Out-of-plane orientation of luminescent excitons in atomically thin indium selenide flakes

Abstract

Van der Waals materials offer a wide range of atomic layers with unique properties that can be easily combined to engineer novel electronic and photonic devices. A missing ingredient of the van der Waals platform is a two-dimensional crystal with naturally occurring out-of-plane luminescent dipole orientation. Here we measure the far-field photoluminescence intensity distribution of bulk InSe and two-dimensional InSe, WSe${}_2$ and MoSe${}_2$. We demonstrate, with the support of ab-initio calculations, that layered InSe flakes sustain luminescent excitons with an intrinsic out-of-plane orientation, in contrast with the in-plane orientation of dipoles we find in two-dimensional WSe${}_2$ and MoSe${}_2$ at room-temperature. These results, combined with the high tunability of the optical response and outstanding transport properties, position layered InSe as a promising semiconductor for novel optoelectronic devices, in particular for hybrid integrated photonic chips which exploit the out-of-plane dipole orientation.

arXiv commentPublished in Nature Communications. 12 pages, 5 figures. Link: https://www.nature.com/articles/s41467-019-11920-4

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• Transferable screened range-separated hybrid functionals for electronic and optical properties of van der Waals materials
• Unveiling the optical emission channels of monolayer semiconductors coupled to silicon nanoantennas
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• Interfacial Charge Transfer and Ultrafast Photonics Application of 2D Graphene/InSe Heterostructure
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