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Title: Two-dimensional van der Waals materials


Graphene is not the only atomically thin material of technological importance. Diverse families of newly harnessed monolayers have far-reaching implications for basic physics, materials science, and engineering.

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Publication Date:
OSTI Identifier:
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physics Today; Journal Volume: 69; Journal Issue: 9; Other Information: (c) 2016 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States

Citation Formats

Ajayan, Pulickel, Kim, Philip, and Banerjee, Kaustav. Two-dimensional van der Waals materials. United States: N. p., 2016. Web. doi:10.1063/PT.3.3297.
Ajayan, Pulickel, Kim, Philip, & Banerjee, Kaustav. Two-dimensional van der Waals materials. United States. doi:10.1063/PT.3.3297.
Ajayan, Pulickel, Kim, Philip, and Banerjee, Kaustav. 2016. "Two-dimensional van der Waals materials". United States. doi:10.1063/PT.3.3297.
title = {Two-dimensional van der Waals materials},
author = {Ajayan, Pulickel and Kim, Philip and Banerjee, Kaustav},
abstractNote = {Graphene is not the only atomically thin material of technological importance. Diverse families of newly harnessed monolayers have far-reaching implications for basic physics, materials science, and engineering.},
doi = {10.1063/PT.3.3297},
journal = {Physics Today},
number = 9,
volume = 69,
place = {United States},
year = 2016,
month = 9
  • We report on a chemical free one-off imprinting method to fabricate two dimensional (2D) van der Waals (vdWs) materials based transistors. Such one-off imprinting technique is the simplest and effective way to prevent unintentional chemical reaction or damage of 2D vdWs active channel during device fabrication process. 2D MoS{sub 2} nanosheets based transistors with a hexagonal-boron-nitride (h-BN) passivation layer, prepared by one-off imprinting, show negligible variations of transfer characteristics after chemical vapor deposition process. In addition, this method enables the fabrication of all 2D MoS{sub 2} transistors consisting of h-BN gate insulator, and graphene source/drain and gate electrodes without anymore » chemical damage.« less
  • Two-dimensional (2D) van der Waals (vdW) heterostructures are a family of artificially-structured materials that promise tunable optoelectronic properties for devices with enhanced functionalities. Compared to stamping, direct epitaxy of vdW heterostructures is ideal for clean interlayer interfaces and scalable device fabrication. Here, we explore the synthesis and preferred orientations of 2D GaSe atomic layers on graphene (Gr) by vdW epitaxy. Guided by the wrinkles on graphene, GaSe nuclei form that share a predominant lattice orientation. Due to vdW epitaxial growth many nuclei grow as perfectly aligned crystals and coalesce to form large (tens of microns), single-crystal flakes. Through theoretical investigationsmore » of interlayer energetics, and measurements of preferred orientations by atomic-resolution STEM and electron diffraction, a 10.9 interlayer rotation of the GaSe lattice with respect to the underlying graphene is found to be the most energetically preferred vdW heterostructure with the largest binding energy and the longest-range ordering. These GaSe/Gr vdW heterostructures exhibit an enhanced Raman E 2 1g band of monolayer GaSe along with highly-quenched photoluminescence due to strong charge transfer. Despite the very large lattice mismatch of GaSe/Gr through vdW epitaxy, the predominant orientation control and convergent formation of large single-crystal flakes demonstrated here is promising for the scalable synthesis of large-area vdW heterostructures for the development of new optical and optoelectronic devices.« less
  • Van der Waals (vdW) heterojunctions consisting of vertically-stacked individual or multiple layers of two-dimensional (2D) layered semiconductors, especially the transition metal dichalcogenides (TMDs), are fascinating new artificial solids just nanometers-thin that promise novel optoelectronic functionalities due to the sensitivity of their electronic and optical properties to strong quantum confinement and interfacial interactions. Here, monolayers of n-type MoSe 2 and p-type Mo 1-xW xSe 2–MoSe 2 are grown by vapor transport methods, then transferred and stamped to form artificial vdW heterostructures with different interlayer orientations. Atomic-resolution Z-contrast electron microscopy and electron diffraction are used to characterize both the individual monolayers andmore » the atomic registry between layers in the bilayer vdW heterostructures. These measurements are compared with photoluminescence and low-frequency Raman spectroscopy, which indicates strong interlayer coupling in heterostructures. Remarkably, the heterojunctions exhibit an unprecedented photoconductivity effect that persists at room temperature for several days. This persistent photoconductivity is shown to be tunable by applying a gate bias that equilibrates the charge distribution. Furthermore, these measurements indicate that such ultrathin vdW heterojunctions can function as rewritable optoelectronic switches or memory elements under time-dependent photo-illumination, an effect which appears promising for new monolayer TMDs-based optoelectronic devices applications.« less
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