Regensburg 2004 – wissenschaftliches Programm

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HL: Halbleiterphysik

HL 51: Si/Ge

HL 51.1: Vortrag

Freitag, 12. März 2004, 11:30–11:45, H17

Selective wet chemical etching of Ge islands grown on Si(001) — •Georgios Katsaros, Carlos Manzano, Giovanni Costantini, Alexander Bittner, Ulrich Denker, Mathieu Stoffel, Oliver Schmidt, and Klaus Kern — Max Planck Institut für Festkörperforschung, Heisenbergstr. 1, D-70569 Stuttgart, Germany

Although Ge quantum dots on Si(001) have been thoroughly studied, relatively little is known about their composition which, on the other hand, is a very important factor in determining their optical and electronic properties. We tackle this problem by means of selective chemical etching in which Ge is removed preferentially over Si (or vice versa). By quantitatively knowing the selectivity of the etchant, the atomic force microscopy images of the structures that remain after the etching of a quantum dot sample can be interpreted in terms of a spatially resolved map of the quantum dot composition. The results obtained by applying this technique to pyramid and dome islands show that the composition of both types of dots is highly anisotropic. This can be ascribed to the kinetic pathway that is responsible for the dot formation, growth and transformation (pyramid-to- dome transition). For every possible application in a device the Ge quantum dots have to be overgrown with Si. By applying selective etching of Si over Ge we were able to remove the Si cap and to get information on the intermixing and the shape changes that take place during capping as well as on the composition of the remaining dots. Finally, using the quantum dots as an etching-resistant No-dqmaskNo-dq we could produce interesting free- standing Ge-rich nanostructures.

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