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Title: Optical modeling of plasma-deposited ZnO films: Electron scattering at different length scales

Abstract

In this work, an optical modeling study on electron scattering mechanisms in plasma-deposited ZnO layers is presented. Because various applications of ZnO films pose a limit on the electron carrier density due to its effect on the film transmittance, higher electron mobility values are generally preferred instead. Hence, insights into the electron scattering contributions affecting the carrier mobility are required. In optical models, the Drude oscillator is adopted to represent the free-electron contribution and the obtained optical mobility can be then correlated with the macroscopic material properties. However, the influence of scattering phenomena on the optical mobility depends on the considered range of photon energy. For example, the grain-boundary scattering is generally not probed by means of optical measurements and the ionized-impurity scattering contribution decreases toward higher photon energies. To understand this frequency dependence and quantify contributions from different scattering phenomena to the mobility, several case studies were analyzed in this work by means of spectroscopic ellipsometry and Fourier transform infrared (IR) spectroscopy. The obtained electrical parameters were compared to the results inferred by Hall measurements. For intrinsic ZnO (i-ZnO), the in-grain mobility was obtained by fitting reflection data with a normal Drude model in the IR range. For Al-dopedmore » ZnO (Al:ZnO), besides a normal Drude fit in the IR range, an Extended Drude fit in the UV-vis range could be used to obtain the in-grain mobility. Scattering mechanisms for a thickness series of Al:ZnO films were discerned using the more intuitive parameter “scattering frequency” instead of the parameter “mobility”. The interaction distance concept was introduced to give a physical interpretation to the frequency dependence of the scattering frequency. This physical interpretation furthermore allows the prediction of which Drude models can be used in a specific frequency range.« less

Authors:
; ; ; ;  [1]; ;  [2]
  1. Department of Applied Physics, Eindhoven University of Technology, P.O. Box 513, 5600 MB Eindhoven (Netherlands)
  2. Department of Applied Physics, Eindhoven University of Technology, P.O. Box 513, 5600 MB Eindhoven, The Netherlands and Solliance, High Tech Campus 5, 5656 AE Eindhoven (Netherlands)
Publication Date:
OSTI Identifier:
22392154
Resource Type:
Journal Article
Journal Name:
Journal of Vacuum Science and Technology. A, Vacuum, Surfaces and Films
Additional Journal Information:
Journal Volume: 33; Journal Issue: 2; Other Information: (c) 2014 American Vacuum Society; Country of input: International Atomic Energy Agency (IAEA); Journal ID: ISSN 0734-2101
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; CARRIER MOBILITY; DEPOSITS; ELECTRON MOBILITY; ELECTRONS; FILMS; FOURIER TRANSFORMATION; GRAIN BOUNDARIES; INFRARED SPECTRA; LENGTH; PHOTONS; SCATTERING; ZINC OXIDES

Citation Formats

Knoops, Harm C. M.,, Loo, Bas W. H. van de, Smit, Sjoerd, Ponomarev, Mikhail V., Weber, Jan-Willem, Sharma, Kashish, Kessels, Wilhelmus M. M., and Creatore, Mariadriana. Optical modeling of plasma-deposited ZnO films: Electron scattering at different length scales. United States: N. p., 2015. Web. doi:10.1116/1.4905086.
Knoops, Harm C. M.,, Loo, Bas W. H. van de, Smit, Sjoerd, Ponomarev, Mikhail V., Weber, Jan-Willem, Sharma, Kashish, Kessels, Wilhelmus M. M., & Creatore, Mariadriana. Optical modeling of plasma-deposited ZnO films: Electron scattering at different length scales. United States. https://doi.org/10.1116/1.4905086
Knoops, Harm C. M.,, Loo, Bas W. H. van de, Smit, Sjoerd, Ponomarev, Mikhail V., Weber, Jan-Willem, Sharma, Kashish, Kessels, Wilhelmus M. M., and Creatore, Mariadriana. 2015. "Optical modeling of plasma-deposited ZnO films: Electron scattering at different length scales". United States. https://doi.org/10.1116/1.4905086.
@article{osti_22392154,
title = {Optical modeling of plasma-deposited ZnO films: Electron scattering at different length scales},
author = {Knoops, Harm C. M., and Loo, Bas W. H. van de and Smit, Sjoerd and Ponomarev, Mikhail V. and Weber, Jan-Willem and Sharma, Kashish and Kessels, Wilhelmus M. M. and Creatore, Mariadriana},
abstractNote = {In this work, an optical modeling study on electron scattering mechanisms in plasma-deposited ZnO layers is presented. Because various applications of ZnO films pose a limit on the electron carrier density due to its effect on the film transmittance, higher electron mobility values are generally preferred instead. Hence, insights into the electron scattering contributions affecting the carrier mobility are required. In optical models, the Drude oscillator is adopted to represent the free-electron contribution and the obtained optical mobility can be then correlated with the macroscopic material properties. However, the influence of scattering phenomena on the optical mobility depends on the considered range of photon energy. For example, the grain-boundary scattering is generally not probed by means of optical measurements and the ionized-impurity scattering contribution decreases toward higher photon energies. To understand this frequency dependence and quantify contributions from different scattering phenomena to the mobility, several case studies were analyzed in this work by means of spectroscopic ellipsometry and Fourier transform infrared (IR) spectroscopy. The obtained electrical parameters were compared to the results inferred by Hall measurements. For intrinsic ZnO (i-ZnO), the in-grain mobility was obtained by fitting reflection data with a normal Drude model in the IR range. For Al-doped ZnO (Al:ZnO), besides a normal Drude fit in the IR range, an Extended Drude fit in the UV-vis range could be used to obtain the in-grain mobility. Scattering mechanisms for a thickness series of Al:ZnO films were discerned using the more intuitive parameter “scattering frequency” instead of the parameter “mobility”. The interaction distance concept was introduced to give a physical interpretation to the frequency dependence of the scattering frequency. This physical interpretation furthermore allows the prediction of which Drude models can be used in a specific frequency range.},
doi = {10.1116/1.4905086},
url = {https://www.osti.gov/biblio/22392154}, journal = {Journal of Vacuum Science and Technology. A, Vacuum, Surfaces and Films},
issn = {0734-2101},
number = 2,
volume = 33,
place = {United States},
year = {Sun Mar 15 00:00:00 EDT 2015},
month = {Sun Mar 15 00:00:00 EDT 2015}
}