*typical representative size, areas/dimensions may vary
||1.2 - 3.0 eV 
||Indium (III) Selenide, Diindium triselenide
|Classification / Family
Transition metal dichalcogenides (TMDCs), 2D semiconductor materials, Nano-electronics, Nano-photonics, Photovoltaic, Materials science
||Synthetic - Chemical Vapour Transport (CVT)
Indium (III) Selenide, or In2Se3, is an interesting III−VI semiconductor due to its multiple phases and excellent optical properties. α-In2Se3 and β-In2Se3 are semiconducting with a layered 2D structure, and they have been the most-studied phases. Like other TMDC materials, their layers are bound together via weak van der Waals forces, and can thus be exfoliated into thin nano-structures.
However, α-In2Se3 and β-In2Se3 phases share the same rhombohedral crystal structure. The primitive unit cell contains three layers, each consisting of five covalently-bonded, monoatomic sheets in the sequence of Se–In–Se–In–Se. For α-In2Se3, the outer Se-atoms in each layer are aligned, whereas in β-In2Se3 they are located at the interstitial sites of the Se-atoms in the neighbouring layers.
Normally, the β-In2Se3 phase only exists at elevated temperatures in bulk single crystals. However, at room temperature it persists in thin layers. This makes it possible for multi-level phase-change memory in a single material system .
Indium(III) selenide has been of great research interest and extensively studied to explore its applications in solar energy harvesting, nonvolatile phase change memory and optoelectronic devices. In2Se3 is particularly desired for photodetection due to its optimum direct-band gap (1.3 eV), efficient absorption and great photon sensitivity.
Indium (III) selenide is manufactured using chemical vapour transport (CVT) crystallisation, with crystals having a purity in excess of 99.999%.
Indium (III) selenide single crystals can be used to prepare monolayer and few-layer In2Se3 by mechanical or liquid exfoliation.
Literature and Reviews
Strong quantum confinement effect in the optical properties of ultrathin α-In2Se3, Adv. Opt. Mater., J. Quereda et al., 14 (12), 1939-1943 (2016); DOI: 10.1002/adom.201600365.
Crystalline–Crystalline Phase Transformation in Two-Dimensional In2Se3 Thin Layers, X. Tao et al., Nano Lett., 13 (8), 3501–3505 (2013); DOI: 10.1021/nl400888p.
Controlled Synthesis of High-Quality Monolayered α-In2Se3 via Physical Vapor Deposition, J. Zhou et al., Nano Lett., 15 (10), 6400–6405 (2015); DOI: 10.1021/acs.nanolett.5b01590.
Extraordinary Photoresponse in Two-Dimensional In2Se3 Nanosheets, R. Jacobs-Gedrim et al., ACS Nano, 8 (11), 514–521 (2014); DIO: 10.1021/nn405037s.
Prediction of intrinsic two-dimensional ferroelectrics in In2Se3 and other III2-VI3 van der Waals materials, W. Ding et al., Nat. Commun., 8:14956 (2017); DOI: 10.1038/ncomms14956.
Room temperature in-plane ferroelectricity in van der Waals In2Se3, C. Zheng et al., Sci. Adv., 4 (7) eaar7720 (2018); DOI: 10.1126/sciadv.aar7720