| AVS 63rd International Symposium & Exhibition | |
| 2D Materials Focus Topic | Wednesday Sessions |
| Session 2D+NS-WeA |
| Session: | Nanostructures including Heterostructures made of 2D Materials |
| Presenter: | Fan Ye, Case Western Reserve University |
| Authors: | F. Ye, Case Western Reserve University J. Lee, Case Western Reserve University J. Hu, Tulane University Z.-Q. Mao, Tulane University J. Wei, Tulane University P.X.-L. Feng, Case Western Reserve University |
| Correspondent: | Click to Email |
Among recently emerging two-dimensional (2D) materials, 1T'-phase semi-metallic tungsten ditelluride (WTe2) [4] possesses unique properties – large, non-saturating magnetoresistance [1] that originates from perfect balance between electrons and holes populations [2], a metallic to insulating transition under low temperature with varying number of layers [3] and superconductivity under high pressure [5]. These properties are not easily accessible in other 2D materials, thus making WTe2 highly attractive for further investigations on their basic properties, especially in the single layer (1L) to few-layer regime.
In this work, we have systematically investigated new Raman signatures, nanomechanical properties [6], and environmental instability of single- and few-layer WTe2. In Raman study, we have observed up to 12 peaks in few-layer WTe2. We find clear softening, stiffening and invariant behaviors in the measured 12 Raman modes as thickness decreases from 8L to 1L. These Raman fingerprints could be an effective ‘thickness indicator’ for identifying layer number in atomically thin WTe2. We have also investigated mechanical properties of few-layer suspended WTe2 by measuring their resonances, and further determined its Young’s modulus to be EY~80GPa. In addition, by employing surface sensitive material characterization tools such as Raman spectroscopy, XPS, and AES, we carefully study the degradation behavior of single- and few-layer WTe2 in ambient conditions [7]. We find that oxidation is the main driving force of WTe2 degradation and it is a self-limiting process. In particular, 1L WTe2 quickly oxidize in ~13mins, while 2L and 3L WTe2 exhibit relatively slower, saturating and self-limiting degradation process over two weeks.
This work paves the way for future investigations and utilization of the multiple new Raman fingerprints of few-layer WTe2, and for exploring mechanical control of WTe2 atomic layers.
[1] X. L. Fan, et al J. Mater. Chem. A .2, 20545–20551 (2014).
[2] M. N. Ali, et al., Nature514, 205-208 (2014).
[3] P. L. Cai, et al., Phys. Rev. Lett. 115, 057202 (2015).
[4] L. Wang, et al., Nat. Comm.6, 8892 (2015).
[5] X.C. Pan, et al., Nat. Comm.6, 7805 (2015).
[6] J. Lee et al., Nanoscale. 8, 7854–7860 (2016).
[7] F. Ye et al., In Submission (2016).