The tip-sample water bridge and light emission from scanning tunnelling microscopy

Area of Science:

• Nanoscale science
• Surface physics
• Spectroscopy

Background:

• Scanning probe microscopy techniques are crucial for nanoscale investigations.
• Understanding water meniscus behavior is vital for nanotechnology applications.
• Light emission from scanning tunnelling microscopy (LESTM) is a developing field.

Purpose of the Study:

• To investigate light emission spectrum from a scanning tunnelling microscope (LESTM) as a function of relative humidity.
• To establish LESTM as a sensitive tool for probing nanoscale water meniscus growth and properties.
• To develop and apply an empirical model for the LESTM light emission process.

Main Methods:

• Investigating LESTM as a function of relative humidity.
• Formulating and applying an empirical model for light emission.
• Analyzing spectral changes and light intensity decay with increasing humidity.
• Comparing water meniscus behavior with non-polar liquids.

Main Results:

• LESTM provides a novel and sensitive method for nanoscale water meniscus analysis.
• An empirical model successfully replicated observed intensity decay and spectral changes.
• Modelling indicated progressive water filling of the tip-sample junction and localized surface plasmons.
• Water molecule structuring asymmetry influenced light emission polarity, unlike non-polar liquids.

Conclusions:

• LESTM offers continuous monitoring of water bridge development with sub-nanometre sensitivity, surpassing discrete detection methods.
• The findings are relevant for applications like dip-pen nanolithography and electrochemical scanning probe microscopy.
• LESTM is a powerful technique for understanding nanoscale liquid behavior and interfacial phenomena.