Breaking network connectivity leads to ultralow thermal conductivities in fully dense amorphous solids
Abstract
We demonstrate a method to reduce the thermal conductivity of fully dense (above the rigidity percolation threshold) amorphous thin films below the minimum limit by systematically changing the coordination number through hydrogenation. Studying a-SiO:H, a-SiC:H, and a-Si:H thin films, we measure the thermal properties using time-domain thermoreflectance to show that thermal conductivity can be reduced below the amorphous limit by a factor of up to two. By experimentally investigating the thermophysical parameters that determine thermal conductivity, we show that sound speed, atomic density, and heat capacity cannot explain the measured reduction in thermal conductivity, revealing that the coordination number can significantly alter the scattering length scale of heat carriers. Reformulating the minimum limit to consider the propensity for energy to transfer through the non-hydrogen network of atoms, we observe greatly improved agreement with experimental data.
Document Details
- Document Type
- Pub Defense Publication
- Publication Date
- Nov 07, 2016
- Source ID
- 10.1063/1.4967309
Entities
People
- Ashutosh Giri
- Hiroyuki Fujiwara
- Jeffrey L Braun
- John T. Gaskins
- Masanori Sato
- Patrick E Hopkins
- Sean W. King
- Takemasa Fujiseki
Organizations
- Gifu University
- Intel Corporation
- Office of Naval Research
- University of Virginia