Aluminium nitride

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For the three-letter acronym, see ALN (disambiguation).
Aluminium nitride[1]
Aluminum Nitride powder
Wurtzite polyhedra.png
Identifiers
CAS number 24304-00-5 YesY
PubChem 90455
ChemSpider 81668 YesY
EC number 246-140-8
ChEBI CHEBI:50884 YesY
RTECS number BD1055000
Jmol-3D images Image 1
Properties
Molecular formula AlN
Molar mass 40.9882 g/mol
Appearance white to pale-yellow solid
Density 3.260 g/cm3
Melting point 2,200 °C (3,990 °F; 2,470 K)
Boiling point 2,517 °C (4,563 °F; 2,790 K) decomposes
Solubility in water reacts
Band gap 6.2 eV (direct)
Electron mobility ~300 cm2/(V·s)
Thermal conductivity 285 W/(m·K)
Refractive index (nD) 1.9–2.2
Structure
Crystal structure Wurtzite
Space group C6v4-P63mc
Coordination
geometry
Tetrahedral
Thermochemistry
Specific
heat capacity
C
30.1 J/mol K
Std molar
entropy
So298
20.2 J/mol K
Std enthalpy of
formation
ΔfHo298
318 kJ/mol
Gibbs free energy ΔG 287.4 kJ/mol
Hazards
NFPA 704
Flammability code 0: Will not burn. E.g., water Health code 1: Exposure would cause irritation but only minor residual injury. E.g., turpentine Reactivity code 0: Normally stable, even under fire exposure conditions, and is not reactive with water. E.g., liquid nitrogen Special hazards (white): no codeNFPA 704 four-colored diamond
Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
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Infobox references

Aluminum nitride (AlN) is a nitride of aluminum. Its wurtzite phase (w-AlN) is a wide band gap (6.2 eV) semiconductor material, giving it potential application for deep ultraviolet optoelectronics.

History[edit]

AlN was first synthesized in 1877, but it was not until the middle of the 1980s that its potential for application in microelectronics was realized due to its relative high thermal conductivity for an electrical insulating ceramic (70–210 W·m−1·K−1 for polycrystalline material, and as high as 285 W·m−1·K−1 for single crystals).[2]

Stability and chemical properties[edit]

Aluminum nitride is stable at high temperatures in inert atmospheres and melts at 2800 °C. In a vacuum, AlN decomposes at ~1800 °C. In the 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. Aluminum nitride is stable in hydrogen and carbon dioxide atmospheres up to 980 °C.[3]

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

Manufacture[edit]

AlN is synthesized by the carbothermal reduction of aluminium oxide or by direct nitridation of aluminium. The use of sintering aids, such as Y2O3 or CaO, and hot pressing is required to produce a dense technical grade material.

Applications[edit]

Epitaxially grown thin film crystalline aluminium nitride is used for surface acoustic wave sensors (SAWs) deposited on silicon wafers because of AlN's piezoelectric properties. One application is an RF filter which is widely used in mobile phones,[4] including called a thin film bulk acoustic resonator (FBAR). This is a MEMS device that uses aluminium nitride sandwiched between two metal layers.[5]

Aluminum nitride is also used to build piezoelectric micromachined ultrasound transducers, which emit and receive ultrasound and which can be used for in-air rangefinding over distances of up to a meter.[6][7]

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

Currently there is much research into developing light-emitting diodes to operate in the ultraviolet using the gallium nitride based semiconductors and, using the alloy aluminum gallium nitride, wavelengths as short as 250 nm have been achieved. In May 2006, an inefficient AlN LED emission at 210 nm has been reported.[8]

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,
  • as a crucible to grow crystals of gallium arsenide,
  • steel and semiconductor manufacturing.

See also[edit]

References[edit]

  1. ^ "Aluminum Nitride". Accuratus. Retrieved 2014-01-01. 
  2. ^ "AlN - Aluminium Nitride". Ioffe Database. Sankt-Peterburg: FTI im. A. F. Ioffe, RAN. Retrieved 2014-01-01. 
  3. ^ L. I. Berger (1997). Semiconductor Materials. CRC Press. pp. 123–124. ISBN 0-8493-8912-7. Retrieved 2014-01-01. 
  4. ^ "Apple, Samsung Cellphone Filter Orders Lift Avago". 
  5. ^ "ACPF-7001: Agilent Technologies Announces FBAR Filter for U.S. PCS Band Mobile Phones and Data Cards". wirelessZONE. EN-Genius Network Ltd. 2002-05-27. Retrieved 2008-10-18. 
  6. ^ "A Gestural Interface for Smart Watches". 
  7. ^ Przybyla, R.; al, et (2014). "3D Ultrasonic Gesture Recognition". International Solid State Circuits Conference. San Francisco. pp. 210–211. 
  8. ^ Y. Taniyasu et al. (2006). "An Aluminium Nitride Light-Emitting Diode with a Wavelength of 210 Nanometres". Nature 441 (7091): 325–328. doi:10.1038/nature04760. PMID 16710416. 

External links[edit]