Interfacially Bound Exciton State in a Hybrid Structure of Monolayer WS₂ and InGaN Quantum Dots

Abstract

van der Waals heterostructures that are usually formed using atomically thin transition-metal dichalcogenides (TMDCs) with a direct band gap in the near-infrared to the visible range are promising candidates for low-dimension optoelectronic applications. The interlayer interaction or coupling between two-dimensional (2D) layer and the substrate or between adjacent 2D layers plays an important role in modifying the properties of the individual 2D material or device performances through Coulomb interaction or forming interlayer excitons. Here, we report the realization of quasi-zero-dimensional (0D) photon emission of WS in a coupled hybrid structure of monolayer WS and InGaN quantum dots (QDs). An interfacially bound exciton, i.e., the coupling between the excitons in WS and the electrons in QDs, has been identified. The emission of this interfacially bound exciton inherits the 0D confinement of QDs as well as the spin-valley physics of excitons in monolayer WS. The effective coupling between 2D materials and conventional semiconductors observed in this work provides an effective way to realize the 0D emission of 2D materials and opens the potential of compact on-chip integration of valleytronics and conventional electronics and optoelectronics.

Trion Binding Energy Variation on Photoluminescence Excitation Energy and Power during Direct to Indirect Bandgap Crossover in Monolayer and Few-Layer MoS2

“…In the last several years, transition metal dichalcogenides attracted interest because of their unique physical and chemical properties. Possessing indirect bandgaps in bulks, they become direct bandgap semiconductors having a thin monolayer (1L) and demonstrate strong visible photoluminescence (PL), which gives a prospect for using them on flexible substrates. − Moreover, the 2D material is a rapidly developed field that is noticeable by a variety of novel 2D hybrids − and a new class of 2D materials as 2D quantum dots, − which are able to effectively tune both the electrical and optical properties of initial 2D crystals.…”

Observation of Diffusion and Drift of the Negative Trions in Monolayer WS2

“…The neutral exciton emission and the defect-related emission emerge at temperatures above 100 K. The binding energy of the trions in this sample is extracted to be 40–45 meV. The unintentionally doped monolayer WS 2 is n-type due to the existence of background donors. − At low temperatures, when the thermal energy of the electrons is smaller than the ionization energy of the background donors, the electrons are trapped by the localized donors, and the monolayer WS 2 is insulating. − Under the above-band gap light illumination, besides the generation of excitons, the background donors in WS 2 are ionized with electrons excited into the conduction band, as schematically illustrated in Figure c. The traps in the h-BN layer may also be ionized, and the excited electrons can be transferred into the conduction band of WS 2 .…”

Theoretical study of Raman scattering in MoS2xSe2(1 − x) layered alloys

“…[1][2][3][4][5][6][7] The variety of discovered 2D materials is also fostering the development of novel hybrid structures. [8][9][10][11] 2D compounds have attracted interest for fundamental studies and applications in high-end electronics, spintronics, optoelectronics, energy harvesting, and flexible electronics. [1][2][3] They can be used as a new generation of transistors, chips, detectors, emitters, Esaki diodes, memory devices, and so forth.…”

“…[1][2][3] They can be used as a new generation of transistors, chips, detectors, emitters, Esaki diodes, memory devices, and so forth. [1][2][3][4][5][6][7][8][9][10][11][12][13] The main advantage of 2D materials is the dependence of their optical and electrical characteristics on the number of layers and on the strong intralayer interaction through covalent bond and the weak interlayer interaction through van der Waals (vdW) attraction. The distinctive interatomic forces in layered structures manifest themselves with typical features in their phonon spectra, for example, the weak dispersion of phonon branches in some directions in the Brillouin zone and the appeared low-wavenumber interlayer modes.…”

“…Therefore, the interlayer and intralayer interactions provide a route to manipulate macroscopic functionality of TMDs and are the keystone in understanding of physics of the intralayer and interlayer interactions between the layers. [1,6,8] TMD alloys consisting of different kinds of chalcogens (MXX', where X and X' are different chalcogens) have been successfully synthesized. [14][15][16] By introducing an additional doped chalcogen, the interactions in TMD alloys are significantly modulated, allowing engineering of their band structures and further enabling observation of many interesting phenomena.…”