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Semiconducting transition metal dichalcogenide (TMD) monolayers are one of the most promising materials for future optoelectronics. When two different TMD monolayers are brought together, the interlayer electronic coupling effects generate a new band structure inherent to the bilayer. We aim to fabricate hetero-bilayers comprising WSe₂ monolayer and WS₂ monolayer and analyze their optical spectroscopic and electronic transport features.
We synthesized WSe₂ and WS₂ monolayers on Si/SiO₂ substrates by chemical vapor deposition. After growth, both monolayers were sequentially transferred onto a pristine Si/SiO₂ substrate to have high quality overlapped areas of heterobilayers. The samples were then annealed to enhance the coupling between layers. Lastly, we patterned Au/Ti contacts on the bilayers by e-beam lithography for electrical property characterization.
The Raman and photoluminescence spectra of the bilayers were compared before and after annealing, and we found a significant decrease in the photoluminescence intensity for both WSe₂ and WS₂. Future work will include the analysis of the electronic transport data to obtain the carrier mobility as a function of stacking angle and possible tunability in the exciton energy emission.