Interdiffusion Processes in Self-Organization of Quantum Dot Nanostructures: Raman Scattering and AFM-Investigtion

Mykhailo Valakh 

Institute of Semiconductor Physics NAS Ukraine, Kyiv, Ukraine

Abstract

It is intended to discuss in this report the results obtained by author and his colleagues for different types of semiconductor nanostructures (Ge/Si, II-VI, III-V) by means of Raman Scattering accompanied by AFM, PL and High-Resolution X-Ray Diffraction. The possible  deviation of the observed growth mechanism from a classical Stranski-Krastnov model will be discussed. This deviation was established to be due to the effect of the giant atomic interdiffusion. It is related not only to the anomalously strong surface diffusion of atoms, but is also stimulated by the large strain gradients in QDs and adjacent regions. The interdiffusion changes the growth kinetics and shape of the QDs.

The peculiarities of the interdiffusion in colloidal core-shell QDs are discussed for different combinations of core and shell materials (Egcore< Egshell and vice versa).

At last, the problem of the spatial lateral ordering of the QDs in multilayer structures is discussed.  By the example of InGaAs/GaAs heterosystem it is shown that the very important condition for lateral ordering is the anisotropy of strain fields in the GaAs buffer layers. In multilayer structures a stepwise (from lower to higher layers) enhancement of the strain anisotropy takes place. This results in the anisotropic surface atomic migration and the formation of laterally ordered island chains or even quantum wires. It is important for application that both dots and wires have high size homogeneity.

 

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Presentation: Invited oral at E-MRS Fall Meeting 2008, Symposium J, by Mykhailo Valakh
See On-line Journal of E-MRS Fall Meeting 2008

Submitted: 2008-05-05 14:30
Revised:   2009-06-07 00:48