Electrochemical strain microscopy: Probing ionic and electrochemical phenomena in solids at the nanometer level

Atomistic and nanometer scale mechanisms of electrochemical reactions and ionic flows in solids in the nanometera-micron range persist as terra incognito in modern science. While structural and electronic phenomena are now accessible to electron and scanning probe microscopy (SPM) techniques, probing nanoscale electrochemistry requires the capability to probe local ionic currents. Here, we discuss principles and applications of electrochemical strain microscopy (ESM), a technique based on probing minute deformations induced by electric bias applied to an SPM tip. ESM imaging and spectroscopy are illustrated for several energy storage and conversion materials. We further argue that down-scaling of physical device structures based on oxides necessitates ionic and electrochemical effects to be taken into account. Future pathways for ESM development are discussed.