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

Photoemission spectroscopies and atomic force microscopy (AFM) were performed on C-60 evaporated on the monohydride Si (100):H-(2 x 1) surface at different temperatures from room temperature up to 900 degrees C. X-ray photoelectron spectroscopy has revealed that the interaction is with the hydrogenated surface only for temperatures below 250 degrees C. Above this temperature the hydrogen starts to desorb and C-60 interacts directly with the clean silicon surface. The bond between C-60 and the Si(100):H-(2 x 1) surface is van der Waals' in character and is estimated to be of the same order of magnitude or even weaker than the C-60-C-60 interaction. AFM analysis was performed on multilayer samples grown in the range between room temperature and 200 degrees C. Room-temperature samples exhibit small Cs, islands. The order of the islands improves strongly when the temperature of the substrate is increased up to 200 degrees 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 Angstrom. (C) 2000 Elsevier Science B.V. All rights reserved.