Phase segregation facilitates exfoliation of franckeite crystals to a single unit cell thickness

Abstract

Weak interlayer van der Waals interactions in bulk crystals facilitate their mechanical exfoliation to monolayer and few-layer two-dimensional (2D) materials, which exhibit striking physical phenomena absent in their bulk form. Here we study a 2D form of a mineral franckeite and show that phase segregation into discrete layers at the sub-nanometre scale facilitates its layered structure and basal cleavage. This behaviour is likely to be common in a wider family of complex crystals and could be exploited for a single-step synthesis of van der Waals heterostructures, as an alternative to stacking of 2D materials. Mechanical exfoliation allowed us to produce crystals down to a single unit cell thickness and rationalise its basal cleavage by atomic-resolution scanning transmission electron microscopy (STEM). We demonstrate p-type electrical conductivity and remarkable electrochemical properties in exfoliated crystals, which shows promise for energy storage applications.

Main text: 19 pages, 5 figures; Supplementary Information: 19 pages, 10 figures

References in corpus (4)

• Two Dimensional Atomic Crystals
• Anomalous Lattice Vibrations of Single and Few-Layer MoS2
• Light-emitting diodes by bandstructure engineering in van der Waals heterostructures
• Interference enhancement of Raman signal of graphene

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• Two-dimensional Janus van der Waals heterojunctions: a review of recent research progresses
• Investigation of the Nonlinear Optical Frequency Conversion in Ultrathin Franckeite Heterostructures
• Near-field refractometry of van der Waals crystals
• Observation of Photoluminescence from a Natural van der Waals Heterostructure
• Vibrational Properties of a Naturally Occurring Semiconducting van der Waals heterostructure