Regensburg 2002 – scientific programme
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DS: Dünne Schichten
DS 18: Schichtherstellung II
DS 18.2: Talk
Thursday, March 14, 2002, 10:30–10:45, HS 31
Properties and Synthesis of C60 - Amorphous Silicon Composite Thin Films — •Petra Reinke1, Ulrich Vetter1, and Peter Oelhafen2 — 1Universität Göttingen, II. Physikalisches Institut, Bunsenstr. 7-9, 37973 Göttingen — 2Universität Basel, Klingelbergstr. 82, CH-4056 Basel
C60 and amorphous silicon are used as building blocks to fabricate a novel composite material. The range of compositions extends from Si-rich layers to C60 films in which only small amounts of Si are embedded (exohedral doping). The films are fabricated by simultaneous evaporation of the two components and no segregation is observed. The characterization of the layers by photoelectron spectroscopy in the X-ray and ultraviolet regime shows that the fullerene molecules remain intact and allows to determine the electronic properties of the internal interface. The interaction is determined by hybridization of the states close to the Fermi energy rather than a charge transfer process and no carbide is present. The valence band offset at the interface is about 1 eV and the internal interfaces thus behave electronically equivalent to the double layer C60 - a-Si system. The embedding of C60 in the rigid silicon matrix severely restricts the vibrations of the macromolecules as obserevd with Raman spectroscopy. The layers are highly temperature stable and the fullerene cages begin to break down at temperatures exceeding 700 C and react with the surrounding Si to form SiC crystallites. The optical properties, in particular luminescence, of the films with low Si content will be discussed with respect to the width and extension of the Si regions. The potential applications of this composite material will also be addressed.