Irreversible Semiconductor-to-semiconductor Transition and Highly Enhanced Photoconductivity of Y2S3 Induced by Structural Modulation

In this study, we investigated the effects of pressure on Y2S3 by examining various properties such as conductance, band gap, photoconductivity, and crystal structure. To do this, we employed electrical transport measurements, UV-vis absorption spectroscopy, X-ray diffraction, Raman spectroscopy, and theoretical calculations. The results obtained from the electrical transport measurements revealed an irreversible semiconductor-to-semiconductor transition in Y2S3 at approximately 10 GPa. Additionally, we observed a gradual decrease in the band gap at low pressure, but a sharp drop starting at around 10 GPa, which corresponded to the change in transport properties. Moreover, the photoconductivity of the decompressed Y2S3 sample was found to be 2-3 orders of magnitude higher than that of the pristine sample. Our X-ray diffraction and Raman measurements provided clear evidence of an irreversible first-order phase transition occurring in Y2S3, transitioning from a monoclinic to an orthorhombic crystal structure at similar to 10 GPa. This phase transition helps to explain the abrupt changes observed in transport, band gap, and photoconductivity. These findings were further confirmed by our first-principle calculations.