CHARGE-TRANSFER OF C-60 ON CU(111) MEASURED USING AN STM HREELS SYSTEM/

Using Scanning Tunneling Microscopy (STM) to monitor the surface morph ology and High Resolution Electron Energy Loss Spectrometry (HREELS) t o measure the vibrational spectrum, we have systematically investigate d the relationship between the surface morphology and charge transfer from Cu(lll) to C-60. Since at 300 K, C-60 is mobile on the Cu(lll) te rrace, but is more strongly bound at the step edge, any C-60 which ads orbs on the terrace will migrate to the step edge where it is immobili zed. Because of this, at very low coverages, the C-60 preferentially a dsorbs at the step edge. The amount of charge transfer from the substr ate to the C-60 can be determined by measuring the amount of frequency shift of the T-1u (IR active) modes. For C-60 adsorbed on the terrace , we determined a transfer of approximately 1.6 electrons/C-60 molecul e. No additional frequency shift of the vibrational modes was seen for C-60 adsorbed at the step edge, indicating that any additional charge transfer at the step edge is small-less than one electron/C-60 molecu le.