Interlayer coupling and the phase transition mechanism of stacked MoS₂/TaS₂ heterostructures discovered using temperature dependent Raman and photoluminescence spectroscopy

Ultrathin 1T (tetragonal)-TaS₂ and monolayer MoS₂ heterostructures were prepared to study their phase transition (PT) mechanisms and band structure modulation. The temperature dependency of photoluminescence (PL) and Raman spectra was utilized to study interlayer coupling and band structure. The PL results indicate that the band structure of MoS₂/TaS₂ heterostructures undergoes a sharp change at 214 K. This is attributed to the PT of 1T-TaS₂ from a Mott insulator state to a metastable state. In addition, the temperature dependency of the MoS₂/TaS₂ Raman spectra illustrates that the phonon vibration of the heterojunction is softened due to the effect of interlayer coupling. The present work could provide an avenue to create material systems with abundant functionalities and physical effects.