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소현섭,황상빈,정대호,이호선 한국물리학회 2017 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.70 No.7
We investigated the optical and the electrical properties of Sn-doped ZnO thin films grown via RF co-sputtering deposition methods at room temperature. Through annealing, the carrier concentrations and mobilities were improved. The ellipsometric angles, and , of the ZnO:Sn thin films were measured via spectroscopic ellipsometry. Dielectric functions were obtained from the ellipsometric angles by using the Drude and the parametric optical constant models. With an increase in the Sn doping concentration, the Drude model amplitude increased substantially. The Urbach and the optical gap energies of the ZnO:Sn films were determined using the dielectric functions. The carrier concentrations and the mobilities of the ZnO:Sn thin films were measured using Hall-effect measurements. The effective mass of ZnO:Sn was estimated to be 0.274m0, assuming that the carrier concentrations measured via ellipsometry and Hall-effect measurements were the same. A shift in the optical gap energy of the Sn-doped ZnO was found to be due to a combination of the Burstein-Moss effect, electron-electron interactions, and electron-impurity scattering. The discrepancy between the measured and the calculated shifts in the optical gap energy is attributed to Sn-alloying effects.
이호석,소현섭,이호선,신혜영,윤석현,안형우,김수동,이수연,정두석,정병기 한국물리학회 2014 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.64 No.11
We investigated the optical properties of Ge1−xSex and Ge1−x−ySexAsy amorphous films by usingspectroscopic ellipsometry and Raman spectroscopy. The dielectric functions and absorptioncoefficients () of the amorphous films were determined from the measured ellipsometric angles( ,). We obtained the optical gap energies and the Urbach energies from the absorption coefficientsand found a strong bowing effect in the optical gap energy of Ge1−x−ySexAsy, where theendpoint binaries were Ge0.50Se0.50 and Ge0.31As0.69. Based on the correlation between the opticalgap energies and the Urbach energies, we attributed the large bowing parameter to electronic disorder. Using Raman spectroscopy, we measured the phonon modes and discussed the compositiondependence of the phonon peak frequencies and lineshapes in terms of structural units. Based onthe composition dependence of the phonons in Ge1−x−ySexAsy, we identified the phonon modes ofGe0.31As0.69. A resonant Raman phenomenon was observed in Ge0.40Se0.60 at a laser excitationof 514 nm (2.41 eV). We verified that this laser energy corresponded to the transition energy ofGe0.40Se0.60 by using the second derivative of the dielectric function of Ge0.40Se0.60.