Measuring the activation energy of thiol desorption using lateral force microscopy

Area of Science:

• Surface science
• Materials science
• Physical chemistry

Background:

• Self-assembled monolayers (SAMs) are crucial for surface modification and device fabrication.
• Understanding the thermal stability of SAMs is essential for their practical applications.
• 16-mercaptohexadecanoic acid (MHA) on gold is a model system for studying SAM behavior.

Purpose of the Study:

• To investigate the thermal stability of MHA SAMs on gold surfaces.
• To correlate changes in lateral force signals with molecular desorption using AFM.
• To determine the activation energy of SAM desorption via a kinetic model.

Main Methods:

• Utilized atomic force microscopy (AFM) to measure lateral force signals.
• Subjected MHA SAMs on gold to controlled heating (40-80 °C) in air for up to 10 hours.
• Applied a kinetic model to analyze friction signal changes and calculate activation energy.

Main Results:

• Observed changes in friction force signals correlating with temperature-induced desorption.
• Successfully developed a kinetic model to link lateral force signals to SAM desorption.
• Calculated an activation energy of 25.4 kcal/mol for MHA SAM detachment from gold.

Conclusions:

• The study successfully quantified the thermal desorption kinetics of MHA SAMs on gold.
• AFM-based friction measurements provide a viable method for determining SAM thermal stability.
• The derived activation energy is consistent with values obtained from more complex techniques, validating the method.