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)