Ultrafast dynamics of nanolayered ferroelectric and photoswitchable polymer films

• Applicant: Professor Dr. Matias Bargheer
• Subject Area: Experimental Condensed Matter Physics
• Term: from 2007 to 2011
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 50234000

In order to utilize specific functions of molecules, molecular groups and nanostructures, it is essential to understand the interplay of electronic excitation and structural changes. Optical excitation of electrons occurs within several femtoseconds (10-15 s) and instantaneously induces forces that govern the nuclear motion. The elementary processes are ultrafast and even in soft matter the magnitude of typical sound velocities of 1-4 nm/ps indicates that expansions and contractions of matter on the nanoscale will occur within picoseconds, although the induced dynamics can continue much longer. The motion of nuclei in turn influences the electronic potentials and changes optical absorption, transmission, reflection and coherent wave-mixing processes. In soft matter, the amplitudes of nuclear motion can be much larger than in solid samples (e.g. semiconductors, ferroelectrics). We will optically excite and observe specific modes in optical pump-probe experiments by tailoring nanoscale structures with layers for particular functions. Ultrafast x-ray diffraction will be used in addition to monitor the nuclear motion more directly, either at dedicated synchrotron beamlines or at the femtosecond x-ray diffractometer.The goal of this project is to demonstrate that the nanostructuring of particular selected combinations of materials can give rise to coupled ultrafast dynamics of nuclei and electrons, which may be useful for novel nanodevices. Two cases of nanoscale multilayers devices will be studied: Ferroelectric polymers with metallic electrodes and nanolayered polymers with embedded molecular photoswitches.

• DFG Programme: Research Grants