Local chemical reaction of benzene on Cu(110) via STM-induced excitation

Abstract

We have investigated the mechanism of the chemical reaction of the benzene molecule adsorbed on Cu(110) surface induced by the injection of tunneling electrons using scanning tunneling microscopy (STM). With the dosing of tunneling electrons of the energy 2-5 eV from the STM tip to the molecule, we have detected the increase of the height of the benzene molecule by 40% in the STM image and the appearance of the vibration feature of the nu(C-H) mode in the inelastic tunneling spectroscopy (IETS) spectrum. It can be understood with a model in which the dissociation of C-H bonds occurs in a benzene molecule that induces a bonding geometry change from flat-lying to up-right configuration, which follows the story of the report of Lauhon and Ho on the STM-induced change of benzene on the Cu(100) surface. [L. J. Lauhon and W. Ho, J. Phys. Chem. A 104, 2463 (2000)]. The reaction probability shows a sharp rise at the sample bias voltage at 2.4 V, which saturates at 3.0 V, which is followed by another sharp rise at the voltage of 4.3 V. No increase of the reaction yield is observed for the negative sample voltage up to 5 eV. In the case of a fully deuterated benzene molecule, it shows the onset at the same energy of 2.4 eV, but the reaction probability is 10(3) smaller than the case of the normal benzene molecule. We propose a model in which the dehydrogenation of the benzene molecule is induced by the formation of the temporal negative ion due to the trapping of the electrons at the unoccupied resonant states formed by the pi orbitals. The existence of the resonant level close to the Fermi level ( approximately 2.4 eV) and multiple levels in less than approximately 5 eV from the Fermi level, indicates a fairly strong interaction of the Cu-pi(*) state of the benzene molecule. We estimated that the large isotope effect of approximately 10(3) can be accounted for with the Menzel-Gomer-Redhead (MGR) model with an assumption of a shallow potential curve for the excited state.

Suppression of electron–vibron coupling in graphene nanoribbons contacted via a single atom

“…3. The middle hydrogen atom at one of the zigzag ends is removed by locally applying a high voltage pulse, similar to the procedures for dehydrogenation of phthalocyanine molecules on Au(111) 31 and ARTICLE benzene on Cu 32,33 . Figure 3a,b show a free GNR before and after applying a voltage pulse of 3.7 V at the left end of the nanostructure, respectively.…”

Simulation of Single Molecule Inelastic Electron Tunneling Signals in Paraphenylene−Vinylene Oligomers and Distyrylbenzene[2.2]paracyclophanes

“…The IET spectrum of benzene has been studied extensively with low-temperature STM: Lauhon and Ho 72,73 and separately Komeda and co-workers 74 have utilized STM-IETS to examine the dehydrogenation of benzene on copper surfaces. Neither group reports any IETS resonance for benzene; however, the dehydrogenated benzene fragment does exhibit C-H stretching peaks.…”

Substrate-mediated interaction and electron-induced diffusion of single lithium atoms on Ag(001)

“…43 The electric filed E ͑V/Å͒ in the tunneling junction can then be approximated with the simplified plate capacitor model according to the formula E͑I͒ =4/8 − log͑I /40͒. 44 Thus, the range of tunneling currents used in the experiment stimulates a large variation of the electric field between the tip and the sample and the hopping yield for a particular manipulation voltage should vary with the current for a field driven mechanism. Figure 5͑c͒ shows the dependence of the manipulation yield for a manipulation voltage of 3.5 eV and different manipulation currents ͑50, 100, 150, 200, and 250 pA͒.…”