20 June 2022
Photo: UHH\Marvin Reuner and Daria Gorelova
In his Nobel Lecture, Herbert Kroemer famously stated that “The interface is the device”. Scientists from DESY and Hamburg University unveiled fundamental electronic and structural dynamics of the hybrid organic/inorganic interface on an ultrafast timescale.
In their experiment at the free-electron laser FLASH at DESY, the scientist obtained time-resolved photoelectron momentum maps of pentacene molecules adsorbed on a metal substrate. Those momentum maps can be related to the electronic orbital in a molecule and interpreted as the probability to find an electron at a certain position in space.
The recent developments of free-electron laser (FEL) based sources opened new opportunities to follow such electronic orbitals on ultrafast timescales. Taking snapshots of slices through molecular orbitals, like in computer tomography or MRI, allows to follow the shape evolution of molecular orbitals and to contribute to a better understanding of chemical reactions across functional interfaces. Such interfaces are on the focus of current interest for organics-based devices with applications in optoelectronics, catalysis and energy storage.
In their work, the scientists photoexcited the interface, and initiate the flow of charge and energy across the interface and followed the molecular orbitals. The shape evolution of the orbitals contained highly precise details about photo-induced electronic and nuclear transformations at the hybrid interface and photo-excited molecules. Combining experimental data with calculations, the scientists could disclose details of intramolecular electron and structure dynamics as well as charge transfer dynamics at the interface.
K. Baumgärtner, C. Metzger, D. Kutnyakhov, M. Heber, F. Pressacco, C. H. Min, T. Peixoto, M. Reiser, C. Kim, W. Lu, R. Shayduk, M. Izquierdo, G. Brenner, F. Roth, A. Schoell, S. Molodtsov, W. Wurth, F. Reinert, A. Madsen, M. Scholz, Ultrafast orbital tomography of a pentacene film using time-resolved momentum microscopy at a FEL, Nature Communications 13, 2741, 2022