Anchoring methane thiol on Cu(100) in different structural configurations: Electronic state dispersion

Abstract

Self-assembled monolayers can be obtained by anchoring thiol molecules through their sulfur headgroup on metal substrates, obtaining long-range ordered configurations. Dimethyl-disulfide $[{(\mathrm{C}{\mathrm{H}}_{3}\mathrm{S})}_{2}]$ adsorbs in a symmetric fourfold chemisorption site as methane thiolate $(\mathrm{C}{\mathrm{H}}_{3}\mathrm{S})$ on the Cu(100) surface, and it builds up regular twofold reconstructed superstructures, $p(2\ifmmode\times\else\texttimes\fi{}2)$ at low dosing and $c(2\ifmmode\times\else\texttimes\fi{}6)∕c(2\ifmmode\times\else\texttimes\fi{}2)$ at higher coverage. Electronic state dispersion of the hybrid interface electronic states has been followed along the main symmetry directions of the surface Brillouin zone in the three different structural phases by means of high-resolution angular-resolved UV photoelectron spectroscopy. The electronic binding energy and bandwidth of the hybrid electronic states are mainly determined by the sulfur atom interaction with the metal surface. The bandwidths ranging from $400\phantom{\rule{0.3em}{0ex}}\text{to}\phantom{\rule{0.3em}{0ex}}780\phantom{\rule{0.3em}{0ex}}\mathrm{meV}$ for the twofold reconstructions depend on the different molecular packing. Comparison with previous experimental and theoretical results on different S-headgroup systems adsorbed on noble metal surfaces indicates a role of the radical tail group.