Temperature dependent photoluminescence from WS2 nanostructures

Owing to their intriguing physical properties, two-dimensional transition metal dichalcogenides such as WS2 and MoS2 have gained significant attention in the research community. Their tunable bandgap justify their use in future optical and nanoelectronics devices. Here, we report the room temperature Raman spectra and temperature dependent photoluminescence of WS2 nanostructures prepared in liquid media. The resonance Raman spectra revealed various first order modes together with higher order modes that were inaccessible with excitation away from resonance absorption. The luminescence from these nanostructures displayed red-shift and linear temperature dependence in the range 293-363K. The observed negative temperature coefficients are very small and may arise from anharmonicity and thermal expansion. Further, optical measurements revealed that WS2 quantum dots exhibits strong spin-orbit coupling approximate to 650meV, larger than observed for monolayer sheets of WS2 (approximate to 400meV). The stronger spin-orbit coupling together with highly luminescent nature make them attractive for applications in spintronics and optoelectronics devices.