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The growth of carbon-based materials by supersonic beam epitaxy: experiments, theory and calculations

ECT* - LISC Seminar
Speaker: 
Simone Taioli (FBK-LISC)
Date: 
05 Mar 2014 - 11:00
Location: 
Villa Tambosi 2nd Floor, Seminar Room
Abstract: 

In this work, we investigate the processes leading to the room-temperature growth of carbon based nano-crystals, notably silicon carbide (SiC) and graphene, by supersonic molecular beam epitaxy technique. In particular, we present both experimental data and computational modeling of the collision of fullerene on silicon and copper surfaces. This intermediate energy impact induces strong chemicalphysical perturbations in the system and, for sufficient translational energy, disruption of molecular bonds and C60 cage breaking, leading to the formation of nanostructures with different stoichiometric character.

Careful and extensive characterization of the material by a variety of experimental techniques (XPS, UPS, Auger, LEED, TEM, Raman) after the collision demonstrates the potentiality of our approach to grow nanostructured materials at room temperature.

On the theoretical side, we show that in these out-of-equilibrium conditions, it is necessary to go beyond the standard implementations of density functional theory, as ab-initio methods based on the Born-Oppenheimer approximation fail to capture the excited-state dynamics. In particular, we analyse the Si- and Cu-C60 collision within the non-adiabatic nuclear dynamics framework, where stochastic hops occur between adiabatic surfaces calculated with time-dependent density functional theory. This theoretical description of the C60 impact on metallic and semiconductive substrates is in good agreement with our experimental findings.