2006 APS March Meeting
Monday–Friday, March 13–17, 2006;
Baltimore, MD
Session G37: Focus Session: Nanoscale Materials Physics of Phase Transitions I
8:00 AM–11:00 AM,
Tuesday, March 14, 2006
Baltimore Convention Center
Room: 340
Sponsoring
Unit:
DMP
Chair: Richard Haglund, Vanderbilt University
Abstract ID: BAPS.2006.MAR.G37.4
Abstract: G37.00004 : Phase transitions in ferroelectric superlattices
8:36 AM–9:12 AM
Preview Abstract
Abstract
Author:
Matthew Dawber
(DPMC, University of Geneva)
The construction of artificial ferroelectric superlattices with fine
periodicity presents exciting possibilities for the development of new
materials with extraordinary properties and furthermore a probe for
understanding the fundamental physics of ferroelectric materials.
Our superlattices of PbTiO$_{3}$/SrTiO$_{3}$ are prepared on conducting
0.5{\%} Nb doped (001) SrTiO$_{3}$ substrates using off-axis RF magnetron
sputtering. Cross-sectional TEM investigations were performed on several
samples and reveal the coherent growth and artificial layering of the
samples.
Further structural characterization using standard $\theta $-2$\theta $
x-ray diffraction was performed on a series of 20 bilayer superlattices in
which the PbTiO$_{3}$ thickness was varied from 54 to 1 unit cells while the
SrTiO$_{3 }$layer thickness was maintained at 3 unit cells. Intuitively one
expects, as the thickness of the PbTiO$_{3}$ layers relative to the
SrTiO$_{3}$ layers is reduced, a decrease of the ferroelectric polarization
which should result in a concomitant decrease of the average lattice
parameter. This is indeed the behaviour we observe for superlattices
PbTiO$_{3}$/SrTiO$_{3}$ n/3 where n is greater than 3. However,
surprisingly, the 2/3 and 1/3 superlattices display larger average lattice
parameters which indicate a recovery of ferroelectricity at very small
PbTiO$_{3}$ layer thicknesses, a finding we confirmed using atomic force
microscopy.
The experimental finding thus stands in stark contrast to the intuitive
expectation of a ferroelectric-paraelectric phase transition in this system
as the ferroelectric component is reduced and we find further that the
temperature of the ferroelectric-paraelectric phase transition is also
greatly modified.
Due to the excellent quality of the samples we are able to present the
results of a number of detailed structural and electrical characterizations,
along with the development of first principles based theoretical models,
which cast further light on the fascinating phase transition behaviour of
this system. Through this we can gain an insight into how we can understand
and control the behaviour of ferroelectricity as the physical dimensions are
reduced and the relevant boundary conditions are modified.
To cite this abstract, use the following reference: http://meetings.aps.org/link/BAPS.2006.MAR.G37.4