Surface and Subsurface Mechanical Testing at the Nanoscale: A Review on Ultrasonic Atomic Force Microscopy

Area of Science:

• Nanoscience and Nanotechnology
• Materials Science
• Surface Physics

Background:

• Nanoscale mechanical property evaluation is critical for nanomaterials, micro/nano-electronics, and nanobiology.
• Atomic force microscopy (AFM) combined with ultrasonic excitation/detection (ultrasonic AFM) offers advanced characterization capabilities.

Purpose of the Study:

• To review research on ultrasonic AFM techniques.
• To focus on imaging methods, physics of surface/subsurface mechanical testing, and applications.

Main Methods:

• Utilizing ultrasonic AFM to mechanically modulate AFM tip-sample contact at ultrasonic frequencies.
• Analyzing AFM cantilever responses to measure mechanical properties.
• Employing ultrasonic AFM for nondestructive visualization of subsurface nanostructures.

Main Results:

• Ultrasonic AFMs nondestructively measure nanoscale elastic and viscoelastic properties (elastic modulus, loss tangent) with nanometer resolution.
• Quantitative characterization of materials ranging from soft polymers to hard coatings is achievable.
• Detection of subsurface features like inclusions, defects, and interfaces up to a few micrometers deep is demonstrated.

Conclusions:

• Ultrasonic AFM is a powerful tool for nanoscale surface and subsurface mechanical characterization.
• This technique significantly contributes to the advancement of nanoscience and nanotechnology.
• Further research focuses on imaging methods, underlying physics, and diverse applications.