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The electronic structure of two-dimensional (2D) semiconductors can be significantly altered by screening effects, either from free charge carriers in the material itself, or by environmental screening from the surrounding medium. The…
Combining single-layer two-dimensional semiconducting transition metal dichalcogenides (TMDs) with graphene layer in van der Waals heterostructures offers an intriguing means of controlling the electronic properties through these…
Bulk layered MX2 transition metal chalcogenides (M = Mo, W and X = S, Se) are known to exhibit an indirect to direct band gap transition as the number of layers is reduced. Previous time-resolved work has principally focused on the…
Monolayer two-dimensional transitional metal dichalcogenides, such as MoS2, WS2 and WSe2, are direct band gap semiconductors with large exciton binding energy. They attract growing attentions for opto-electronic applications including solar…
We calculate from first principles the electronic structure and optical properties of a number of transition metal dichalcogenide (TMD) bilayer heterostructures consisting of MoS2 layers sandwiched with WS2, MoSe2, MoTe2, BN, or graphene…
Geometrical confinement effect in exfoliated sheets of layered materials leads to significant evolution of energy dispersion with decreasing layer thickness. Molybdenum disulphide (MoS2) was recently found to exhibit indirect to direct gap…
Understanding and controlling the photoexcited quasiparticle (QP) dynamics in monolayer transition metal dichalcogenides lays the foundation for exploring the strongly interacting, non-equilibrium 2D quasiparticle and polaritonic states in…
Transition metal dichalcogenides (TMDs) are emerging as promising two-dimensional (2d) semiconductors for optoelectronic and flexible devices. However, a microscopic explanation of their photophysics -- of pivotal importance for the…
Light emission in atomically thin heterostructures is known to depend on the type of materials, number and stacking sequence of the constituent layers. Here we show that the thickness of a two-dimensional substrate can be crucial in…
We present in-depth measurements of the electronic band structure of the transition-metal dichalcogenides (TMDs) MoS2 and WS2 using angle-resolved photoemission spectroscopy, with focus on the energy splittings in their valence bands at the…
Two-dimensional (2D) layered transition metal dichalcogenides (TMDs) have emerged as promising materials for electronic, optoelectronic, and valleytronic applications. Recent work suggests drastic changes of the band gap and exciton binding…
Monolayer transition-metal dichalcogenides are direct gap semiconductors with great promise for optoelectronic devices. Although spatial correlation of electrons and holes plays a key role, there is little experimental information on such…
Due to its high carrier mobility, broadband absorption, and fast response time, graphene is attractive for optoelectronics and photodetection applications. However, the extraction of photoelectrons in conventional metal-graphene junction…
Twisted bilayers of two-dimensional materials, such as twisted bilayer graphene, often feature flat electronic bands that enable the observation of electron correlation effects. In this work, we study the electronic structure of twisted…
We report a strain-induced direct-to-indirect band gap transition in mechanically deformed WS2 monolayers (MLs). The necessary amount of strain is attained by proton irradiation of bulk WS2 and the ensuing formation of one-ML-thick,…
Two-dimensional dilute magnetic semiconductors has been recently reported in semiconducting transition metal dichalcogenides by the introduction of spin-polarized transition metal atoms as dopants. This is the case of vanadium-doped WS$_2$…
Transition metal dichalcogenides (TMD) monolayers, holding potential as good sunlight absorbers, are promising materials for next-generation optoelectronic devices. They may enable ultrathin photovoltaic(PV) devices thanks to their…
Monolayers of transition-metal dichalcogenides (TMDs) hold great promise as future nanoelectronic and optoelectronic devices. An essential feature for achieving high device performance is the use of suitable supporting substrates, which can…
Monolayers of transition metal dichalcogenides are semiconducting materials which offer many prospects in optoelectronics. A monolayer of molybdenum disulfide (MoS2) has a direct bandgap of 1.88 eV. Hence, when excited with optical photon…
We directly measure the electronic structure of twisted graphene/MoS2 van der Waals heterostructures, in which both graphene and MoS2 are monolayers. We use cathode lens microscopy and microprobe angle-resolved photoemission spectroscopy…