Conversion of electromagnetic into acoustic energy using Sn, Au, and Cu films at low temperatures

A. Zemel*, Y. Goldstein

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

14 Scopus citations

Abstract

Transverse acoustic waves were generated electromagnetically at 9 GHz using thin films of tin, gold, and copper on silicon substrates. We report measurements of the conversion efficiency α of electromagnetic into acoustic energy as a function of temperature and film thickness at and below 4.2 K and preliminary results at liquid-N2 temperature. The highest conversion efficiencies found at 4.2 K for Sn and Au were 1 × 10-5 and 2.5 × 10-5, respectively. In the temperature range of 1.4-4.2 K, the values of α for normal metals were found to be practically temperature as well as microwave-power independent. The value of α for superconducting tin decreases strongly below the superconducting transition temperature and becomes magnetic field and microwave-power dependent. This is in agreement with our previous results on indium. Using gold films we measured the thickness dependence of α in the range of π<q d<4π, where q is the acoustic wave number in the metal in d is the film thickness. We find a pronounced maximum at q d=2π and indications for another maximum at q d=4π. The values of α at 4.2 K as well as the temperature and thickness dependence of α are found to be in good agreement with the theory based on diffuse surface scattering of the conduction electrons.

Original languageEnglish
Pages (from-to)1499-1505
Number of pages7
JournalPhysical Review B
Volume9
Issue number4
DOIs
StatePublished - 1974

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