Nanoscale Mapping of Cu‐Ion Transport in van der Waals Layered CuCrP₂S₆

Abstract

Ionic conduction of metal thiophosphates (MTPs) is attracting growing attention for promising applications in electrochemical storage and tunable physical properties. Especially, metal‐ion migration in copper thiophosphate has been identified as a key factor for the control of their microstructure and phase transition. However, direct evidence for the coupling between Cu‐ion motions and the crystal lattice has been elusive at the nanometer scale. Here, the room temperature diffusion kinetics of Cu ions in layered CuCrP2S6 (CCPS) is demonstrated. A tip‐enhanced electric field based on scanning probe microscopy (SPM) has been used as the driving force for Cu‐ion motions through van der Waals gaps. The strong coupling between Cu‐ion concentration and crystal lattice and the resulting serial structural transitions have been probed directly by the comprehensive utilization of spatially resolved Raman spectra, cross‐section energy dispersion spectrum (EDS), and high‐resolution transmission electron microscopy (HR‐TEM). This knowledge improves the understanding of the effect of intrinsic Cu‐ion migration on the structure transformation in layered van der Waals materials and provides feedback to the nanoscale mechanisms of nanometer devices based on iontronics.

Ferroelectric Polarization‐Enhanced Performance of Flexible CuInP2S6 Piezoelectric Nanogenerator for Biomechanical Energy Harvesting and Voice Recognition Applications

“…When the Cu + ions transfer from one octahedron to the neighboring one under the applied external voltage, there are two options available to the cooper ions: "up" or "down" site (stage I). [47,49,52] The Cu + ions occupied the "up" site represent upward polarization (stage II). Correspondingly, the Cu + ions moved to the "down" site means the downward polarization.…”

Cu+ Migration and Resultant Tunable Rectification in CuInP2S6

“…An irreversible Cu + loss occurs, accompanied by the decomposition of CuCrP 2 S 6 into Cu 2 S and CrP, and finally CrPS 4 . These irreversible processes together lead to a permanent topography and composition change, which is unfavorable for the device applications . To avoid this harmful reaction, the maximum negative tip voltage should be well considered.…”

“…These irreversible processes together lead to a permanent topography and composition change, which is unfavorable for the device applications. 35 To avoid this harmful reaction, the maximum negative tip voltage should be well considered. The surface bump that has been reported reversible in previous and current works represented an intermediate state before destruction.…”

Spin evolution and flip in the oxygen reduction reaction: a theoretical study of Cu(Ni)XP2S6(X = In, Bi and Cr)

“…The calculated lattice constants are in good agreement with those in the literature (Table S1 †). 35,41,44,46,47 All CXPS are dynamically stable because there are negligible imaginary frequencies at the G points in their phonon dispersions (Fig. S1 †).…”