Single- and Few-Layer WTe2 and Their Suspended Nanostructures: Raman Signatures and Nanomechanical Resonances

Abstract: Single crystal tungsten ditelluride (WTe2) has recently been discovered to exhibit non-saturating extreme magnetoresistance in bulk; it has also emerged as a new layered material from which atomic layer crystals can be extracted. While atomically thin WTe2 is attractive for its unique properties, little study has been conducted on single- and few-layer WTe2. Here we report the isolation of single- and few-layer WTe2, as well as fabrication and characterization of the first WTe2 suspended nanostructures. We have observed new Raman signatures of few-layer WTe2 that have been theoretically predicted but not yet reported to date, in both on-substrate and suspended WTe2 flakes. We have further probed the nanomechanical properties of suspended WTe2 structures by measuring their flexural resonances, and obtain a Young's modulus of E_Y~80GPa for the suspended WTe2 flakes. This study paves the way for future investigations and utilization of the multiple new Raman fingerprints of single- and few-layer WTe2, and for exploring mechanical control of WTe2 atomic layers.