Thermal conductivity reduction of crystalline silicon by high-pressure torsion
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 International Institute of Carbon-Neutral Energy Research (WPI – I2CNER), Kyushu University, 744 Motooka, Fukuoka 819-0395, Japan
4 Department of Materials Science and Engineering and Materials Research Laboratory, University of Illinois, Urbana, IL 61801, USA
Nanoscale Research Letters 2014, 9:326 doi:10.1186/1556-276X-9-326Published: 28 June 2014
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.