Regensburg 2019 – scientific programme

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TT: Fachverband Tiefe Temperaturen

TT 28: Cryotechnique: Refrigeration and Thermometry

TT 28.5: Talk

Tuesday, April 2, 2019, 12:15–12:30, H23

Crossover of dominant energy relaxation mechanism in normal metal films — •Libin Wang and Jukka Pekola — QTF Centre of Excellence, Department of Applied Physics, Aalto University, FI-00076 Aalto, Finland

For normal metals at low temperature, the electrons are known to be well decoupled from the phonons. When a constant heating is applied to the normal metal, the electron temperature will be elevated above the phonon temperature, which leads to the hot electron effect. For thin normal metal films at low temperature, the high thermal resistance (R_ep) between electrons and phonons in the metal films will dominate over the thermal boundary resistance (R_d) between the metal film and insulating substrate, and become the bottleneck for energy relaxation in the films. By increasing the film thickness or temperature, the ratio of R_ep/ R_d will increase and to some point the dominant energy relaxation constrain will be the thermal boundary resistance between films phonons and substrate phonons. Here we will present the experimental observation of this crossover in normal metal films on the silicon substrate at temperature below 0.2K, where phonons in metal films are supposed to be two dimensional (2D). The derived thermal boundary resistance between 2D phonons and the substrate is a few times higher than that when the phonons are in the three dimensional (3D). The observed crossover for the dominant energy relaxation mechanism in normal metal films has significant benifit in understanding of thermal behavior of nanoelectronic devices at low temperature.