SURFACE MOBILITY OF C-60 ON SIO2

The interaction of a collisionless beam of thermal C60 nanoclusters wi th a silicon dioxide surface has been investigated with modulated mole cular beam-mass spectroscopic techniques. Analysis of the amplitude an d phase lag of the desorbed C60 shows the interaction mechanism to inv olve the elementary steps of sticking, desorption, and long-range surf ace diffusion. Surface diffusion coefficients determined in this measu rement indicate that surface C60 nanoclusters approach two-dimensional gas-like behavior. The sticking probability of C60 clusters on SiO2 i s determined to be unity. The best fit desorption rate constant k(d) f or C60 from SiO2 is 5 x 10(10) exp(-23 kcal/mol/RT) in agreement with previous temperature programmed desorption experiments. The efficienci es of electron impact ionization of C60 to C60+ and C60++ is measured for electron energies from 10 to 105 eV for neutrals at 875 K.