Abstract
We examine the role of a silicon-based amorphous insulating substrate in the thermal relaxation in thin , , and / films at temperatures above 5 K. The samples studied consist of metal bridges on an amorphous insulating layer lying on or suspended above a crystalline substrate. Noise thermometry is used to measure the electron temperature of the films as a function of Joule power per unit area . In all samples, we observe a dependence, with exponent , which is inconsistent with both electron-phonon coupling and Kapitza thermal resistance. In suspended samples, the functional dependence of on the length of the amorphous insulating layer is consistent with the linear temperature dependence of the thermal conductivity, which is related to lattice excitations (diffusons) for a phonon mean free path shorter than the dominant phonon wavelength. Our findings are important for understanding the operation of devices embedded in amorphous dielectrics.
- Received 18 January 2021
- Revised 26 March 2021
- Accepted 14 April 2021
DOI:https://doi.org/10.1103/PhysRevApplied.15.054014
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