Title: Near infrared to UV dielectric functions of Al doped ZnO films deposited on c-plane sapphire substrate using pulsed laser deposition
Authors: Thangavel, R.
Yaseen, Mohammad Tariq
Chang, Yia Chung
Hsu, Chia-Hao
Yeh, Kuo-Wei
Wu, Maw Kuen
Department of Photonics
Keywords: Thin films;Raman spectroscopy;X-ray diffraction;Electrical properties;Optical properties
Issue Date: 1-Nov-2013
Abstract: Transparent conducting polycrystalline Al-doped ZnO (AZO) films were deposited on sapphire substrates at substrate temperatures ranging from 200 to 300 degrees C by pulsed laser deposition (PLD). X-ray diffraction measurement shows that the crystalline quality of AZO films was improved with increased substrate temperature. The electrical and optical properties of the AZO films have been systematically studied via various experimental tools. The room-temperature micro-photoluminescence (mu-PL) spectra show a strong ultraviolet (UV) excitonic emission and weak deep-level emission, which indicate low structural defects in the films. A Raman shift of about 11 cm(-1) is observed for the first-order longitudinal-optical (LO) phonon peak for AZO films when compared to the LO phonon peak of bulk ZnO. The Raman spectra obtained with UV resonant excitation at room temperature show multi-phonon LO modes up to third order. Optical response due to free electrons of the AZO films was characterized in the photon energy range from 0.6 to 6.5 eV by spectroscopic ellipsometry (SE). The free electron response was expressed by a simple Drude model combined with the Cauchy model are reported. (C) 2013 Elsevier Ltd. All rights reserved.
URI: http://dx.doi.org/10.1016/j.jpcs.2013.05.020
ISSN: 0022-3697
DOI: 10.1016/j.jpcs.2013.05.020
Volume: 74
Issue: 11
Begin Page: 1533
End Page: 1537
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