Atomic ordering dependence on growth method in Ge:Si(001) islands: Influence of surface kinetic and thermodynamic interdiffusion mechanisms

A. Malachias, M. Stoffel, M. Schmidbauer, T. Ü. Schulli, G. Medeiros-Ribeiro, O. G. Schmidt, Rogerio Magalhães-Paniago, and T. H. Metzger

Phys. Rev. B 82, 035307 – Published 15 July 2010

Abstract

Interdiffusion in self-assembled Ge:Si(001) islands has been explained by models based on either thermodynamic and/or surface kinetic considerations. In order to analyze the relevance of bulk and surface diffusion on the final composition state, we performed a set of controlled x-ray diffraction experiments to study both composition and atomic ordering in Ge/Si(001) islands grown by different methods. Surface diffusion strongly enhances the overall interdiffusion during island growth by solid source molecular beam epitaxy while chemical-vapor-deposited islands are closer to thermodynamic model systems. The growth conditions play a crucial role on the appearance of atomic ordering. In particular, a remarkable correlation between atomic ordering and surface diffusion kinetics is found.

Received 15 April 2010

DOI:https://doi.org/10.1103/PhysRevB.82.035307

Authors & Affiliations

A. Malachias^1,*, M. Stoffel^2,3, M. Schmidbauer⁴, T. Ü. Schulli⁵, G. Medeiros-Ribeiro⁶, O. G. Schmidt³, Rogerio Magalhães-Paniago⁷, and T. H. Metzger^5,8

¹Laboratório Nacional de Luz Síncrotron, CP 6192, CEP 13083-970, Campinas, Brazil
²Institut Jean Lamour, UMR CNRS 7198, Nancy-Université, BP 239, F-54506 Vandœuvre-lès-Nancy, France
³Institute for Integrative Nanosciences, IFW Dresden, Helmholtzstr. 20, 01069 Dresden, Germany
⁴Leibniz Institut für Kristallzüchtung, Max-Born-Str. 2, D-12489 Berlin, Germany
⁵European Synchrotron Research Facility, BP 220, Grenoble, France
⁶Hewlett-Packard Laboratories, Palo Alto, California 94304, USA
⁷Departamento de Física, Universidade Federal de Minas Gerais, CP 702, 30123-970 Belo Horizonte, MG, Brazil
⁸Department of Biomaterials, Max Planck Institute of Colloids and Interfaces, 14424 Potsdam, Germany

^*Present address: Laboratório Nacional de Luz Síncrotron C.P. 6192–Campinas, Brazil; amalachias@lnls.br

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Vol. 82, Iss. 3 — 15 July 2010

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Images

Figure 1
(Color online) (a) Longitudinal $(θ − 2 θ)$ scans in the vicinity of the Si(400) reflection for sample MBE-b at two energies: $11 103 eV$ (Ge $K$ edge) and $11 040 eV$ . (b) The solid line represents the vertical Ge concentration profile obtained from (a) as a function of the local in-plane lattice parameter (Ref. 14). The dots represent laterally averaged local compositions from the analysis of transversal scans. (c) Selected transversal $(θ)$ scans performed at the positions labeled 1, 2, and 3 in (a). The open dots are measured data while the solid lines are fits with a lateral composition model (Ref. 24). (d) Lateral composition profiles used for fitting transversal scans in (c). (e) Local lattice parameter map for MBE-b islands (Ref. 14). (f) Lateral concentration profile map for MBE-b islands.Reuse & Permissions
Figure 2
(Color online) (a) Vertical (solid line) and laterally averaged (dots) Ge concentration profiles extracted from anomalous diffraction measurements on LPE islands. The concentration profiles are graphically represented as a function of height in (b) vertical only and (c) lateral. (d) Ge Vertical and laterally averaged concentration profiles for CVD islands (Ref. 24). These profiles are represented as a function of island height in (e) and (f), respectively.Reuse & Permissions
Figure 3
(Color online) Representation of Ge vertical concentration profiles for islands of samples (a) MBE-a, (b) MBE-c, and (c) MBE-d. The ratio between integrated Ge volume fraction and nominal Ge concentration inside the islands studied in this work is shown in (d). The line plotted across solid dots for MBE islands is a guide to the eyes. An Arrhenius plot for Si volume inside the MBE samples is seen in (e).Reuse & Permissions
Figure 4
(Color online) Reciprocal space maps of (400) [(a)–(c)] and (200) reflections [(d)–(f)] for [(a) and (d)] LPE, [(b) and (e)] CVD, and [(c) and (f)] MBE-b samples. The vertical H axis of (d) and (e) are equivalent. Intensity color scales in the (400) maps were normalized to the unit—taken at the island peak position—and to the intensity ratio relative to such maximum at the (200) maps.Reuse & Permissions
Figure 5
(Color online) (a) Transversal scans at $H = 3.95$ and $H = 1.975$ for the (400) and (200) reciprocal space maps, respectively, measured for the CVD sample. (b) Bragg-Williams order parameter $S$ as a function of the normalized height for LPE and CVD islands. (c) Values of $S$ for all MBE samples measured in this work.Reuse & Permissions
Figure 6
(Color online) (a) Representation of Bragg-Williams order parameter $S$ and the $S / S_{max}$ ratio (see text) for LPE and CVD islands. The color scale for these maps is the same for both samples. (b) Maps of $S$ and $S / S_{max}$ for all MBE islands. The color scales for these four samples are shown in the bottom of the figure.Reuse & Permissions

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