The direct-to-indirect band gap crossover in two-dimensional van der Waals Indium Selenide crystals

Mudd, G.W.; Molas, M.R.; Chen, X.; Z�lyomi, V.; Nogajewski, K.; Kudrynskyi, Zakhar R.; Kovalyuk, Zakhar D.; Yusa, G.; Makarovsky, Oleg; Eaves, Laurence; Potemski, M.; Fal'ko, V.I.; Patan�, Amalia

Abstract

The electronic band structure of van der Waals (vdW) layered crystals has properties that depend on the composition, thickness and stacking of the component layers. Here we use density functional theory and high field magneto-optics to investigate the metal chalcogenide InSe, a recent addition to the family of vdW layered crystals, which transforms from a direct to an indirect band gap semiconductor as the number of layers is reduced. We investigate this direct-to-indirect bandgap crossover, demonstrate a highly tuneable optical response from the near infrared to the visible spectrum with decreasing layer thickness down to 2 layers, and report quantum dot-like optical emissions distributed over a wide range of energy. Our analysis also indicates that electron and exciton effective masses are weakly dependent on the layer thickness and are significantly smaller than in other vdW crystals. These properties are unprecedented within the large family of vdW crystals and demonstrates the potential of InSe for electronic and photonic technologies.

Citation

Mudd, G., Molas, M., Chen, X., Zólyomi, V., Nogajewski, K., Kudrynskyi, Z. R., Kovalyuk, Z. D., Yusa, G., Makarovsky, O., Eaves, L., Potemski, M., Fal'ko, V., & Patanè, A. (2016). The direct-to-indirect band gap crossover in two-dimensional van der Waals Indium Selenide crystals. Scientific Reports, 6(1), Article 39619. https://doi.org/10.1038/srep39619

• Journal Article Type: Article
• Acceptance Date: Nov 23, 2016
• Online Publication Date: Dec 23, 2016
• Publication Date: 2016-12
• Deposit Date: Jan 3, 2017
• Publicly Available Date: Jan 3, 2017
• Journal: Scientific Reports
• Electronic ISSN: 2045-2322
• Publisher: Nature Publishing Group
• Peer Reviewed: Peer Reviewed
• Volume: 6
• Issue: 1
• Article Number: 39619
• DOI: https://doi.org/10.1038/srep39619
• Public URL: https://nottingham-repository.worktribe.com/output/832420
• Publisher URL: http://www.nature.com/articles/srep39619
• Related Public URLs: https://rdmc.nottingham.ac.uk/handle/internal/72
• Contract Date: Jan 3, 2017