Practical method to limit tip-sample contact stress and prevent wear in amplitude modulation atomic force microscopy

Area of Science:

• Materials Science
• Nanotechnology
• Surface Science

Background:

• Amplitude Modulation Atomic Force Microscopy (AM-AFM) offers high-resolution imaging with reduced tip-sample interaction compared to contact mode.
• Despite reduced interaction, tip and sample wear occur due to high-frequency interactions and intermittent contact stresses.

Purpose of the Study:

• To introduce a method for selecting AM-AFM probe and free oscillation amplitudes to prevent excessive tip/sample contact stress.
• To provide a framework for minimizing wear while maintaining image quality.

Main Methods:

• Developed analytical formulations based on Hertzian and DMT-like contact models.
• Introduced stress maps and simplified formulas to determine allowable oscillation amplitudes based on cantilever and sample properties.
• Validated the method experimentally using various silicon tips and ultrananocrystalline diamond samples.

Main Results:

• The proposed method successfully preserved sharp silicon tips during high-quality AM-AFM imaging on a hard sample.
• Experimental runs using parameters exceeding the calculated stress limits resulted in significant tip wear.
• Demonstrated the effectiveness of the scheme in maintaining tip integrity and sample quality.

Conclusions:

• The developed method enhances understanding of contact stresses in AM-AFM.
• Enables users to select appropriate cantilevers and parameters to minimize wear and extend tip lifespan.
• Facilitates damage-free high-resolution imaging for both tip and sample.