Electromechanical coupling is ubiquitous in nature and underpins thefunctionality of materials and systems as diverse as ferroelectric andmultiferroic materials, electrochemical devices, and biological systems, andstrain-based scanning probe microscopy (s-SPM) techniques have emerged as apowerful tool in characterizing and manipulating electromechanical coupling atthe nanoscale. Uncovering underlying mechanisms of electromechanical couplingin these diverse materials and systems, however, is a difficult outstandingproblem, and questions and confusions arise from recent experiment observationsof electromechanical coupling and its apparent polarity switching in someunexpected materials. We propose a series of s-SPM experiments to identifydifferent microscopic mechanisms underpinning electromechanical coupling, anddemonstrate their feasibility using three representative materials. Byemploying a combination of spectroscopic studies and different modes of s-SPM,we show that it is possible to distinguish electromechanical coupling arisingfrom spontaneous polarization, induced dipole moment, and ionic Vegard strain,and this offer a clear guidance on using s-SPM to study a wide variety offunctional materials and systems.
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