Pump-probe measurements of the thermal conductivity tensor for materials lacking in-plane symmetry
Abstract
We previously demonstrated an extension of time-domain thermoreflectance (TDTR) which utilizes offset pump and probe laser locations to measure in-plane thermal transport properties of multilayers. However, the technique was limited to systems of transversely isotropic materials studied using axisymmetric laser intensities. Here, we extend the mathematics so that data reduction can be performed on non-transversely isotropic systems. An analytic solution of the diffusion equation for an N-layer system is given, where each layer has a homogenous but otherwise arbitrary thermal conductivity tensor and the illuminating spots have arbitrary intensity profiles. As a demonstration, we use both TDTR and time-resolved magneto-optic Kerr effect measurements to obtain thermal conductivity tensor elements of <110> α-SiO2. We show that the out-of-phase beam offset sweep has full-width half-maxima that contains nearly independent sensitivity to the in-plane thermal conductivity corresponding to the scanning direction. Also, we demonstrate a Nb-V alloy as a low thermal conductivity TDTR transducer layer that helps improve the accuracy of in-plane measurements.
Document Details
- Document Type
- Pub Defense Publication
- Publication Date
- Oct 01, 2014
- Source ID
- 10.1063/1.4897622
Entities
People
- David G. Cahill
- Joseph P Feser
- Jun Liu
Organizations
- Army Research Office
- University of Delaware
- University of Illinois Urbana–Champaign