Enhanced Trion Emission and Carrier Dynamics in Monolayer WS₂ Coupled with Plasmonic Nanocavity

Abstract

room temperature owing to the strong geometrical confinement and weak dielectric screening. [3] Moreover, excitons can further bind an electron or a hole to form charged excitons that are also called as trions. [4] The rich excitonic physics and complex excitonic dynamics have motivated extensive studies devoted to the fundamental understanding of the novel photophysics of TMDs. [5] Owing to the crucial application prospects of trions in light-emitting diodes (LEDs) and valleytronic devices, [6] the study of trion emission in TMDs is of great significance for the development of 2D materials to fabricate advanced photonics and optoelectronic devices. [7] Trions composed of three charged particles often show properties that are different from excitons properties, such as easy manipulation by electric field and high degree of valley polarization. [8,9] Thus, it is meaningful to control the emission of various quasi-particles. [10] Some previous researchers have demonstrated that trion emission is determined by the concentration of excess electrons or holes. [11] Further, trion emission can be controlled by several methods, such as chemical doping, [12,13] electrical tuning, [14,15] substrate effect, [16] surface functionalization, [17] dynamic photoionization of neutral donors, [18] and electrons transfer in TMD heterostructures. [19]

Directional Emission from Tungsten Disulfide Monolayer Coupled to Plasmonic Nanowire‐on‐Mirror Cavity

“…[ 19 ] Such nanocavities are also studied in the context of Purcell enhancement, [ 18 ] remote excitation of the molecules, [ 19 ] spontaneous emission enhancement, [ 18 ] wavevector distribution, [ 19 ] and trion enhancement. [ 20 ]…”

“…To this end, studying the optical transition characteristics of TMDs in vicinity of a plasmonic nanostructure near resonance has gained relevance. [ 21–24 ] A variety of prospects, such as PL and Raman enhancement, [ 25,26 ] enhanced spin–orbit interaction, [ 20,27 ] remote excitation of SERS, [ 28 ] spectrum tailoring, [ 29 ] strong coupling, [ 30 ] and trion enhancement, [ 20 ] have been achieved using such configuration. For these purposes, many plasmonic structures, such as bowtie antenna, [ 31 ] nanodisk array, [ 32 ] nanocube, [ 29 ] nanoparticle, [ 30 ] and NW, [ 20,28 ] have been either fabricated over TMDs [ 33 ] or TMDs is transferred onto the structures.…”

“…[ 21–24 ] A variety of prospects, such as PL and Raman enhancement, [ 25,26 ] enhanced spin–orbit interaction, [ 20,27 ] remote excitation of SERS, [ 28 ] spectrum tailoring, [ 29 ] strong coupling, [ 30 ] and trion enhancement, [ 20 ] have been achieved using such configuration. For these purposes, many plasmonic structures, such as bowtie antenna, [ 31 ] nanodisk array, [ 32 ] nanocube, [ 29 ] nanoparticle, [ 30 ] and NW, [ 20,28 ] have been either fabricated over TMDs [ 33 ] or TMDs is transferred onto the structures. [ 34 ] Specifically, in the context of 2D materials, TMDs have been coupled to a single AgNW for studying remote SERS, [ 27 ] second‐harmonic generation, [ 35–38 ] logic operation, [ 39 ] Rabi splitting, [ 40 ] and plasmon–exciton interconversion.…”

“…[ 34 ] Specifically, in the context of 2D materials, TMDs have been coupled to a single AgNW for studying remote SERS, [ 27 ] second‐harmonic generation, [ 35–38 ] logic operation, [ 39 ] Rabi splitting, [ 40 ] and plasmon–exciton interconversion. [ 20 ] Silver film–AgNW cavity has been recently utilized for the trion enhancement and enhancing the spin–orbit coupling. [ 20 ]…”

Out-of-plane emission of trions in monolayer WSe2 revealed by whispering gallery modes of dielectric microresonators

“…14 This panorama puts into evidence the necessity of identify, among the different excitonic complexes existing in 2D semiconductors, those with a suitable dipole orientation for their optimal application in the emerging field of integrated photonic circuits based on 2D materials. [32][33][34][35][36][37] This question is particularly relevant for the development of novel devices based on monolayer (ML) TMDs, since strong spin-orbit coupling makes these materials offer, apart from bright and long-lived dark excitons, 38,39 high-order charge-complexes with unexplored dipolar characteristics, such as bound excitons, trions, [40][41][42][43][44] and biexcitons. 45 These complexes are technologically promising as they can manifest even at room temperature, [46][47][48] have an intrinsic charge and spin degrees of freedom that facilitate their manipulation by the application of an electric or a magnetic field, 45,49 possess a valley degree of freedom (as free-excitons), permit new optical gain mechanisms at extremely low carrier densities, 50 and can be further used as entangled photon sources.…”