The environmental stability characterization of exfoliated few-layer CrXTe3 (X = Si, Ge) nanosheets

Two dimensional van der Waals layered CrXTe3 (X = Si, Ge) crystals have attracted great attention recently due to the observation of fascinating long range magnetic order. However, the detailed environmental stability of surface chemical reactivity of CrXTe3 has not been explored yet. Herein, we have studied the ambient air oxidation of exfoliated few-layer CrXTe3 (X = Si, Ge) nanosheets using optical microscopy, atomic force microscopy and Raman spectra. The optical contrast decreases, and surface roughness and thickness increase with exposure time for few-layer CrXTe3. The stability of CrGeTe3 flakes is superior to that of CrSiTe3. CrSiTe3 nanosheets degrade almost immediately after exposure to air, while CrGeTe3 above 11 nm can be air stable for 24 h. Under high power laser excitation or exposure to the air for sufficient time, it is found that amorphous Te and TeOx are formed initially and continually converted to TeO2, resulting in the degradation of CrXTe3. Our results shed light on environmental effects on the surface evolution of CrXTe3 and highlight the need for developing suitable protecting strategies in future CrXTe3-based devices.