The doctoral dissertations of the former Helsinki University of Technology (TKK) and Aalto University Schools of Technology (CHEM, ELEC, ENG, SCI) published in electronic format are available in the electronic publications archive of Aalto University - Aaltodoc.
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Monte Carlo Simulations in the Study of Semiconductor Surfaces

Laura Juvonen

Dissertation for the degree of Doctor of Science in Technology to be presented with due permission of the Department of Electrical and Communications Engineering for public examination and debate in Auditorium S1 at Helsinki University of Technology (Espoo, Finland) on the 4th of June, 2004, at 12 o'clock noon.

Overview in PDF format (ISBN 951-22-7128-1)   [1742 KB]
Dissertation is also available in print (ISBN 951-22-7127-3)

Abstract

In this thesis, the Monte Carlo method is applied for the study of semiconductor surfaces. The focus is in the investigation of structural properties of epitaxially grown thin films on the Si(001) surface. Semiconductor surfaces are typically characterized by complicated energy landscapes, and the properties of these systems are often strongly influenced by long-range elastic effects. The Monte Carlo method is an attractive choice for large-scale relaxational problems because it is not bound to the true dynamical evolution of the system. This freedom can be utilized in designing new advanced algorithms which can significantly speed up the equilibration process. When combined with the computational efficiency of classical potentials, this approach can be used to reach even experimentally accessible time and length scales.

In this work, different silicon potentials are tested to evaluate their ability to describe the properties of Si(001), including the surface reconstruction and various defect structures. Significant differences are found in the performance of the tested models. Some of the potentials are poorly suited for finite-temperature surface simulations, while the Stillinger-Weber (SW) potential gives a fairly accurate overall description of Si(001).

The SW model is applied to study the effects of lattice-mismatch induced strain in the heteroepitaxial growth of Ge on Si(001). The surface undergoes a structural evolution in which the morphological changes are driven by a complex interplay between different temperature-dependent strain-relief mechanisms. The simulations provide a good overall explanation for experimental observations.

A new hybrid Monte Carlo – Molecular Dynamics algorithm is introduced for the study of relaxational problems involving large-scale configurational rearrangement. It is designed to circumvent the problem of getting trapped into deep metastable states in systems with complicated energy landscapes. The algorithm is used here to study islands and vacancy structures on the Si(001) surface, but in general, the same approach could be applied to study other semiconductor surfaces as well.

This thesis consists of an overview and of the following 8 publications:

  1. Kuronen A., Nurminen L. and Kaski K., 2000. Computer simulation of nucleation on patterned surfaces. In: Merhari L., Wille L. T., Gonsalves K., Gyure M. F., Matsui S. and Whitman L. J. (editors), Materials Issues and Modeling for Device Nanofabrication. Materials Research Society Symposium Proceedings, volume 584, pages 239-244. © 2000 Materials Research Society. By permission.
  2. Nurminen L., Kuronen A. and Kaski K., 2001. Kinetic Monte Carlo simulation of nucleation on patterned substrates. Physical Review B 63, pages 035407 : 1-7. © 2001 American Physical Society. By permission.
  3. Nurminen L., Kuronen A. and Kaski K., 2001. Simulation of the early stages of growth on a patterned substrate. In: Landau D. P., Lewis S. P. and Shuttler H.-B. (editors), Computer Simulation Studies in Condensed Matter Physics XIV, pages 62-66. © 2001 Springer-Verlag. By permission.
  4. Nurminen L., Tavazza F., Landau D. P., Kuronen A. and Kaski K., 2002. Monte Carlo simulation of the surface structure of Ge on Si(001). In: Landau D. P., Lewis S. P. and Shuttler H.-B. (editors), Computer Simulation Studies in Condensed Matter Physics XV, pages 142-146. © 2002 Springer-Verlag. By permission.
  5. Nurminen L., Tavazza F., Landau D. P., Kuronen A. and Kaski K., 2003. Comparative study of Si(001) surface structure and interatomic potentials in finite-temperature simulations. Physical Review B 67, pages 035405 : 1-10. © 2003 American Physical Society. By permission.
  6. Nurminen L., Tavazza F., Landau D. P., Kuronen A. and Kaski K., 2003. Reconstruction and intermixing in thin Ge layers on Si(001). Physical Review B 68, pages 085326 : 1-10. © 2003 American Physical Society. By permission.
  7. Nurminen L., Tavazza F., Landau D. P., Kuronen A. and Kaski K., Simulation of islands and vacancy structures for Si/Ge-covered Si(001) using a hybrid MC-MD algorithm. In: Landau D. P., Lewis S. P. and Shuttler H.-B. (editors), Computer Simulation Studies in Condensed Matter Physics XVII, in press. © 2004 by authors and © 2004 Springer-Verlag. By permission.
  8. Tavazza F., Nurminen L., Landau D. P., Kuronen A. and Kaski K., A new hybrid MC-MD algorithm for the study of islands and step-edges on semiconductor surfaces: application to Si/Si(001). Physical Review E, accepted for publication. © 2004 by authors and © 2004 American Physical Society. By permission.

Keywords: Monte Carlo, computer simulations, semiconductors, surfaces, thin layers, epitaxy, silicon, germanium, classical potentials

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© 2004 Helsinki University of Technology

Last update 2011-05-26