Electronic and optical properties of {Theta}-Al{sub 2}O{sub 3} and comparison to {alpha}-Al{sub 2}O{sub 3}

Journal Article · Mon Jun 01 04:00:00 EDT 1998 · Physical Review, B: Condensed Matter

DOI:https://doi.org/10.1103/PhysRevB.57.15219· OSTI ID:642511

Mo, S ^[1]; Ching, W Y ^[1]

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1. Department of Physics, University of Missouri-Kansas City, Kansas City, Missouri 64110 (United States)

{Theta}-Al{sub 2}O{sub 3} is a metastable phase of alumina with local Al coordinations closely related to those in {gamma}-Al{sub 2}O{sub 3}. The electronic structure and the linear optical properties of {Theta}-Al{sub 2}O{sub 3} are studied by means of first-principles local density calculations. The results are compared with the stable phase {alpha}-Al{sub 2}O{sub 3}. An indirect band gap of 4.64 eV is obtained, which is about 1.6 eV smaller than that of {alpha}-Al{sub 2}O{sub 3}. The other band structure parameters are found to be quite close, and the calculated density of states (DOS) differ from that of {alpha}-Al{sub 2}O{sub 3} in fine details. Site- and orbital-resolved partial DOS show significant dependence on local coordinations for both Al and O atoms. They are in reasonable agreement with the experimental energy loss near edge spectra of {gamma}-Al{sub 2}O{sub 3}. Effective charge and bond order calculations show {Theta}-Al{sub 2}O{sub 3} to be comparable to {alpha}-Al{sub 2}O{sub 3}. For the linear optical properties, a refractive index 1.73 is obtained, which is close to 1.78 for {alpha}-Al{sub 2}O{sub 3}. The bulk plasmon peak in the energy loss function of {Theta}-Al{sub 2}O{sub 3} is located at 22.6 eV, which is lower by about 1 eV than that in {alpha}-Al{sub 2}O{sub 3}. The anisotropy in the optical properties of {alpha}-Al{sub 2}O{sub 3} occurs mainly at the low photon energy region of less than 20 eV, and that for the {Theta}-Al{sub 2}O{sub 3} is insignificant. [S0163-1829(98)00424-X] thinsp {copyright} {ital 1998} {ital The American Physical Society}

• Research Organization: University of Missouri
• DOE Contract Number: FG02-84ER45170
• OSTI ID: 642511
• Journal Information: Physical Review, B: Condensed Matter, Journal Name: Physical Review, B: Condensed Matter Journal Issue: 24 Vol. 57; ISSN 0163-1829; ISSN PRBMDO
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
ALUMINIUM OXIDES
CERAMICS
ELECTRONIC STRUCTURE
ENERGY GAP
OPTICAL PROPERTIES
PLASMONS
REFRACTIVE INDEX
SAPPHIRE