Strain relaxation mechanism of semiconductor thin films
Kim, Chinkyo
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https://hdl.handle.net/2142/30821
Description
Title
Strain relaxation mechanism of semiconductor thin films
Author(s)
Kim, Chinkyo
Issue Date
1998
Director of Research (if dissertation) or Advisor (if thesis)
Robinson, Ian K.
Department of Study
Physics
Discipline
Physics
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
x-ray diffraction (XRD)
synchrotron radiation x-ray diffraction
Strain
crystals
crystal surface reconstruction
strain relaxation of crystalline materials
Language
en
Abstract
For the atoms at clean surface of crystal, the atomic bonding environment is
very different from that of deep inside bulk crystal. This fact forces those atoms to
rearrange themselves in such a way that reconstruction occurs with the total energy
being minimized. Reconstruction also takes place when foreign atoms are deposited
on a clean surface. This strain experienced by individual atoms will propagate into
a bulk crystal down to a few layers, sometimes even to several layers. Using x-ray
diffraction, the positions as well as thermal vibrational amplitudes of these strained
atoms can be determined. In the first part of this thesis, we present the surface
reconstruction and a strain analysis of Sb/Si(ll1) using synchrotron radiation x-ray
diffraction.
Another case when we can observe macroscopic strain is heteroepitaxial film
growth. Even though there is lattice mismatch between substrate and film, pseudomorphic
film growth is usually possible at the initial stage of growth, so the film is
grown under strain. However, it becomes energetically favorable to introduce misfit
dislocations above a certain thickness of film growth, which is called a critical thickness.
In this case, strain is considered in the continuum elastic sense, defined by the
lattice constant of the material. From measurement of the positions of multiple Bragg
reflections, accurate values of lattice constant can be obtained using x-ray diffraction
as a function of film thickness and a critical thickness can be determined. The second
part of the thesis is a study of III-nitride thin films grown on sapphire (0001)
substrate with molecular beam epitaxy. Irradiation experiments were also performed to investigate whether strain relaxation takes place in SiGe films and GaN films to
look for indications of metastability.
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