Experimental characterisation of defect-induced phonon lifetime shortening

Le résumé fourni par la source

Abstract Phonon-mediated heat transport is of wide importance, particularly in thermal management for the rapidly advancing microelectronics industry. Since lattice imperfections strongly influence phonon scattering, which in turn determine thermal conductivity, it is crucial to understand phonon lifetimes and how they are influenced by material defects. To date, direct measurements of phonon lifetimes have been extremely limited; most studies have relied on indirect measurements of thermal properties, or theoretical calculations with limited validation. Here, we present direct experimental measurement of defect-induced lifetime shortening of acoustic surface phonons. Defects are found to contribute a temperature-independent component to the linewidths of Rayleigh wave (RW) phonons on a Ni(111) surface. We also characterised the increase in phonon scattering with both surface defect density and phonon wave vector. A quantitative estimate of the strength of the interaction between a phonon-mode and a surface line-defect is extracted from the data. Looking forwards, we anticipate direct characterisation of defect-phonon interactions in 2D systems will be of significant value to the active fields of phononics and nanoscale heat flow.

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