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Table 2082. Properties of Al2O3.

Amorphous Al2O3
γ - Al2O3
α - Al2O3
Crystal structure
    Hexagonal: stable
Lattice parameters (Å)
    a = 4.76; c = 13.0
Space group
  Fd-3m (227) R-3c (167)
Melting Point (°C)
Density (g/cm3)
Hardness (GPa)
Modulus of elasticity (GPa)
Poisson's ratio
Thermal expansion coefficient (10-6 K-1)
    6.5 (25 - 200 °C)
Flexural strength (MPa)
Compressive strength (MPa)
Tensile strength (MPa)
Fracture toughness (MPa m1/2)
Static dielectric constant (K)
Conduction band (CB) offset on Si (silicon) substrate
Band gap energy (eV)
8.8 7.1 eV 8.4 eV
Surface free energy (ergs/cm2)
900 at 1000 °C    
Work function (eV) of some compounds with Al2O3
4.85-5.2 for TiN
Effective electron masses (me/m0)
    Γ-M: 0.39; Γ-A: 0.41; Γ-K:0.39
Effective hole masses (mh/m0)
  Γ-M: 6.20; Γ-A:0.36; Γ-K:6.40

Figure 2082a shows the variation of micro-hardness with deposition temperature for Al2O3.

Variation of micro-hardness with deposition temperature for Al2O3

Figure 2082a. Variation of micro-hardness with deposition temperature for Al2O3.

It was suggested that the binding energies of Al 2p (74.10 eV) and O 1s (530.70 eV) peaks were lowered by 0.4 eV and 0.5 eV, respectively, after annealing because of a phase transition from an amorphous phase to the γ -Al2O3 phase. [1, 2]

Figure 2082b shows the REELS spectra for the Al2O3/SiO2 thin films on Si substrates, before and after annealing, at a primary energy of 1.0 keV. The onset due to electron–hole excitation corresponds to the band gap values of the dielectric films. Therefore, the band gap energy is given by the crossing point found by drawing a linear fit line from a point near the onset of the loss spectrum to the background level. [3 -5].

REELS spectra at an energy of 1.0 keV for Al2O3/SiO2 thin films

Figure 2082b. REELS spectra at an energy of 1.0 keV for Al2O3/SiO2 thin films on Si substrates before annealing and after annealing. Adapted from [3]










[1] Moulder J F, Stickle W F, Sobol P E and Bomben K D 1995 Handbook of X-Ray Photoelectron Spectroscopy ed J Chastain and R C King Jr (Eden Prairie: Physical Electronics, Inc.)
[2] Yoshitake M, Song W, Libra J, Masek K, Sutara F, Matolin V and Prince K C 2008 J. Appl. Phys. 103 033707.
[3] Dahlang Tahir, Hyuk Lan Kwon, Hye Chung Shin, Suhk Kun Oh, Hee Jae Kang, Sung Heo, Jae Gwan Chung, Jae Cheol Lee, and Sven Tougaard, Electronic and optical properties of Al2O3/SiO2 thin films grown on Si substrate, J. Phys. D: Appl. Phys. 43 (2010) 255301.
[4] Jin H, Oh S K, Cho Y J, Kang H J and Tougaard S 2007 J. Appl. Phys. 102 053709.
[5] Tahir D, Lee E K, Tham T T, Oh S K, Kang H J, Hua J, Heo S, Park J C, Chung J G and Lee J C 2009 Appl. Phys. Lett. 94 212902.





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