Project Details
Projekt
Dynamics of monodisperse clusters under the fast Scanning Tunneling Microscope
Subject Area
Physical Chemistry of Solids and Surfaces, Material Characterisation
Term
from 2012 to 2021
Project identifier
Deutsche Forschungsgemeinschaft (DFG) - Project number 230413507
In this research project, the structure and dynamics of supported clusters are studied by Scanning Tunneling Microscopy (STM) with an unprecedented combination of size and site control, as well as high temporal and spatial resolution. The true monodispersity provides an identical chemical environment for each cluster, thus any measured differences can be traced back to dynamic effects on individual clusters such as isomerism and the related structural fluctuations (fluctionality), adsorption-induced modifications, as well as chemical transformations. At the same time, the monodispersity allows for a statistically sound, quantitative access to the description of these processes. We want to use this control for tracing the fundamental mechanisms that govern cluster stability and reactivity at the atomic scale. This is pivotal for heterogeneous catalysis and any other application of cluster-assembled materials, where nanostructured matter, intrinsically energetically frustrated, requires stabilization or even re-generation, as for example in catalytic processes. In our previous project, we have implemented special fast STM techniques for the detection of the cluster dynamics, by imaging (FastSTM) and by tracking (cluster Tracking) that were never used before for the study of size-selected clusters. We have also established a valid experimental platform of size-selected Palladium clusters on Moiré-graphene films and boron nitride analogues for which isomer-dependent diffusion, cluster coalescence and dispersion could be studied in detail.The renewal of the project aims at revealing, temporally resolved, the dynamic response under thermal, chemical and reaction-induced stress by using the two techniques implemented in the first part of the project. The dynamical response of the clusters regards changes in morphology, position or electronic structure, studied with a time resolution down to 10 ms. We want to trace diffusion paths, to correlate structural fluctuations with mobility, to map adsorbate-cluster interactions and to follow entire reactions of different degrees of exothermicity. Especially with our tracking method we intend to extract quantitative information such as activation energies and entropies for diffusion and reaction processes. In particular, we aim at distinguishing local and global diffusion on periodically wettable surfaces and to determine the exponent characterizing the diffusion behaviour. By changing the support and the dimension of the cluster by size control, the heat dissipation involved in all the processes mentioned above can be controlled and thus a systematic access to the physics of energy dissipation can be obtained. For the evaluation of the obtained results, the full toolkit developed by the molecular dynamics community can be applied and the quantitative results directly linked to simulations.
DFG Programme
Research Grants
