Electric-Field-Induced Depolarization of Si–C Bond Leads to a Strongly Reduced Barrier for Alkyl-Hopping on Si(001)

Abstract

Tip-induced hopping of the ethyl fragment (−C2H5) of diethyl ether molecules reacted on Si(001) was shown to be a field-driven process. Although the hopping rate increases continuously with increasing bias voltage, it remains constant when varying the tunneling current. No hopping events are observed at 50 K. The process is thus concluded to be thermally activated with the respective energy barrier being reduced by the applied electric field. At a positive sample bias, the field in the tunneling gap is strong enough to effectively depolarize and thus weaken the covalent Si–C bond. The effect of this depolarization on the hopping barrier is quantified and compared to the strength of the electric field.

Tip-Induced $β$-Hydrogen Dissociation in an Alkyl Group Bound on Si(001)

“…According to the number of configurations reacted at 50 K, this minority species accounts for less than 3 % of the initial configurations. Field-induced effects, which are also largely independent of the tunneling current [25], can be ruled out: also at 50 K, we observe the process to take place only with the tip very close to the adsorbate, in contrast to the nonlocal character of field-induced processes [25,39,40].…”

“…3(a). From (a) to (b), the configuration has changed due to hopping of the ethyl fragment on-top of one dimer, leading to the observed symmetric configuration [25]. In Fig.…”

“…One method to manipulate adsorbates on the molecular level is scanning tunneling microscopy (STM) [14][15][16][17][18][19][20]. Often, these studies focus on tip-induced lateral or vertical movement of an adsorbed species [21][22][23][24][25] or the reaction from an intermediate into a covalently bound final state [20,26,27].…”

Making and breaking of chemical bonds in single nanoconfined molecules

“…Scanning tunneling microscopy (STM) allows to control chemical reactions of individual molecules confined to surfaces with utmost precision, which enables, e.g., the investigation of charged intermediate states (12) and of highly reactive molecular species (13). STM enables creating and breaking single chemical bonds, e.g., for ligand transfer (14), and provides diverse reaction control parameters for spectroscopic and real-space studies: (i) the injected tunneling electrons, (ii) their energy, (iii) the electric field in the tunneling junction, and (iv) the proximity of the STM tip (15)(16)(17)(18)(19). With this, STM can contribute to the understanding of singlemolecule reactions that are of fundamental interest (20), even under otherwise hardly accessible nanoconfinement conditions (19,21).…”

Oxide-Metal Interaction Probed by Scanning Tunneling Microscope Manipulation of Cr2O7 Clusters on Au(111)

“…The atomic structures and local electronic states of supported nanostructures can be obtained by STM topography and spectroscopy, respectively. In the tunneling junction of STM, atoms and molecules can be manipulated by a variety of ways owing to several interactions including electron excitation from tunneling electrons, − electric field in STM junction, − and mechanic force from tip scanning. , The interfacial interactions between supported species and substrates have been investigated by the STM manipulation of supported organic molecules. , With respect to oxide nanostructures, only a few examples of tip-induced structural transformation phenomena have been reported, e.g., desorption of a VO group from VO x and phase transformation of CoO x . STM manipulation may offer an effective method to probe the oxide–support interactions, which deserves deep investigations.…”