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 research has been conducted on single- and few-layer WTe₂. Here we report the isolation of single- and few-layer WTe₂, as well as the fabrication and characterization of the first WTe₂ suspended nanostructures. We have observed new Raman signatures of single- and few-layer WTe₂ that have been theoretically predicted but have not been 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 ≈ 80 GPa for the suspended WTe₂ flakes. This study paves the way for future investigations and utilizations of the multiple new Raman fingerprints of single- and few-layer WTe₂, and for explorations of mechanical control of WTe₂ atomic layers.