Gate-Tunable Bound Exciton Manifolds in Monolayer MoSe₂

Abstract

Two-dimensional (2D) semiconductors with point defects are predicted to host a variety of bound exciton complexes analogous to trions and biexcitons due to strong many-body effects. However, despite the common observation of defect-mediated subgap emission, the existence of such complexes remains elusive. Here, we report the observation of bound exciton (BX) complex manifolds in monolayer MoSe2 with intentionally created monoselenium vacancies (VSe) using proton beam irradiation. The emission intensity of different BX peaks is found to exhibit contrasting dependence on electrostatic doping near the onset of free electron injection. The observed trend is consistent with the model in which free excitons exist in equilibrium with excitons bound to neutral and charged VSe defects, which act as deep acceptors. These complexes are more strongly bound than trions and biexcitons, surviving up to around 180 K, and exhibit moderate valley polarization memory, indicating partial free exciton character.

Photovoltage and Photocurrent Absorption Spectra of Sulfur Vacancies Locally Patterned in Monolayer MoS2

“…Last but not least, a recent photocurrent experiment on a lateral p–n junction in WSe 2 revealed a distinctive sharp photocurrent resonance under resonant excitation of the underlying local excitons . The latter are localized most likely due to an extended strain potential or as defect-bound excitons . Both are not expected to show the spectrally broad sub-bandgap photocurrent responses as discussed here.…”

Temperature and power-dependent photoluminescence spectroscopy in suspended WSe2 monolayer

“…Due to the absence of the thermal fluctuations, the reduced optical linewidth allows us to resolve and analyze close-by excitonic emissions with confidence, making it possible to distinguish different types of excitons. Under low temperatures, it becomes feasible to observe emission from the bound excitons with low thermal stability to study the interaction between neutral exciton and intrinsic defects in the lattice [23][24][25]. On the other hand, in high-purity TMD monolayer under low temperature, meticulous measurements of excited (Rydberg) excitons states can be achieved [22,26,27].…”

Optically Driven Both Classical and Quantum Unary, Binary, and Ternary Logic Gates on Co-Decorated Graphene Nanoflakes

“…In particular, the transition metal doped π-conjugated GNFs complexes (TM-GNFs) occupy an important position, due to the wide variety of their structures (the various π binding sites of GNFs for the attachment of metal atoms) and magnetic properties. − With the emergence of CMOS devices utilizing spin manipulation, these doped structures (TM-GNFs) are experimentally more feasible . In addition, the sp 2 hybridization and the bond conjugation of such structures can also facilitate the ultrafast spin-transfer processes. − …”