The influence of coadsorbed sodium atoms on the chemisorption of benzoic acid on Si(100)-2 x 1

The adsorption of benzoic acid on Na-Si(100)-2 x 1 (Theta(Na) = 0.5) at roo m temperature leads to benzoate in a bidentate coordination. High-resolutio n electron energy loss spectroscopy spectra show an intense v(s)(OCO) stret ching vibration, which is characteristic for benzoate aligned perpendicular to the substrate surface. In contrast, we observe monodentate benzoate spe cies following the exposure of Si(100)-2 x 1 to benzoic acid at room temper ature. On both surfaces, the dissociated hydrogen atom bonds to one of the silicon surface atoms. Removal of benzoate from Na-Si(100)-2 x 1 is observe d after heating the silicon substrate to 300 degrees C for 1 min. (C) 1999 Elsevier Science B.V. All rights reserved.