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HL: Fachverband Halbleiterphysik
HL 24: Thermal Properties
HL 24.3: Vortrag
Dienstag, 18. März 2025, 12:45–13:00, H14
Signature of thermal phonon mean free paths monitored by Raman thermometry — •Katharina Dudde1, Mahmoud Elhajhasan1, Guillaume Würsch1, Julian Themann1, Nakib Protik2, Dwaipayan Paul2, Giuseppe Romano3, and Gordon Callsen1 — 1Institut für Festkörperphysik, Universität Bremen, Germany — 2Institut für Physik und IRIS Adlershof, Humboldt-Universität zu Berlin, Germany — 3MIT-IMB Watson AI Lab, IBM Research, Cambridge, MA, USA
For an understanding of thermal phonon interference effects, one requires knowledge about the related phonon mean free paths lmfp. In the recent past, spectroscopy methods were developed to determine lmfp based on this idea: One performs thermal transport measurements under the variation of a characteristic experimental length scale L aiming to extract effective thermal properties such as the effective thermal conductivity κeff(L). In this contribution, we analyze how non-invasive one-laser Raman thermometry (1LRT) can pose a novel option to perform thermal phonon lmfp spectroscopy. Therefore, we first analyze bulk silicon at 293 K, while varying the laser focus spot radius (we). Here, we find a strong dependence of κeff on we. This dependence is more pronounced at 200 K, because lmfp is increased. The second variable length scale for 1LRT is the light penetration depth (hα), which is varied in a set of measurements for silicon membranes at 293 K. Again, a dependence of κeff on hα is observed. Finally, our variation of we or hα during 1LRT provides first insight into the impact of different thermal phonon lmfp ranges on κeff.
Keywords: Raman thermometry; Phonon mean free path; Thermal conductivity; Silicon; Spectroscopy