Gallium(III) oxide

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Gallium(III) oxide
Names
Other names
gallium trioxide, gallium sesquioxide
Identifiers
3D model (JSmol)
ChemSpider
ECHA InfoCard 100.031.525 Edit this at Wikidata
RTECS number
  • LW9650000
  • InChI=1S/2Ga.3O checkY
    Key: QZQVBEXLDFYHSR-UHFFFAOYSA-N checkY
  • InChI=1/2Ga.3O/rGa2O3/c3-1-5-2-4
    Key: QZQVBEXLDFYHSR-OGCFUIRMAC
  • O=[Ga]O[Ga]=O
Properties
Ga2O3
Molar mass 187.444 g/mol
Appearance white crystalline powder
Density 6.44 g/cm3, alpha
5.88 g/cm3, beta
Melting point 1900°C, alpha
1725°C, beta [1]
insoluble
Solubility soluble in most acids
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
checkY verify (what is checkY☒N ?)

Gallium(III) oxide (Ga2O3) is a chemical compound used in vacuum deposition and as part of the manufacturing of semiconductor devices.[2]

Preparation

Gallium oxide is precipitated in hydrated form upon neutralization of acidic or basic solution of gallium salt. Also, it is formed on heating gallium in air or by thermally decomposing gallium nitrate at 200-250˚C. It can occur in five different modifications, α,β,δ,γ and ε. Of these modifications β-Ga2O3 is the most stable form.[3]

Preparation Methods for the Five Modifications

  • β-Ga2O3 is prepared by heating nitrate, acetate, oxalate or other organic derivatives above 1000˚C.
  • α-Ga2O3 can be obtained by heating β-Ga2O3 at 65kbars and 1100˚C for 1 hour giving a crystalline structure. The hydrated form can be prepared by decomposing precipitated and "aged" gallium hydroxide at 500˚C.
  • γ-Ga2O3 is prepared by rapidly heating the hydroxide gel at 400˚C-500˚C.
  • δ-Ga2O3 is obtained by heating Ga(NO3)3 at 250˚C.
  • ε-Ga2O3 is prepared by briefly heating δ-Ga2O3 at 550˚C for 30 minutes.[4]

Crystal Structure

The β-Ga2O3, with a melting point of 1740˚C, is the most stable crystalline modification. The oxide ions are in a distorted cubic closest packing arrangement, and the gallium (III) ions are in distorted tetrahedral and octahedral sites, with Ga-O bond distances of 1.83 and 2.00 Å respectively. These distortions are in fact the reasons for the great level of stability of β-Ga2O3.[5]

Applications and Uses

Gallium(III) oxide is an important functional material. It has been studied in the use of lasers, phosphors and luminescent materials,[6] has been shown to demonstrate catalytic properties and has also been used as an insulating barrier in tight junctions.[7] The stable oxide of gallium, monoclinic β-Ga2O3, has current applications in gas sensors and luminescent phosphors and can be applied to dielectric coatings for solar cells. This stable oxide has also shown potential for deep-ultraviolet transparent conductive oxides.[8]

Nanotechnology

Nanoribbons and nanosheets of Ga2O3 can be synthesized either by high temperature reaction of Ga0 with water or by evaporation of GaN at high temperature in the presence of oxygen. Analysis of the products of the thermal evaporation reaction is done using X-ray diffraction , scanning electron microscopy (SEM), transmission electron microscopy (TEM) and energy-dispersive X-ray spectroscopy (EDS). Such analysis showed that the resulting structures were wool-like and gray in color.

SEM reveals that the products consist of wire-like nanostructures and sheet-type structures. The TEM image shows the ribbon-like structure of Ga2O3. The EDS confirms that the nanostructures obtained are in fact Ga2O3.

The nanoribbon and nanosheets structures of Ga2O3 are pure, structurally uniform, single crystalline and free from dislocation. The structure of nanoribbons and nanosheets, that is, their wave-like and sheet-like shape, also indicates that their growth is as a result of growth kinetics, vapor-liquid-solid (VLS) method and vapor-solid method (VS). VLS and VS are two common growth mechanisms for nanowires. The VLS process, catalytic-assisted in nature, is one in which the metal particle is located at the growth of the wire and acts as the catalytic active site. For the VS process, oxide vapor, which is evaporated from the starting oxide at a higher temperature xone, directly deposits on a substrate at a lower temperature region and grows into ribbon-like nanostructures.[9]

Optical Uses

It is important to accurately determine the optical functions as these are essential for device simulations and improvement in material preparation. The thin Ga2O3 films are of commercial interest as gas sensitive material and Ga2O3 based glasses are among the best optical materials used in advanced technologies. Ellipsometry is a procedure that can be used to determine optical functions of the β-Ga2O3.[10]

Catalyst

β-Gallium (III) oxide is also very important in the production of catalysts . It is needed for the preparation of Ga2O3-Al2O3 catalyst. The preparation of this catalyst involves reacting Al2O3 with aqueous solutions of gallium nitrate, followed by evaporation to dryness at 393K, and calcining in air (i.e.thermal decomposition of the compound) for 4 hours at 823K.[11]

See also

References

  1. ^ Pradyot Patnaik. Handbook of Inorganic Chemicals. McGraw-Hill, 2002, ISBN 0070494398
  2. ^ "Gallium oxide powder (Ga2O3)". READE Advanced Materials. Retrieved 2006-07-30. [dead link]
  3. ^ Bailar, J; Emeléus, H; Nyholm, R; Trotman-Dickenson, A. Comprehensive Inorganic Chemistry. 1973, 1, 1091
  4. ^ Bailar, J; Emeléus, H; Nyholm, R; Trotman-Dickenson, A. Comprehensive Inorganic Chemistry. 1973, 1, 1091
  5. ^ King, R; Encyclopedia of Inorganic Chemistry. 1994, 3, 1256
  6. ^ Bailar, J; Emeléus, H; Nyholm, R; Trotman-Dickenson, A. Comprehensive Inorganic Chemistry. 1973, 1, 1091.
  7. ^ Dai, Z; Pan, Z; Wang, Z. J. Phys. Chem. B. 2002, 106, 902.
  8. ^ Reiben, M; Henrion, W; Hong, M; Mannaerts, J; Fleischer, M. Applied Physics Letters. 2002, 81, 251.
  9. ^ Dai, Z; Pan, Z; Wang, Z. J. Phys. Chem. B. 2002, 106, 902.
  10. ^ Reiben, M; Henrion, W; Hong, M; Mannaerts, J; Fleischer, M. Applied Physics Letters. 2002, 81, 251.
  11. ^ Shimizu, K; Takamatsu, M; Nishi, K; Yoshida, H; Satsuma, A; Tanaka, T; Yoshida, S; Hattori, T. J. Phys. Chem. 1999. 103, 1543.

^ "Gallium Oxide Powder (Ga2O3)". Reade Advanced Materials.

<http://www.reade.com/component/content/article/233-gallium-oxide-powder-ga2o3-gallium-oxide-digallium-trioxide-gallium-sesquioxide-gallium-trioxide-gallium-3-trioxide-gallia-gallium-iii-oxide-gallium-oxide-ga2o3-gallium-oxide-ga2o3-digallium-trioxide-gallia?q=gallium+oxide>.

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