Valence Modifications in Hygroscopic VI3Degraded Crystals via Soft X-ray Synchrotron Radiation

Among van der Waals crystals, transition metal trihalide VI3 has drawn attention for its magnetic and orbital properties. However, its chemical instability under ambient conditions makes its exploitation challenging for technological implementation. In this context, here we show how synchrotron radiation soft X-rays induce changes in the valence state of hygroscopic VI3 crystals aged in high-vacuum conditions. By combining X-ray absorption and X-ray photoemission spectroscopies, we show as-cleaved and aged chemical degradation of the VI3 crystal surface, with the formation of vanadates, and its valence modifications under high-flux soft X-ray beam exposure, revealing that superficial hygroscopic contamination couples relatively weakly to the crystal surface.