Stacking Dependance of optical properties in TMD van der Waal Heterostructure

In our study, we fabricated 3R- and 2H- stacked hBN/WSe₂-WS₂/hBN vdWH and observed an intriguing strong raman quenching behavior on out of plane vibration mode (A_1g) of WSe₂ and significant modulation of out-of-plane vibration mode of WS₂ in the vdWH when excited with most commonly used 532nm CW laser at room temperature. Moreover, we also observed the strong stacking dependance of the ILE emission where the ILE intensity in 2H stacked vdWH is in general 2x or more than ILE in 3R-HS at room temperature and remains the same behavior down to 20K.

We found those results only occur when WSe₂ is in strong interaction with WS₂ in the stacking geometry really close to 3R stacking (0 degree). This WSe₂ A_1g raman mode diminishes from vdWH while all the raman modes from adjacent layer (WS₂) is still in present at room temperature in the vdWH.  Such strong stacking dependance raman behavior has not been reported and this result highly suggesting the strong raman modulation is caused by the strong interaction between WSe₂ and WS₂ in 3R stacking. Excitation energy dependance raman at room temperature reveals this strong raman quenching could possibly due to raman resonance effect and tensile strain in the system.  As similar raman modulation effect by excitation energy could also be found in WSe₂ 3R- vs 2H- homobilayer.