Elasticity Modulation Due to Polarization Reversal and Ionic Motion in the Ferroelectric Superionic Conductor KTiOPO₄

Abstract

The coupling between ionic degrees of freedom and ferroelectricity has received renewed attention in recent years, given that surface electrochemical processes have been shown to be intrinsically linked to ferroelectric phase stability in ultrathin ferroelectric films. However, the coupling between bulk ionic transport and local polarization switching has received less attention, as typically the bulk ionic mobilities are low for common ferroelectrics at room temperature. Here, we use the coupled band-excitation method in conjunction with site-correlated time-of-flight secondary ion mass spectrometry, to determine the coupling between ferroelectric switching and ionic motion in single crystal KTiOPO. The local scanning probe measurements indicate a substantial softening, as determined by resonant frequency changes, during reversal of polarization along one direction. These changes are correlated with the mass spectrometry measurements, showing a polarization-dependent accumulation of K ions at the polar surfaces, thus corroborating their role in the screening process. These studies shed light on the interplay between ionic dynamics and bulk ferroelectric switching and have implications for studies on domain wall conductivity, chemical switching, and bulk and surface-screening phenomena.

Influence of Humidity on Local Polarization Reversal in a Rb:KTP Single Crystal

“…The growing interest to the local KTP studies by various SPM techniques has been stimulated by the demonstration of the increased conductivity of the domain walls , and coupling between bulk ionic transport and ferroelectricity . The switching spectroscopy PFM analysis has been applied to map the distribution of hysteresis loop parameters over the periodically poled KTP sample; however, the shape of the growing domains has not been analyzed. Thus, the local polarization reversal in KTP by a biased PFM tip lacks comprehensive studies.…”

Ion adsorption-induced reversible polarization switching of a van der Waals layered ferroelectric

“…Although applying an external electric field is the most common approach to switching polarization state, a growing body of research indicates that voltage-induced electrochemical phenomena can be remarkable ranging from vacancy ordering, deposition to surface damage [8][9][10][11] . Preeminent examples include well-known ferroelectric ion conductor KTiOPO 4 12,13 and its homologous compounds 14,15 of which the periodical polarization switching utilizing electric field suffers from their high conductivity [16][17][18] .…”

Toward Electrochemical Studies on the Nanometer and Atomic Scales: Progress, Challenges, and Opportunities

“…Focused X-ray methods provide information on a material’s structure with ∼10 nm resolution, allowing insight into the nature of grain boundaries, extended defects, and dislocations. ,− Techniques such as micro-Raman − and time-of flight secondary ion mass spectrometry (ToF-SIMS) provide information on the chemical state of the surface. Recent studies enabled by combined AFM-ToF-SIMS instruments have provided insight into the chemical changes during AFM scanning and biasing. − Further developments of these methods and the associated workflows based on image registration will enable comprehensive probing of chemistry and electrochemistry of surfaces and nanoscale volumes and elucidating the concurrent structural and chemical changes.…”