Tolerance to Stretching in Thiol-Terminated Single-Molecule Junctions Characterized by Surface-Enhanced Raman Scattering

Abstract

We investigated the change in the metal−molecule interaction in a 1,4benzenedithiol (BDT) single-molecule junction using a combination of surface-enhanced Raman scattering spectra and current−voltage curves. During the stretching process, the conductance of the junction systematically decreased, accompanied by an increase in the vibrational energy of the CC stretching mode. By analyzing the current−voltage curves and Raman spectra, we found that the interaction between the π orbital of BDT and the electronic states of Au was diminished by the orientation change of BDT during the stretching process. A comparison with a 4,4′-bipyridine single-molecule junction revealed that the reduction of coupling of the Au−S contacts was smaller than that of Au−pyridine contacts. Therefore, the electronic states originating from the contact geometry are responsible for the tolerance to the stretching of thiol-terminated molecular junctions.

Surface-Enhanced Raman Scattering Stimulated by Strong Metal–Molecule Interactions in a C60 Single-Molecule Junction

“…In the adsorbed state, the charge transfer between Au and C 60 weakens the CC bond in C 60 , leading to a redshift of the vibrational energy in the adsorbed states. The ratio of the vibrational energy to the coupling value was estimated to be 60 (cm –1 /V) from the values of the HC and LC states . The ratio is comparable to that obtained by the SMJ with aromatic rings under controlled metal–molecule interactions.…”

Water Splitting Induced by Visible Light at a Copper‐Based Single‐Molecule Junction

“…The variation in the vibration energy originates from the variation in the interaction between Cu and water molecule. [60,62] The value of the vibration energy in the single molecule junction is influenced by the strength of the metal-molecule interaction. [60,62] For example, for Pt/hydrogen molecule/Pt junctions, the vibration energy shifts with a change in the stretch length.…”

“…[60,62] The value of the vibration energy in the single molecule junction is influenced by the strength of the metal-molecule interaction. [60,62] For example, for Pt/hydrogen molecule/Pt junctions, the vibration energy shifts with a change in the stretch length. [60] These conductance behaviors and IET spectra indicate that the conductance states at 0.1 G 0 are attributed to the Cu/water molecule/Cu junction, as we will discuss further in the following section with the first-principles calculations.…”

Grid-Based Correlation Analysis to Identify Rare Quantum Transport Behaviors

“…[7][8][9] A significant and ongoing challenge in the investigation of transport through single molecule systems, however, is extracting meaning from the large and stochastic datasets typically produced by experimental techniques such as the scanning tunneling break junction (STM-BJ) [10][11][12][13][14][15][16] and mechanically controlled break junction (MCBJ). [17][18][19][20][21][22][23][24] Both of these methods involve forming and then breaking a thin metal constriction to create a single-molecule junction in the nano-gap between two metal electrodes. The primary data collected is the conductance (G = I / V) through the junction during the breaking process as a function of how much the two sides have been pulled apart, known as a "breaking trace".…”

“…Single-molecule electronics have the potential to enable cheap and efficient circuit fabrication at the ultimate size limit and also provide an appealing test-bed for exploring intriguing physical phenomena at the nanoscale such as quantum interference, − spin filtering, , and interfacial coupling. − A significant and ongoing challenge in the investigation of transport through single-molecule systems, however, is extracting meaning from the large and stochastic data sets typically produced by experimental techniques such as the scanning tunneling microscope break junction (STM-BJ) − and mechanically controlled break junction (MCBJ). − Both of these methods involve forming and then breaking a thin metal constriction to create a single-molecule junction in the nanogap between two metal electrodes. The primary data collected is the conductance ( G = I / V ) through the junction during the breaking process as a function of how much the two sides have been pulled apart, known as a “breaking trace”.…”