Berlin 2005 – wissenschaftliches Programm
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O: Oberflächenphysik
O 32: Nanostrukturen III
O 32.3: Vortrag
Montag, 7. März 2005, 11:15–11:30, TU EB202
Field controlled growth of nanoscale adsorbate layers — •Carsten Nowak1, Guido Schmitz2 und Reiner Kirchheim1 — 1Institut für Materialphysik, Friedrich-Hund-Platz 1, D-37077 Göttingen — 2Institut für Materialphysik, Wilhelm-Klemm-Str. 10, D-48149 Münster
In the presence of strong electrostatic fields at the apex of needle-shaped substrates the formation of amorphous layers with a field-dependent stationary profile can be observed. We attribute this to the attraction of residual gas molecules to the tip due to polarisation.
For a quantitative evaluation we derived a local polarisation potential, describing the polarisation interaction between an uncharged molecule and the tip.
Comparison with the experiment reveals that the shape of the deposited amorphous layers corresponds to equipotential surfaces of the polarisation potential. The formation of a stationary profile, corresponding to a certain tip voltage, can be explained by the transition of the residual gas molecules from the physisorbed to the chemisorbed state and therefore by the necessity to overcome the activation energy of chemisorption.
As this process is restricted to regions of strongest curvature, probably this mechanism can be made responsible also for the growth of nanowires by deposition of molecular gases that has been reported recently [1].
[1] S.-W. Cheng and H.-F. Cheung. Role of electric field on formation of silicon nanowires. J. Appl. Phys., 94(2):1190, 2003.