Regensburg 2010 – wissenschaftliches Programm
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HL: Fachverband Halbleiterphysik
HL 5: Ultra-fast Phenomena
HL 5.5: Vortrag
Montag, 22. März 2010, 11:30–11:45, H17
Time resolved investigation and resonant sub harmonic driving of confined acoustic phonon modes in freestanding silicon membranes — Mike Hettich1, •Axel Bruchhausen1, Raphael Gebs1, Florian Hudert1, Daniel Issenmann1, Olivier Schecker1, Reimar Waitz1, Artur Erbe1, Elke Scheer1, Adnen Mlayah2, Jean-Roch Huntzinger3, and Thomas Dekorsy1 — 1Department of Physics and Center of Applied Photonics, Universität Konstanz, Germany — 2CEMES-CNRS, Université de Toulouse, France — 3GES-UMR 5650, CNRS, Université Montpellier 2, France
The vibrational dynamics of thin silicon membranes have been investigated by asynchronous optical sampling (ASOPS)[1].
The small thickness of the silicon membranes leads to a confinement of the acoustic phonon modes and therefore to a discretization of the phonon frequency spectrum. Odd harmonics of the fundamental mode (19 GHz for a 221nm thick membrane) up to the 25th order have been observed [2].
In order to measure the phonon lifetimes which exceed the measurement window of 1.2ns the repetition rates of the pump and probe laser are tuned to a subharmonic of the fundamental mode. By using this approach the phonon modes are resonantly driven and in analogy to a mechanical resonator the lifetime and the quality factor of the phonon modes can be determined. We observe a Q-factor of 500 which is a significant value for a nanomechanical resonator at room temperatur.
[1] A. Bartels et al., Rev. Sci. Instr. 78, 035107 (2007).
[2] F. Hudert et al., Phys. Rev. B 78, 201307(R) (2009).