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 | |
| Properties | |
| Density and phase | 5.27 g/cm3, solid |
| Solubility in water | Insoluble |
| Melting point | 1525 °C |
| Boiling point | ? °C |
| structure | |
| Crystal structure | cubic(c=0.5668 nm) |
| point group | Td |
| 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.[1]
- 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. 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
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
- Oxford University Safety Data
- Reading University optical data