Layer by Layer behavior of C60 during growth and sputter erosion

FERRON J.

Playa del Carmen

Workshop; VIII Taller de Colisiones Inelásticas en la Materia; 2016

ICF-UNAM

In this work we combine Auger Electron Spectroscopy (AES), Energy LossSpectroscopy (ELS), Monte Carlo and Molecular Dynamics, to study the growth,and thermally and ion sputter induced desorption of C60 over differentsubstrates, namely Cu(111), Si(100) and graphene. The ability of AES, ascompared to more local probes, to follow the process in a dynamical way, allowsus to study the growth of C60 below and over one ML, including thechange of C60 growing over either Si or Cu to the growth over a C60film. In the same way, we can follow the C60 desorption by heatingthe sample and under ion (He and Ar) bombardment. We found that the growth proceeds always as layer by layer. This resultshows that differences in diffusion barriers are not as important as one canthink following the idea of diffusion by a jumping mechanism. We propose thatthe sticking coefficient, governed by the adsorption energy, is the responsibleof the differences observed between Cu and Si. Our results also point out to adifferent charge transfer among fullerene molecules and these surfaces.The sputtering experiments show, in a quite surprising way, that the erosionof C60 proceeds also in a LbL way. Although one is immediatelytempted to think in a thermal process, through MD we found that it isdetermined by the back sputtering of substrate atoms.