Giant magneto resistivity in Fe 3-x Zn x O 4 nanowire
structures
Slide 2
Contents Introduction Strongly correlated electron systems in
nanoscale Property of (Fe, Zn) 3 O 4 Fabrication method of
nanostructures Purpose Experiments and results Conclusion
Slide 3
Contents Introduction Strongly correlated electron systems in
nanoscale Property of (Fe, Zn) 3 O 4 Fabrication method of
nanostructures Purpose Experiments and results Conclusion
Slide 4
Coulomb interaction U 5eV This important system is studied with
keen interest all over the world. VO2VO2 YBa 2 Cu 3 O 7 (La,Ca)MnO
3 Electric crystal Metal-insulator transition Ferromagnetism at
high temperature Giant magneto resistance Ferromagnetism at high
temperature Giant magneto resistance Insulator Anti-ferromagnetism
Insulator Anti-ferromagnetism MeltingMelting Super conductivity at
high temperature Introduction strongly correlated electron
system
Slide 5
VO 2 LPCMO Introduction strongly correlated electron systems in
nanoscale 100nm M. Fth et al, Science 285 (1999)1540 Ferromagnetic
Anti-Ferromagnetic M. M. Qazilbash et al, Science 318 (2007) 1750,
Metal Insulator (La, Pr,Ca)MnO 3 film STM image VO 2 film SNIM
image 500nm Different domains exist separately each other. Domain
size is ~ a few hundred nm
Slide 6
500nm Introduction strongly correlated electron systems in
nanoscale InsulatorMetal Y. Yanagisawa et al Appl. PHYSICS LETTERS
89 (2006) 253121 (La, Pr,Ca)MnO 3 Nanostructure of domain scale
show new physical properties? Enormous Magneto Resistive effect was
observed in nanosize.
Slide 7
Introduction strongly correlated electron systemsin nanoscale
500nm (La, Pr,Ca)MnO 3 film Charge Ordering Insulator Ferromagnetic
metal 1m Change of MRgraduallysuddenly
Slide 8
Contents Introduction Strongly correlated electron systems in
nanoscale Property of (Fe, Zn) 3 O 4 Fabrication method of
nanostructures Purpose Experiments and results Conclusion
Slide 9
Introduction Fe 3 O 4 and Fe 3-x Zn x O 4 Fe 3 O 4
Ferrimagnetic metal @ RT A site: Fe 3+ B site: Fe 2+, Fe 3+
A-Bsite: Super-exchange interaction Anti-ferromagnetic coupling
B-Bsite: Double-exchange interaction Metallic conductivity Fe 3+ In
A-site is substituted with Zn 2+ Control of super exchange
interaction Magnetisation increase Decrease of Fe 2+ (Carrier)
Semiconductor Fe 3-X Zn x O 4 :
Slide 10
Introduction Property of Fe 3-x Zn x O 4 At Room temperature
Ferromagnetism Semiconductor Spinel structure Earth-friendly
material (Fe, Zn) Candidate of spintronics devices
Slide 11
Contents Introduction Strongly correlated electron systems in
nanoscale Property of (Fe, Zn) 3 O 4 Fabrication method of
nanostructures Purpose Experiments and results Conclusion
Slide 12
Introduction How to fabricate nanostructures AFM Lithography
General fabrication technique of oxide nanostructure is required
Difficulty in controlling fine size Degradation of reproducibility
MR was observed We need to fabricate smaller structure than
ever
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Top down High controllability of size, position, and form More
advanced technique is required to fabricate more precise structure
Introduction Top down technique and Bottom up technique Ex.) Nano
Imprint Lithography, AFM Lithography, e-Beam Lithography, etc
Bottom up Size of thin film can be controlled in the atomic layer
scale (a few ) There is a difficulty in controlling size, position,
and shape Ex.) Pulsed Laser Deposition, MOCVD, etc
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Combination of Top down and Bottom up High controllability of
size, shape, and position Structures with the atomic layer size can
be fabricated Pulsed Laser Deposition Nano Imprint Lithography
Introduction Combination of Top down and Bottom up
Slide 15
500nm 45nm 1m Ion Milling Introduction Fabrication of ZnO
nanobox Acetone cleaning Polymers on substrateZnO-deposited
substrate
Slide 16
Contents Introduction Strongly correlated electron systems in
nanoscale Property of (Fe, Zn) 3 O 4 Fabrication method of
nanostructures Purpose Experiments and results Conclusion
Slide 17
Purpose Y. Yanagisawa et al Appl. PHYSICS LETTERS 89 (2006)
253121 (La, Pr,Ca)MnO 3 film at 10K GMR was observed 500nm 45nm ZnO
Fabrication method was established
Slide 18
Purpose Fabrication of FZO nanowire by utilizing sidewall
growth Next purpose Application of FZO nanowire to spintronics
devices Emergency of GMR at Room temperature
Slide 19
Contents Introduction Strongly correlated electron systems in
nanoscale Property of (Fe, Zn) 3 O 4 Fabrication method of
nanostructures Purpose Experiments and results Conclusion
Slide 20
Top down (NIL) Size and position can be controlled by the array
of resist pattern Experimental method Fabrication of FZO nanowire
utilizing sidewall growth Substrate Regist Mold
Slide 21
Experimental method Fabrication of FZO nanowire utilizing
sidewall growth Utilizing sidewall growth (Horizontal growth can be
controlled) FZO Sidewall growth substrate Organic resist Bottom up
(PLD) @RT
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Experimental method 1.Deposition on Plane Substrate 1-1.
Control thin films thickness 1-2. Optimize crystallization
condition by annealing 2.Deposition on Nano-patterned substrate
Fabricate FZO nanowire using sidewall growth Deposition@ Room
temperature
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Experiment 1-1. Control thickness of FZO sidewall Film
thickness Sidewall thickness Film thickness time Sidewall thickness
can be controlled by changing deposition time Deposition on plain
substrate Deposition time [min.] Films thickness [nm] Measurement:
AFM Temperature: RT Substrate: MgO(001) P O2 : 1x10 -2 Pa
Deposition time: 30-90 min. T=1.14t T: Films thickness t:
deposition time
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Experiment 1-2. Searching for crystallizing condition of FZO
Peak of (111)-oriented FZO was observed. Crystallization of FZO was
succeeded by annealing. Temperature : 600 ~ 800 P O2 : 110 -4 ~ 110
-1 Pa Annealing time: 5hrs. Substrate: Al2O3
Slide 25
Experiment 2. FZO nanowire I am trying to fabricate FZO
nanowire. Finally, I will measure the MR and apply it to
spintronics devices.
Slide 26
Contents Introduction Strongly correlated electron systems in
nanoscale Property of (Fe, Zn) 3 O 4 Fabrication method of
nanostructures Purpose Experiments and results Conclusion
Slide 27
I am trying to fabricate FZO nanowire. The nanostructure
fabrication technique: combination of Top-down and Bottom-up
process utilizing sidewall growth was suggested. Time-dependency of
FZO-thin-films thickness is observed. Crystallization condition of
FZO on Al 2 O 3 was optimized.
Slide 28
Slide 29
Slide 30
Experimental method Fabrication of FZO nanowire utilizing
sidewall growth
Slide 31
Searching for crystallizing condition of FZO Peak of FZO
(111)-oriented was observed. 600 , Po 2 = 110 -3 mbar 700 , Po 2 =
110 -4 mbar Intensity (a.u.) 2 ()
Slide 32
FZO on MgO substrate MgO Al 2 O 3 (0001) MgO substrate 800
anneal Intensity (a.u.)
Slide 33
Experiment 1. Deposition on plain substrate Control of sidewall
thickness Crystallization method Experiment on plain substrate 1-1.
Control thin films thickness 2-2. Optimize crystallization
condition by annealing Measurement: 1. AFM :2. XRD Substrate:
MgO(001) P O2 : 1x10 -2 Pa Temperature: RT Deposition time: 30-90
min. Temperature : 600 ~ 800 P O2 : 110 -4 ~ 110 -1 Pa Annealing
time: 5hrs. Should be learned.
Slide 34
Experiment 1-2. Searching for crystallizing condition of FZO
Crystallized FZO can be prepared by annealing.
Slide 35
Seeking growth condition for fabricating FZO nanowire Method of
crystallization Optimization of the condition Optimization of the
condition Crystallizing condition of ZnO: Crystallize by annealing
:XRD( ) : 550,950 :5hrs.,6hrs.
Slide 36
Experiment Establishing the fabrication technique of oxide
nanostructures by combining Top down and Bottom up At first Making
a prototype by ZnO Establishing the fabricating process Making sure
accuracy and reproducibility Measuring the physical properties Zn O
ZnO Oxide semiconductor Eg=3.37V It is easy to grow on any
substrates at room temperature It can be c-axis oriented crystal at
room temperature