Zinc selenide

Zinc selenide
General
Other names	zinc(II) selenide
Molecular formula	ZnSe
Molar mass	144.35 g/mol
Appearance	light yellow solid
CAS number	1315-09-9
Properties
Density and phase	5.27 g/cm3, solid
Solubility in water	Insoluble
Melting point	1525 °C
Boiling point	? °C
Crystal structure	cubic(c=0.5668 nm)
Bandgap	2.7 eV (bulk)
Thermodynamic data
Standard enthalpy of formation ΔfH°solid	−177.6 kJ/mol
Standard molar entropy S°solid	???? J.K−1.mol−1
Hazards
EU classification	Dangerous for the environment (N)
R-phrases	R20 R22 R36 R38 R23/R25,R33
S-phrases	?????
NFPA ???
Supplementary data page
Structure and properties	n, εr, etc.
Thermodynamic data	Phase behaviour Solid, liquid, gas
Spectral data	UV, IR, NMR, MS
Regulatory data	Flash point, RTECS number, etc.
Related compounds
Other anions	Zinc sulfide Zinc oxide Zinc telluride
Other cations	Cadmium selenide Mercury selenide
Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa) Infobox disclaimer and references

Zinc selenide (ZnSe), is a light yellow binary solid compound. It is an intrinsic semiconductor with a band gap of about 2.7 eV at 25 °C. It has a standard enthalpy of formation of 177.6 kJ/mol at 25 °C. It adopts a Zincblende lattice structure with lattice constant a=566.8 picometers.

ZnSe rarely occurs in nature. It is found in the mineral stilleite named after Hans Stille.

Applications

• ZnSe is used to form II-VI light-emitting diodes and diode lasers. It emits blue light. It is susceptible to n-type doping with, for instance, halogen elements. P-type doping is more difficult, but can be achieved by introducing nitrogen.
• 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 (0.6 µm to 20 µm). The refractive index is about 2.67 at 550 nm (green), and about 2.40 at 10.6 µm (LWIR). ZnSe is produced as microcrystalline sheets by synthesis from H2Se 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 micrometres 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. An early form of low grade ZnSe was marketed as Irtran-4 but this is obsolete. Also, Raytran a trade mark of the Raytheon company) is no longer available. 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 coatings are generally employed.

• ZnSe doped 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 reacts with acids to form toxic hydrogen selenide gas.

It is grown by chemical vapour deposition techniques including MOVPE.

See also

• Zinc sulfide
• Zinc telluride
• Cadmium selenide
• Cadmium telluride

References

• Cr²⁺ 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

External links

• Notre Dame University Safety Data
• Oxford University Safety Data
• Stilleite at webmineral.com
• Reading University optical data