Thermal conductivity reduction of crystalline silicon by high-pressure torsion

Sivasankaran Harish; Mitsuru Tabara; Yoshifumi Ikoma; Zenji Horita; Yasuyuki Takata; David G Cahill; Masamichi Kohno

doi:10.1186/1556-276X-9-326

Thermal conductivity reduction of crystalline silicon by high-pressure torsion

Nanoscale Res Lett. 2014 Jun 28;9(1):326. doi: 10.1186/1556-276X-9-326. eCollection 2014.

Authors

Sivasankaran Harish¹, Mitsuru Tabara¹, Yoshifumi Ikoma², Zenji Horita³, Yasuyuki Takata⁴, David G Cahill⁵, Masamichi Kohno⁴

Affiliations

¹ Department of Mechanical Engineering, Kyushu University, 744 Motooka, Fukuoka 819-0395, Japan.
² Department of Materials Science and Engineering, Kyushu University, 744 Motooka, Fukuoka 819-0395, Japan.
³ Department of Materials Science and Engineering, Kyushu University, 744 Motooka, Fukuoka 819-0395, Japan ; International Institute of Carbon-Neutral Energy Research (WPI - I2CNER), Kyushu University, 744 Motooka, Fukuoka 819-0395, Japan.
⁴ Department of Mechanical Engineering, Kyushu University, 744 Motooka, Fukuoka 819-0395, Japan ; International Institute of Carbon-Neutral Energy Research (WPI - I2CNER), Kyushu University, 744 Motooka, Fukuoka 819-0395, Japan.
⁵ International Institute of Carbon-Neutral Energy Research (WPI - I2CNER), Kyushu University, 744 Motooka, Fukuoka 819-0395, Japan ; Department of Materials Science and Engineering and Materials Research Laboratory, University of Illinois, Urbana, IL 61801, USA.

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.

Keywords: High-pressure torsion; Silicon thermal conductivity; Thermoelectrics; Time domain thermoreflectance.