Picosecond resolution of phonon dynamics with pulsed synchrotron radiation

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In the first part of the research project we proposed to study the lattice dynamics of semicon-ductor crystals, in particular multilayered nanostructures as well as ferroelectric lattice excita-tions by using ultrafast time-resolved x-ray scattering. A novel approach was proposed which uses the short pulse x-ray emission at the synchrotron ANKA and using its 500 MHz repeti-tion rate for a pump-probe setup. Radiation pulses emitted at ANKA can be extremely short (down to 1 ps) when using the so-called low-alpha mode of operation. The setup has been completed within the past period and is operational. Within this proposal we want to conduct ASOXS experiments on isotopically pure multilayers of silicon, respectively germanium. The phonon motion should reveal information about the nature of the phonon barrier in these mul-tilayered systems that are proposed to serve as thermoelectric materials. With ASOXS we also get access to the dynamics of the local motion in barium titanate ferroelectric crystals. The local motion and symmetry should give an independent access to the nature of the ferroelectric phase transition and solve a long-standing problem on the description of dis-placive versus diffusive ferroelectric order.