Sub-100fm piezoresponse force microscopy using interferometric dual-amplitude resonance tracking

Advances in noise resolution of scanning probe microscopes have enabled observation of ever smaller signals, such as Moiré patterns in twisted 2D materials and the piezoelectric response of weakly ferroelectric materials such as hafnia. The development of an interferometric atomic force microscope (AFM) with an unprecedented low noise floor for a general-purpose instrument (5fm√Hz) has enabled the characterization of material responses that are smaller than can be readily observed using the traditional optical beam detection.

Quantitative imaging of nanoscale electromechanical phenomena requires high sensitivity while avoiding artifacts induced by large drive biases. Conventional PFM often relies on high voltages to overcome optical detection noise, leading to various non-ideal effects including Schottky conduction, electrostatic crosstalk, localized Joule heating, tip-induced polarization switching and even tip or sample destruction. To avoid these, we introduce interferometrically detected, resonance-enhanced dual AC resonance tracking (iDART), which combines femtometer-scale displacement sensitivity of QPDI with contact resonance amplification. This combination allows iDART to achieve 10x or greater signal-to-noise improvement over current state of the art PFM approaches. In this talk, we will demonstrate how iDART allows routine and repeatable nano-electromechanical imaging and switching spectroscopy of weak Hafnium-based ferroelectric memory materials as well as a variety of other materials. These results position iDART as a powerful approach for non-intrusive probing electromechanical systems with an extremely high signal to noise ratio, extending functional imaging capabilities to thin films, 2D ferroelectrics, beyond-CMOS technologies and biomaterials.