Cross-sectional imaging of individual layers and buried interfaces of graphene-based heterostructures and superlattices.

By Sarah Haigh, A. Gholinia, R. Jalil, S. Romani, L. Britnell, D. Elias, K. Novoselov, L. Ponomarenko, A.K. Geim, R. Gorbachev. Nature Materials, 2012

698 citations recorded by the source corpus.

By stacking various two-dimensional (2D) atomic crystals on top of each other, it is possible to create multilayer heterostructures and devices with designed electronic properties. However, various adsorbates become trapped between layers during their assembly, and this not only affects the resulting quality but also prevents the formation of a true artificial layered crystal upheld by van der Waals interaction, creating instead a laminate glued together by contamination. Transmission electron microscopy (TEM) has shown that graphene and boron nitride monolayers, the two best characterized 2D crystals, are densely covered with hydrocarbons (even after thermal annealing in high vacuum) and exhibit only small clean patches suitable for atomic resolution imaging. This observation seems detrimental for any realistic prospect of creating van der Waals materials and heterostructures with atomically sharp interfaces. Here we employ cross sectional TEM to take a side view of several graphene-boron nitride heterostructures. We find that the trapped hydrocarbons segregate into isolated pockets, leaving the interfaces atomically clean. Moreover, we observe a clear correlation between interface roughness and the electronic quality of encapsulated graphene. This work proves the concept of heterostructures assembled with atomic layer precision and provides their first TEM images.

Subfields: Atomic and Molecular Physics, and Optics, Materials Chemistry

View Paper: https://www.semanticscholar.org/paper/492223f39ec6b88a88813ec188832e729bcf1833

How researchers see this paper

The researchers whose trusted networks rank it highest, strongest advocate first. Every researcher gets a different order.

In Atomic and Molecular Physics, and Optics

In Materials Chemistry

Citations in the corpus

Momentum-space indirect interlayer excitons in transition-metal dichalcogenide van der Waals heterostructures (2018, background): “Spin-orbit interactions were generally not taken into account and the inclusion of these interactions does not alter any of our conclusions as spin-orbit-dependent interlayer interactions have never been reported before [2, 18].”
2D materials and van der Waals heterostructures (2016, background): “The transmission electron microscopy (TEM) studies (55) demonstrate that interfaces can be atomically flat and free of any contamination [Fig.”
Light-emitting diodes by band-structure engineering in van der Waals heterostructures. (2014, background): “Cross sectional imaging Details of cross sectional imaging of heterostructures produced from 2D materials can be found in [5].”
Strong Light-Matter Interactions in Heterostructures of Atomically Thin Films (2013, methodology): “In the fabrication procedure, the flakes were transferred with the “dry transfer” technique (in the case of micromechanically cleaved graphene) (7, 8) with thorough annealing (27) at each stage to ensure minimal contamination between the layers (28) and low-level doping of the graphene layers.”
Strained Bubbles in van der Waals Heterostructures as Local Emitters of Photoluminescence with Adjustable Wavelength (2019, background): “This process is usually referred to as self-cleansing (31,32) and typically occurs when monolayer graphene or TMDCs are deposited on lipophilic substrates (32).”