Regensburg 2000 – wissenschaftliches Programm

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O: Oberflächenphysik

O 8: Epitaxie und Wachstum (II)

O 8.11: Vortrag

Montag, 27. März 2000, 18:45–19:00, H36

Scaling Behavior in Spiral Growth of PbTe (111) under Conditions far from Thermodynamic Equilibrium — •K. Wiesauer and G. Springholz — Institut fuer Halbeiterphysik, Johannes Kepler Universitaet, A-4040 Linz

Spiral growth of bulk single crystals grown from the melt or from vapor phase under conditions close to thermodynamic equilibrium, mediated by the existence of threading dislocations is a well known phenomenon. It is described by the Burton-Cabrera-Frank (BCF) growth theory, predicting the shapes and step spacings within the growth spirals on the surface in terms of the supersaturation of the growth system. On the contrary, growth of epitaxial thin film systems by methods such as molecular beam epitaxy is carried out far from thermodynamic equilibrium due to negligible reevaporation of atomic species from the solid surface, i.e., at extremely high supersaturations. Several experimental studies of a large variety of different materials systems have shown that growth spirals may be formed under such conditions as well. In the present work, we have studied in detail the formation of growth spirals for PbTe (111) molecular beam epitaxy for a wide range of growth conditions. It is shown that the step spacing within the growth spirals follows a completely different scaling behavior as compared to the BCF theory, and a scaling exponent of 1/3 is obtained for growth rate variations by almost 3 orders of magnitude. In addition, a dramatic influence of the beam flux composition on the spiral step spacing is found. This is effect is discussed in terms of changes in the surface kinetics.