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Untersuchungen zur Wechselwirkung von Buckminsterfullerenen mit Siliziumoberflächen und zur Dotierung von Metall/Silizium-Grenzflächen mit Buckminsterfullerenen
The present work investigates the interaction between buckminsterfullerene molecules (C60) and silicon surfaces as well as the influence of buckminsterfullerenes on metal/silicon interfaces. The knowledge about the mechanism of surface/molecule interaction between the technologically important semiconductor Si and C60 molecules may lead to new applications of fullerenes. In this context the present study compares the adsorption and the growth mechanisms as well as the desorption of C60 molecules which were evaporated onto well-prepared Si(111)-7x7-, Si(111):H-1x1- and Si(111):Ag-(sqrt(3) x sqrt(3))R30°-surfaces using Auger electron spectroscopy (AES), low-energy electron diffraction (LEED) under ultra-high vacuum conditions. The electronic structure of C60-covered Si(111)-7x7-, Si(111)-1x1-, Si(111):H-1x1-and Si(111):Ag-(sqrt(3) x sqrt(3))R30°-surfaces was investigated using ultraviolet and X-ray photoelectron spectroscopy (UPS, XPS). From these experiments the molecule/surface interaction mechanisms can be identified. Crystalline C60 is a new semiconductor material. Therefore, evaporating C60 onto Si surfaces builds up a semiconductor heterostructure. The electronic properties of this heterostructure are characterized by the band discontinuities at the C60/Si interface. Using UPS and XPS the valence-band discontinuity at this semiconductor/semiconductor interface were determined. Additionally, metal/Si contacts were produced on initially clean silicon surfaces which were covered with distinct amounts of C60 before Ag-, Pb- or Pd-contacts were evaporated. The transport properties of these contacts were studied by current-voltage-chracteristics to determine the influence of C60-layers on the Schottky barrier heights of the metal/Si contacts.
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