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Straining Suspended Graphene
The electronic properties of graphene are best displayed by suspended sheets free from contact with an underlying substrate. Klimov et al. (p. 1557) probed how deformation of suspended graphene sheets could lead to further tuning of its electronic properties with a scanning tunneling microscope; the graphene sheets could also be deformed via an electric field from an underlying electrode. Spectroscopic studies reveal that the induced strain led to charge-carrier localization into spatially confined quantum dots, an effect consistent with the formation of strain-induced pseudomagnetic fields.
We determined the electromechanical properties of a suspended graphene layer by scanning tunneling microscopy (STM) and scanning tunneling spectroscopy (STS) measurements, as well as computational simulations of the graphene-membrane mechanics and morphology. A graphene membrane was continuously deformed by controlling the competing interactions with a STM probe tip and the electric field from a back-gate electrode. The probe tip–induced deformation created a localized strain field in the graphene lattice. STS measurements on the deformed suspended graphene display an electronic spectrum completely different from that of graphene supported by a substrate. The spectrum indicates the formation of a spatially confined quantum dot, in agreement with recent predictions of confinement by strain-induced pseudomagnetic fields.