CHEMISORPTION OF L-CYSTEINE ON Au(111)/Si(111) AND $Si(111)\sqrt{3} \times \sqrt{3}-{\rm Au}$ SURFACES

Abstract

The electronic structures of L-cysteine adsorbed on Au (111)/ Si (111) and [Formula: see text] surfaces were studied by using X-ray photoelectron spectroscopy (XPS). L-cysteine multilayers on Au (111)/ Si (111) and [Formula: see text] surfaces were prepared under UHV condition. L-cysteine monolayers were obtained by annealing such multilayer sample up to 130°C. In the case of the Au (111)/ Si (111) surface, we observed no chemical shift and no change in the peak intensity ratios among C1s , N1s , O1s and S 2p before and after annealing. On the other hand, the component attributed to COOH group in C1s spectra decreased after annealing. In addition, O1s XPS spectra of monolayer on the [Formula: see text] surface was composed of two distinct peaks, which indicates that there are two kinds of O atoms in different conformations. These observations indicate that the COOH group adsorbs directly to a surface atoms and dissociate by the interaction with the substrate Si (111) trimer atoms.