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Title: Interplay of electron correlations and localization in disordered β-tantalum films: Evidence from dc transport and spectroscopic ellipsometry study

We report the dc transport (5 K ≲ T ≲ 380 K) and spectroscopic ellipsometry (0.8 eV ≤ hν ≤ 8.5 eV, T ≃ 300 K) study of β-Ta films prepared by rf sputtering deposition as a function of their thickness in the range 2.5 nm ≲ d ≲ 200 nm. The dc transport of the β-Ta films with a thickness d ≳ 25 nm is characterized by negative temperature coefficient of resistivity (TCR) caused by localization effects peculiar of highly disordered metals. Their dielectric function spectra display non-metallic-like behavior due to the presence of the pronounced band at 2 eV. We found that with increasing TCR absolute value, specifying elevated degree disorder, the optical spectral weight (SW) of free charge carriers decreases. The associated SW is recovered in the range of Mott-Hubbard transitions, indicating the mechanism of localization enhancement by electronic correlations in disordered metals.
Authors:
 [1] ;  [2] ;  [3] ; ;  [1] ; ; ; ;  [4]
  1. Institute of Physics, Academy of Sciences of the Czech Republic, Na Slovance 2, 18221 Prague (Czech Republic)
  2. (United Kingdom)
  3. (Russian Federation)
  4. Lebedev Physical Institute, Russian Academy of Sciences, Leninsky prospect 53, 119991 Moscow (Russian Federation)
Publication Date:
OSTI Identifier:
22420247
Resource Type:
Journal Article
Resource Relation:
Journal Name: Applied Physics Letters; Journal Volume: 106; Journal Issue: 5; Other Information: (c) 2015 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; CHARGE CARRIERS; DEPOSITION; ELECTRON CORRELATION; ELLIPSOMETRY; EV RANGE 01-10; FILMS; SPUTTERING; TANTALUM; TEMPERATURE COEFFICIENT; TEMPERATURE RANGE 0000-0013 K; TEMPERATURE RANGE 0013-0065 K; TEMPERATURE RANGE 0065-0273 K; TEMPERATURE RANGE 0273-0400 K