic acid on Si(100) studied by surface NEXAFS

The structure of the surface formate chemisorbed on Si(100) at 300 K was studied by near edge X-ray absorption fine structure (NEXAFS) at the carbon K-edge. By probing the incidence-angle-dependent NEXAFS spectra, it was determined that the CDO group bond of the surface formate is tilted away from the surface normal by an average angle of 21 +/- 2 degrees. This geometry is analogous to the dihedral angle (21 degrees) of the O=C-O-Si group of silyl formate in the gas phase. This finding indicates that the surface formate and the gas-phase silyl formate have similar steric structures. It could be expected that the electronic structure of the chemisorbed formate is also similar to that of the gas-phase silyl formate, (C) 1999 Elsevier Science B.V. All rights reserved.