Bridging Mechanical and Electrical Analyses in AFM: Advances, Techniques, and Applications

Abstract

Microscopy has long expanded humanity’s understanding of the microscopic world, transcending limitations of the naked eye. The atomic force microscope (AFM), in particular, marks a major advancement in this field, enabling nanoscale investigations of materials through direct physical probing of their surface. Unlike traditional microscopes that use light or electrons, AFM’s unique methodology allows for both imaging on the atomic scale and precise manipulation of a material’s mechanical, electrical, and chemical properties. A key advantage also lies in its capacity for multimodal analysis, where multiple properties can be simultaneously measured to provide comprehensive insights into material behavior.

In the current landscape of miniaturizing electronics and optimizing energy materials, the interplay between mechanical and electrical properties has gained particular importance. The precise integration of these properties is vital for advancing nanotechnology, and AFM allows the elucidation of these effects on the nanoscale. This is especially relevant for multifunctional materials that respond to both mechanical and electrical stimuli, and as surface properties exert a pronounced influence on material behavior at reduced scales, the capabilities of the AFM have informed the design and characterization of many smart, dielectric, and energy materials over the past decades.

In this article, we present our group’s recent works on the integration of mechanical and electrical analyses using AFM-based characterization techniques. We begin by tracing the progression from early piezoresponse force microscopy (PFM) studies, which investigated domain growth and switching characteristics in ferroelectric films, as well as the surface charge dynamics of polar domains. Based on these foundations, we introduce a surface scraping-based method of imaging─charge gradient microscopy─for rapid characterization of these domains and showcase a novel three-dimensional lithography technique that exploits asymmetric wear rates of up and down domains. This method underscores the strongly coupled interactions between the mechanical and electrical properties of dielectrics, with the potential for scaling to device-relevant dimensions.

The discussion then transitions from piezoelectric electromechanical dynamics to ionic electrochemical phenomena, where electrical stimuli similarly induce mechanical surface deformations detectable by an AFM tip. We explore a multimodal approach in electrochemical strain microscopy (ESM) to investigate functional components in composite materials, demonstrating how friction mapping can be employed to identify specific material components. Additionally, we introduce mechanically and electrically modulated spectroscopy techniques, including nanoindentation, PFM hysteresis, and current–voltage spectroscopy, emphasizing the potential of spectroscopic methods to be customized for eliciting targeted material response. Finally, the challenges and future directions in AFM-based research are addressed, as we offer approaches to enhance the reliability, accuracy, and data throughput of AFM measurements. We anticipate that these integrated approaches, which bridge mechanical and electrical analyses at the nanoscale, will accelerate material discovery and fuel innovation across diverse fields, from energy storage to nanoelectronics.