How to measure forces with atomic force microscopy without significant influence from nonlinear optical lever...

Area of Science:

• Physics
• Materials Science
• Nanotechnology

Background:

• Atomic Force Microscopy (AFM) commonly uses an optical lever technique to measure cantilever deflection.
• A nonlinear relationship between the detected signal and actual cantilever deflection is often ignored in AFM literature.
• This nonlinearity is typically assumed to only affect measurements with large cantilever deflections.

Purpose of the Study:

• To investigate the reasons behind the nonlinear detector response in AFM's optical lever technique.
• To compare experimental findings with theoretical calculations regarding this nonlinearity.
• To determine the impact of this nonlinearity on AFM studies, particularly those using soft or short cantilevers.

Main Methods:

• Designed specific experiments to probe the nonlinear detector response.
• Performed calculations to correlate with experimental observations.
• Analyzed the influence of cantilever properties on the nonlinearity.

Main Results:

• Experimental results confirm a significant nonlinear relationship between the detected signal and cantilever deflection.
• The nonlinearity is shown to affect AFM studies even with soft or short cantilevers, contrary to common assumptions.
• Identified the primary cause of the nonlinearity through analysis.

Conclusions:

• The nonlinear detector response in AFM's optical lever technique is a critical factor affecting measurement accuracy.
• Soft or short cantilevers are particularly susceptible to this nonlinearity, impacting data interpretation.
• A practical guideline for selecting appropriate cantilevers under various experimental conditions is proposed based on the findings.