Regensburg 2007 – scientific programme

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DY: Fachverband Dynamik und Statistische Physik

DY 10: Growth processes and surface properties

DY 10.2: Talk

Monday, March 26, 2007, 16:45–17:00, H5

Relevance of surface viscous flow, surface diffusion and ballistic effects in keV ion smoothing of amorphous surfaces — •Sebastian Vauth and S. G. Mayr — I. Physikalisches Institut, Georg-August-Universität Göttingen, Friedrich-Hund-Platz 1, 37077 Göttingen, Germany

Amorphous metal or semiconductor thin films often show a dramatic smoothing reaction, when appropriately bombarded with keV heavy ions. Surface diffusion, surface viscous flow and ballistic effects have been suggested as possible candidates for the dominant atomic-scale smoothing mechanism. In the present study we compare the relative relevance of these processes by employing multiscale modeling, viz. a combination of molecular dynamics (MD) and continuum rate equations. This is achieved by deriving continuum expressions for a coarse-grained picture and calculating the corresponding coefficients from MD simulations. For this purpose diffusion constants, viscosities and lateral transport due to momentum transfer are evaluated. We observe the dominance of surface viscous flow over surface diffusion for any surface morphology while ballistic smoothing dominates for structures above a certain size threshold. These results are found to be valid for both, strong and fragile glasses, as represented by amorphous Si and CuTi.

This work is financially supported by the DFG Sonderforschungsbereich 602, TP B3.