Ferroelectric nanostructures and their processing issues
Transcript of Ferroelectric nanostructures and their processing issues
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Ion Elena-Daniela
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FE nanostructures
Processing issues
Potential applications
Ferroelectricity, Ferroelectric materials FE nanostructure, Size limit in ferroelectricity
Invasive and Non-invasive approachCharacterization of FE nanostructure
Outline
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Important Events
1921 Discovery of ferroelectricity in Rochelle Salt
40’s Barium titanate era
60’s Age of high science
80’s Age of integration
1990-present Age of miniaturization
def = reversibility of the direction of the electric dipole by means of an applied electric field in a polar crystal
Materials which exhibit ferroelectricity are called ferroelectric materials
Ferroelectricity
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32 Symmetry Points groups
21 Noncentrosymetric
20 PiezoelectricPolarized under stress
10 PyroelectricSpontaneously polarized
SubgroupFerroelectric
Spontaneously polarizedPolarization reversible
TungstenBronze
Oxygen OctahedralABO3
Pyrochlore Layer structure
11 Centrosymetric
Non-piezoelectric
Ceramic Perovskite
Pi = dijk jk
(Direct Effect)
ijdkijCo
nverse Effect
Ps = T
Ferroelectric materials
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e.g. Perovskite oxide – ABO3 BaTiO3, PbTiO3, Pb(ZrxTi1-x)O3,
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Reversible spontaneous polarization-1 or 0 data bits (binary data storage media)
Piezoelectric effect-Piezoelectric actuators, sonar detectors
Pyroelectric effectPyroelectric detectorsfor infrared detection, imaging, thermometry, ...
Applications
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• 3D→2D transition : bulk to thin film• 2D→1D transition : thin film to wire• 2D→0D transition : thin film to nanostructures
F. D. Morrison et al. Rev. Adv. Mater. Sci. 4 (2003) 114
Alexe et al.APL- 75, 1793, (1999)Ma et al.
APL, 83, 3770 (2003)
Luo et al.APL, 83, 3, 440, (2003)
Yun et. al. Nano Letters, S1530, (2002)
Ferroelectric nanostructures
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• Switching @ nanoscale
• P=10 µC/cm2, ε = 200
• a = 10 nm Q = P·S ≈ 60 e
• a = 2 nm Q = P·S ≈ 3 e
Size limit in ferroelectricity
Rudinger et. al. Appl. Phys. A, 80, 1247 (2005)
2
2
2
1
o
C
VPW
Factors that influence the ferroelectric properties in nanostructure:Grain size,Mechanical bondary conditions,...
Wc > kBT
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Electron Beam Direct Writing
Focussed Ion Beam Patterning
LithographyMethods
NANOSTRUCTURES
Focussed Ion Beam Patterning Electron Beam
Direct Writing
LithographyMethods
Self-PatterningChemical Routes
Self-PatterningPhysical RoutesSelf-Patterning
Physical Routes
Self-PatterningChemical Routes
Invasive and Non-invasive approach
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Focussed Ion Beam Patterning
FIB equipment• similar to SEM• a highly focussed beam of gallium ions
• purposes: imaging, and micromachining
• nanopatterning - resolution ~ 20 nm
•gallium doping, damaged surface layer
C.S. Ganpule et.al. APL 75, 409 (1999)
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Electron Beam Direct Writing
Alexe, Harnagea and Hesse, J. Electroceram. 12, 69 (2004)
• solution: metalorganic compounds (Sr-, Bi-, Pb-ethylhexanoate, Ti-, Zr-isopropylene and Ta-methoxide ) or metal colloids and solvent: xylene and 2-methoxiethanol• patterning by scanning an electron beam
•Powerful method to prepare arrays of ferroelectric cells with lateral sizes down to 75nm
•Expensive equipment and time
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LithographyMethods
• Photolithography• Soft lithography Nanoimprint
Alexe, Harnagea and Hesse, J. Electroceram. 12, 69 (2004)
Large-area and low-cost ferroelectric cells below 100nm in lateral size
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Self-PatterningPhysical Routes
Pulsed Laser Deposition
Met.Org. Chem.Vap. Deposition
Chemical Solution Deposition
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Pulsed Laser Deposition
1. Laser radiation interaction with the target 2. Dynamic of the ablation 3. Transport of the ablated material to a charger and a furnace 4. Nucleation and growth
Seol et al. - Appl. Phys. Lett., 81, 1894, 2002
Crystalline nanoparticles ~ 4-20nm
Complex experimental set-up, low yield
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Met.Org. Chem.Vap. Deposition
Large surface coating areaUsed in combination with FIB, EBDW
Expensive equipement
Metal organic precursor:Tetraethyl lead - Pb(C2H5)4
Titanium isopropoxide: Ti(i-OC3H7)4
Zirconium tert-butoxide: Zr (t-OC4H9)4
M. Shimizu et.al.-Jpn. J. Apl. Phys, 33, 5168 (1994)
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R.W. Schwartz et al. / C. R. Chimie 7 (2004) 433–461
Metal carboxylate:R-COOMM: PbR: CH3-, C2H5-
Metal alkoxide: M(OR)x
M: Ti, Zr, (OR): (OC3H7), (OC4H9)
Solvent: CH3OC2H5OH
Chemical Solution
Deposition(Sol-gel)
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Self-PatterningChemical Routes
Pb(O2C2H3)2 R= [H2O]/ [Pb]Zr(OC4H9)4 pH=11Ti(OC4H9)4
C4H10O
11-PT-15
11-PZ-15
11- PZT-15
BET: 58nm
BET: 109nm
BET: 144nm
Cost-effective, various shapes
Agglomeration
(Sol-gel)
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Self-PatterningChemical Routes
Synthesis, Functionalization and surface treatment of NanoparticlesMarie-Isabelle Baraton/ ASP 2003
Alexe, Harnagea and Hesse, J. Electroceram. 12, 69 (2004)
Microemulsion
Removal of the surfactant
Uniforme particles in nm range
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Characterization of ferroelectric nanostructures
• Piezoresponse Scanning Force Microscopy (PFM)
M. Alexe, C. Harnagea and D. Hesse, J. Electroceram. 12, 69 (2004)
C.H. Ahn, K.M. Rabe, J.M. Tiscone, Science, 303, 488, (2004)
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Potential applications
Many others to come!!!
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Thank you for your attention!