Direct imaging of meniscus formation in atomic force microscopy using environmental scanning electron microscopy

Area of Science:

• Surface science
• Atomic Force Microscopy (AFM)
• Environmental Scanning Electron Microscopy (ESEM)

Background:

• Investigating meniscus formation at the interface between an Atomic Force Microscopy (AFM) tip and a surface.
• Utilizing Environmental Scanning Electron Microscopy (ESEM) for in-situ imaging of this phenomenon.

Discussion:

• Observed meniscus heights (100-1200 nm) at high relative humidity (70%-99%) are orders of magnitude larger than predicted by the Kelvin equation.
• The Kelvin equation, typically assuming spherical geometry, may not accurately model meniscus formation under these conditions.
• Hysteresis in meniscus height was observed, correlating with changes in relative humidity (increasing vs. decreasing).

Key Insights:

• ESEM imaging provides direct visualization of nanoscale meniscus formation.
• Significant discrepancies exist between experimental observations and theoretical predictions for water meniscus size at high humidity.
• The observed hysteresis suggests complex surface interactions and water vapor adsorption dynamics.

Outlook:

• Further theoretical modeling is needed to account for non-spherical geometries and surface heterogeneities.
• Understanding meniscus behavior is crucial for AFM-based measurements in humid environments.
• Exploring the impact of surface chemistry and topography on meniscus formation and hysteresis.