Direct evidence of ${\mathrm{C}}_{60}$ chemical bonding on $\mathrm{Si}\mathrm{}\left(100\right)\mathrm{}$

The deposition of ${\mathrm{C}}_{60}$ on $\mathrm{Si}\mathrm{}\left(100\right):\mathrm{H}2\times 1$ surface was investigated as a function of substrate temperature in the range RT-800 $°\mathrm{C}$ by means of photoemission spectroscopies. In this range, the interaction of ${\mathrm{C}}_{60}$ molecules with both the hydrogenated and the bare $\mathrm{Si}\mathrm{}\left(100\right)2\times 1$ surface could be studied and followed until the temperature was high enough to cause the fragmentation of ${\mathrm{C}}_{60}$ cage and the formation of SiC layers. It is found that the fullerene molecules physisorb on the hydrogenated surface but form a covalent bond on the clean surface. The transition from physisorption to chemisorption entails the appearance of a new peak in the ultraviolet photoemission spectroscopy spectra intermediate between that of the HOMO (highest occupied molecular orbital) and HOMO-1 bands.