Figure 5
Stability testing of WTe2 flakes in ambient air by (a) high-resolution elemental XPS spectra and (b) Raman spectroscopy. XPS reveals an increase in Te-O bonding in the Td 3d and O 1s spectra with minor changes in the W 4d spectra, indicating the formation of TeO2 on the surface. The Raman spectrum after 13 days of air exposure (blue) shows small changes in intensity of the two in-plane modes in the 160-167 cm−1 region. The Raman spectrum of a laser-degraded sample (red) suggests that photon-assisted oxidation can lead to rapid degradation of WTe2 via the formation of TeO2.
