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Ohki Labo.Ohki Labo.Research ActivitiesResearch Activities
1. Polymer Gr.Polymer Gr. (Polymer material)(Polymer material) Environment problems, Global heating, Environment problems, Global heating, BiodegradabilityBiodegradability, , Environment-friendly material,Environment-friendly material, Nanocomposite, etc…Nanocomposite, etc…
2. Electronic Device Gr.Electronic Device Gr. (MOS Tr. Novel material for (MOS Tr. Novel material for a gate insulating filma gate insulating film)) High-k material for next-generation electronic device,High-k material for next-generation electronic device, Synchrotron orbit radiation,Synchrotron orbit radiation, etc…etc…
3. Applied Optics Gr.Applied Optics Gr. Biosensor, Photocatalyst, Metamaterial, Biosensor, Photocatalyst, Metamaterial, Optical fiver, Photonic crystal, etc…Optical fiver, Photonic crystal, etc…
Reserch Group of Ohki laboratory
Development of environment-friendly materialsDevelopment of environment-friendly materials
Polymer Gr.
Temperature dependenceTemperature dependence
Electric conduction propertiesElectric conduction properties
Space charge distributionSpace charge distribution
Breakdown characteristicsBreakdown characteristics
Ion migrationIon migrationTHz spectroscopyTHz spectroscopy
Dielectric propertiesDielectric properties
BiodegradablePolymers
Nanocomposites Printed circuitboards
Nondisruptive diagnostic method of cable degradation.We look into possible aNondisruptive diagnostic method of cable degradation.We look into possible application of broad spectrum impedance spectroscope (BIS).pplication of broad spectrum impedance spectroscope (BIS).In the future,In the future, this data will be of assistance of the standard about evaluatinthis data will be of assistance of the standard about evaluating power cable of atomic power plant.g power cable of atomic power plant.
Monitoring and diagnostic testing of cable degradationMonitoring and diagnostic testing of cable degradation 2006-2010 2006-2010
0 20 40 60 80 100 110-100-80-60-40-20
020406080
100120140160
Phas
e (d
eg.)
Frequency (MHz)
sound damaged difference between sound and damaged cables
Offering technical advantagesOffering technical advantages of high density implementable electronic circuiof high density implementable electronic circuit substrate by polymer nanocomposite technique.t substrate by polymer nanocomposite technique.
The Knowledge Cluster InitiativeThe Knowledge Cluster Initiative 2007-20112007-2011
Made from plant
Cycloid type recycling system
Polymer with low environmental loads
Natural reduction system Compost processing
H2O
resolved by bacteria
Biodegradable Polymers
CO2The natural world cycle
photosynthesis
microbe
decomposition
microbe
destruction
digestion
enzyme
saccharide starch cellulose
Digestion synthesis chemical synthesis etc
Biodegradable Plastics
Polymer nanocomposite and its problem
Property changes associated with nanostructuration is influenced by the interface between the polymer and the nano-filler.
Polymer nanocomposite (NC) is a mixture of polymer and nano-sized filler.
Effect of nano-filler addition in permittivity (nanostructuration)• in some NC : decrease• in some NC : no change• in some NC : increase
From where does the property difference come?
fillerfiller
polymerpolymer
1.2 nm
SiO2 1.2 nm
SiO2
The increase of leak current by tunneling effect has been caused.
The thickness of a gate insulating film has been reduced to approximately 1 nm.
Low power consumption
High speed Highly integratedMoore’s Law
Employment of high- gate insulating filmEmployment of highEmployment of high-- gate insulating filmgate insulating film
The thickness of a gate insulating film can be increased even if a transistor is miniaturized.
The thickness of a gate insulating film can be increased even if a transistor is miniaturized.
dCox
0
The higher , the higher Cox
The higher , the higher Cox
Employment of LaAlO3 as high-dielectric materialEmployment of LaAlOLaAlO33 as high-dielectric material
Electronic Device Gr.
Crystal defects of LaAlO3
Problems of high-Problems of high- gate insulating material gate insulating materialProblems of high-Problems of high- gate insulating material gate insulating material
Method for detecting crystal defectsMethod for detecting crystal defectsMethod for detecting crystal defectsMethod for detecting crystal defects
2. Electron Paramagnetic Resonance (EPR)
1. Photoluminescence (PL)
Fig. LaAlO3 single crystal (Perovskite structure)
Insulating materials haveInsulating materials have defectsdefects therein.
The defects form a localized level in a forbidden band.
The localized level causes leak current.
Photoluminescence (PL)Photoluminescence (PL)
Upper level
Energy level
Electron
Excitation ofan electron
Lower level
h
Electron
Upper level
Lower level
h
Energy level
An electron absorbs photon energy to be excited.
An electron drops to a lower level,
emitting energy as light.
720 740 760 7800
10
20
30
Detected Photon Energy [eV]
PL
In
ten
sity
[a.u
.]
PL64_AS1_SLIT010_1.TXTPL64_AS2_SLIT010_1.TXTPL64_AS3_SLIT010_1.TXTPL64_AS4_SLIT010_1.TXTPL64_SI1000_SLIT010_1.TXT
740 760 780 8000
10
20
30
Wavelength [nm]
PL
In
ten
sity
[a.u
.]
[1] J. Heber et al.,: Z. Phys. 246 (1971) 261.
The PL spectral shapes are very similar.The PL spectral shapes are very similar.
R line luminescence of doped Cr3+ in LaAlO3[1]
LaAlO3 Single crystal
Detected Photon Energy [eV]
Exc
itat
ion
Ph
oton
En
ergy
[eV
]
Eg = 5.6 eV
Presence of CrCr3+ 3+ impurityimpurity is indicated by PL.
Wavelength [nm]
Electron Spin Resonance (ESR)Electron Spin Resonance (ESR)
B0
E antiparallel
parallel
Principle of EPRPrinciple of EPRPrinciple of EPR
= E = E
Electron Spin Resonance
E = geBB0
ms = +1/2
ms = -1/2
= h
e-
e-
Microwave-absorption measurementMicrowave-absorption measurement
Zeeman Split
Crystal field of octahedral
symmetry
Cr3+Cr3+
S =3/2
3d 3 electron configuration
3dCr
A 2
3d
3dCr
A 2
3d
3dCr
A 2
3d
3d3
Cr3+
4A2
3d3
[2] D. Kiro, W. Low and A. Zuman, Paramagnetic Resonance vol 1, ed. W. Low, (New York, Academic, 1962), pp. 44-50.
H: Magnetic field
H is parallel to direction of ( 111) .
Angle-resolved EPR spectra of the LaAlO3 single crystal (111) at room temperature.
Angler dependence of the spectrum of Cr3+ in LaAlO3.[2]
The ESR spectral shapes are The ESR spectral shapes are very similar.very similar.
Presence of Cr3+ impurityCr3+ impurity is indicated by ESR and PL.
Biomolecules can be detected!
Proteins, cells, … # Excitation of waveguide mode # Surface plasmon resonance
etc…
PC
Signal converter
Analyte
Specific adsorption
Applied Optics Gr. Applied Optics Gr. -Biosensor--Biosensor-
BiosensorBiosensor
Analyte
Detector
Streptavidin (SA)
Waveguide
Polarizer
Laser
Teflon cuvette
Prism
Waveguide mode
Reflection layer
Kretschmann configuration
Ref
lect
ance
0
1
Incident angle
After adsorption
Before adsorption
Angle shiftAngle shift
BiosensingBiosensing systemsystem usingusing aa waveguide-modewaveguide-mode sensorsensor
Our previous researchOur previous research
Ex. Detection of streptavidin (A kind of protein)
This system : sensitive compared with conventional SPR sensors (~ 40 times).
Biotin probe(Vitamin)
Present research (1)Present research (1)
Streptavidin (SA)(Transparent substance)
SA labeled with Au nanoparticles
Ultrasensitive detection of SA by
labeling with Au nanoparticles (Au-SA).
Present research Present research Ultrasensitive biomolecular detectionUltrasensitive biomolecular detection
Previous method Improved method
Au nanoparticles(Opaque)
Immobilization of biotin on the surface
Injection of solution (10 pM Au-SA)
Measurement of reflectance
After 20 hours
Experimental procedures Experimental procedures
Measurement of reflectance
Present research (2)Present research (2)
30oHe-Ne laser
Polarizer
SiO2 glass prism
SiO2 glass layer
Si layer
SiO2 glass substrate
Detector
Au-SA
Biotinprobe
Comparison of reflection spectra before and after the Au-SA adsorption.
500 nm
Average number density : 2 m-2
Au-SA
SEM image of the surface after the adsorption of Au-SASEM image of the surface after the adsorption of Au-SA
Present research (3)Present research (3)
69 70 71 72 730
0.2
0.4
0.6
0.8
1
Incident angle [deg]
Ref
lect
ance
SA付きAu吸着前SA付きAu吸着開始1時間後SA付きAu吸着開始2時間後SA付きAu吸着開始3時間後SA付きAu吸着開始20時間後
Au-SA吸着前Au-SA吸着後
69 70 71 72 730
0.2
0.4
0.6
0.8
1
Incident angle [deg]
Ref
lect
ance
Au-SA吸着前Au-SA吸着後
Au-SA吸着前Au-SA吸着後
Au-SA with a number density of only 2 m-2 can be detected.
○ Before adsorption of Au-SA△ After adsorption of Au-SA
Au-SA
-0.053
70.6 70.7 70.8 70.9 71 71.10.6
0.7
0.8
Incident angle [deg]
Ref
lect
ance
SA付きAu吸着前SA付きAu吸着開始1時間後SA付きAu吸着開始2時間後SA付きAu吸着開始3時間後SA付きAu吸着開始20時間後
Au-SA吸着前Au-SA吸着後
Ultrasensitive detection of SA by labeling with Au nanoparticles Ultrasensitive detection of SA by labeling with Au nanoparticles
Present research (4)Present research (4)