  Thin films of potassium doped C60, an organic semiconductor, have been grown
on silicon. The films were grown in ultra-high vacuum by thermal evaporation of
C60 onto oxide-terminated silicon as well as reconstructed Si(111). The
substrate termination had a drastic influence on the C60 growth mode which is
directly reflected in the electrical properties of the films. Measured on the
single domain length scale, these films revealed resistivities comparable to
bulk single crystals. In situ electrical transport properties were correlated
to the morphology of the film determined by scanning tunneling microscopy. The
observed excess conductivity above the superconducting transition can be
attributed to two-dimensional fluctuations.
