Regensburg 2007 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 17: Poster Session I (Nanostructures at Surfaces; Metal Substrates: Epitaxy and Growth; Methods: Scanning Probe Techniques; Phase Transitions)
O 17.64: Poster
Montag, 26. März 2007, 17:30–20:30, Poster C
Homoepitaxy under the influence of step edge barriers in the presence of screw dislocations — •Oliver Ricken1, Alex Redinger1, Joachim Krug2, and Thomas Michely1 — 1II. Physikalisches Institut, Universität zu Köln — 2Institut für Theoretische Physik, Universität zu Köln
The presence of screw dislocations solves the nucleation problem in crystal growth and allows growth even for supersaturation too small for nucleation. Growth spirals are also frequently observed in thin film deposition. In classical models for spiral growth a fixed slope of the resulting cone is predicted. Motivated by the observation of growth spirals in organic thin film growth with shapes similar to those of mounds in homoepitaxy with step edge barriers, we performed a set of model experiments. The growth of Pt on Pt(111) is studied by STM after creation of screw dislocations on the surface in a temperature range from 250 K to 450 K. The screw dislocations are produced by the mechanism of “dislocation loop punching” through He+ bombardment. Growth spirals and normal mounds are observed after deposition and can be directly compared in the STM images. Both mound types show the typical 3D-growth mound forms with a plateau on top and deep crevices between them. However, growth spirals show much smaller plateaus and average base areas than normal mounds, but are, on average, taller. The smaller plateaus of growth spirals compared to mounds result, because the dislocation obviates the nucleation problem on the top terrace, which is analogous to an increase in the effective step edge barrier energy.