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In-Situ Nanomechanics of Carbon Nanotubes and Graphene (invited presentation)

J.Y. Huang
Sandia National Laboratories, US

Keywords: carbon nanotubes, graphene, nanomechanics, Joule heating, sublimation

Abstract:

In this talk, I will review our recent progress in using a transmission electron microscopy – scanning probe microscopy (TEM-SPM) platform to probe the electrical and mechanical properties of carbon nanotubes and graphene [1]. First, individual multiwall carbon nanotubes are peeled off layer-by-layer by electric breakdown inside the TEM. This provided new insights into the transport property of nanotubes. Second, plastic deformation, such as superplasticity, kink motion, dislocation climb, and vacancy migration, was discovered in nanotubes for the first time. Third, We induced sublimation of suspended few-layer graphene by in-situ Joule-heating inside a TEM. The graphene sublimation fronts consisted of mostly (1100} zigzag edges. Under appropriate conditions, a fractal-like “coastline” morphology was observed. Extensive multiple-layer reconstructions at the graphene edges led to the formation of unique carbon nanostructures, such as sp2-bonded bilayer edges (BLEs) and nanotubes connected to BLEs. Flat fullerenes/nanopods and nanotubes tunneling multiple layers of graphene sheets were also observed. Remarkably, more than 99% of the graphene edges observed during sublimation are BLEs rather than monolayer edges (MLEs), indicating that BLEs are the stable edges in graphene at high temperatures. We reproduced the “coastline” sublimation morphologies by kinetic Monte Carlo (kMC) simulations. The simulation revealed geometrical and topological features unique to quasi 2-dimensional (2D) graphene sublimation and reconstructions. These reconstructions were enabled by bending, which cannot occur in first-order phase transformations of 3D bulk materials. These results indicate that substrate of multiple-layer graphene can offer unique opportunities for tailoring carbon-based nanostructures and engineering novel nano-devices with complex topologies. Emerging directions of using the TEM-SPM platform to conduct cutting edge research in nanoscience and energy research will be highlighted. References 1. J.Y. Huang et al., Nature 439, 281 (2006); J.Y. Huang et al., Phys. Rev. Lett. 94, 236802 (2005); 97, 075501 (2006); 98, 185501 (2007); 99, 175593 (2007); 100, 035503 (2008); J.Y. Huang et al., Phys. Rev. B, 78, 155436 (2008); PNAS 106, 10103 (2009); Nano Research 3, 43 (2010); J. Feng et al., Phys. Rev. B 80, 165407 (2009)
 
 
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