Thermal relaxation in metal films limited by diffuson lattice excitations of amorphous substrates

Abstract

Here we examine the role of the amorphous insulating substrate in the thermal relaxation in thin NbN, InO${}_x$, and Au/Ni films at temperatures above 5 K. The studied samples are made up of metal bridges on an amorphous insulating layer lying on or suspended above a crystalline substrate. Noise thermometry was used to measure the electron temperature $T_e$ of the films as a function of Joule power per unit of area $P_{2D}$. In all samples, we observe the dependence $P_{2D}\propto T_e^n$ with the exponent $n\simeq 2$, which is inconsistent with both electron-phonon coupling and Kapitza thermal resistance. In suspended samples, the functional dependence of $P_{2D}(T_e)$ on the length of the amorphous insulating layer is consistent with the linear $T$-dependence of the thermal conductivity, which is related to lattice excitations (diffusons) for the phonon mean free path smaller than the dominant phonon wavelength. Our findings are important for understanding the operation of devices embedded in amorphous dielectrics.

9 pages, 5 figures

References in corpus (7)

• Electric Field Effect in Atomically Thin Carbon Films
• Energy Dissipation and Transport in Nanoscale Devices
• Quantum breakdown of superconductivity in low-dimensional materials
• The Ioffe-Regel criterion and diffusion of vibrations in random lattices
• Energy transport in jammed sphere packings
• Superconducting single-photon detectors with saturated dependence of quantum efficiency vs. bias current
• High field termination of a Cooper-pair insulator

Cited by in corpus (5)

• Self-Heating Hotspots in Superconducting Nanowires Cooled by Phonon Black-Body Radiation
• Phonon heat capacity and self-heating normal domains in NbTiN nanostrips
• Fundamental limits of few-layer NbSe${}_2$ microbolometers at terahertz frequencies
• Local bistability under microwave heating for spatially mapping disordered superconductors
• Local thermometry of NbSe${}_2$ flake with delta-$T$ noise measurements