Welcome to the research group on clusters and nanostructures!
|Structural Transition in Atomic Chains Driven by Transient Doping
One-dimensional systems are notoriously difficult to dope because the dopant atoms interrupt the continuity of the quantum wires. Here we propose an alternative route based on transient doping, where charge carriers are provided by an external source. Doping is achieved via charge injection from the tip of a scanning tunneling microscope, driving the quasi one-dimensional system into an excited structural phase. Time-dependent measurements enable access to the system’s dynamics revealing rapid fluctuations due to a competition between excitation and decay. The current-dependent lifetimes hint at a barrierless decay of the excited (i.e. doped) state, letting the system behave like an optically excited molecule in close analogy to an excimer.
Article in Phys. Rev. Lett.
|Conï¬ned Doping on a Metallic Atomic Chain Structure
Using atomically precise scanning tunneling spectroscopy the concept of doping is pushed to the ultimate limit. On an array of atomic chains it is shown that single doping atoms contribute their electrons to a small chain section, terminated by the very dopants themselves. Like an ant on a blade of grass the electrons can only move in either direction, without the possibility to escape sideways. Such conï¬ned doping is a direct consequence of reduced dimensionality and is not observed in higher dimensions.
Article in Phys. Rev. Lett.
|Periodic variations in the local surface potential of Si(111)-(5Ã2)-Au
The local surface potential has been mapped by scanning tunneling spectroscopy on a quasi one-dimensional system. The method is based on the analysis of energy positions of so-called field emission resonances (FER). Simple models reproduce the FER perfectly and allow extraction of the potential landscape. This landscape is conï¬rmed by density functional theory calculations, revealing attractive wells along the chains.
Article in Phys. Rev. B
|A Study of the Global Chirp Dependence on the Interaction of Intense Colored Double Pulses with Clusters
The yields of highly charged atomic ions produced in the
exposure of xenon clusters embedded in helium nanodroplets by intense colored double pulses show a notable sensitivity on the order of the subpulses. The only slight difference in their spectral composition leads to a flipping of the optimal laser parameters for effective multielectron ionization above certain charge states, which appears to be quite robust with respect to the chosen pulse fluence and reflects an avalanche-like developing cluster ionization scenario.
Article published in Eur. Phys. J. D
|In-situ studies of the catalytic activity of size-selected silver clusters
The catalytic activity and dynamical shape changes in size-selected nanoclusters at work are studied under realistic reaction conditions by using a combination of simultaneous temperature-programmed reaction with in situ grazing-incidence small angle x-ray scattering and ex-situ high-resolution transmission electron microscopy. This approach allows drawing a direct correlation between nanocatalyst size, composition, shape, and its function under realistic reaction conditions. First-principle calculations yield surface energies which result in particle shapes resembling the experimentally observed shapes of partially oxidized silver clusters. These studies shed new light on the detailed mechanisms of nano-catalysts.
Article at Catalysis today ________Article at J. Chem. Phys.
|Structure and energetics of Si(111)-(5×2)-Au
A new structural model for the Si(111)-5×2-Au reconstruction is proposed. The model incorporates a revised experimental value of 0.6 monolayer for the coverage of gold atoms. Five main theoretical results, obtained from ï¬rst-principles total-energy calculations, support the model. Knowing the structure of this chain system allows for detailed interpretation of present and future experimental data.
Article at Phys. Rev. B
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