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O: Fachverband Oberflächenphysik

O 46: Time-resolved spectroscopies I

O 46.5: Vortrag

Donnerstag, 26. März 2009, 11:30–11:45, SCH A315

Mechanical Oscillations of Nanostructures — •Richard Taubert¹, Florian Hudert², Albrecht Bartels^2,3, and Thomas Dekorsy² — ¹Universität Stuttgart — ²Universität Konstanz — ³Gigaoptics GmbH, Konstanz, Deutschland

Understanding the mechanical properties of nanostructures has been a field of large interest during the last years. We present a method to investigate the phonon dynamics in nanostructures by time-resolved optical measurements. A new technique, Asynchronous Optical Sampling (ASOPS) is used to carry out pump-probe spectroscopy. Instead of using one laser and a mechanical delay line to generate pump- and probe-beams, two separated lasers, whose repetition rates are slightly detuned by several kHz are used. This allows the measurement of mechanical oscillations with GHz line width and a signal-to-noise ratio of 10⁷ within 100 seconds of measurement time.

Time-resolved measurements on metallic and semiconductor superlattices as well as metallic nano-triangles and nano-tetrahedrons are presented. The measurements on the superlattices clearly resolve the first-order back-folded longitudinal acoustic phonons at the zone center. Furthermore, it is possible to do precise layer thickness and superlattice-period measurements. The mechanical oscillations of metallic triangles and pyramids with different edge lengths are observed and the influence of geometry, size and substrate are investigated.