Selective internal manipulation of a single molecule by scanning tunneling microscopy

Area of Science:

• Surface science
• Molecular engineering
• Nanotechnology

Background:

• Polyaromatic molecules offer unique electronic and structural properties.
• Controlled manipulation of molecules on surfaces is key for nanoscale applications.
• Silicon surfaces provide a versatile platform for molecular assembly.

Purpose of the Study:

• To investigate the adsorption and manipulation of a specifically designed polyaromatic molecule, Trima.
• To explore the potential of Trima for bridging surfaces and undergoing electron-induced rotational motion.
• To understand the voltage-dependent behavior of Trima during scanning tunneling microscopy (STM) manipulation.

Main Methods:

• Synthesis and characterization of the 1,4"-paratriphenyldimethylacetone (Trima) molecule.
• Adsorption studies on Si(100)-2 x 1 surfaces using complementary STM and synchrotron radiation techniques.
• In-situ manipulation of individual Trima molecules using STM tip with controlled voltage pulses.

Main Results:

• Trima chemisorbs effectively onto the Si(100)-2 x 1 surface, bridging adjacent dimer rows as designed.
• STM manipulation revealed selective internal modifications of the molecule.
• Molecular modifications were found to be highly voltage-dependent and correlated with the molecule's pi-pi* electronic transition.

Conclusions:

• The designed Trima molecule exhibits predictable adsorption behavior on silicon surfaces.
• STM manipulation allows for precise control over molecular modifications, driven by electronic excitation.
• This study demonstrates a pathway for voltage-controlled molecular rotors on surfaces.