book of abstracts - IM2NP

A B S T R A C T S TUESDAY, JUNE 29 N A N O S E A 2 0 1 0
3 – Conclusion
The nucleation process of SiGe self-assembled islands epitaxially grown on Si substrate by Surface Thermal
Diffusion has been experimentally studied. The method allowed to investigate the growth process over a
wide range of Ge coverages at the same time. From the evolution of size and density exhibited by the
nucleated islands as a function of the Ge coverage, we propose a model where the surface diffusion on the
long scale is kinematically limited, while the SiGe islands grow reaching a quasi-equilibrium state depending
on the local final conditions.
4 – Bibliography
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[3] G. Medeiros-Ribeiro et al., Science 279, 353 (1998).
[4] H. J. Kim et al., J. Appl. Phys. 95, 6065 (2004).
[5] A. Rastelli et al., Nano Lett. 8, 1404 (2008).
[6] T.U.Schülli et al.,APL 89, 143114 (2006); M. Brehm et al., Appl. Phys. Lett. 93, 121901 (2008)
[7] Y. Tu and J. Tersoff, Phys. Rev. Lett. 98, 096103 (2007).
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9H30-9H50
Exploiting the interface between randomly nucleated and ordered dots for
unrolling SiGe/Si dot properties on a micrometer scale.
M. Grydlik, M. Brehm, F. Hackl, F. Schäffler, T. Fromherz, and G. Bauer (Institute of
Semiconductor and Solid State Physics, Johannes Kepler University, Linz) martyna.grydlik@jku.at
1 – Introduction
Ordering of quantum dots in pre-defined positions is supposed to fulfill necessity of their addressability. In
the last years this ordering became feasible in several semiconductor hetero-systems like InAs on GaAs(001)
and SiGe on Si(001). For the understanding of basic growth phenomena of such dots and, even more
important, for many applications, fields with small pit-periods (40 nm – 300 nm) are produced, e.g. by means
of electron beam, focused ion beam or interference lithography, offering only limited test areas of pitpatterned
substrate.
2 – Abstract
In this work we demonstrate for the representative SiGe hetero-system that the border of such fields can
influence the quantum dots growth inside the pit-patterned field over a lateral distance up to 50 µm inside the
field. The pits act as favorite nucleation sites for islanding and therefore act as material sink for the Ge that is
deposited outside of the field. This strong lateral surface diffusion effect can be exploited in order to unroll
the evolution of quantum dots growth on pit-patterned substrates within these 50 µm. The middle of the field
represents the Ge lean environment while the border represents a situation where a larger amount of Ge is
available per pit, i.e., the dots at the border become larger than the ones in the middle.
We studied the evolution of dot-shapes and Ge concentrations via atomic force microscopy (AFM) and µ-
photoluminescence (PL) measurements. From the shift of the PL originating from dots with different shape,
Ge concentrations of the dots can be extracted. From AFM measurements of the dot volumes we evaluated
material capture rates for different dot types.
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