Photocarrier relaxation pathway in two-dimensional semiconducting transition metal dichalcogenides.

Two-dimensional crystals of semiconducting transition metal dichalcogenides absorb a large fraction of incident photons in the visible frequencies despite being atomically thin. It has been suggested that the strong absorption is due to the parallel band or 'band nesting' effect and corresponding divergence in the joint density of states. Here, we use photoluminescence excitation spectroscopy to show that the band nesting in mono- and bilayer MX2 (M=Mo, W and X=S, Se) results in excitation-dependent characteristic relaxation pathways of the photoexcited carriers.

Large thermoelectricity via variable range hopping in chemical vapor deposition grown single-layer MoS2.

Ultrathin layers of semiconducting molybdenum disulfide (MoS2) offer significant prospects in future electronic and optoelectronic applications. Although an increasing number of experiments bring light into the electronic transport properties of these crystals, their thermoelectric properties are much less known. In particular, thermoelectricity in chemical vapor deposition grown MoS2, which is more practical for wafer-scale applications, still remains unexplored.

Lattice dynamics in mono- and few-layer sheets of WS2 and WSe2.

Thickness is one of the fundamental parameters that define the electronic, optical, and thermal properties of two-dimensional (2D) crystals. Phonons in molybdenum disulfide (MoS2) were recently found to exhibit unique thickness dependence due to the interplay between short and long range interactions. Here we report Raman spectra of atomically thin sheets of WS2 and WSe2, isoelectronic compounds of MoS2, in the mono- to few-layer thickness regime.