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Title: Electrical and thermal properties of polycrystalline Si thin films with phononic crystal nanopatterning for thermoelectric applications

Electrical and thermal properties of polycrystalline Si thin films with two-dimensional phononic patterning were investigated at room temperature. Electrical and thermal conductivities for the phononic crystal nanostructures with a variety of radii of the circular holes were measured to systematically investigate the impact of the nanopatterning. The concept of phonon-glass and electron-crystal is valid in the investigated electron and phonon transport systems with the neck size of 80 nm. The thermal conductivity is more sensitive than the electrical conductivity to the nanopatterning due to the longer mean free path of the thermal phonons than that of the charge carriers. The values of the figure of merit ZT were 0.065 and 0.035, and the enhancement factors were 2 and 4 for the p-doped and n-doped phononic crystals compared to the unpatterned thin films, respectively, when the characteristic size of the phononic crystal nanostructure is below 100 nm. The greater enhancement factor of ZT for the n-doped sample seems to result from the strong phonon scattering by heavy phosphorus atoms at the grain boundaries.
Authors:
 [1] ;  [2] ;  [3] ;  [1] ; ; ;  [4]
  1. Institute of Industrial Science, The University of Tokyo, Tokyo 153–8505 (Japan)
  2. (Japan)
  3. (IMTEK), University of Freiburg, Freiburg 79110 (Germany)
  4. Department of Microsystems Engineering (IMTEK), University of Freiburg, Freiburg 79110 (Germany)
Publication Date:
OSTI Identifier:
22423745
Resource Type:
Journal Article
Resource Relation:
Journal Name: Applied Physics Letters; Journal Volume: 106; Journal Issue: 22; Other Information: (c) 2015 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; 77 NANOSCIENCE AND NANOTECHNOLOGY; DOPED MATERIALS; ELECTRIC CONDUCTIVITY; GRAIN BOUNDARIES; NANOSTRUCTURES; PHONONS; PHOSPHORUS; POLYCRYSTALS; SILICON; TEMPERATURE RANGE 0273-0400 K; THERMAL CONDUCTIVITY; THIN FILMS; TWO-DIMENSIONAL SYSTEMS