Chemical conversion of defects is an effective way to functionalize graphene. The dynamic process of rotating a trimer of silicon atoms in monolayer graphene was activated and monitored using an aberration-corrected scanning transmission electron microscope (STEM). The silicon trimer rotates as a single unit in stepwise jumps while the surrounding carbon atoms remain fixed. Theoretical calculations indicate that the energy barrier to rotate the trimer is about 2 eV, corresponding to a tangential force of only 4.3 nN parallel to the graphene layer. This small force, provided by an electron beam to any of the three silicon atoms, generates a torque on the trimer and results in a rotation of 60° in about 140 femtoseconds. This result suggests that controlled replacement of carbon atoms in graphene may produce in-plane dots, wires, or arrays for fabrication of other useful nanostructures or nanodevices.
Zhiqing Yang, Lichang Yin, Jaekwang Lee, Wencai Ren, Hui-Ming Cheng, Hengqiang Ye, Sokrates T. Pantelides, Stephen J. Pennycook, and Matthew F. Chisholm, “Direct Observation of Atomic Dynamics and Silicon Doping at a Topological Defect in Graphene,” Angew. Chem. Int. Ed. 53, 8908-8914 (2014). DOI: 10.1002/anie.201403382
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