4:15 PM - 4:30 PM
▼ [18p-E208-9] Vibrational symmetry of a single molecule revealed by tip-enhanced Raman spectroscopy
Keywords:Tip-enhanced Raman spectroscopy
The scanning tunneling microscope (STM) is a powerful tool for studying various nanoscale materials with atomic scale spatial resolution. Despite the atom scale spatial sensitivity however, the STM lacks the chemical sensitivity crucial to the investigation of nanomaterials. Raman spectroscopy on the other hand has a very strong chemical sensitivity but its spatial resolution is highly restricted by the diffraction limit of light allowing only about several hundreds of nanometer resolution. Combining these two powerful experiments into a technique called STM-tip enhanced Raman spectroscopy (STM-TERS) alleviates the limitation of STM and Raman allowing for simultaneous subnanometer spatial resolution and high chemical sensitivity.
In this report, we demonstrate the capability of STM-TERS in investigating an isolated, single molecule. We perform the STM-TERS measurement on an isolated copper naphthalocyanine molecule shown in figure 1(a) and (b). We found that by careful tuning of the excitation light, we are able to achieve molecular resonance conditions at the single molecule level. Under such conditions, we report that the lateral component of the electric field at the STM junction plays a significant role in the enhancement process contrary to what was previously reported for non-resonance TERS experiments. With this, we are able to investigate the vibrational motion of the molecule with components perpendicular to the tip which was not demonstrated before. By taking the STM-TERS signals in the vicinity of the molecule, we obtained hyperspectral STM-TERS maps figure 1(d-f) which reveal the vibrational symmetry of the molecule. Such information obtained from this experiment will aid in the design and discovery of new nanomaterials for novel applications.
In this report, we demonstrate the capability of STM-TERS in investigating an isolated, single molecule. We perform the STM-TERS measurement on an isolated copper naphthalocyanine molecule shown in figure 1(a) and (b). We found that by careful tuning of the excitation light, we are able to achieve molecular resonance conditions at the single molecule level. Under such conditions, we report that the lateral component of the electric field at the STM junction plays a significant role in the enhancement process contrary to what was previously reported for non-resonance TERS experiments. With this, we are able to investigate the vibrational motion of the molecule with components perpendicular to the tip which was not demonstrated before. By taking the STM-TERS signals in the vicinity of the molecule, we obtained hyperspectral STM-TERS maps figure 1(d-f) which reveal the vibrational symmetry of the molecule. Such information obtained from this experiment will aid in the design and discovery of new nanomaterials for novel applications.