Atomically Thin MoS 2 : A New Direct-Gap Semiconductor¶
Why this mattered¶
TBD
Abstract¶
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.
Related¶
- cite → Measurement of the Elastic Properties and Intrinsic Strength of Monolayer Graphene — The monolayer MoS2 paper cites graphene strength measurements as evidence that atomically thin two-dimensional crystals can be mechanically robust.
- cite → Emerging Photoluminescence in Monolayer MoS2 — Both MoS2 papers report that monolayer MoS2 exhibits strong photoluminescence because its band gap becomes direct at single-layer thickness.
- cite → Two-dimensional atomic crystals — The MoS2 direct-gap study builds on the broader two-dimensional atomic-crystal framework established for isolating and studying monolayers.
- enables → Layer-dependent ferromagnetism in a van der Waals crystal down to the monolayer limit — Monolayer MoS2 established atomically thin transition-metal dichalcogenides as experimentally accessible semiconductors, enabling later monolayer van der Waals magnet studies.
- cite ← Layer-dependent ferromagnetism in a van der Waals crystal down to the monolayer limit — Layer-dependent ferromagnetism in a van der Waals crystal cites monolayer MoS2's direct-gap transition as precedent for layer-dependent electronic properties in 2D materials.
- cite ← Phosphorene: An Unexplored 2D Semiconductor with a High Hole Mobility — The phosphorene paper cites monolayer MoS2's direct band gap as a benchmark showing that atomically thin semiconductors can have technologically useful electronic properties.
- cite ← Single-layer MoS2 transistors — The transistor paper builds on the finding that monolayer MoS2 has a direct band gap suitable for electronic devices.
- cite ← Van der Waals heterostructures — Geim and Grigorieva cite Mak et al. for the direct bandgap that emerges in monolayer MoS2, motivating transition-metal dichalcogenides as optoelectronic layers in heterostructures.
- enables ← Two-dimensional atomic crystals — The isolation of two-dimensional crystals enabled the study of monolayer MoS2 as an atomically thin direct-gap semiconductor.