Indium(II) selenide
Chemical compound
From Wikipedia, the free encyclopedia
Indium(II) selenide (InSe) is an inorganic compound composed of indium and selenium. It is a III-VI layered semiconductor. The solid has a structure consisting of two-dimensional layers bonded together only by van der Waals forces. Each layer has the atoms in the order Se-In-In-Se.[2]
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| InSe | |
| Molar mass | 193.789 g·mol−1 |
| Density | 5.0 |
| Melting point | 611 °C (1,132 °F; 884 K)[1] |
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Potential applications are for field effect transistors, optoelectronics, photovoltaic, non-linear optics, strain gauges,[2] and methanol gas sensors.[3]
Formation
Indium(II) selenide can be formed via a number of different methods. A method to make the bulk solid is the Bridgman/Stockbarger method, in which the elements indium and selenium are heated to over 900 °C in a sealed capsule, and then slowly cooled over about a month.[4] Another method is electrodeposition from a water solution of indium(I) sulfate and selenium dioxide.[5]
Properties
_selenide_polytopes.png)
There are three polytopes or crystal forms. β, ε are hexagonal with unit cells spanning two layers. γ has rhombohedral crystal system, with the unit cell including four layers.[2]
β-Indium(II) selenide can be exfoliated into two-dimensional sheets using sticky tape. In a vacuum these form smooth layers. However, when exposed to air, the layers become corrugated because of chemisorption of air molecules.[6] Exfoliation can also take place in isopropanol liquid.[7]
Indium (II) selenide is stable in ambient conditions of oxygen and water vapour, unlike many other semiconductors.[2]
| polytope | space group | unit cell | band gap | eV |
|---|---|---|---|---|
| β | P63/mmc | a=4.005 c=16.660 Z=4 | direct | 1.28 |
| γ | R3m | a=7.1286 Å, c=19.382 Å and Z=6 | direct | 1.29 |
| ε | P6m2 | indirect | 1.4 |
Doping
The properties of indium(II) selenide can be varied by way of altering the exact ratio of elements from 1:1, creating vacancies. It is hard to get an exact equality. The properties can be compensated by transition element doping. Other elements that can be included in small concentrations are boron,[8] silver,[9] and cadmium.[10]
