Enhancing subsurface imaging in ultrasonic atomic force microscopy with optimized contact force.

Area of Science:

• Materials Science
• Nanotechnology
• Microscopy

Background:

• Ultrasonic atomic force microscopy (UAFM) is vital for nondestructive subsurface imaging of materials and biological samples.
• Image contrast in UAFM is critically dependent on the probe-sample contact force, affecting stress field propagation.
• Optimizing contact force is key to improving subsurface imaging resolution and detectable depth.

Purpose of the Study:

• To propose a model for determining the optimal contact force in UAFM.
• To enhance subsurface imaging contrast, resolution, and detectable depth.
• To improve UAFM performance across a wide range of material Young's moduli (tens to hundreds of GPa).

Main Methods:

• Development of a predictive model for optimal contact force in UAFM.
• Experimental validation of the model's impact on imaging quality.
• Analysis of imaging parameters including contrast, resolution, and depth.

Main Results:

• The proposed model significantly improved UAFM imaging quality.
• Achieved detectable subsurface depth exceeding 337.7 nm.
• Attained lateral resolution below 56.9 nm, outperforming arbitrary force experiments.

Conclusions:

• The developed model provides a pathway for optimizing UAFM subsurface imaging.
• Enhanced contrast, higher resolution, and greater detectable depth were demonstrated.
• This work advances the capabilities of subsurface imaging techniques.