Imaging the dynamics of individually adsorbed molecules

Area of Science:

• Surface Science
• Scanning Probe Microscopy
• Molecular Dynamics

Background:

• Noise in experimental signals is often discarded, yet contains valuable information.
• Scanning Tunneling Microscopy (STM) is limited in studying fast dynamic processes at the atomic scale due to its slow nature.
• Understanding molecular motion and electronic states on surfaces is crucial for nanoscience.

Purpose of the Study:

• To develop a real-time characterization method for random telegraph noise in STM.
• To overcome the temporal limitations of standard STM for studying dynamic processes.
• To gain insight into the dynamics and electronic structure of individual molecules on surfaces.

Main Methods:

• Real-time characterization of random telegraph noise in the tunneling current signal.
• Measurement of hopping rate, noise amplitude, and state occupation as a function of tunneling parameters.
• Generation of spatially resolved maps of molecular dynamics.

Main Results:

• Successfully characterized random telegraph noise, revealing molecular dynamics.
• Identified an electron-driven hindered rotation of copper phthalocyanine molecules on Cu(111) between equilibrium and metastable states.
• Provided spatially resolved maps of molecular motion and electronic properties.

Conclusions:

• The developed technique provides access to transiently populated states, enabling detailed study of molecular dynamics.
• This approach offers a complete characterization of molecules, from surface dynamics to electronic structure at the single-molecule level.
• The method overcomes the limitations of conventional STM for studying fast surface processes.