Thermal conductivity reduction of crystalline silicon by high-pressure torsion
Abstract
We report a dramatic and irreversible reduction in the lattice thermal conductivity of bulk crystalline silicon when subjected to intense plastic strain under a pressure of 24 GPa using high-pressure torsion (HPT). Thermal conductivity of the HPT-processed samples were measured using picosecond time domain thermoreflectance. Thermal conductivity measurements show that the HPT-processed samples have a lattice thermal conductivity reduction by a factor of approximately 20 (from intrinsic single crystalline value of 142 Wm-1 K-1 to approximately 7.6 Wm-1 K-1). Thermal conductivity reduction in HPT-processed silicon is attributed to the formation of nanograin boundaries and metastable Si-III/XII phases which act as phonon scattering sites, and because of a large density of lattice defects introduced by HPT processing. Annealing the samples at 873 K increases the thermal conductivity due to the reduction in the density of secondary phases and lattice defects.
- Publication:
-
Nanoscale Research Letters
- Pub Date:
- June 2014
- DOI:
- 10.1186/1556-276X-9-326
- Bibcode:
- 2014NRL.....9..326H
- Keywords:
-
- Silicon thermal conductivity;
- High-pressure torsion;
- Time domain thermoreflectance;
- Thermoelectrics