Simultaneous assembly of van der Waals heterostructures into multiple nanodevices

Abstract

van der Waals heterostructures (vdWH) are made of different two-dimensional (2D) layers stacked on top of each other, forming a single material with unique properties that differ from those of the individual 2D constituent layers, and that can be modulated through the interlayer interaction. These hetero-materials can be artificially made by mechanical stamping, solution processing or epitaxial growth. Alternatively, franckeite has been recently described as an example of a naturally-occurring vdWH that can be exfoliated down to nanometer thicknesses. Research on vdWHs has so far been limited to manually exfoliated and stamped individual devices. Here, a scalable and fast method to fabricate vdWH nanodevices from liquid phase exfoliated nanoflakes is reported. The transport and positioning of the flakes into localized submicrometer structures is achieved simultaneously in multiple devices via a dielectrophoretic process. The complex vdWH is preserved after dielectrophoresis and the properties of the resulting field-effect transistors are equivalent to those fabricated via mechanical exfoliation and stamping. The combination of liquid phase exfoliation and dielectrophoretic assembly is particularly suited for the study of vdWHs and applications where large-scale fabrication is required.

Nonlinear Optical Response in Natural van der Waals Heterostructures

“…Combining different 2D materials into vdWH to prepare p–n junctions, photodetectors, and other devices will likely achieve unexpected performance, and the preparation of superlattices has become an unique platform to explore and observe novel quantum phenomena. [ 24–27 ] To date, the most extensive method of stacking 2D layers to prepare the vdWH relies on a deterministic placement way, which is cumbersome and susceptible to improper lattice orientation control and the presence of undesirable interlayer adsorbates. [ 28,29 ] In 2017, Gomez et al [ 30 ] and Dryfe et al [ 31 ] both presented the method to fabricate ultrathin heterostructures by exfoliating natural franckeite.…”

Symmetry Breakdown in Franckeite: Spontaneous Strain, Rippling, and Interlayer Moiré

“…(17) Franckeite has been exfoliated (mechanically and by liquid phase exfoliation) down to the single unit cell and the exfoliated flakes have been assembled into electronic devices and photodetectors operating in the near-infrared range. (13,14,(18)(19)(20)(21) Here we present a study of an intriguing feature of franckeite: although the crystal is composed of isotropic 2D layers, the crystal exhibits a spontaneous rippling that makes the material structurally anisotropic. We show that rippling comes together with an inhomogeneous in-plane strain profile and anisotropic electrical and optical properties.…”

Mechanical and liquid phase exfoliation of cylindrite: a natural van der Waals superlattice with intrinsic magnetic interactions

“…The sulfosalt mineral franckeite has been recently reported as the first example of exfoliated naturally occurring vdW superlattices. [27][28][29][30][31][32] Interestingly, the sulfosalt family has other examples of natural vdW superlattices that could be exfoliated as well.…”