X-ray study of the ordering phase transition at the Cu3Au (111) surface
Zhu, Xiaomei
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https://hdl.handle.net/2142/23862
Description
Title
X-ray study of the ordering phase transition at the Cu3Au (111) surface
Author(s)
Zhu, Xiaomei
Issue Date
1991
Doctoral Committee Chair(s)
Zabel, Hartmut
Department of Study
Physics
Discipline
Physics
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
x-ray study
ordering phase transition
glancing incidence x-ray scattering
surface behavior
Language
en
Abstract
We have studied the phase transition at the (111) surface of Cu3Au by glancing incidence
x-ray scattering. The experiment was designed to approach the general question of surface
behavior near a bulk first order phase transition. We have studied three aspects of the phase
transition: the surface order parameters, the order parameter fluctuations and the ordering
kinetics.
We found that close to the transition temperature, the surface ordering is inhomogeneous.
Small clusters coexist with large ordered antiphase domains in the surface region. The
number of the clusters increases with increasing temperature. These small clusters can be
either disordered clusters or small antiphase domains. We suggest that the formation of
small clusters is related to the heterophase fluctuations.
The surface order parameter measurement has two possible explanations. The first possibility
is that the surface order parameters approach zero continuously with temperature.
The second possibility is that the surface order parameters have a finite jump at the transition
point, while the number of small clusters increases with temperature so that the total
surface area which are not occupied by the clusters approach zero continuously.
The ordering kinetics at the surface has some of the same feature as the bulk. After the
sample is quenched, small ordered domains nucleate at the surface. However, the coarsening
of antiphase domains originates only deep in the bulk and propagates to the surface.
We suggest that the phase transition at the (111) surface of Cu3Au IS a first order
transition with strong heterophase fluctuations.
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