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Zinc selenide

Names
Other names Zinc selenide Stilleite
Identifiers
CAS Number	1315-09-9
ECHA InfoCard	100.013.873
PubChem CID	4298215
CompTox Dashboard (EPA)	DTXSID80893851
Properties
Chemical formula	ZnSe
Molar mass	144.35 g/mol
Appearance	light yellow solid
Density	5.27 g/cm
Melting point	1525 °C
Solubility in water	negligible
Band gap	2.82 eV (10 ºK)
Refractive index (nD)	2.67 (550 nm) 2.40 (10.6 µm)
Structure
Crystal structure	Zincblende (cubic)
Lattice constant	a = 566.8 pm
Coordination geometry	Tetrahedral (Zn) Tetrahedral (Se)
Thermochemistry
Std enthalpy of formation (ΔfH298)	−177.6 kJ/mol
Related compounds
Other anions	Zinc oxide Zinc sulfide Zinc telluride
Other cations	Cadmium selenide Mercury selenide
Except where otherwise noted, data are given for materials in their standard state (at 25 °C , 100 kPa). Y verify (what is  ?) Infobox references

Zinc selenide (ZnSe), is a light yellow binary solid compound. It is an intrinsic semiconductor with a band gap of about 2.70 eV at 25 °C. ZnSe rarely occurs in nature. It is found in the mineral stilleite named after Hans Stille.

Properties

ZnSe can be made in both hexagonal (wurtzite) and cubic (zincblende) crystal structure.

It is a wide-bandgap semiconductor of the II-VI semiconductor group (since zinc and selenium belong to the 2nd and 6th groups of the periodic table, respectively). The material can be doped n-type doping with, for instance, halogen elements. P-type doping is more difficult, but can be achieved by introducing nitrogen.

Applications

• ZnSe is used to form II-VI light-emitting diodes and diode lasers. It emits blue light.
• ZnSe doped with chromium (ZnSe:Cr) has been used as an infrared laser gain medium emitting at about 2.5 µm.
• It is used as an infrared optical material with a remarkably wide transmission wavelength range (0.45 µm to 21.5 µm). The refractive index is about 2.67 at 550 nm (green), and about 2.40 at 10.6 µm (LWIR). Similar to zinc sulfide, ZnSe is produced as microcrystalline sheets by synthesis from hydrogen selenide gas and zinc vapour. Lasertran (trademark of Rohm & Haas) grade is especially free of absorption and inclusions and is used particularly for CO₂ laser optics at 10.6 µm wavelength. It is thus a very important IR material. In daily life, it can be found as the entrance optic in the new range of "in-ear" clinical thermometers and can be just seen as a small yellow window. Zinc selenide can slowly react with atmospheric moisture if poorly polished, but this is not generally a serious problem. Except where optics are use in spectroscopy or at the brewster angle, antireflection or beamsplitting optical coatings are generally employed.
• ZnSe activated with tellurium (ZnSe(Te)) is a scintillator with emission peak at 640 nm, suitable for matching with photodiodes. It is used in x-ray and gamma ray detectors. ZnSe scintillators are significantly different from the ZnS ones.

Chemistry

ZnSe is insoluble in water, but reacts with acids to form toxic hydrogen selenide gas.

It can be deposited as a thin film by chemical vapour deposition techniques including MOVPE and vacuum evaporation.

References

1. Cr excitation levels in ZnSe and ZnS, G. Grebe, G. Roussos and H.-J. Schulz, J. Phys. C: Solid State Phys. vol. 9 pp. 4511-4516 (1976) doi:10.1088/0022-3719/9/24/020
2. http://www.kayelaby.npl.co.uk/general_physics/2_5/2_5_8.html Kaye and Laby online at NPL

External links

• II-VI - INFRARED optical data & more
• University of Reading, Infrared Multilayer Laboratory optical data

• Zinc compounds
• Selenides
• Semiconductor materials
• Optical materials
• Phosphors and scintillators
• Laser gain media
• Compound semiconductors