Seeing the invisible: Nanoscopy with acoustic AFM

Abstract

Acoustic atomic force microscopy (AFM) addresses the limitations of traditional imaging for seeing the invisible subsurface nanofeatures with the advantages of both the noninvasive penetration of ultrasound and the nanoscale resolution of AFM. This review emphasizes key achievements and recent advancements of the acoustic AFM, focusing on improvements in multi-modal excitation, multi-scheme operation, multi-component applications, and multi-parameter imaging. Theoretical algorithms and limitations including amplitude attenuation, frequency shift, phase transition, and energy consumption are analyzed, and discrepancies among models, simulations, and experiments are discussed. The review also examines the applications of acoustic AFM in advanced semiconductor nanodevices, the characterization of functional material properties, and the monitoring of living systems. Results emphasize the potential of integrating ultrasonic AFM with quantum sensing and artificial intelligence to develop refined nanoscale fluctuation models, innovate multi-modal probes, and create high-throughput data processing algorithms. These advancements aim to achieve wide-field, high-throughput, ultra-high spatial-temporal resolution, and real-time dynamic nondestructive monitoring of samples with complex structures and environments, paving the way for the next generation of ultrasonic AFM.