We present a systematic investigation of the electronic properties of bulk and few layer ReS2 van der Waals crystals using low temperature optical spectroscopy. Weak photoluminescence emission is observed from two non-degenerate band edge excitonic transitions separated by ∼20 meV. The comparable emission intensity of both excitonic transitions is incompatible with a fully thermalized (Boltzmann) distribution of excitons, indicating the hot nature of the emission. While DFT calculations predict bilayer ReS2 to have a direct fundamental band gap, our optical data suggests that the fundamental gap is indirect in all cases.
Bibliographical noteFunding Information:
This work was partially supported by BLAPHENE and STRABOT projects, which received funding from the IDEX Toulouse, Emergence program, ‘Programme des Investissements d’Avenir’ under the program ANR-11-IDEX-0002-02, reference ANR-10-LABX-0037-NEXT, and by the PAN–CNRS collaboration within the PICS 2016-2018 agreement.MB appreciates support from the Polish Ministry ofScience and Higher Education within the Mobilnosc Plus program (grant no. 1648/MOB/V/2017/0). AK and TH acknowledge funding of Deutsche Forschungsgemeinschaft via the FlagERA project HE 3543/27-1 and ZIH Dresden for providing computational resources.
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All Science Journal Classification (ASJC) codes
- Materials Science(all)
- Condensed Matter Physics
- Mechanics of Materials
- Mechanical Engineering