Dielectric modeling of transmittance spectra of thin ZnO:Al films

A dielectric model comprising band gap transitions and free electron excitations (Drude model) is successfully applied to simulate transmittance spectra of ZnO films doped with 0.5%, 1% and 2% Al. The Drude formula contains a frequency-dependent damping term in order to get a good fit in the visible...

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Bibliographic Details
Published in:Thin solid films 2006-02, Vol.496 (2), p.520-525
Main Authors: Qiao, Zhaohui, Agashe, Chitra, Mergel, Dieter
Format: Article
Language:English
Subjects:
Condensed matter: electronic structure, electrical, magnetic, and optical properties
Cross-disciplinary physics: materials science
rheology
Dielectric properties of solids and liquids
Dielectrics, piezoelectrics, and ferroelectrics and their properties
Electrical properties
Exact sciences and technology
Laser deposition
Materials science
Methods of deposition of films and coatings
film growth and epitaxy
Optical properties
Optical properties and condensed-matter spectroscopy and other interactions of matter with particles and radiation
Permittivity (dielectric function)
Physics
Semiconductors
Visible and ultraviolet spectra
Zinc oxide
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Summary:A dielectric model comprising band gap transitions and free electron excitations (Drude model) is successfully applied to simulate transmittance spectra of ZnO films doped with 0.5%, 1% and 2% Al. The Drude formula contains a frequency-dependent damping term in order to get a good fit in the visible spectral region. Useful physical parameters obtained from the fit are electron density and mobility within the grains, film thickness, band gap and refractive index. The optically determined film thickness agrees with that obtained with the stylus method within 2%. The optically determined electronic parameters are compared with those obtained by electrical measurements. Contrary to thin In 2O 3:Sn films, the Drude mobility inside the grains is similar to the direct current Hall mobility indicating more perfect film growth without forming pronounced grain boundaries. Maximum value is 35 cm 2/V s. The effective electron mass is estimated to be about 0.6 of the free electron mass. The refractive index at 550 nm decreases with increasing electron density.
ISSN:0040-6090
1879-2731
DOI:10.1016/j.tsf.2005.08.282