1953-32

International Workshop on the Frontiers of Modern Plasma Physics

R. Hatakeyama

14 - 25 July 2008

Tohoku University,Dept. of Electronic EngineeringSendaiJapan

Q-Machine Plasmas Yielding New Experimental Methodologies of Sheared-Flowand Nano-Quantum Physics.

1

Q-Machine Plasmas Yielding New Experimental Methodologies of Sheared-Flow and Nano-Quantum

Physics

R. Hatakeyama and T. Kaneko

Department of Electronic Engineering, Tohoku University, Sendai / Japan

International Workshop on The Frontiers of Modern Plasma PhysicsAbdus Salam ICTP, Trieste/Italy, 21-25 July 2008

2

The Q machine has been used since the 1960s (~1958) : Ion acoustic, electron plasma, ion cyclotron, drift, … waves and instabilities, nonlinear phenomena such as double layers, …. in magnetized plasmas⇒ Modification to sheared-flow physics study

Innovative transformation of Q machines into the contribution to nano physics & chemistry fields since 1995.

ALKALI METALBEAM OVEN

Work function of solid and ionization potential of atom.

Contact Ionization

3

1. Q-Machine Modification Corresponding to Sheared-Flow

Plasma Physics Study

1. Q1. Q--Machine Modification Machine Modification Corresponding to ShearedCorresponding to Sheared--Flow Flow

Plasma Physics Study Plasma Physics Study

4

Both the ion and electron emitters are concentrically segmented.

Experimental Setup

Rev. Sci. Instrum. 73 (2002) 4218

(0 V) (0 V)(-60 V)

5

Phys. Scripta T107 (2004) 200 Trans. Fusion Sci. Technol. 47 (2005) 128Trans. Fusion Sci. Technol. 51 (2007) 103Plasma Fusion Res. 3 (2008) S1011

Potassium ionflow shear

Cesium ionflow shear

super-position

Effect of hybrid ions

Electron EmitterDetermine space potential

⇒ E×B flow velocityControl of perpendicular

flow velocity shear

Ion EmitterDetermine ion flow energy parallel to BControl of parallel flow velocity shear

super-position

Superposition of K and Cs Ion Flow Velocity ShearsSuperposition of B|| and B⊥ Flow Velocity Shears

-5 0 5r (cm)

φ (V

)

Vee2 = 0 V Vee1(V)

1 V

-2.0-1.0-0.70.01.0

0 20 40VC (V)

No.2

No.1

No.2

r (cm)0

2.5

-2.5

φ Fi||

B|| ShearsB⊥ Shears

Phys. Rev. Lett. 90 (2003) 125001 Phys. Rev. Lett. 92 (2004) 069502Phys. Plasmas 12 (2005) 072103 Phys. Plasmas 12 (2005) 102106

-1.92 -1.84 -1.76 -1.68

-1.6

-0.8

0.0

0.8

1.6

2.4(%)

Vee1 (V)V

ie1 (

V)

0

5.0

10.0

15.0

20.0

Vie2= 1.0 V，Vee2= -2.00 VNormalized fluctuation amplitude at r = -1.0 cm (shear region).

A B

B⊥ shear

B//

shea

r No B// shear

No

B⊥

shea

r

turbulent

Superposition of K and Cs Ion Flow Velocity Shears (Drift Wave)

Superposition of B|| and B⊥ Flow Velocity Shears (Drift Wave)

0 4 8

–1.6

–0.8

0.0

0.8

1.6

2.4

Vie1 (V)

ω/2π (kHz)

0 1 2 3 40

1

2

3

Δ Vie (V)

I es/I e

s (%

)0 1 2 3 4

0

1

2

3

I es/I e

s (%

)

Δ Vie (V)

Cs K

Cs＋K 0 1 2 3 402

4

6

8

I es/I e

s (%

)

Δ Vie (V)0 1 2 3 4

0

1

2

3

Δ Vie (V)

I es/I e

s (%

)

1 2 3 4 5 6 7 8 9 100

1

2

3

0

0.2

0.4

0.6

Time (a.u.)

n e (×

109

cm

3 )

neTe

T e (e

V)

7

Electron Temperature Gradient Instabilitiesin Magnetized Plasmas

8

Temperature Gradient Driven Modes in Magnetically Confined Plasmas

• ITG modes are the most plausible candidate for the anomaly of ion channel thermal transport.

• EXB sheared flow suppression effects on ITG modes are identified[1,2].

Ion Temperature Gradient (ITG) Modes Electron Temperature Gradient (ETG) Modes

• ETG modes are also the plausible candidate for the electron transport properties of tokamak devices [3].

• ETG modes are difficult to be stabilized by EXB shear.

INTRODUCTION

[1] Z. Gao, H. Sanuki , K. Itoh, and J.Q. Dong, Phys. Plasmas 10 (2003) 2831.[2] Z. Gao, J. Q. Dong, and H.Sanuki, Phys. Plasmas 11 (2004) 3053. [3] Y.C. Lee, J. Q. Dong, P.N. Guzdar, and C.S. Liu, Phys. Fluids 30 (1987) 1331.

9

Why ETG Mode is Important?

• Experimental observation expresses that the low frequency instability is driven by ETG and nonlinear effects of ETG modes generate significant electron transport.

• The growth rate of ETG mode is about 20 times larger than that of short wave length ITG mode.

• It is an important issue to reduce the electron thermal transport observed in magnetically confined fusion devices.

• Therefore it is necessary to examine the role of ETG driven mode in a linear machine so that the result would be applicable in tokamak plasmas.

10

ITG mode

ETG mode

Theoretically investigated by Z. Gao, et al., Phys. Plasmas 10 (2003) 2831, 11 (2004) 3053.

Stabilization by ExB shear

ie

ieie nd

Td

,

,, ln

ln=η = electron, ion temperature gradient, and VE‘ is the EXB shear velocity.Where,

11

To produce and control electron temperature gradient (ETG) using a thermionic electron superimposed electron cyclotron resonance (ECR) plasma and applying voltages to two different sized mesh grids and finally to examine the stabilization of ETG mode by E X B sheared suppression in a linear machine..

• In laboratory experiments, several techniques have been applied to the control of the electron temperature[4-6], but it is difficult to realize spatially different electron temperatures at a localized area.

[4] G. T. Hoang, et al. Phys. Rev. Lett. 87 (2001) 125001.[5] F. Porcelli, E. Rossi, G. Cima, and A Wootton , Phys. Rev. Lett. 82 (1999) 1458.[6] K. Kato, S. Iizuka, and N. Sato, Appl. Phys. Lett. 65 (1994) 816.

Objective

12

EXPERIMENTAL APPARATUS

13

Electron emitter (W hot plate)

Grid bias: additional discharge generates low Te electron

Deformation of density and temperature profiles from source to experimental region due to mesh grids

Electron emitter (W hot plate)

Construction of mesh grids

Supply of thermionic low Te electrons from electron emitter (EE)

Thermionic electrons superimposed (SI) ECR plasma50 mm

Grid 2

Grid 1

High Te electrons in ECR plasma

14

–5 0 5r (cm)

φ (V

)

VH2 = 0.0 V

VH1 = 1.0 V1 V

0.0 V

–0.65 V

–1.0 V

–2.0 V

By applying different voltages to the electrodes 1, 2, and 3, radial profiles of plasma potentials can be changed and as a resultE X B shear is generated in t h e c e n t r a l r e g i o n

EXB sheared suppression

E X B shear is generated

15

Formation and Control of ETG in thermionic electron superimposed ECR plasmas by changing vg2

vg2=-5V vg2= -10V vg2=-50V

vg1= floating potential

No ETG is formed Small ETG is formed ETG becomes large

-5 0 50

2

4

r (cm)

T e (e

V)

-5 0 50

2

4

r (cm)

T e (e

V)

-5 0 50

2

4

r (cm)

T e (e

V)

-5 0 50

4

8

r (cm)

n e (

10

8 cm

-3)

-5 0 50

4

8

r (cm)

n e (

10

8 cm

-3)

-5 0 50

4

8

r (cm)

n e (

10

8 cm

-3)

16

2. Innovative Transformation of Q Machine Corresponding to

Nano Physics & Chemistry Study

2. Innovative Transformation 2. Innovative Transformation of Q Machine Corresponding to of Q Machine Corresponding to

NanoNano Physics & Chemistry Study Physics & Chemistry Study

17

Electron-based electronics & Information technology

Atom

＋－

Exploiting both the two

Semiconductor spintronics

Charge(Semiconductor)

Spin(Magnetic materials)

Electron

● Gaseous atom encapsulated fullerene（H, He, F, N, ･･･）

ＮLong spin lifetimeSharp resonance

Quantum computer(Atomic nitrogen encapsulated fullerene)

●Endohedral metallofullerene

Ｍ＋－

Fe

ferromagnetic

Magnetic semiconductor

Endofullerene-based nanoelectronics

Pseudo atom

Charge transfer

Single molecular orientation switchingHigh efficiency solar cellHigh-temperature superconductivity

(Atom encapsulated fullerene)

18

Phys. Plasmas 1 (1994) 3480

J. Vac. Sci. Technol. A 14(1996) 615

Generation of Alkali-Fullerene Plasma

Slightly Positive Bias

Positive-Negative Ions Interaction

19

Pair C60-Ion and H-ion Plasmas

Phys. Rev. Lett. 91 (2003) 205005 Phys. Rev. Lett., 95 (2005) 175003 Phys. Rev. E, 75 (2007) 056403 Phys. Plasmas, 14 (2007) 055704

20

Periodic Table

Alkali-Metals

Halogens

21

Alkali-Halogen ( Cs＋− I－ ) Plasma Generation

Salt: KCl, CsCl, CsI, ….Appl. Phys. Lett. 8888 (2006) 191501

22

(10,10)

http://www.photon.t.u-tokyo.ac.jp/index-j.htmlFrom the home page of Maruyama Lab, Univ. Tokyo

23by slight differences of their structure (without any impurity doping)by slight differences of their structure (without any impurity dby slight differences of their structure (without any impurity doping)oping)

Translation vector Chiral vector

Arm chair tubeArm chair tube

ZigZig--ZagZag tubetube(Narrow gap)

ChiralChiral tubetube(Wide gap)

Metal

Semiconductor

Tube electric properties drastically change from metal to semicoTube electric properties drastically change from metal to semiconductornductor

24

SWNT: single-walled nanotube MWNT: multi-walled nanotube

There are 3 basic types of nanotubes

DWNT: double-walled nanotube

Appl. Phys. Lett. 83 (2003) 119 J. Appl. Phys. 96 (2004) 6053

Creation of Evolved Carbon NanotubesCreation of Evolved Carbon NanotubesCreation of Evolved Carbon Nanotubes

Diameter: ~ nmLength: < nm ~ μm ~ mm

25

Electron Temperature

26

Freestanding growth of individual SWNTs on a flat substrate

From these results(SEM, TEM, Raman)

Freestanding-individual SWNTs have been successfully produced on a silicon-based flat substrate due to plasma-sheath effect !!Chem. Phys. Lett. 381381 (2003) 422; Jap. J. Appl. Phys. (Exp. Lett.) 4343 (2004)

L1278; Nanotechnol. 1717 (2006) 2223 ; Appl. Phys. Lett. 9292 (2008) 031502

On

SiO

2/Si

On

Cu

wire

(e) A

s gr

own

stat

e w

asdi

rect

ly o

bser

ved

by T

EM

Cu wire

Cu wire

・Dgs : 20, 70 mm,・PRF : 40 W,・Tpro : 60, 180 sec,・Tsub: 700, 750℃

27

Isolated Bundled

Emission energy [eV]Ex

cita

tion

ener

gy [e

V]

8

2

2

4

8

2

2

4

8

2

2

4

(e)

1.0 1.2 1.4

(d)

1.0 1.2 1.4

(c)

1.0 1.2 1.4

(b)

1.0 1.2 1.4

(a)2.4

1.82.0

2.2

1.0 1.2 1.4

Unique photoluminescence features in freestanding SWNTs

J. Am. Chem. Soc. 130 (2008) 8101

Passage time [h]0 5 10

–1

0

1

I int(6

,5)→

(6,5

) t

I int(6

,5)→

bund

let

0)()( )5,6( =

∂∂

+∂

∂

ttS

ttS bundle

The continuous equation for PL intensity is found to hold in the time trance of isolated and bundled tubes.

Exciton energies transfer from isolated to bundled tubes caused the PL brightening.

Excitation (S22)

–2 0 20

1

Energy [eV]

DO

S (a

.u.)

(8, 7)

(S11)Emission

28

3. Inner Nano – Space Control of Carbon Nanotubes Based on

Fundamental Plasma Physics

3. Inner Nano 3. Inner Nano –– Space Control of Space Control of Carbon Nanotubes Based on Carbon Nanotubes Based on

Fundamental Plasma PhysicsFundamental Plasma Physics

“Charge and Spin of Electrons are expected to be effectively exploited”

““Charge and Spin of Electrons are Charge and Spin of Electrons are expected to be effectively exploitedexpected to be effectively exploited””

29

Formation of Atom / Molecule Encapsulated Single- and Double-WalledCarbon Nanotubes Using Different-Polarity Ion Plasmas

Formation of Atom / Molecule EncapsulatedFormation of Atom / Molecule Encapsulated SingleSingle-- and Doubleand Double--WalledWalledCarbon Nanotubes Using DifferentCarbon Nanotubes Using Different--Polarity Ion PlasmasPolarity Ion Plasmas

13.6Å 40Å

30

SWNTs/DWNTsSWNTs/DWNTs

Plasma Experimental Method

0 V < φap < 50 V

-300 V < φap < 0 V

Junction Formation inside SWNT/DWNT

Stationary Operation

Compound Formation inside SWNT/DWNT

Pulsed Operation

31

2 nm 2 nm

SWNTs DWNTs

2 nm

C60@DWNTs

2 nm 2 nm

Cs@DWNTsDWNTsC60@SWNTs

5 nm

I@SWNTs

Cs@SWNTs

Fe(C5H5)2@SWNTs

Fe@SWNTs

1 nm1 nm

DNA@SWNTs

2 nm

TEM Images of Atoms and Molecules Encapsulated SWNTs / DWNTs

5 nm

Ca@SWNTs

Appl. Phys. Lett. 7979 (2001) 4213 Chem. Commun. 11 (2003) 152

Phys. Rev. B 6868 (2003) 075410

Thin Solid Films 464-465 (2004) 299

Appl. Phys. Lett. 89 (2006) 093110

Jpn. J. Appl. Phys. 45 ( 2006) L428Chem. Phys. Lett. 417417 (2006) 288; Jpn. J. Appl. Phys. 45 (2006) 8335

32

TEM Images of Pristine and Various Fullerenes Encapsulated SWNTs

Scale bar: 2 nm

C60@SWNT C70@SWNT C84@SWNTPristine SWNT

ellipse

C59N@SWNT

e)

33

Electronic Structure inside Atom Encapsulated SWNT

Theoretical calculation!Theoretical calculation!

Bright field STEM imageBright field STEM imageZ-contrast imageZ-contrast image

Encapsulated

Empty

Encapsulated

Empty

Phys. Rev. B 6868(2003) 075410

Cs unfilled Cs filled

STS / STM ResultSTS / STS / STM ResultSTM Result

Collaboration with Y. Kuk’ group Phys. Rev. Lett. 99 (2007) 256407

34

4. Electromagnetic Properties of Atom/Molecule Encapsulated

Carbon Nanotubes

4. Electromagnetic Properties of 4. Electromagnetic Properties of Atom/Molecule Encapsulated Atom/Molecule Encapsulated

Carbon NanotubesCarbon Nanotubes

35

4.1 Control of Semiconducting Properties of Single-Walled

Carbon Nanotubes

4.1 Control of Semiconducting 4.1 Control of Semiconducting Properties of SingleProperties of Single--Walled Walled

Carbon Carbon NanotubesNanotubes

36

A schematic of SWNT-FET

SWNT

An AFM image of SWNT- FET

Field-Effect Transistors (FETs) Based on SWNT

Jpn. J. Appl. Phys. 44 (2005) 1606

Source Drain

IDS VD

VG

Ａu Ａu

p- and n-type transport properties appear.

Pristine SWNT

Cn@SWNT

(n = 60, 70, 84)

IDS - VG characteristics(VDS = 1 V, in vacuum, at 297 K)

IDS - VG characteristics(VDS = 1 V, in vacuum, at 297 K)

C59N@SWNT

-40 -20 0 20 400

50

100

150

200

250

VG(V)

I DS(n

A)

Ptistine SWNTC60@SWNTC59N@SWNT

J. Am. Chem. Soc. 130 (2008) 2714.

p n

37

Transport Properties of Cs@SWNT(In Vacuum, Room Temp., VDS = 1 V)

45 minD = 6.5×104 /nm2

60 minD = 8.6×104 /nm2

-22.2 V -29.6 V

-35.6 V

15 minD = 2.2×104 /nm2

30 minD = 4.3×104 /nm2

Dependence of Ion Dose on Electrical Characteristics of Cs@SWNTs

p-type

n-type

• As the amount of dosed Cs increases, the threshold for p-type shifts left.

• After 60 min Cs irradiation Cs@SWNT shows completely n-type behavior.

• As the amount of dosed Cs increases, the threshold for p-type shifts left.

• After 60 min Cs irradiation Cs@SWNT shows completely n-type behavior.

Electronic structure of SWNT can be controlled by adjusting an amount of dosed Cs atoms.

Electronic structure of SWNT can be controlled by adjusting an amount of dosed Cs atoms.

Appl. Phys. Lett. 89 (2006) 093121

Cs: Electron donor

38

Transport Properties of I @SWNT（In Vacuum，Room Temp.）30 min

Dependence of Ion Dose on Electrical Characteristics of I@SWNT

–40 –20 0 20 400

1

2

I DS

(nA

)

VG (V)

VDS=500 mV

–40 –20 0 20 400

100

200

I DS

(nA

)

VG (V)

VDS=100 mV

–40 –20 0 20 400

20

40

I DS (

nA)

VG (V)

VDS=100 mV

0 500

1

2

3

I DS (

nA)

VG (V)

VDS=100 mV

60 min

120 min 240 min

−20 V −10 V

+10 V +60 V

Enhanced p-type

• As the amount of dosed I increases, the threshold for p-type shifts right.

• After 240 min I irradiation I@SWNT shows a clear enhanced p-type behavior with threshold at 60 V.

• As the amount of dosed I increases, the threshold for p-type shifts right.

• After 240 min I irradiation I@SWNT shows a clear enhanced p-type behavior with threshold at 60 V.

Jpn. J. Appl. Phys., 47 (2008) 2044Jpn. J. Appl. Phys., 47 (2008) 2044

I: Electron acceptor

39

4.2 Formation of Nano pn Junctionsby Controlling Different-Polarity

Ion Plasmas

4.2 Formation of Nano 4.2 Formation of Nano pnpn JunctionsJunctionsby Controlling Differentby Controlling Different--Polarity Polarity

Ion PlasmasIon Plasmas

40

Controlled Formation of Nano pn Junctions [(Cs/C60)@SWNT]

Pulsed Operation

C60

Cs

5 nm

0 V < φap < 50 V

-300 V < φap < 0 V

41

Using Alkali-Halogen ( Cs＋- I－ ) Plasma

I− Cs+

Nano pn Junction

Halogens

Alkali-Metals

42

Nano pn Junction Formed by (Cs/I) @ DWNTICs

-1.0 -0.5 0.0 0.5 1.00

10

20

30

I DS (

nA)

V

DS(V)

For ideal diode measured at V

G= -40 V

IDS = IS (e qVDS / nKBT -1)

IS = 10-12 A; n = 1.5; T= 300 K

A B C D

-40 -20 0 20 400

10

20

30

VG (V)

I DS(

nA)

VDS = 1V

Video link

I-

Cs+

43

Nano pn Junction with stable rectifying behavior of (Cs/I)@DWNT and (Cs/I)@SWNT in air

Output characteristics keep stable even in air, indicating p-n junction in SWNTs & DWNTswith high-performance can be fabricated by hetero-atoms or -molecules encapsulation.

-1.0 -0.5 0.0 0.5 1.00

10

20

30

40

50

VG= -40 V

I D

S (nA

)

VDS(V)

In vacuum In air For ideal diode

I Cs

0

1

0 2-2

0

10

VDS [V]

Vacuum

Air

I DS

[nA

]

CsI

(Cs/I)@DWNT (Cs/I)@SWNT

(Baseline upshift for clarity)

44

4.3 4.3 4.3 Coulomb Oscillation Characteristics

― Quantum Dot Formation ―

of Encapsulated Carbon Nanotube

45

VG

I

The energy level is quantized in a quantum dotThe energy level is quantized in a quantum dot

Current through only when the quantum energy level matches with the fermi energy of drain electrode

Current through only when the quantum energy level matches with the fermi energy of drain electrode

The static energy level in quantum dot can be controlled by externally applied VG

(VDS : constant)

The quantum dot size can be estimated with the Coulomb

oscillation

Investigate the effect of alkali-atom encapsulation on SWNTs

The quantum dot size can be estimated with the Coulomb

oscillation

Investigate the effect of alkali-atom encapsulation on SWNTs

( )dLL

VC

G /2lnπε2e 0

g ≈Δ=

Fig.：Quantum dot and Coulomb oscillation formed by a single dot

L: Dot sized: SWNT diameter

ΔVG

Coulomb oscillation

Tunneling barrier Tunneling barrier

Quantum dot

CarrierSource electrode potential

Drain electrode potential

Potential in a quantum dot

46

Coulomb Oscillations Observed in Encapsulated Nanotubes

-15 -10 -5 0 5 10 15

0.0

0.3

0.6

0.9

1.2

I DS (n

A)

VG(V) -40 -20 0 20 40 60

0.0

0.2

0.4

0.6

0.8

I DS (n

A)

VG(V)

Cs@SWNT C60@SWNT

Fe@SWNT Cs@DWNT

Quantum dots formed in nanotubes due to foreign materials encapsulation.

47

SummaryHistorical evolutions over 50 years of Q-machine plasma

researches are reviewed, where a special emphasis is placed on experimental methodologies of sheared-flow and nano-quantum physics.

Following the drift-wave studies on superposition effects of parallel and perpendicular flow velocity shears and hybrid ions flow velocity shears, an experiment on electron temperature gradient (ETG) instabilities is started, where the large ETG is successfully generated with the radial density profile kept uniform using thermionic electron superimposed ECR plasma.

The innovative transformation of Q machine plasmas for nano physics and chemistry studies has been performed in order to create novel nano-structures and new functional nano-materials by controlling inner nano-spaces of fullerenes and carbon nanotubes.

48

Welcome to

Fukuoka, J

apan

49

50

R. Hatakeyama (Chairman)Department of Electronic Engineering, Tohoku University6-6-05 Aoba, Aramaki, Aoba-ku, Sendai 980-8579, JapanTelephone: +81-22-795-7045Facsimile: +81-22-263-9375E-mail: ISGLP@ecei.tohoku.ac.jp

International Interdisciplinary-Symposium on Gaseous and Liquid Plasmas

(ISGLP2008)September 5-6, 2008

Tohoku University / Sendai, Japan

http://www.plasma.ecei.tohoku.ac.jp/ISGLP/August 2008Final announcement/program

August 2008Four-page papers deadline for a proceedings volume

June 2008Second announcement

May 2008One-page abstract deadline

March 2008First announcement and call for papersCalendar of Events

Satellite Meeting of International Congress on Plasma Physics (ICPP2008)