The ability to tune the thermal conductivity of semiconductor materials is of interest for thermoelectric applications, in particular, for doped silicon, which can be readily integrated in electronic microstructures and have a high thermoelectric power factor. Here, we examine the impact of nanovoids on the thermal conductivity of highly doped, high-power factor polysilicon thin films using time-domain thermoreflectance. Voids are formed through ion implantation and annealing, evolving from many small (∼4 nm mean diameter) voids after 500 °C anneal to fewer, larger (∼29 nm mean diameter) voids with a constant total volume fraction after staged thermal annealing to 1000 °C. The thermal conductivity is reduced to 65% of the non-implanted reference film conductivity after implantation and 500 °C anneal, increasing with anneal temperature until fully restored after 800 °C anneal. The void size distributions are determined experimentally using small-angle and wide-angle X-ray scattering. While we believe multiple physical mechanisms are at play, we are able to corroborate the positive correlation between measurements of thermal conductivity and void size with Monte Carlo calculations and a scattering probability based on Matthiessen's rule. The data suggest an opportunity for thermal conductivity suppression combined with the high power factor for increased material zT and efficiency of nanostructured polysilicon as a thermoelectric material.

Dunham, M., Lorenzi, B., Andrews, S., Sood, A., Asheghi, M., Narducci, D., et al. (2016). Enhanced phonon scattering by nanovoids in high thermoelectric power factor polysilicon thin films. APPLIED PHYSICS LETTERS, 109(25), 253104 [10.1063/1.4972483].

Enhanced phonon scattering by nanovoids in high thermoelectric power factor polysilicon thin films

LORENZI, BRUNO
Secondo
;
NARDUCCI, DARIO
Penultimo
;
2016

Abstract

The ability to tune the thermal conductivity of semiconductor materials is of interest for thermoelectric applications, in particular, for doped silicon, which can be readily integrated in electronic microstructures and have a high thermoelectric power factor. Here, we examine the impact of nanovoids on the thermal conductivity of highly doped, high-power factor polysilicon thin films using time-domain thermoreflectance. Voids are formed through ion implantation and annealing, evolving from many small (∼4 nm mean diameter) voids after 500 °C anneal to fewer, larger (∼29 nm mean diameter) voids with a constant total volume fraction after staged thermal annealing to 1000 °C. The thermal conductivity is reduced to 65% of the non-implanted reference film conductivity after implantation and 500 °C anneal, increasing with anneal temperature until fully restored after 800 °C anneal. The void size distributions are determined experimentally using small-angle and wide-angle X-ray scattering. While we believe multiple physical mechanisms are at play, we are able to corroborate the positive correlation between measurements of thermal conductivity and void size with Monte Carlo calculations and a scattering probability based on Matthiessen's rule. The data suggest an opportunity for thermal conductivity suppression combined with the high power factor for increased material zT and efficiency of nanostructured polysilicon as a thermoelectric material.
Articolo in rivista - Articolo scientifico
Physics and Astronomy (miscellaneous)
English
253104
Dunham, M., Lorenzi, B., Andrews, S., Sood, A., Asheghi, M., Narducci, D., et al. (2016). Enhanced phonon scattering by nanovoids in high thermoelectric power factor polysilicon thin films. APPLIED PHYSICS LETTERS, 109(25), 253104 [10.1063/1.4972483].
Dunham, M; Lorenzi, B; Andrews, S; Sood, A; Asheghi, M; Narducci, D; Goodson, K
File in questo prodotto:
Non ci sono file associati a questo prodotto.

I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.

Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/10281/144187
Citazioni
  • Scopus 20
  • ???jsp.display-item.citation.isi??? 17
Social impact