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Title: Infrared optical properties of amorphous and nanocrystalline Ta{sub 2}O{sub 5} thin films

The optical constants of tantalum pentoxide (Ta{sub 2}O{sub 5}) are determined in a broad spectral region from the visible to the far infrared. Ta{sub 2}O{sub 5} films of various thicknesses from approximately 170 to 1600 nm are deposited using reactive magnetron sputtering on Si substrates. X-ray diffraction shows that the as-deposited films are amorphous, and annealing in air at 800 °C results in the formation of nanocrystalline Ta{sub 2}O{sub 5}. Ellipsometry is used to obtain the dispersion in the visible and near-infrared. Two Fourier-transform infrared spectrometers are used to measure the transmittance and reflectance at wavelengths from 1 to 1000 μm. The surface topography and microstructure of the samples are examined using atomic force microscopy, confocal microscopy, and scanning electron microscopy. Classical Lorentz oscillators are employed to model the absorption bands due to phonons and impurities. A simple model is introduced to account for light scattering in the annealed films, which contain micro-cracks. For the unannealed samples, an effective-medium approximation is used to take into account the adsorbed moisture in the film and a Drude free-electron term is also added to model the broad background absorption.
Authors:
; ;  [1] ;  [2] ;  [3] ;  [2] ; ;  [4] ;  [5]
  1. George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332 (United States)
  2. Nanoelectronic Materials Branch, Materials and Manufacturing Directorate, Air Force Research Laboratory, Wright Patterson AFB, Ohio 45433 (United States)
  3. (United States)
  4. Department of Physics, University of Florida, Gainesville, Florida 32611 (United States)
  5. Department of Physics, University of North Florida, Jacksonville, Florida 32254 (United States)
Publication Date:
OSTI Identifier:
22218096
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Applied Physics; Journal Volume: 114; Journal Issue: 8; Other Information: (c) 2013 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; ABSORPTION; ANNEALING; ATOMIC FORCE MICROSCOPY; CRACKS; ELLIPSOMETRY; FOURIER TRANSFORMATION; INFRARED SPECTRA; INFRARED SPECTROMETERS; LIGHT SCATTERING; MAGNETRONS; NANOSTRUCTURES; REFRACTIVE INDEX; SCANNING ELECTRON MICROSCOPY; SPUTTERING; TANTALUM OXIDES; THIN FILMS; X-RAY DIFFRACTION