Ferroelectric nanomaterials for electronic technique

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Ferroelectric nanomaterials for electronic
technique
M. D. Glinchuk Institute for Problems of
Materials Science National Academy of Sciences of
Ukraine Kiev, Ukraine E-mail glin_at_ipms.kiev.ua
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I. Main fields of ferroelectric materials
application in electronic technique

• capacitors
• piezoelectric devices (ultrasound sources,
  resonators, filters, phones, microphones,
  piezotransformators etc.)
• radiolocation and communication systems (the
  devices on surface acoustic waves, waveguides,
  coders and decoders etc.)
• devices for night vision, high harmonic
  generation
• systems for recording and reading of information
• piezoelectric devices, heat-visioners for
  medicine and biology
• posistors for the systems of thermal regime
  control

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II. Anomalous properties near the phase
transitions as the basis for applications
Giant dielectric permittivity of relaxor
ferroelectric (Pb,La)TiO3 B.-G. Kim et al.,
Phys. Rev. Lett. 86, 3404 (2001)
Temperature dependence of electrical resistance
of (Ba,Sr)TiO3Y3Nb5 ceramics Z. He et al.,
J. Phys.Cond. Matter 16, 6961 (2004)
Shortcomings of bulk ferroelectrics strong
dependence of the properties on temperature and
scattering of phase transition temperatures while
for application we mostly need room temperature
the necessity for integration with semiconductors
and metals the demands for the devices
miniaturization the materials, energy and money
savings. All these shortcomings can be overcome
in the nanomaterials.
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III. Size effects of ferroelectric nanomaterials
properties
Size dependence of the transition temperature
from ferroelectric (FE) to paraelectric (PE) phase
Dependence of dielectric permittivity on
nanoparticles mean sizes
Glinchuk M.D., Eliseev E.A., Stephanovich V.A.,
J. Appl. Phys., 93(2), 1150 (2003) Physica B,
332, 356 (2002) Glinchuk M.D., Morozovska A.N.,
Phys. Stat. Sol., 238, 81 (2003)
Powder PbTiO3
Powder PbTiO3
E. Erdem et al., J. Phys. Condens. Matter 18,
3861 (2006)
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III. Size effects of ferroelectric nanomaterials
properties
The physical background of the properties size
effects, including size-driven ferroelectricparae
lectric phase transition is the influence of
surface which can not be neglected at nanosizes.
The main peculiarities is the appearance of the
properties gradients and so their inhomogeneity,
the influence of mechanical conditions on the
surface (confinement conditions) and the
essential contribution of depolarization field.
As the result the new properties absent in bulk
materials appear in ferroelectric nanos. In what
follows I will demonstrate some of the new
properties.
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IV. New phases originated from mechanical
conditions on the surface of ferroelectric thin
films
PbTiO3 film on SrTiO3 substrate
PbTiO3 film on SrTiO3 Nb substrate
The deformation of the film due to mismatch
between the parameters of the film and substrate
Um (b a)/b (a, b are their lattice constants)
and the surface piezoelectric effect induce
built-in electric field. This field lead to
electret state in the thinnest film. With the
thickness increase the self-polarized
ferroelectric phase appears. The phenomenon of
self-polarization is very useful for the films
application e.g. in pyroelectric devices because
it allows to omit the costly process of
polarization by external field. Ferroelectric
phase can be conserved in the thinnest film (up
to monolayer) by special choice of the pair
filmsubstrate.
Glinchuk M.D., Morozovska A.N., Eliseev E.A., J.
Appl. Phys. 99, 114102 (2006) Glinchuk M.D.,
Morozovska A.N., J. Phys. Cond. Matter 16, 3517
(2004) Eliseev E.A., Glinchuk M.D., Phys. Stat.
Sol. (b) 241, R52 (2004) Glinchuk M.D.,
Morozovska A.N., Eliseev E.A., Integrated
Ferroelectrics, 64, 17 (2005)
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V. Conservation and enhancement of ferroelectric
properties in nanotubes and nanowires
Effective piezoresponse of PbZr0.52Ti0.48O3
nanotube (outer diameter 700 nm, thickness of
wall 90 nm, the length about 30 mm) in dependence
on applied voltage. Symbols experimental data
solid line theory.
Scheme of perovskite structure deformation under
external pressure
Pressure on lateral surface of nanowire due to
surface tension enhances the polar properties of
nanos
A.N.Morozovska, E.A.Eliseev and M.D. Glinchuk,
Phys. Rev. B. 73, 214106 (2006)
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V. Conservation and enhancement of ferroelectric
properties in nanotubes and nanowires
Nanorods of Rochel salt (RS) r 30 nm, l 500 nm
Remanent polarization PSV dependence on
temperature and hysteresis loop for RS nanorods
with radius 15 nm. Symbols experimental data
solid lines theory.
D. Yadlovker and S. Berger, Phys. Rev. B 71,
184112 (2005)
A.N.Morozovska, E.A.Eliseev and M.D. Glinchuk,
Phys. Rev. B. 76, 014102 (2007)
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V. Conservation and enhancement of ferroelectric
properties in nanotubes and nanowires
Nanotubes with walls of different thickness
Nanorods
Effective surface tension and decrease of
depolarizaton field on cylindrical surface are
the reasons of ferroelectric properties
enhancement in nanorods and nanotubes of
perovskite (Q12 lt 0) ferroelectrics. This effect
is very useful for development of new
nanomaterials with high polar properties (better
than in bulk).
A.N. Morozovska, E.A Eliseev and M.D. Glinchuk,
Physica B, 387, 358 (2007) Phase Transitions
80, 71 (2007)
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VI. Phase states and giant magnetoelectric effect
induced by surface tension in ferroic
nanoparticles

• Ferroelectric phase has to appear at room
  temperature in nanorods and nanowires with r ? 50
  nm of incipient ferroelectrics, which conserve
  paraelectric phase up to 0 K in bulk. The
  existence of ferroelectric phase at room
  temperature will be useful for development of new
  generation of the devices on the basis of
  nanostructures.
• The ferromagnetic phase observed in spherical
  nanoparticles with radius 730 nm at
  room temperature of nonmagnetic in bulk materials
  CeO2, Al2O3, ZnO, SnO2 etc. (Phys. Rev. B 74,
  161306(R) (2006)) can be induced by surface
  tension that increases inversely proportional to
  the particle radius.
• The giant magnetoelectric coupling which
  increase dielectric tunability about two orders
  of magnitude was predicted in multiferroic
  nanorods due to surface tension influence. The
  phenomenon is very important for application
  because it will allow to write information by
  electric field and read it by magnetic field.

A.N.Morozovska, E.A.Eliseev and M.D. Glinchuk,
Phys. Rev. B 76, 014102 (2007) M.D. Glinchuk,
E.A.Eliseev, A.N.Morozovska and R.Blinc, Phys.
Rev. B 77, 024106 (2008)
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VII. Electronic technique devices for nowadays or
nearest future applications
1. Pyroelectric infrared sensors on the basis of
thin (from tens to hundreds nm) ferroelectric
films PbZr0.5Ti0.5O3 on the SiSiO2 substrates,
which are generating electric current at
temperature changing (e.g. due to infrared
irradiation) are widely used as the detectors
sensing the living organisms presence (frequently
nonwanted), sensing the temperature enhancement
under the fire beginning and producing the alarm
signals they are useful also for medical
examination of humans health. Nowadays there is
multimillion production of pyrosensors and
transducers in Simens, Marconni, Muratta etc. The
important advantage of thin ferroelectric films
is their self-polarization, its nature being
found out by us.
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VII. Electronic technique devices for nowadays or
nearest future applications
2. The ferroelectric devices for an information
recording. The concept of recording is the
polarization PS ? 0 and PS 0 corresponds
respectively to 1 and 0 (binary system), i.e. it
is related to the switching of polarization. The
coercive field in the bulk ferroelectrics is
about several kV/cm, while semiconductor devices
in the integrated scheme are working at a few
V/cm. Because of this it is necessary to use thin
films, where the coercive field is small enough.
In comparison with magnetic films ferroelectric
ones have the advantage of larger memory, of
energy saving, of higher rate of information
exchange e.g. in mobile phones, photocameras,
videocameras etc. In these important consumer
equipment many ferroelectric capacitors are use
to provide the work of the devices on necessary
frequencies. The main problem of
ferroelectric memory is the process of reading
related to depolarization current, that lead to
the film deterioration with time. Contrary in the
magnetic films the information recording process
can destruct the film. Because of this the
scientists and engineers are discussing now the
possibility to use multiferroics, i.e. the
materials with coexistence of ferroelectric and
ferromagnetic order with strong magnetoelectric
coupling, so that an information can be recorded
with the help of electric field and can be read
with the help of magnetic field. It was mentioned
earlier that such possibility can occur in
nanoparticles as our calculations had shown. Many
firms in all the world (Toshiba, Samsung,
Integrated Semiconductors, Matsushita etc.) are
working on the problems related to the production
of improved ferroelectric films for memory
devices.
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VII. Electronic technique devices for nowadays or
nearest future applications
3. Other applications
Nanoparticles and nanocomposites (sphere, tubes,
rods, wires)
Profiled nanostructures (nanodomains,
superlattices)
Nanofilms and their multilayers (epitaxial,
textured, polycrystalline)
Optical generators of higher harmonics,
transducers, frequency converters, parametric
amplifiers. Memory systems of new generation.
Ferroelectric micro- and nanolithography
Applications
Micro- and nano-electromechanical systems. Energy
transducers and accumulators. Long-term memory
elements on the basis of thin films.
Multielemental piezo- and pyrosensors. Optical
devices
Pyroelectric detectors. Three-dimention
architecture of ferroelectric memory. Photon
devices. Electrooptical and nonlinear optical
devices. New generation of printers
Enlargement of sensitivity. High density of
information recording. Improvement of quality
factors, cost decrease
Enlargement of spectral region, controlling of
angular dependence. Increase of recording
density, enhancement of stability. High
decoupling ability
Space-saving, integrability with modern
semiconductor devices, the decrease of
manipulated voltage in 10103 times. High density
of information recording, minor time of access.
Development of ferroelectric nanos with new
properties in comparison with bulk materials
Advantages
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Conclusions

• In the system nanofilmsubstrate the choice of
  substrate can essentially influence the film
  phase diagram and properties, namely
• For compressed films self-polarized
  ferroelectric state can be conserved up to
  several lattice constants thickness.
  Self-polarized films are very useful for the
  development of high-quality pyrosensors and
  modern memory systems.
• For stretched films built-in electric field
  originated from the mechanical stress in the
  system nanofilmsubstrate induces elektret-like
  polar state. Its properties can be useful in
  construction of pyroelectric detectors and
  actuators without hysteresis.
• The possibility to obtain giant dielectric
  permittivity (from 105 to 106) is shown in
  multilayers of thin films relaxor
  ferroelectricparaelectric, which is important
  for development of space-saving capacitors of new
  generation.
• The enhancement of ferroelectric properties in
  the cylindrical nanoparticles (rods, wires,
  tubes) of ferroelectrics with perovskite
  structure arises due to surface tension on the
  lateral surface and to the decrease of
  depolarization field for cylindrical geometry.
  Array of cylindrical nanoparticles can be used
  for the creation of modern memory systems,
  pyroelectric detectors.
• It was shown for the first time that surface
  tension which increase at nanoparticle radius
  decrease can lead to the appearance of
  ferroelectric or/and magnetic state with giant
  magnetoelectric effect in nanoparticles with
  radius smaller than 50 nm. This effect will be
  useful to control the work of the devices both by
  electric or magnetic field.

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Thank you for attention