Size-tunable Lateral Confinement in Monolayer Semiconductors

Abstract

Three-dimensional confinement allows semiconductor quantum dots to exhibit size-tunable electronic and optical properties that enable a wide range of opto-electronic applications from displays, solar cells and bio-medical imaging to single-electron devices. Additional modalities such as spin and valley properties in monolayer transition metal dichalcogenides provide further degrees of freedom requisite for information processing and spintronics. In nanostructures, however, spatial confinement can cause hybridization that inhibits the robustness of these emergent properties. Here, we show that laterally-confined excitons in monolayer MoS2 nanodots can be created through top-down nanopatterning with controlled size tunability. Unlike chemically-exfoliated monolayer nanoparticles, the lithographically patterned monolayer semiconductor nanodots down to a radius of 15 nm exhibit the same valley polarization as in a continuous monolayer sheet. The inherited bulk spin and valley properties, the size dependence of excitonic energies, and the ability to fabricate MoS2 nanostructures using semiconductor-compatible processing suggest that monolayer semiconductor nanodots have potential to be multimodal building blocks of integrated optoelectronics and spintronics systems.

Investigating the phonon line shapes of TMDs: An analytical approach

“…35 This may be due to the limitation in the synthesis of TMD quantum dots. [37][38][39][40][41][42][43] The majority of the reports on TMD quantum dots have focused on the optical properties. [39][40][41]43 The phonon confinement effect manifests behavior similar to the shifting behavior of the phonon modes due to the layered effect, depending on the nature of the phonon dispersion.…”

Hyperfine interaction in atomically thin transition metal dichalcogenides

“…Indeed, any disorder in 2D structures leads to the localization of the charge carrier wavefunction [33][34][35], which increases the spin and valley coherence times. In TMD MLs the charge carrier localization can be reached by means of the chemical exfoliation [36][37][38], lithographic nanopatterning [39], wrinkles [40], homojunctions [41], or defects [42][43][44].…”

Discrete quantum dot like emitters in monolayer MoSe2: Spatial mapping, magneto-optics, and charge tuning

“…[4][5][6] The 2D host materials have the advantage of being cost efficient, with highly tunable properties 3,7 and optical access to the electron valley index in momentum space, 8,9 an additional degree of freedom compared to other solid state qubits in III-V quantum dots (QDs) or NV centres in diamond, for example. There are several approaches to achieve 3D quantum confinement, such as patterning TMD MLs, 10 chemically synthesized TMD nano-crystals, [11][12][13][14][15][16] and defect engineering. [17][18][19][20] In photoluminescence (PL) experiments at T ¼ 4 K, we observe QD-like, discrete emission lines (full width at half maximum (FWHM) typ.…”