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Dielectric modeling of transmittance and ellipsometric spectra of thin In 2 O 3 :Sn films
Author(s) -
Qiao Zhaohui,
Mergel Dieter
Publication year - 2010
Publication title -
physica status solidi (a)
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.532
H-Index - 104
eISSN - 1862-6319
pISSN - 1862-6300
DOI - 10.1002/pssa.200983710
Subject(s) - materials science , refractive index , band gap , thin film , transmittance , dielectric , drude model , optics , spectral line , surface roughness , free electron model , sputter deposition , ellipsometry , surface finish , condensed matter physics , sputtering , optoelectronics , composite material , nanotechnology , physics , laser , astronomy
Thin ITO films with thickness between 0.05 and 0.4 µm were deposited on quartz substrates by direct‐current magnetron‐sputtering. The films' ellipsometric and transmittance spectra between 280 and 2500 nm were simulated simultaneously with a computer program based on dielectric modeling. The dielectric function used is the sum of three types of electronic excitations: intraband transitions of free electrons (extended Drude model), band gap transitions, and interband transitions into the upper half of the conduction band. A successful fit of the simulated to the experimental curves was obtained with a two‐layer model (bulk and surface layers) and applying the Bruggeman effective‐medium approach. From the simulation, film thickness, refractive index, band gap, and free carrier density can be obtained. The thickness of the surface layer is comparable with the surface roughness determined by AFM measurements.