No abstract

The adsorption of diethyl ether (Et 2 O) on Si(001) was studied by means of scanning tunneling microscopy (STM) and photoelectron spectroscopy. Et 2 O reacts on Si(001) via a datively bonded intermediate, which was isolated at surface temperatures below 100 K. At higher surface temperature, Et 2 O converts dissociatively into the final state by cleaving one O−C bond; the resulting −O−C 2 H 5 and −C 2 H 5 fragments are found to attach on two Si dimers of neighboring dimer rows. Tipinduced hopping of the −C 2 H 5 fragment on one dimer was observed at positive sample bias. The results are discussed in the context of recent experiments on the reaction of tetrahydrofuran (THF) on Si(001) (Mette et al. ChemPhysChem 2014, 15, 3725) and allow a more general description of the reaction of ethers on Si(001).

The reaction of tetrahydrofuran (THF), an otherwise inert solvent molecule, on Si(001) was experimentally studied in ultra-high vacuum. Using scanning tunneling microscopy (STM) and photoelectron spectroscopy at variable temperature, we could both isolate a datively bound intermediate state of THF on Si(001), as well as the final configuration that bridges two dimer rows of the Si(001) surface after ether cleavage. The latter configuration implies splitting of the OC bond, which is typically kinetically suppressed. THF thus exhibits a hitherto unknown reactivity on Si(001).

Photons can excite the collective and single-particle excitations in metals; the collective plasmonic excitations are of keen interest in physics, chemistry, optics, and nanotechnology because they enhance coupling of the electromagnetic energy and can drive nonlinear processes in electronic materials, particularly where their dielectric function ε(ω) approaches zero. We investigate the nonlinear angle-resolved two-photon photoemission (2PP) spectroscopy of Ag(111) surface through the ε(ω) near-zero region. In addition to the Einsteinian single-particle photoemission, the 2PP spectra report unequivocal signatures of nonlocal dielectric, plasmonically enhanced, excitation processes.