The Use of Synchrotron Radiation to study Overgrowth Phenomena in InAs/GaAs Nanostructures
type: CreativeWork
description: This work focuses on the investigation of overgrowth phenomena in InAs/GaAs nanostructures using synchrotron radiation. Surface-sensitive grazing incidence small angle x-ray scattering (GISAXS) and grazing incidence diffraction (GID) are applied to study shape, strain, and interdiffusion in self-organised grown nanostructures. The technique of anomalous x-ray diffraction at the weak (200) superstructure reflection enhances the chemical sensitivity of the measurements. For the investigation of (partially) buried nanostructures finite-element simulations (FEM) have been performed. The following sample systems were investigated: ((1)) Free-standing and buried InGaAs quantum dots: Free-standing In(x)Ga(1-x)As islands grown on GaAs (001) by molecular beam epitaxy (MBE) with a nominal concentration of x=0.5 have been investigated. Contrast variation close to the K edge of As by anomalous GID at the (200) superstructure reflection is used for a direct determination of the InAs concentration as a function of the lateral strain in the quantum dots (QDs). The evaluation of intensity mappings recorded in reciprocal space close to the (200) reflection together with atomic force micrographs (AFM) allows to attribute the strain and the InAs concentration to a certain height in the quantum dots. Thereby, a three-dimensional model of the strain and interdiffusion profile of the InGaAs QDs can be reconstructed. A discussion of measurements taken on buried InGaAs QDs and free-standing islands grown on the strain modulated surface of a buried QD layer shows the limits of this technique. ((2)) InGaAs quantum rings: The formation of nanoscopic InGaAs ring structures on a GaAs (001) substrate takes place when InAs quantum dots, grown by Stranski-Krastanov self-organisation, are covered by a thin layer of GaAs. The shape transformation into rings is governed by strain, diffusion and surface tension, quantities which are of importance to understand magneto-optical and electronic applicatio…
abstract: This work focuses on the investigation of overgrowth phenomena in InAs/GaAs nanostructures using synchrotron radiation. Surface-sensitive grazing incidence small angle x-ray scattering (GISAXS) and grazing incidence diffraction (GID) are applied to study shape, strain, and interdiffusion in self-organised grown nanostructures. The technique of anomalous x-ray diffraction at the weak (200) superstructure reflection enhances the chemical sensitivity of the measurements. For the investigation of (partially) buried nanostructures finite-element simulations (FEM) have been performed. The following sample systems were investigated: ((1)) Free-standing and buried InGaAs quantum dots: Free-standing In(x)Ga(1-x)As islands grown on GaAs (001) by molecular beam epitaxy (MBE) with a nominal concentration of x=0.5 have been investigated. Contrast variation close to the K edge of As by anomalous GID at the (200) superstructure reflection is used for a direct determination of the InAs concentration as a function of the lateral strain in the quantum dots (QDs). The evaluation of intensity mappings recorded in reciprocal space close to the (200) reflection together with atomic force micrographs (AFM) allows to attribute the strain and the InAs concentration to a certain height in the quantum dots. Thereby, a three-dimensional model of the strain and interdiffusion profile of the InGaAs QDs can be reconstructed. A discussion of measurements taken on buried InGaAs QDs and free-standing islands grown on the strain modulated surface of a buried QD layer shows the limits of this technique. ((2)) InGaAs quantum rings: The formation of nanoscopic InGaAs ring structures on a GaAs (001) substrate takes place when InAs quantum dots, grown by Stranski-Krastanov self-organisation, are covered by a thin layer of GaAs. The shape transformation into rings is governed by strain, diffusion and surface tension, quantities which are of importance to understand magneto-optical and electronic applicatio…
author: Sztucki, Michael
date published: 2004-06-24
date modified: 2026-07-24T02:51:58Z
provider: Ludwig Maxmilians Universität München
publisher: Networked Digital Library of Theses and Dissertations
type: WebPage
source organization: Ludwig-Maximilians-Universität