title: Bond character of thiophene on Ge(100): Effects of coverage and temperature.
abstract: We have studied the adsorption and decomposition of thiophene (C4H4S) on Ge(100) using scanning tunneling microscopy (STM), high-resolution core-level photoemission spectroscopy (HRPES), and density functional theory (DFT) calculation. Analysis of S 2p core-level spectra reveals three adsorption geometries, which we assign to a Ge-S dative bonding state, a [4 + 2] cycloaddition bonding state, and a decomposed bonding state (desulfurization reaction product). Furthermore, we found that the number ratio of the three adsorption geometries depended on the molecular coverage and the annealing temperature. At low coverages, the kinetically favorable dative bonding state is initially formed at room temperature. As the molecular coverage increases, thermodynamically stable [4 + 2] cycloaddition reaction products are additionally produced. In addition, we found that as the surface temperature increased, the [4 + 2] cycloaddition reaction product either possibly desorbed as molecular thiophene or decomposed to form a metallocycle-like species (C4H4Ge2) and a sulfide (Ge2S). We systematically elucidate the changes in the bonding states of adsorbed thiophene on Ge(100) according to the thiophene coverage and annealing temperature.
authors.affiliation: Department of Chemistry and School of Molecular Science (BK21), Korea Advanced Institute of Science and Technology, Daejeon 305-701, Republic of Korea.
authors.forename: Seok Min
authors.initials: SM
authors.lastname: Jeon
authors.forename: Soon Jung
authors.initials: SJ
authors.lastname: Jung
authors.forename: Hyeong-Do
authors.initials: HD
authors.lastname: Kim
authors.forename: Do Kyung
authors.initials: DK
authors.lastname: Lim
authors.forename: Hangil
authors.initials: H
authors.lastname: Lee
authors.forename: Sehun
authors.initials: S
authors.lastname: Kim