グラフェンエッジの物理とスピン素子応用

春山純志

青山学院大学大学院理工学研究科機能物質創成コース

-ナノリボンとアンチドット格子-

スコッチテープ方式の開発

マンチェスター大学 Geim,Novoselov

Graphene World

２００４年

絶句 激怒

頑張ろう

2010 ノーベル物理学賞

イグノーベル賞2000 分子・バイオ磁性体の浮遊

With Michael Berry

frog.mpg

「グラフェン物性の新展開」 座長：押山・青木先生

(1) 安藤 恒也 (東工大院理工物性) はじめに(2) 榎 敏明 (東工大院理工化学)

ナノグラフェンとそのエッジの幾何学構造に依存した電子状態・磁性(3) 春山 純志 (青学大理工)

グラフェンナノリボンとナノ細孔グラフェン：エッジと電子物性(4) 福山 寛 (東大院理)

走査トンネル分光法で探るグラフェンとグラファイト表面の電子状態(5) 若林 克法 (物材機構MANA)

グラフェンナノリボン・エッジ電子物性の理論

(6) 樽茶 清悟 (東大工) 3層グラフェンの電気伝導とバンド構造

(7) 長田 俊人 (東大物性研) グラフェン接合系における量子ホール端伝導

(8) 越野 幹人 (東北大理) グラフェンの量子物性－ディラック点における特異な物理

来春物理学会シンポジウム 領域７ ＠新潟

３月２７日午後

グラフェンの電子状態

グラフェンシート

sp2混成軌道 σバンド

グラフェンバンド構造

ディラック点

VG

半金属 Gap less半導体

ディラックコーン

リニア

空π

占有π

pz πバンド

巨大平均自由行程、高移動度、強スピン位相コヒーレンス

le > ~ 10μm Lφ > ∼50μm

電子：Mass less Dirac Fermion

Kkk’ 結合反結合

二個のスピノル

Ｋ点での線形エネルギー分散

相対論的ディラック方程式で質量０としたニュートリノの方程式で記述

ベリー位相CNTs後方散乱 前方散乱

μ>200,000 cm2V-1s-1

時間反転対称性同位相 アンダーソン局在

逆位相 反局在位相差 π

ベリー位相による後方散乱の消滅東工大・安藤

炭素：スピン・軌道相互作用は無いスピン反転

散乱源

干渉

入口

出口

UCF, AB(AAS)効果

Ns = ∼1012 cm-2

Grapheneの特異な量子物性異常整数量子ホール効果

Rxy-1=±4(N+1/2)e2/h

Y. Zhang, H. Stormer, P. Kim, Narture 438, 201 (2005)

室温量子ホール効果

K. S. Novoselov, P. Kim, et al., Science 315, 1379 (2007)

Suspended Graphene

分数量子ホール効果

Ns <∼3.5 ×1011 cm-2

μ∼100,000 cm2V-1s-1

K. Bolotin, H.L. Stormer, P. Kim, Narture 462, 196 (2005)

LG=150nm

超高電子移動度

IBM

fT=100GHz(LG=260um)

Samsung

Touch Panel for i-Pod

Contents

1.背景

２．カーボンナノチューブの酸化開口+熱処理で形成した低欠陥グラフェンナノリボン

欠陥ナノリボンの約７倍のエネルギーバンドギャップ

３．多孔質アルミナ膜マスクで形成した低欠陥アンチドット（ナノ細孔）格子グラフェン

細孔エッジに起因した室温強磁性の発現異常磁気抵抗振動

Non-lithographic

４．今後 素子応用 電場によるエッジ偏極スピンの制御

PRL

温故知新

Nature Nanotech & Latest Highlights, News & Views

Nature Nanotech In-depth Review

Arm Chair

zigzag

zigzag

Edge atomic structures of Graphene (Graphite)

Arm chair

Graphene nanoribbon

Flat band

Arm chair Zigzag

Tight-binding

Band gap

K.Nakata et al., Phys. Rev. B 54, 17954 (1996)

Strong Electron localizationHigh EDOSSpin polarization

Edge states of Graphene (Graphite)

Spin polarization and ferromagnetism at zigzag edges with hydrogen termination

Kusakabe and Maruyama, Phys. Rev. B 67, 092406 (2003)

Up spin Down spin

Hydrogen

local-spin-density approximation

Why graphene edges are important and interesting??

1. Band gap engineering

3. All carbon magnetism (magnets)

4. Spin Current & (Quantum) Spin Hall Effect

2. Electron correlation with localized edge electrons

So many theoretical reports, but no experimental reports

Large damages by lithographic methods

Non-lithographic methods

Contents

1.背景

Non-lithographic 温故知新

２．カーボンナノチューブの酸化開口+熱処理で形成した低欠陥グラフェンナノリボン

欠陥ナノリボンの約７倍のエネルギーバンドギャップ

Nature Nanotech & Latest Highlights, News & Views

Arm Chair

Advance online publication 19th Dec.NanoelectronicsArticle by Shimizu et al.Graphene nanoribbons manufactured by annealing unzipped carbon nanotubes have been measured to have a large energy bandgap.

Latest highlights

Nature Nanotechnology | News and ViewsNanoelectronics: Graphene gets a better gapStephan RocheJournal name: Nature Nanotechnology Volume: 6, Pages: 8–9 Year published: (2011)

DOI:doi:10.1038/nnano.2011.262 Published online 23 December 2010

Nature Nanotechnology 6, 45-50 (2011)

Introduction of energy band gaps

Absence of energy band gaps

Destruction of symmetry in bilayer graphenesVoltages, Carrier doping, Substrate

Carrier confinement into 1D space GNRs

Semi metal, Zero- gap semiconductor

Han, Kim et al., Phys. Rev. Lett., 104, 056801 (2010)

Disordered Graphene Nano-ribbon(Lithographic)

Hopping conductance

Stochastic Coulomb diamond

Large difference between Δ & EaLarge transport gaps Δ

Ec=e2/2C

J.Tour et al., Nature 458, 872 (2009)

Rice University, Smalley Institute for Nanoscale Science and Technology

①Formation of GNRs on substrate by air blow②３stepped annealing（high vacuum, H2）

Our originality

Low-defect GNR formed by unzipping of MWCNTs

1μm

200nm

As-depo

Our originality①Formation of GNRs on substrate by air blow

②by air blowing to droplet①by brushing

AFM

Brush Air blowIsolated 47 58Rectangle 14 26Monolayer 5 15

Formation of GNRs on Si-substrate by air blow

Number of GNRs within 5mm2-substrate

②3-stepped annealing during FET formation process

Our originality for deoxidization and carrier doping

Right after formation of GNRs on substrate High vacuum・ 800 °C

Right before formation of EB mark H2 atmosphere・800 °C

Right before formation of FET electrode High vacuum ・300 °C

For deoxidization & Recovery of defects

For carrier doping

For cleaning

for long time

HRTEM

Raman

AFM

As-grown nanoribbon

FET

Quality of GNRs: low defects

Before annealing

After annealing

AISTSuenaga

Nature Nanotech. 6, 45-50 (2011)

Electronic transport for 4 different-type GNRs

W Width (nm)N Layer number

Nature Nanotech. 6, 45-50 (2011)

Correlation of ambipolar feature with annealing time at high vacuum

Deoxidization：p-type Ambipolar

t = 0

t = 24h

Electronic transport：Zero-bias anomaly & Transport gap

ΔVBG = 1V

Small transport gap

Low defects

W=75nmN=1

Nature Nanotech. 6, 45-50 (2011)

Single-electron Spectroscopy

No stochastic diamonds

Disordered GNRsLow-defects GNRCoulomb diamonds

Stochastic diamonds due to defects (Q-dots connected in

series)Low defects

W=75nmN=1

Nature Nanotech. 6, 45-50 (2011)

Energy band gap in thermal-activation relationships

7-times larger EaNo hopping conductance

Transport gap close to Ea values

55meV

Nature Nanotech. 6, 45-50 (2011)

Louie et al., UC BerkeleyTheory for energy band gaps of GNRs with arm chair edge

GWA

LDA

3 eV for W=1nm

Ea∼30 meVfor W∼100nm

Q1: The large band gaps are relevant for large-width GNRs?

le ∼300nm

W < 300nm

Remaining 1D

Mean free path ∼300nm

GNR Width < 300nm

One dimensionality

GNR length (nm)

Res

istiv

ity (h

/4e2

)

100 300200 400 500

1

2

3

4

00

Measurement of mean free path

W ∼100nm

Remained 1D in large width GNRs

Ballistic transport regime

Dai Stanford

Contents1.背景

２．カーボンナノチューブの酸化開口+熱処理で形成した低欠陥グラフェンナノリボン

欠陥ナノリボンの約７倍のエネルギーバンドギャップ

Non-lithographic 温故知新

Arm Chair

３．多孔質アルミナ膜マスクで形成した低欠陥アンチドット（ナノ細孔）格子グラフェン

細孔エッジに起因した室温強磁性の発現 （単層）

Nature Nanotech In-depth Review zigzag

Flat bandZigzag

Tight-binding

K.Nakata et al., Phys. Rev. B 54, 17954 (1996)

Strong Electron localizationHigh EDOS

Electron localization and spin polarization in zigzag-edge Graphene Y.Son, S.G.Louie et al.,

Spin polarization and magnetism in zigzag-edge nanoribbon

On one edge On both edges

Hunt’s rule

H. Lee et al.,. Phys. Rev. B 72, 174431 (2005)

first-principles density-functional calculations

Ferro Anti-Ferro

Maximizing exchange energy gain

Spin interaction

Spin polarization and ferromagnetism at zigzag edges with hydrogen termination

Kusakabe and Maruyama, Phys. Rev. B 67, 092406 (2003)

Up spin Down spin

Hydrogen

Local-spin-density approximation

Mono-H

Di-H

Under magnetic field

EF

Zigzag edges

Group-theoretical consideration

Why graphene edges are important and interesting??

1. Band gap engineering

3. All carbon magnetism (magnets)

4. Control of edge spin by electric field : (Quantum) Spin Hall Effect

2. Electron correlation with localized edge electrons

So many theoretical reports, but few experimental reports

Large damages by lithographic methods

Non-lithographic methods

Example of defect-spin related Ferromagnetism

Cervenka et al., Nature Physics 5, 840 (2009)

ZIGZAG?Arm chair Uncontrollable and

unclear

T. Enoki et al., Sol. Stat. Comm. 149, 1144 (2009)

Zigzag-edge related Ferromagnetism in Activated carbon Fibers

Mechanically exfoliated Graphene

Hexagonal nano pores

Zigzag edge

Formation of low-defect graphene nano-pore arrays by porous alumina templates

GNR

Careful Ar etchingHigh vacuum and Hydrogen annealing at 800℃

SEM images of Porous alumina templates

φ ∼ 50nmPore spacing ∼ 40nm

φ ∼ 80nmPore spacing ∼ 20nm

φ ∼ 15nmPore spacing ∼ 20nm

Advantage of porous alumina template for formation of low-defect GNPAs

zigzag

Non-lithographicHexagonal-shaped nano-pores

①Low defect GNPAs

②Alignment of edge structures of all boundaries to hexagonal carbon lattice of graphene ∼50%Six boundaries/one AD

③Large ensemble of GNRs

GNRs

a b c

AFM STMSEM

Images of graphene nano-pore arrays

After annealing

High EDOS at pore edges

Possible zigzag edge

Tokyo Univ.Matsui and Fukuyama

Raman spectroscopy on annealingBefore After

②Reduced defects

①Alignment of edge chirality to

hexagonal carbon lattice of graphene

Sample Number1 2 3 4 5 6 7 8

I(D)/I

(G)

0.5

0.25

0.75

Ferro No Ferro

Before

After

∼50%Zigzag Arm

chair?

Kraus, V.Klitzing et al., Nano Lett. 10, 4544 (2010)

Raman spectroscopy of aligned hexagonal pores on graphene Round

Round Hexagonal

Hexagonal

D peak maps

②Reduced defects

①Alignment of edge chirality to

hexagonal carbon lattice of graphene

1000-1000 -500 5000-1000 -500 0 500 1000-6.0e-5

-4.0e-5

-2.0e-5

0.0

2.0e-5

4.0e-5

6.0e-5

0.4

0.2

-0.4

0

-0.2

1000-500 5000-1000

0

-400

-800

400

800

1000-1000 -500 5000

Mag

netic

mom

ent

(×μ B

/edg

e on

e π-

orbi

tal)

a b c

T = 2K T = 2KT = 2K

0

30

20

-10

-20

10

-301000500-1000 -500 0

T = 300K

10000-500 500-1000

Magnetic Field (gauss)

T = 300K0.2

0

0.1

-0.1

-0.2

-500-1000 10005000

T = 300KHydrogen

Hydrogen Oxygen

Oxygen

No antidots

No antidots

d e f

0.3

-0.3

Magnetization (μem

u/100μm2)M

agne

tic m

omen

t (a.

u.)

Hydrogen OxygenNo nano-pores

Magnetization measurement

5/11 samples

Reconfirmation of no contribution of parasitic factors

Si

Bulk Graphene

Si

Porous alumina template

No Ferromagnetism

Magnetic Field (gauss)

0.2

-0.2

0

1000-1000 500-500 0

Hydrogen

Mag

netic

mom

ent

(×μ B

/edg

e on

e π

orbi

tal)

Hydrogen

W=∼40nmW=∼10nm

10005000-500-1000

T = 300KT = 300K

Pore spacing (W:GNR-width) and Ferromagnetism

0.34

W=20nm

0.2Farromagnetismderived from nano-pore edges

GNR

zigzag edges

Nano-pores

W

Spin polarization and magnetism of zigzag-edge nanoribbon

On one edge On both edgesHunt’s rule

H. Lee et al.,. Phys. Rev. B 72, 174431 (2005)

first-principles density-functional calculations

Ferro Anti-Ferro

Mono-Hydrogenation

Hydrogen atom

Localized π orbital

Localized π orbital

1.42Å2.46Å

No Hydrogenation

Localized π orbital

Localized π orbital

Dangling bond

Edge spin configuration

Beforehydrogen annealing

After hydrogen annealing

①Total area of bulk-graphenes used for formation of nano-pore array: ∼4 cm2

②Area of one hexagonal unit cell: S = 6(3-1/2/2)(a/2)2 = ∼4300 nm2; a = [80 nm(pore diameter) + 20nm (pore spacing)]

③Total number of nano-pores: ①/② = 4 cm2 /4300 nm2 = ∼1011

④Total number of dangling bond per one hexagonal pore:40 nm/(0.142 nm×31/2)×6 = 166×6 = ∼1000

⑤Total number of edge dangling bonds of the nano-pore graphene used for SQUID: ③×④=1014

⑥Saturation magnetization value per one edge dangling bond: 1.2×10-6 (emu)×10-3/(⑤=1014) = 1.2×10-23 (J/T)

⑦Magnetic moment per one edge dangling bond:(⑥=1.2×10-23)/(μB=9.3×10-24)= ∼1.3μB

Estimation of edge-carbon magnetic moment

Correlation of Flat band and Spin polarization with Hydrogen termination

H. Lee et al.,. Phys. Rev. B 72, 174431 (2005)

FerroMajority Spin Minority Spin

Up Spin Down Spin

Antiferro

Mono-H Di-H Di+Mono

Mono-Hydrogenation

Hydrogen atom

Localized π orbital

Localized π orbital

Possible mono-H termination of edge dangling bonds

After hydrogen annealing

GNR

zigzag edges

Nano-pores

Number of H atoms should be equal on both edges of a GNR (neighboring two nano-pore edges)

Di-H termination results in sp3 and σ orbital

Suppression of ferromagnetism

Mono-H

①Total area of bulk-graphenes used for formation of nano-pore array: ∼4 cm2

②Area of one hexagonal unit cell: S = 6(3-1/2/2)(a/2)2 = ∼4300 nm2; a = [80 nm(pore diameter) + 20nm (pore spacing)]

③Total number of nano-pores: ①/② = 4 cm2 /4300 nm2 = ∼1011

④Total number of dangling bond per one hexagonal pore:40 nm/(0.142 nm×31/2)×6 = 166×6 = ∼1000

⑤Total number of edge dangling bonds of the nano-pore graphene used for SQUID: ③×④=1014

⑥Saturation magnetization value per one edge dangling bond: 1.2×10-6 (emu)×10-3/(⑤=1014) = 1.2×10-23 (J/T)

⑦Magnetic moment per one edge dangling bond:(⑥=1.2×10-23)/(μB=9.3×10-24)= ∼1.3μB

⑧Magnetic moment per one edge π-orbital after mono-hydrogenation of dangling bond: (⑦=1.3μB)/3 = ∼0.43μB

Estimation of edge-carbon magnetic moment

Elimination of Magnetic moment at zigzag edges with Oxygen termination

R.G.A. Veiga, et al., J. Chem. Phys. 128, 201101 (2008)

No oxygenOxygen

Edge

Spin paired C-O

Suppression of Ferromagnetism in Graphitenano-pore arrays with Hydrogen-terminated

edges

HydrogenT = 2K

Mag

netiz

atio

n (μ

emu/

100μ

m2 ) 4

-2

0

2

-4

HydrogenT = 300K

-1

-0.5

0

0.5

1

Magnetic Field (gauss)10005000500-1000 5000-500

Elimination of Magnetic moment by Interlayer coupling in Zigzag-edge graphite with Hydrogen termination

No termination

Lee, H. et al. Chem.Phys.Lett. 398 207 (2004)

Contents1.背景

２．カーボンナノチューブの酸化開口+熱処理で形成した低欠陥グラフェンナノリボン

欠陥ナノリボンの約７倍のエネルギーバンドギャップ

３．多孔質アルミナ膜マスクで形成した低欠陥アンチドット（ナノ細孔）格子グラフェン

細孔エッジに起因した室温強磁性の発現

Non-lithographic

異常磁気抵抗振動 （約10層）

PRL

温故知新

Nature Nanotech & Latest Highlights, News & Views

Arm Chair

zigzag

Antidot Lattice on Semiconductor 2DEG (∼1990)

M. Kato,S. Katsumoto, Y. Iye, PRB 77, 155318 (2008).

D. Weiss, K. von Klitzing et al., PRL 70, 4118 (1993)

Rc = (πnS)1/2 (h/2π)/eB∆BABT = (h/e)/S

Commensurability peak

Aharonov-Bohm-type Oscillation

Antidots

-

Antidot

Cyclotron orbit

High B

Low B

Under enough antidot spacing

Anomalous FQHEsφ∼200nm/Ls∼600nm = ∼1/3

Anomalous filling factor

Antidots

No antidots

Composite Fermion

Kang, Stormer, PRL71, 3850 (1993)

In Graphenes： How edge-localized electrons are interacted with cyclotron-moton electrons?

Antidot Lattice as a scattering center for electrons on 2DEG

Antidot Lattice Graphene

T. Shen et al., APL 93, 122102 (2008).

S.Russo et al., PRB 77, 085413 (2008).

J. Bai et al., Nature Nanotech. 5, 190 (2010).

Only a few publications No reports for edges

FESEM images of ADLGs

100

0

-100

50

-50

1000-1000 -500 5000-1000 -500 0 500 1000-6.0e-5

-4.0e-5

-2.0e-5

0.0

2.0e-5

4.0e-5

6.0e-560

20

40

-60

0

-40

-20

1000-500 5000-1000

0

-400

-800

400

800

1000-1000 -500 5000Mag

netiz

atio

n (e

mu/

100μ

m2 )

Magnetic field (gauss)

(a) (b) (c)

T = 2K T = 2KT = 2K

Hydrogen Oxygen No antidots

All-carbon Ferromagnetism in ADLG with Hydrogen-terminated edges

Mono-layer graphene

Evidence for zigzag at antidot edgeCorrelation of localized electrons

with MR oscillations??

Aharonov-Bohm-type Oscillations in H2-terminated ADLGs

Commensurability peak φ= ∼80 nmAD Space ∼80 nm

2Rc = (πnS)1/2 (h/2π)/eB= a

nS ∼ 4 × 1011 cm-2

le = 2D/vF ∼ 800 nm > 2π(a/2) = ∼ 540 nm

ΔB = ∼ 200 mT

∆BABT = (h/e)/(S)

Sample B

Fourier Spectrum

AB-type oscillation

Low B

High B

Low B ΔB∼200 mT

Electron trajectories on honey-comb ADL and magnetoresistance oscillations

∆BABT=(h/e)/S S = 6(3-1/2/2)(a/2)2

Quantized electron orbitals around antidotsin an unit cell

a = ∼160 nm

En = h2/2mL2(n - Φ/φ0)

AB-type oscillation

2Rc = (πnS)1/2 (h/2π)/eB= a

nS ∼ 4 × 1011 cm-2

le = 2D/vF ∼ 800 nm > 2π(a/2) = ∼ 540 nm

En = h2/2mL2(n - Φ/φ0)

Aharonov-Bohm-type effect

∆BABT=(h/e)/S

Anomalous MR Oscillations in ADL- multi-layered Graphenes

Commensurability peak φ= ∼80 nm

Sample B

Fourier Spectrum

2Rc = (πnS)1/2 (h/2π)/eB= a

nS ∼ 4 × 1011 cm-2

le = 2D/vF ∼ 800 nm > 2π(a/2) = ∼ 540 nm

ΔB∼260 mT High B

High B

S: r for pore radius

ΔB∼260 mT

Electron trajectories on honey-comb ADL and magnetoresistance oscillations

∆B=(h/e)/(πr2) with r = ∼ 40 nm

Antidot radius

Absent AB effect

Bohr–Sommerfeld quantization condition Φ=Bπr2=m(h/e) m: integer

Like flux quanta in superconductor

Edge-Localized electrons

Quantization of magnetic flux

-

∆BAB = (h/e)/(πr2)

Aharonov-Bohm effect

2Rc = (πnS)1/2 (h/2π)/eB= a

nS ∼ 4 × 1011 cm-2

le = 2D/vF ∼ 800 nm > 2π(a/2) = ∼ 540 nm

En = h2/2mL2(n - Φ/φ0)

Aharonov-Bohm-type effect

Vector potential A

Ensemble average Disappearance

∆BABT=(h/e)/S

Fourier Spectrum

△B2 = ∼70 mT ∆BABT =(h/e)/S = ∼50 mT

Contribution of larger unit cell (2nd unit cell)

Contents1.背景

２．カーボンナノチューブの酸化開口+熱処理で形成した低欠陥グラフェンナノリボン

欠陥ナノリボンの約７倍のエネルギーバンドギャップ

３．多孔質アルミナ膜マスクで形成した低欠陥アンチドット（ナノ細孔）格子グラフェン

細孔エッジに起因した異常磁気抵抗振動

室温強磁性の発現

Non-lithographic

（約10層）

（単層）

４．今後 電場によるエッジ偏極スピンの制御

温故知新

Nature Nanotech & Latest Highlights, News & Views

Arm Chair

zigzag

Y-W. Son, S.Louie et al., Nature 444, 347–349 (2006)

0.0

Eext = 0.0 0.05 0.1 VA -1

Spin Current & Filter

Eext

0.05

0.1

Jsy = (h/2e)(J↑y − J↓y )

Ｅ

S. Murakami, N. Nagaosa, and S. C. Zhang, Science 301,1348 (2003).

J. Sinova, et al., Phys. Rev. Lett. 92 126603 (2004)

Spin Current & Spin Hall EffectLuttinger模型

Rashba型スピン軌道相互作用

半導体

遷移金属

Pt/Ni-Fe 接合

Sr2RuO4

強磁性/非磁性複合構造

異常ホール効果

スピンホール効果

東北大 高梨

強磁性体

多バンド現象 h/∆Eに比例 τに独立

Kane, C. L. and Mele, E. J.,. Phys.Rev. Lett. 95, 226801 (2005)

(Quantum) Spin Hall Effect in Graphene

QSHE regime Insulating regime

Modulation of flat band

M.Schmidt & D.Loss, Phys. Rev. B 81, 165439 (2010)

Spin Hall Effect in graphen/graphen junction with hydrogen termination

No SO Interaction

H-CH-C

sp3 SOI

M.Schmidt & D.Loss, Phys. Rev. B 81, 165439 (2010)

SO Interaction

Spin Hall Effect in graphen/graphen junction with hydrogen termination

Edge Bulk

Conclusion

1．カーボンナノチューブの酸化開口・熱処理で形成した低欠陥グラフェンナノリボン

欠陥ナノリボンの約７倍のエネルギーバンドギャップ

2．多孔質アルミナ膜マスクで形成した低欠陥アンチドット格子グラフェン

細孔エッジに起因した異常磁気抵抗振動

室温強磁性の発現

Non-lithographic

今後： 細いGNRの電子輸送特性磁性の起源解明＆制御電場によるエッジスピン制御

グラフェンのエッジと電子・磁気物性

炭素磁石

Arm Chair

zigzag

MIT: Millie Dresselhaus

Colombia University: Philip Kim

Rice University: James Tour

Tokyo Institute of Technology: T.Ando, T.Enoki

Tokyo University: S.Tarucha, M.Yamamoto, H.Fukuyama, T.Matsui, H. Aoki

Tokyo University, ISSP: Y.Iye, S.Katsumoto, T.Otsuka

AIST: K. Suenaga

My students and staffJapan Science and Technology Agency:CREST

Hidetoshi Fukuyama

Jun Akimitsu

So many thanks to