Pressure-induced metallization and isostructural transitions in MoS2

A joint experimental X-ray diffraction, Raman spectroscopy and electrical conductivity measurements, and theoretical study has been performed on molybdenum disulfide (MoS₂) up to 67 GPa. We observe discontinuous changes in Raman spectra and synchrotron x-ray diffraction patterns which provide evidence for isostructural phase transitions. These isostructural phase transitions are accompanied by pressure-induced metallization as evident from the four-probe resistivity measurement. Our theoretical calculations reveal that metallization happens due to overlap of valence and conduction bands as the interlayer spacing reduces upon pressurization. Upon decompression, both isostructural transition and metallization are found to be reversible. Our study on pressure-induced tuning of bandgap/conductivity in MoS₂ will play a vital role in the development of the next generation devices based on transition metal dichalcogenides.