Dresden 2014 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 100: Surface Dynamics II

O 100.5: Vortrag

Freitag, 4. April 2014, 11:30–11:45, PHY C 213

2D-Polymer superstructure dynamics on graphene mapped by ultrafast low-energy electron diffraction — •Max Gulde, Simon Schweda, Sascha Schäfer, and Claus Ropers — IV. Physical Institute, University of Göttingen, Germany

Time-resolved diffraction methods currently serve as powerful tools to elucidate the ultrafast structural dynamics of bulk media. Corresponding experimental developments for the investigation of transient processes on surfaces and other 2D systems have proven to be challenging. Here, we present the implementation of ultrafast low-energy electron diffraction (ULEED) in a laser pump / electron probe setup allowing for a temporal resolution of few picoseconds.

The surface sensitivity of ULEED is utilized to investigate the dynamical behavior of an ultrathin bilayer system, composed of a polymethyl methacrylate (PMMA) superstructure on a freestanding, single layer graphene substrate. In particular, ultrafast partial melting of two-dimensional folded chain crystals is observed, paralleled by the appearance of an expanded amorphous phase. The structural evolution of the crystallites and the amorphous phase are mapped, showing characteristic time constants between 50 ps and 300 ps.