Growth of thin C60 films on hydrogenated Si(100) surfaces

Photoemission spectroscopies and atomic force microscopy (AFM) were performed on C60 evaporated on the monohydride Si(100):H-(2×1) surface at different temperatures from room temperature up to 900°C. X-ray photoelectron spectroscopy has revealed that the interaction is with the hydrogenated surface only for temperatures below 250°C. Above this temperature the hydrogen starts to desorb and C60 interacts directly with the clean silicon surface. The bond between C60 and the Si(100):H-(2×1) surface is van der Waalsʹ in character and is estimated to be of the same order of magnitude or even weaker than the C60–C60 interaction. AFM analysis was performed on multilayer samples grown in the range between room temperature and 200°C. Room-temperature samples exhibit small C60 islands. The order of the islands improves strongly when the temperature of the substrate is increased up to 200°C. At this temperature the islands are all ordered with the hexagonal shape typical of C60 growth along the (111) direction and a lateral size of about 3000 Å.