Molybdenum disulfide

Spectroscopy

Quantum mechanics

Photoconductivity

Metallurgy

Materials science

Chromatography

Photoluminescence

Band gap

Physics

Nanotechnology

Luminescence

Condensed matter physics

Analytical Chemistry (journal)

Monolayer

Chemistry

Quantum dot

Optoelectronics

Physical Review Letters

The electronic properties of ultrathin crystals of molybdenum disulfide consisting of N=1,2,…,6 S-Mo-S monolayers have been investigated by optical spectroscopy. Through characterization by absorption, photoluminescence, and photoconductivity spectroscopy, we trace the effect of quantum confinement on the material's electronic structure. With decreasing thickness, the indirect band gap, which lies below the direct gap in the bulk material, shifts upwards in energy by more than 0.6 eV. This leads to a crossover to a direct-gap material in the limit of the single monolayer. Unlike the bulk material, the MoS₂ monolayer emits light strongly. The freestanding monolayer exhibits an increase in luminescence quantum efficiency by more than a factor of 10⁴ compared with the bulk material.

Atomically Thin<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msub><mml:mi>MoS</mml:mi><mml:mn>2</mml:mn></mml:msub></mml:math>: A New Direct-Gap Semiconductor

Atomically ThinMoS2: A New Direct-Gap Semiconductor