Indium(II) selenide
{{Chembox
|Section1={{Chembox Identifiers
| CASNo = 1312-42-1
| ChemSpiderID = 4906850
| PubChem = 101946410
| StdInChI=1S/In.Se
| StdInChIKey = NMHFBDQVKIZULJ-UHFFFAOYSA-N
| SMILES = [Se].[In]
}}
|Section2={{Chembox Properties
| In=1|Se=1
| Density = 5.0
| MeltingPtC=611
}}
}}
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.{{cite journal |last1=Politano |first1=A. |last2=Campi |first2=D. |last3=Cattelan |first3=M. |last4=Ben Amara |first4=I. |last5=Jaziri |first5=S. |last6=Mazzotti |first6=A. |last7=Barinov |first7=A. |last8=Gürbulak |first8=B. |last9=Duman |first9=S. |last10=Agnoli |first10=S. |last11=Caputi |first11=L. S. |last12=Granozzi |first12=G. |last13=Cupolillo |first13=A. |title=Indium selenide: an insight into electronic band structure and surface excitations |journal=Scientific Reports |date=December 2017 |volume=7 |issue=1 |pages=3445 |doi=10.1038/s41598-017-03186-x|pmid=28611385 |bibcode=2017NatSR...7.3445P |doi-access=free |pmc=5469805 }}{{open access}}
Potential applications are for field effect transistors, optoelectronics, photovoltaic, non-linear optics, strain gauges, and methanol gas sensors.{{cite journal |last1=Marvan |first1=Petr |last2=Mazánek |first2=Vlastimil |last3=Sofer |first3=Zdeněk |title=Shear-force exfoliation of indium and gallium chalcogenides for selective gas sensing applications |journal=Nanoscale |date=2019 |volume=11 |issue=10 |pages=4310–4317 |doi=10.1039/C8NR09294J|pmid=30788468 |s2cid=206138673 }}
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.{{cite journal |last1=Boukhvalov |first1=Danil |last2=Gürbulak |first2=Bekir |last3=Duman |first3=Songül |last4=Wang |first4=Lin |last5=Politano |first5=Antonio |last6=Caputi |first6=Lorenzo |last7=Chiarello |first7=Gennaro |last8=Cupolillo |first8=Anna |title=The Advent of Indium Selenide: Synthesis, Electronic Properties, Ambient Stability and Applications |journal=Nanomaterials |date=5 November 2017 |volume=7 |issue=11 |pages=372 |doi=10.3390/nano7110372|pmid=29113090 |pmc=5707589 |doi-access=free }} Another method is electrodeposition from a water solution of indium(I) sulfate and selenium dioxide.{{cite journal |last1=Demir |first1=Kübra Çınar |last2=Demir |first2=Emre |last3=Yüksel |first3=Seniye |last4=Coşkun |first4=Cevdet |title=Influence of deposition conditions on nanostructured InSe thin films |journal=Current Applied Physics |date=December 2019 |volume=19 |issue=12 |pages=1404–1413 |doi=10.1016/j.cap.2019.09.008|bibcode=2019CAP....19.1404D |s2cid=203143299 }}
Properties
File:Indium (II) 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.
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.{{cite journal |last1=Dmitriev |first1=A. I. |last2=Vishnjak |first2=V. V. |last3=Lashkarev |first3=G. V. |last4=Karbovskyi |first4=V. L. |last5=Kovaljuk |first5=Z. D. |last6=Bahtinov |first6=A. P. |title=Investigation of the morphology of the van der Waals surface of the InSe single crystal |journal=Physics of the Solid State |date=March 2011 |volume=53 |issue=3 |pages=622–633 |doi=10.1134/S1063783411030085|bibcode=2011PhSS...53..622D |s2cid=121113583 }} Exfoliation can also take place in isopropanol liquid.{{cite journal |last1=Petroni |first1=Elisa |last2=Lago |first2=Emanuele |last3=Bellani |first3=Sebastiano |last4=Boukhvalov |first4=Danil W. |last5=Politano |first5=Antonio |last6=Gürbulak |first6=Bekir |last7=Duman |first7=Songül |last8=Prato |first8=Mirko |last9=Gentiluomo |first9=Silvia |last10=Oropesa-Nuñez |first10=Reinier |last11=Panda |first11=Jaya-Kumar |last12=Toth |first12=Peter S. |last13=Del Rio Castillo |first13=Antonio Esau |last14=Pellegrini |first14=Vittorio |last15=Bonaccorso |first15=Francesco |title=Liquid-Phase Exfoliated Indium-Selenide Flakes and Their Application in Hydrogen Evolution Reaction |journal=Small |date=June 2018 |volume=14 |issue=26 |pages=1800749 |doi=10.1002/smll.201800749|pmid=29845748 |arxiv=1903.08967 |s2cid=44172633 }}
Indium (II) selenide is stable in ambient conditions of oxygen and water vapour, unlike many other semiconductors.
| class="wikitable"
!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 | P{{overline|6}}m2 | 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,{{cite journal |last1=Ertap |first1=Hüseyin |last2=Karabulut |first2=Mevlut |title=Structural and electrical properties of boron doped InSe single crystals |journal=Materials Research Express |date=5 December 2018 |volume=6 |issue=3 |pages=035901 |doi=10.1088/2053-1591/aaf2f6|s2cid=105206868 }} silver,{{cite journal |last1=Gürbulak |first1=Bekir |last2=Şata |first2=Mehmet |last3=Dogan |first3=Seydi |last4=Duman |first4=Songul |last5=Ashkhasi |first5=Afsoun |last6=Keskenler |first6=E. Fahri |title=Structural characterizations and optical properties of InSe and InSe:Ag semiconductors grown by Bridgman/Stockbarger technique |journal=Physica E: Low-dimensional Systems and Nanostructures |date=November 2014 |volume=64 |pages=106–111 |doi=10.1016/j.physe.2014.07.002|bibcode=2014PhyE...64..106G }} and cadmium.{{cite web |last1=Evtodiev |first1=Igor |title=Excitonic absorption of the light in heterojunctions Bi 2 O 3-InSe |url=http://dspace.usm.md:8080/xmlui/handle/123456789/1763 |date=2009}}