STRUCTURAL STUDIES OF ADSORBED ALKANETHIOLS ON CU(111) BY USE OF S AND C K-EDGE X-RAY-ABSORPTION FINE-STRUCTURES

Surface structures of submonolayer alkanethiol CH3(CH2)(n-1)SH (n=6,12 ) adsorbed on Cu(111) at room temperature (0.3 ML) were investigated b y means of S K-edge surface extended X-ray absorption fine structure ( EXAFS) and S, C K-edge near-edge X-ray absorption fine structure (NEXA FS) spectroscopies. Polarization dependence of the C K-edge NEXAFS spe ctra revealed that alkanethiol molecules adsorb with the tilt angle of 12+/-10 degrees from the surface normal. The S K-edge surface EXAFS d etermined that the S-Cu distance is 2.31+/-0.02 Angstrom and that the S atoms locate at a deep three-fold hollow site with significant later al outward movements of the nearest neighbor Cu atoms. (C) 1998 Elsevi er Science B.V. All rights reserved.