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O: Fachverband Oberflächenphysik

O 43: Graphene I

O 43.5: Vortrag

Mittwoch, 24. März 2010, 11:30–11:45, H31

Ab-initio determination of the electronic and optical properties of functionalized group IV monolayers for optoelectronic and photovoltaic devices. — •Margherita Marsili — ETSF, Dipartimento di Fisica Università di Roma `Tor Vergata' (Italy)

Graphene, one of the most intensively material studied recently, is well known as being metallic. The absence of an electronic gap limits its possible use in electronic and optoelectronic devices. A route to the opening of a gap is the functionalization of graphene through the absorption of molecules. In particular a reversible metal-insulator transition of graphene upon hydrogenization has been experimentally achieved, after it was theoretically predicted. Graphane, the fully hydrogenated graphene, has indeed a wide gap of almost 6 eV. The extent of the electronic gap of graphane limits its use in photovoltaic devices, one of the key technologies for the attainment of green energy. Possible solutions are either to functionalize graphene with other molecules, or to change the backbone material looking at the other group IV elements such as Si and Ge. Here we present results exploring both paths: the optical properties of different molecules on graphane and on polysilane and polygermyne (Si and Ge counterparts of graphane) monolayers are investigated also including many-body effects beyond density functional theory. Many-body effects are also crucial in the quantitative description of a material's electron affinity. Hydrogenated diamond surfaces are known to have negative electron affinity, therefore the effect of hydrogen on graphene's electron affinity is also determined taking into account self-energy effects.