Tungsten ditelluride (WTe2) is yet another member of the transition metal dichalcogenide family. Unlike other dichalcogenides, tungsten telluride is a semi-metal. In 2015, a Nature [1] paper reported a non-saturating magnetoresistance in this compound which makes it an exciting systems for fundamental transport studies. As with other layered systems, Raman spectroscopy is a fast and non-destructive way to characterize this two-dimensional system. Don’t forget that we offer WTe2 is in our 2D crystal shop. In this article we examine WTe2 Raman spectrum.
The Raman spectrum of bulk WTe2 shows four main peaks in the region 100cm-1 – 300 cm-1, Figure 1. These are are approximately located at 118, 134, 164 and 212 cm-1. and are noted as the A13, A14, A17 and A19 respectively [2].
These peaks evolve with layer thickness:
- The A13 and A14 modes becomes completely extinct in monolayer WTe2
- The A14 mode modes completely extinct in bilayer WTe2
- The A17 mode does not shift with with layer thickness and finally
- The A19 mode blueshifts (shifts to higher wavenumber) for thinner layers.
In conclusion, the most reliable way to identify monolayer WTe2 is the existence of only two Raman peaks in the region 100cm-1 – 300 cm-1.
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Figure 1. Raman spectrum of monolayer and few-layer Tungsten Ditelluride (WTe2). The blue dash lines indicate the changes in the Raman spectrum with layer thickness.
References
[1] Large non-saturating magnetoresistance in WTe2. Ali et al Nature 2014
[2] Anomalous Lattice Dynamics of Mono-, Bi-, and Tri-layer WTe2. Kim et al arXiv 2015
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