Aluminium nitride



Aluminium nitride
Other names aluminium nitride
Identifiers
CAS number 24304-00-5
Properties
Molecular formula AlN
Molar mass 40.988g/mol
Appearance crystalline solid, bluish white
Melting point

2200 °C

Boiling point

2517 °C

Except where noted otherwise, data are given for
materials in their standard state
(at 25 °C, 100 kPa)
Infobox disclaimer and references

Aluminium nitride (Aldeep ultraviolet optoelectronics.

History

AlN was first synthesised in 1877, but it was not until the middle of the 1980s that its potential for application in microelectronics was realised due to its relative high ceramic (70-210 W•m−1•K−1 for polycrystalline material, and as high as 275 W•m−1•K−1 for single crystals).

Chemical description and properties

Aluminium nitride is a (mostly) covalently bonded material, and has a hexagonal crystal structure which is isomorphic with one of the polytypes of zinc sulfide known as wurtzite. The space group for this structure is P63mc.

The material is stable at very high temperatures in inert atmospheres. In air, surface oxidation occurs above 700°C, and even at room temperature, surface oxide layers of 5-10 nm have been detected. This oxide layer protects the material up to 1370°C. Above this temperature bulk oxidation occurs. Aluminium nitride is stable in hydrogen and carbon dioxide atmospheres up to 980°C.

The material dissolves slowly in mineral acids through grain boundary attack, and in strong alkalis through attack on the aluminum nitride grains. The material hydrolyzes slowly in water. Aluminium nitride is resistant to attack from most molten salts including cryolite.

Manufacture

AlN is synthesised by carbothermal reduction of alumina or by direct nitridation of aluminium. The use of sintering aids and hot pressing is required to produce a dense technical grade material.

Applications

Metallization methods are available to allow AlN to be used in electronics applications similar to those of alumina and BeO.

Currently there is much research into developing bandgap of single crystal AlN has been measured (using vacuum UV reflectivity) at 6.2 eV. This allows a wavelength of around 200 nm to be achieved, in principle. However, there are many difficulties to be overcome if such emitters are to become a commercial reality.

Among the applications of AlN are

  • opto-electronics,
  • dielectric layers in optical storage media,
  • electronic substrates, chip carriers where high thermal conductivity is essential,
  • military applications.

MEMS field.

See also

References

    Academic

    • Ioffe data archive
    • Electronic Structure of AlN
    • MSDS (University of Oxford)

    Commercial suppliers

    • Ceramic Substrates and Components Ltd
    • Goodfellow
    • NanoAmor's AlN Nanoparticles
     
    This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Aluminium_nitride". A list of authors is available in Wikipedia.