Exciton behaviors at the metal-semiconductor interface

The application of transition metal dichalcogenides in optoelectronics technology requires an understanding of how metal-semiconductor contacts impact exciton photophysics. In this study we explore changes in excitons at the interface of monolayer tungsten diselenide (1L-WSe₂) and a series of conventional metals. Low-temperature hyperspectral PL measurements reveal intriguing changes in exciton linewidth and energy on approach to the junction that persist over multiple microns. In particular, the neutral exciton experiences a blueshift as the interface between the metal and WSe₂ is approached, a phenomenon that persists at higher temperatures. These results are difficult to rectify as a charge doping effect since electrostatic gating of WSe₂ leads to insignificant shifts of the exciton.¹ Lattice strain from the contact is also not responsible since a redshift would be expected.² The precise mechanisms governing this effect therefore remain an open question but a critical one for the 2D community.

1. Li, Z. et al. Nat. Commun. 9, 3719 (2018).
2. Aas, S. et al. Opt. Express 26, 28672 (2018).