Robust sliding-induced electrostatic domain patterns in exfoliated ReS2 flakes

Abstract

[EN]nterlayer sliding in low-symmetry van der Waals materials has emerged as a mechanism to generate out-of-plane electric polarization without conventional ionic displacements, yet its experimental manifestation in realistic multilayer flakes remains difficult to identify unambiguously. Here, we provide evidence that exfoliated ReS flakes exhibit unanticipated arrangements of electrostatic₂ domains that are consistent with sliding-induced ferroelectric polarization. A correlative approach is used in which Kelvin probe force microscopy (KPFM), low-energy and UV-photoemission electron microscopies (LEEM and UV-PEEM) and Raman micro-spectroscopy are combined. KPFM reveals rich patterns of surface-potential domains which are not related to any topographic feature. A subset of such domains is detectable by dark-field LEEM and UV-PEEM images while there is no detectable correlation with spatially resolved micro-Raman. Data analysis allows us to rule out ferroelastic reorientation, strain gradients or thickness variations as the primary origin of the electrostatic contrast, and points to a stacking-sensitive electrostatic categorization. The results are consistently explained by sliding-induced ferroelectric polarization in multilayer ReS . Sliding ferroelectricity in₂ this system manifests as a reconfigurable electrostatic texture that can be directly accessed by local surface-potential mapping and is sensitive to thermal and electrical perturbations. Correlative studies involving KPFM prove to be a powerful strategy to identify sliding ferroelectricity in low-symmetry two-dimensional materials, beyond conventional but complex to interpret transport- or piezoelectric force microscopy-based approaches