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We report on preparation of clean C60 surface and study of the core level electron structure of C60 single crystal surface and ionic dielectric NaCl film evolution of structural transformation, as a function of coverage. We studied films of NaCl with thicknesses up to 7 ML onto the C60 substrate, which was used as insulating layer for the field-effect transistor. The x-ray photoemission studies used monochromatic AlKα photons were conducted in commercial VG ESCALAB UHV spectrometer equipped with a hemispherical energy analyzer. The Na1s and Cl2p XP spectra positions, were observed almost constant at different coverage, while C1s peak is shifted on 5 eV to the larger binding energy side at coverage more than 2 ML. We also observed that C1s spectra area exhibit only about 30% change as function of coverage even for 7 ML, while Na1s and Cl2p spectra grows substantially without saturation. This behavior was explained due to island NaCl films formation. Although metallic interface layer formation between NaCl and C60 was proposed, the electron transport measurements did not reveal conductivity change of C60 surface as function of NaCl coverage. To overcome the island mode formation problem we prepared the NaCl films on C60 at liquid nitrogen temperature, and finally the field-effect transistor on C60 single crystals was developed. |