Temperature dependent behavior of thermal conductivity of sub-5 nm Ir film: Defect-electron scattering quantified by residual thermal resistivity
Abstract
By studying the temperature-dependent behavior (300 K down to 43 K) of electron thermal conductivity (κ) in a 3.2 nm-thin Ir film, we quantify the extremely confined defect-electron scatterings and isolate the intrinsic phonon-electron scattering that is shared by the bulk Ir. At low temperatures below 50 K, κ of the film has almost two orders of magnitude reduction from that of bulk Ir. The film has ∂κ/∂T > 0, while the bulk Ir has ∂κ/∂T < 0. We introduce a unified thermal resistivity (Θ = T/κ) to interpret these completely different κ ∼ T relations. It is found that the film and the bulk Ir share a very similar Θ ∼ T trend, while they have a different residual part (Θ0) at 0 K limit: Θ0 ∼ 0 for the bulk Ir, and Θ0 = 5.5 m·K2/W for the film. The Ir film and the bulk Ir have very close ∂Θ/∂T (75–290 K): 6.33 × 10−3 m K/W for the film and 7.62 × 10−3 m K/W for the bulk Ir. This strongly confirms the similar phonon-electron scattering in them. Therefore, the residual thermal resistivity provides an unprecedented way to quantitatively evaluating defect-electron scattering (Θ0) in heat conduction. Moreover, the interfacial thermal conductance across the grain boundaries is found larger than that of Al/Cu interface, and its value is proportional to temperature, largely due to the electron's specific heat. A unified interfacial thermal conductance is also defined and firmly proves this relation. Additionally, the electron reflection coefficient is found to be large (88%) and almost temperature independent.
Document Details
- Document Type
- Pub Defense Publication
- Publication Date
- Jan 13, 2015
- Source ID
- 10.1063/1.4905607
Entities
People
- Shen Xu
- Xinwei Wang
- Zaoli Xu
- Zhe Cheng
Organizations
- Army Research Office
- Iowa State University
- National Science Foundation
- Office of Naval Research
- Shanghai Polytechnic University