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Phonon-Mediated Synthesis, Processing and Manipulation of Two-Dimensional Materials

We demonstrate the intriguing possibility of harnessing phonon sources, in particular, surface acoustic waves (SAW), for synthesizing and manipulating two-dimensional materials. For example, the large surface accelerations associated with the SAW vibration—on the order of 10 million g’s—can be employed for micro/nanoscale material processing, in particular, for debundling carbon nanotube agglomerates. These large mechanical stresses, together with the high intensity electric field inherent in the electromechanical coupling of the acoustic wave during SAW microcentrifugation and nebulisation, can also be used to rapidly exfoliate bulk three-dimensional crystalline transitional metal dichalcogenides such as molybdenum disulphide (MoS2) into monolayer and few-layer nanosheets with high yield. Finally, the SAW can be exploited for the manipulation of quasiparticles in these two-dimensional materials. For example, we show the possibility for reversibly modulating trion to exciton transition, and their subsequent transport and hence spatial separation within the material.

Keywords: 2d crystals, exfoliation, nanosheet, acoustics, piezoelectricity, carbon nanotube