TY - JOUR

T1 - Cross-sectional imaging of individual layers and buried interfaces of graphene-based heterostructures and superlattices

AU - Haigh, S. J.

AU - Gholinia, A.

AU - Jalil, R.

AU - Romani, S.

AU - Britnell, L.

AU - Elias, D. C.

AU - Novoselov, K. S.

AU - Ponomarenko, L. A.

AU - Geim, A. K.

AU - Gorbachev, R.

PY - 2012/7/29

Y1 - 2012/7/29

N2 - By stacking various two-dimensional (2D) atomic crystals1 on top of each other, it is possible to create multilayer heterostructures and devices with designed electronic properties2, 3, 4, 5. 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 imaging6, 7, 8, 9, 10. 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.

AB - By stacking various two-dimensional (2D) atomic crystals1 on top of each other, it is possible to create multilayer heterostructures and devices with designed electronic properties2, 3, 4, 5. 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 imaging6, 7, 8, 9, 10. 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.

UR - http://www.scopus.com/inward/record.url?scp=84866379080&partnerID=8YFLogxK

U2 - 10.1038/nmat3386

DO - 10.1038/nmat3386

M3 - Journal article

VL - 11

SP - 764

EP - 767

JO - Nature Materials

JF - Nature Materials

SN - 1476-1122

IS - 9

ER -