Local electromechanical response in doped ceria: Rigorous analysis of the phase and amplitude

Characterization of the ionic transport and corresponding electro-elastic deformations in cerium oxide at the nanoscale are important for the understanding of the mechanism of the local response under an external electric field, especially the mechanisms of the `non-Newnham''-type giant electrostriction. Here, we introduce a methodological approach to the analysis of signals in the piezoresponse force microscopy/electrochemical strain microscopy allowing decoupling ionic motion, electrostriction, and electrostatic contributions to the electromechanical signals based on a precise analysis of the electromechanical amplitude and phase as a function of temperature, and AC and DC biases. The ionic motion was demonstrated to be hampered in a 30-300°C temperature range, the typical operational range of commercial SPM microscopes. The local electromechanical response was interpreted as a mixture of the electrostatic-force-meditated response and conventional electrostriction.