THE CHEMISORPTION OF C-60 ON SI(100)-(2X1)

The adsorption of C60 on Si(100)-(2 X 1) has been investigated by temperature-programmed desorption (TPD) spectroscopy and Auger electron spectroscopy (AES). The binding of the first monolayer of C60 to the clean (2 X 1) silicon (100) is strong; such that the carbon overlayer is not removed until the substrate is heated to over 1150 K. After desorption of the multilayer peak by heating to 600 K, a graphite-like carbon AES peak is observed. Heating of the C60 monolayer between 900 and 1150 K causes the carbon AES peak shape to change and the ratio of the carbon peak height to the silicon peak height to increase, indicating a change in the structure of the film. The lower bound for the strength of the C60 to Si(100)-(2 X 1) bond is estimated to be 56 kcal/mol and the C60 molecule dissociates before this bond is thermally activated. This result offers an explanation of the recent enhanced nucleation of diamond by C60 and C70 on Si(100).