*typical representative size, areas/dimensions may vary
||1.3 - 2.0 eV 
|Classification / Family
Transition metal dichalcogenides (TMDCs), 2D semiconductor materials, Inorganic semiconductors, Nano-electronics, Nano-photonics, Photovoltaics
||Synthetic - Chemical Vapour Transport (CVT)
||600 °C (lit.)
||Dark brown crystal
Indium selenide belongs to the IIIA−VIA family group of 2D layered semiconductors. Each of its layers has a honeycomb lattice made of indium and selenium atoms. The layers are bound by relatively weak van der Waals forces which allow mechanical or wet exfoliation to obtain atomically thin films.
A single layer of InSe consists of four mono-atomic sheets of hexagonally arranged atoms tetrahedrally linked in the sequence of Se–In–In–Se via covalent bonds. Each of the two indium atoms is bound to three neighbouring selenides. At room temperature under ambient conditions, InSe crystallises in a rhombohedral layered phase, known as γ-InSe with a space group of R3m.
Indium selenide has a room-temperature electron mobility of 2,000 cm2V-1s-1, which is significantly higher than that of silicon, and even higher than few-layer dichalcogenides.
Bulk InSe has a direct band gap of ~ 1.3 eV with anisotropic electronic properties, and has potential applications in photovoltaics. Mechanically-exfoliated InSe flakes of single crystals have been effectively used as photodetectors with good response and quantum efficiency. Field-effect transistors with an active channel of InSe are characterised by an electron mobility of 103 cm2V-1s-1. In addition, with excellent flexibility and ambient stability, InSe is also a promising candidate for applications in strain engineering, nonlinear optics, and fast ultra-thin electronic devices.
Indium selenide (InSe) is manufactured using chemical vapour transport (CVT) crystallisation, with crystals having a purity in excess of 99.999%.
Indium selenide single crystals can be used to prepare monolayer and few-layer InSe, by mechanical or liquid exfoliation.
Literature and Reviews
The direct-to-indirect band gap crossover in two-dimensional van der Waals Indium Selenide crystals, G. W. Mudd et al., Sci. Rep., 6:39619 (2016); DOI: 10.1038/srep39619.
High Performance and Bendable Few-Layered InSe Photodetectors with Broad Spectral Response, S. Tamalampudi et al., Nano Lett. 2014, 14, 2800−2806 (2014); doi: 10.1021/nl500817g.
Structural modification and band-gap crossover in indium selenide nanosheets, M. Airo et al., RSC Adv., 6, 40777 (2016); DOI: 10.1039/c6ra00262e.
Enhanced Light Emission from the Ridge of Two-Dimensional InSe Flakes, Y. Li et al., Nano Lett., 18, 5078−5084 (2018); DOI: 10.1021/acs.nanolett.8b01940.
Nanotexturing To Enhance Photoluminescent Response of Atomically Thin Indium Selenide with Highly Tunable Band Gap, M. Brotons-Gisbert et al., Nano Lett., 16, 3221−3229 (2016); DOI: 10.1021/acs.nanolett.6b00689.
Electrons and phonons in single layers of hexagonal indium chalcogenides from ab initio calculations, V. Zólyomi et al., Phys. Rev. B 89, 205416 (2014); doi: 10.1103/PhysRevB.89.205416.
The Advent of Indium Selenide: Synthesis, Electronic Properties, Ambient Stability and Applications, D. Boukhvalov et al., Nanomaterials, 7, 372 (2017); doi: 10.3390/nano7110372.