Quantifying electron transfer during hyperthermal scattering of C+60 from Au(111) and n-alkylthiol self-assembled monolayers

摘要

A tandem time-of-flight mass spectrometer with an intermediate surface was used to quantify electron transfer during glancing incidence scattering of hyperthermal C-60(+) (E-coll=250-500 eV, theta(in)=75 degrees) from (i) self-assembled monolayers of n-alkylthiols on gold (of various chain lengths), (ii) partly fluorinated alkylthiols on gold, as well as (iii) clean gold surfaces. Self-assembled monolayers (SAMs) behave as insulating layers with their thicknesses determining the electron tunneling probability during collision. Correspondingly, a roughly exponential dependence of the neutralization probability on the chain length n was found. A pronounced dependence of the neutral yield on the primary beam kinetic energy indicates that dynamic SAM deformation and associated projectile penetration depth also play a role in determining electron transfer efficiency. Results are consistent with the molecular deformability of SAMs as determined with other experimental methods.