We investigated the optical properties of amorphous and crystalline antimony (Sb)-doped tin dioxide (SnO2) thin films grown using the co-sputtering deposition method at room temperature. We used undoped and Sb-doped (8 wt. %) SnO2 targets. Varying the relative power ratio of the two targets, we controlled the Sb-composition of the SnO2:Sb thin films up to 2.3 at. % of Sb contents. Through annealing, the as-grown amorphous SnO2:Sb thin films were transformed to crystalline thin films. Dielectric functions were obtained from the measured ellipsometry angles, Ψ and Δ, using the Drude and parametric optical constant models. We determined the absorption coefficients and optical gap energies of the SnO2:Sb thin films from the dielectric functions. We found increasing optical gap energy with increasing Sb composition. Increases in the Drude tail amplitudes, a signature of free carrier concentrations, were found in annealed, crystalline thin films with increasing Sb composition. The increase in the optical gap energy with increasing Sb composition was mainly attributed to the Burstein-Moss effect. Using Hall effect measurements, we obtained Hall carrier concentrations (NHall) and electron Hall mobilities (μHall). The carrier concentrations and mobilities increased from 2.6 × 1019 cm−3 and 1.0 cm2/(V s) to 2.0 × 1020 cm−1 and 7.2 cm2/(V s), respectively, with increasing Sb contents. This result suggests that the nominally undoped SnO2 films are unintentionally n-type doped. Assuming that the NHall and optical carrier concentrations (Nopt) were the same, we obtained the effective masses of the SnO2:Sb thin films with increasing Sb compositions. The effective masses of the SnO2:Sb thin films increased from 0.245 m0 to 0.4 m0 with increasing Sb doping contents, and the nonparabolicity of the conduction band was estimated. We discussed the relation between the optical (μopt) and Hall (μHall) mobilities as a function of Sb contents and grain sizes.
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28 August 2015
Research Article|
August 25 2015
Optical properties of amorphous and crystalline Sb-doped SnO2 thin films studied with spectroscopic ellipsometry: Optical gap energy and effective mass
Hyeon Seob So;
Hyeon Seob So
Department of Applied Physics,
Kyung Hee University
, Yong-In 446-701, South Korea
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Jun-Woo Park;
Jun-Woo Park
Department of Applied Physics,
Kyung Hee University
, Yong-In 446-701, South Korea
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Dae Ho Jung;
Dae Ho Jung
Department of Applied Physics,
Kyung Hee University
, Yong-In 446-701, South Korea
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Kun Hee Ko;
Kun Hee Ko
Department of Applied Physics,
Kyung Hee University
, Yong-In 446-701, South Korea
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a)
Author to whom correspondence should be addressed. Electronic mail: hlee@khu.ac.kr
J. Appl. Phys. 118, 085303 (2015)
Article history
Received:
June 14 2015
Accepted:
August 12 2015
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Citation
Hyeon Seob So, Jun-Woo Park, Dae Ho Jung, Kun Hee Ko, Hosun Lee; Optical properties of amorphous and crystalline Sb-doped SnO2 thin films studied with spectroscopic ellipsometry: Optical gap energy and effective mass. J. Appl. Phys. 28 August 2015; 118 (8): 085303. https://doi.org/10.1063/1.4929487
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