Surface Raman Spectroscopy of trans-Stilbene on Ag/Ge(111): Surface-Induced Effects

Abstract

The vibrational features of self-organized submonolayer trans-stilbene on the Ag/Ge(111)−(√3 × √3)R30° surface have been investigated by Raman spectroscopy in ultrahigh vacuum at 100 K. A red shift in the CC stretching mode of the olefinic group at 1625 cm−1 and enhanced Raman activity of the peak at 1568 cm−1 were observed, as compared with those corresponding to a multilayer trans-stilbene. Electronic interaction between trans-stilbene and the underneath surface and Raman spectra were calculated based on density functional theory. The calculated Raman spectra are in good agreement with the experimental results, supporting the calculated molecular geometry of the adsorbed trans-stilbene, which exhibits a predominant bond elongation in the olefinic group and a torsional angle between the phenyl ring and the olefinic plane. Analysis of the partial density of states shows that the lowest unoccupied molecular orbital is broadened and lowered to cross the surface Fermi level by the interaction with the surface, facilitating surface charge transfer and thus destabilizing the CC double bond.

Surface‐enhanced Raman scattering of 4,4'‐diaminostilbene: Dependence of spectral features and resonant enhancement on surface coverage

“…The suppression of ethylenic modes can be induced by CT between DAS and Ag adatoms accompanied by destabilization and elongation of double bond. Such deformation of ethylenic double bond was already assumed from the spectroscopic measurements and theoretical calculations by Chou et al for trans‐stilbene adsorbed on Ag/Ge(111) surface . It is important to note that these authors also observed the red shift of the ethylenic stretching mode when the surface coverage by trans‐stilbene molecules changed from submonolayer to multilayer.…”

Optically and thermally induced molecular switching processes at metal surfaces

“…Beside studies on the adsorption behavior of stilbenes adsorbed on Cu(110) [166], Si(100) [167] and Ag/Ge(111)-√ 3 [168,169], respectively, photoinduced trans/cisisomerization of the parent unsubstituted stilbene on Ag/Ge(111)-√ 3 has been analyzed by scanning tunneling spectroscopy [170,60]. Thereby a biexciton-assisted photoisomerization model has been proposed in order to explain the optically-induced conformational change of stilbene pairs.…”

Study of the Substrate-Induced Strain of As-Grown Graphene on Cu(100) Using Temperature-Dependent Raman Spectroscopy: Estimating the Mode Grüneisen Parameter with Temperature

“…In situ Raman measurements were carried out in a home-built UHV chamber with a routine base pressure of ∼4 × 10 –10 Torr using a 514.5 nm Ar ion laser or 532 nm diode laser as the excitation light source. A more detailed description has been reported elsewhere. , A laser-line filter was used to eliminate adjunct plasma emission lines. The laser beam was focused using a cylindrical lens and impinged, via a glass viewport, to the sample with an incident angle of 65°.…”