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Alumina

Crystal: Al2O3

Structure: Corundum

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As grown, tends to have 1000 ppm carbon and ~10 ppm transition metals and similar alkali metals.

 

Cohesive energy:

eV

Lattice parameter:

3.95 (a ) Å

 

3.5 (b )

Density:

g/cm3

Remark: ~4.7*1022 sites/cm3

 

 

Stiffness constants: in 1011 dynes/cm2, at room temperature

 

c11: 46.5 (Ref.1)

c12: 12.4

c44: 23.3

c33: 56.3

Poisson ratio:

Compressibility (in 1011 dynes/cm2):

Sound velocity: ~6*105 cm/sec.

 

Debye temperature: 980 K

Melting temperature: 2070 ° C

Neel temperature: K

 

Phonon spectrum discussed by: H. Bialas, H.J. Stolz, Phys.Rev. B21, 325 (1975)

 

Transverse optic phonon T0 (k=0): cm-1

Longitude optic phonon L0 (k=0): cm-1

 

Gruneissen constant:

Ratio e*/e:

 

Photoelastic constants:

p11:

p12:

p44:

 

 

Band gap:

direct: eV.

indirect: eV.

 

Gap: < 9.5 eV. (Ref.8)

First exciton: 9.25 eV. (Ref.8)

Valence band width: 11.6 eV. (Ref.2)

Valence band width, etc.: Sol. St. Comm. 23, 163 (1977)

V.B. density of states: Surf. Sci. 81, 519 (1979)

Valence band-conduction band energy: 15.0 eV, with characteristic damping Ig w with 2p hn =8.0 eV

Plasma frequency: 19.5 eV for a -Al2O3 and 18.3 eV for g -Al2O3 : Sol. St. Comm. 19, 444

a -Al2O3 and g -Al2O3 energy loss data: W.Tews, R.Gundler, Phys. Stat. Sol. 109, 255 (1982)

Which gives:

Plasma frequency:

23.2 eV(amorphous)

 

24.0 eV (polycrystal g ) slightly wide

 

26.0 (a , poly or single crystal)

 

Estimates of exciton: 9.2 eV

 

Gap (probably a form): 10.8 eV

 

Band structure discussed by: Weakliem and McCluve, J. Appl. Phys. Suppl.33, 347 (1962)

Band structure of a -Al2O3: R.A. Evarestev, A.N. Ermoskin, V.A. Lovchikov, Phys Stat. Sol. 99, 387 (1980)

Al2O3 electronic structure: I. Batra, J.Phys. C15, 5399 (1982)

 

Static dielectric constant: // =11.54 and ^ =9.34, or //=11.589 and ^ =9.395 (Ref.3), or //=11.64 and ^ =9.5 (Ref.4)

Optic dielectric constant: ~3 (Ref.5)

Samsonov gives n=1.7, them e (¥ )=2.9, Also: //=3.1 and ^ =3.2 (Ref.4)

 

Electron mobility: see Ref.6 and 7

Hole mobility: idem

Polaron coupling constant: a = ( for m*=1 )

Effective mass:

conduction band:

valence band:

 

Electron affinity: (in eV., from bottom of conduction band under vacuum)

 

Spin-orbit coupling: (valence band)

 

Cation polarisation: Å-3

Anion polarisation: Å-3

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Other information:

 

 

 

 

 

 

 

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References:

 

1. Watchman, J. Res. Nat. Bul. St. 64A, 213

 

2. Sol. St. Comm. 23, 163

 

3. J. Appl. Phys. 45, 2852 (1974)

 

4. Phys. Rev. B16, 1717

 

5. J. Appl. Phys. 43, 2448 (1972)

 

6. R. C. Hughes, Phys.Rev.B19, 5321 (1979)

 

7. Phys. Rev. B16, 5452 (1972)

 

8. Sov. Phys. Sol. St. 21, 47 (1979)

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