Atomic-resolution imaging in liquid by frequency modulation atomic force microscopy using small cantilevers with...

Area of Science:

• Materials Science
• Nanotechnology
• Surface Science

Background:

• Liquid-environment atomic force microscopy (AFM) is crucial for studying biological and chemical processes at interfaces.
• Optimizing cantilever dimensions is key to enhancing force sensitivity in liquid AFM.

Purpose of the Study:

• To investigate the theoretical and experimental performance of liquid-environment FM-AFM with varying cantilever dimensions.
• To identify and address challenges hindering the achievement of theoretically predicted performance with smaller cantilevers.
• To demonstrate improved atomic-resolution imaging and force measurements in liquid using optimized small cantilevers.

Main Methods:

• Theoretical analysis and experimental investigation of frequency modulation atomic force microscopy (FM-AFM) using cantilevers of different dimensions.
• Development of a stable photothermal excitation system using a temperature-controlled laser diode and polarization-maintaining optical fiber.
• Modification of electron beam deposition (EBD) tips by silicon coating to enhance tip-sample interaction.
• Atomic-resolution imaging of mica and measurement of oscillatory hydration forces in liquid.

Main Results:

• Reduced cantilever dimensions improve minimum detectable force, provided tip height is adequate relative to width.
• Stable photothermal excitation of small cantilevers requires high laser pointing stability, achieved via a specialized laser system.
• Electron beam deposition (EBD) tips show weak tip-sample interaction; silicon coating significantly enhances this interaction.
• Atomic-resolution imaging of mica in liquid was achieved using a small, megahertz-order resonance frequency cantilever.
• Experimental demonstration of improved minimum detectable force in oscillatory hydration force measurements using small cantilevers.

Conclusions:

• Optimized small cantilevers, coupled with stable laser excitation and enhanced tip-sample interaction, significantly improve performance in liquid FM-AFM.
• The developed techniques enable atomic-scale imaging and sensitive force measurements in liquid environments.
• This work paves the way for more detailed investigations of interfacial phenomena in liquid media using AFM.