maria losurdo nim nil - european commission · pdf filemaria losurdo nim_nil laurea cum laude...

Maria LOSURDO NIM_NIL Laurea cum laude in Chemistry from University of Bari, Italy

Joint PhD from Ecole Polytechnique (Palaiseau-France) and University of Bari,

Italy in Materials Science.

Senior Scientist in the Institute of Inorganic Methodologies and of Plasmas at

National Council of Reserach (CNR), and an Adjunct Professor at the

Department of Electrical and Computer Engineering of the Duke University at

Durham, NC-US.

Co-editor of 2 Journals: “EP-JAP” and "ISRN Materials Science"

Specialist in CVD growth of materials and ellipsometry

She approached graphene by her expertise in CVD growth and plasma processing of SiC.; she is co-author of a US patent on “Metal-aided graphenization of SiC”

Location, 09/09/2009 Page 1N.N. (Speaker), Name of the Partner Brussels, March 21-22, 2011

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Graphenein

Maria Losurdo and Giovanni Bruno

Large Area Fabrication of 3D Negative Index Materials by

NanoImprint Lithography

[email protected]

[email protected]

Location, 09/09/2009 Page 2N.N. (Speaker), Name of the Partner Page 2

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Outline

NIMNIL Consortium

NIMNIL Objective

Graphene for Metamaterials in the NIMNIL context

Processing/Structuring of Graphene

Synthesis of Grapheneexfoliation

SiC “graphenization”

CVD

Real-Time Monitoring and Controlling Graphene growth

Summary/Outlook


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Consortium

Duration: 3 years

Starting date: 01.09.09Coordinator: Profactor GmbH; Iris Bergmair

[email protected]

Consortium Structuring Graphene

Synthesis of Graphene Real Time Monitoring Conclusions

Objectives Graphene for Metamaterials

Characterisation


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Project Objectives

Design of NIMs

• New structure designs for NIMs

• New material Graphene

Fabrication of NIMs

• NIL as fabrication method

• Deposition & Structuring of Graphene

• Large area NIMs

• 3D NIMs

Characterisation of NIMs

• Optical properties of Graphene and its structures

• Ellipsometry, Raman, AFM/SEM

• Transmission, reflection, phase measurements

Demonstration of NIMs

• 3D NIM prism

NIM= Negative Index Materials

Objectives Structuring Graphene


Consortium Graphene for Metamaterials

Characterisation


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Graphene for Metamaterials

Original concepts for using graphene

Structuring graphene

Fabrication of graphene

Characterisation of graphene

Main activities relate to:



Objectives

Characterisation



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[Science, 328, (2010) p.582]

2 In the Infrared and Terahertz:Electroptical Modulation

1Medium composite consisting of

single- or few-layer graphene on

nanostructured metal films

grapheneSilver metamaterial

structure

In the Visible:

Graphene has potential to cover the range

Visible-infrared-terahertz by 2 approaches



Objectives

Characterisation



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Graphene in a Photonic Metamaterial: Approach-1

[N. Papasimakis et al. OPTICS EXPRESS 18, 8353 (2010)]

IR: Graphene on Gold

Graphene modifies the transmission

spectrum of such a metamaterial leading to

an increase of transmission exceeding 250%.

graphene

Change o

f T

ransm

issio

n w

ith G

raphene

Wavelength (nm)

oxidized cleaned 1h 1day 3day 5day12.5

13.0

13.5

14.0

14.5

15.0

P

SI

@ A

g p

lasm

on

pe

ak

TIME of AIR EXPOSURE

Visible: Graphene on Silver

2

mx2

m

Silver fishnet

5

mx5

m

Silver gratings

Plasma Passivation of Ag + Transfer of graphene ontop 1 2

Graphene limits/inhibits silver oxidation

370 368 366

As deposited gratings

After processing

Ag

AgO

AgGraphene enhances resonance

2 3 4

20

25

30

35

40

PS

I°

Photon Energy (eV)

Ag as-grown

after passivation

enhancem

ent



Objectives

Characterisation



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Graphene in Metamaterials: Approach-2

The height of structures is 2 nm

Graphene Swiss Cross structures.

Linewidth is 20 nm. Layer height is 500 pm

Graphene Fishnet

structures.

Line width is 70 nm

100 µm

100m

a) exfoliated graphene is placed on the substrate.

b) resist is patterned on the graphene by nanoimprint lithography

c) an O2 plasma etching of graphene takes place on the area

without mask

d) a graphene pattern is obtained after removing the resist

(b)

(c)

(d)

(a)

GrapheneResist

Mold

Graphene

Graphene

Graphene

Graphene is nanostructured to achieve Controlled Size and Shape layers

using NIL and an O2 plasma



Objectives

Characterisation

Structuring Graphene


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CVD-G on Cu

Controlled Etching of Graphene

Magnification 20.000x. Line width is 1.5 µm

CVD-G on Ni

Graphene Gratings on Nickel and Copper by CVD structured using NIL and an O2 plasma

1000 1500 2000 2500 3000 3500

Wavenumber (cm-1)

G

2D

G2D

1500 2000 2500

Wavenumber (cm-1)



Objectives

Characterisation



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Synthesis Routes to Graphene in NIMNIL

2719

TIMET

EM

PE

RA

TU

RE

( C

)

Cle

an

ing &

An

ne

alin

g o

f su

bstr

ate

H2

flo

w

Gra

ph

ene

gro

wth

CH4 inCH4 out

Co

olin

g d

ow

n

H2

flo

w

CH4 + H2/Ar graphene

T900 C, P<4 Torr1

2

3

1200 1400 1600 1800 2000 2200 2400 2600 2800

2D

G

Wavenumber (cm-1)

1587cm-1

2705cm-1

FWHM=39cm-1

FWHM=31cm-1

I2D/IG=2.8

CVD on Polycrystalline&foils Nickel and Copper3


Synthesis of Graphene

Exfoliation of Graphite

100 µm

100m

1

SiC Decomposition

1594

24cm-1

1200 1400 1600 1800 2000 2200 2400 2600 2800

Wavenumber (cm-1)

2719

2

G

D


Real Time Monitoring Conclusions

Objectives

Characterisation


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Graphene CVD: Implementation of Growth Process

Peculiarities of our CVD growth processes:Integration of a Remote Plasma Source

Integration of in-situ Real Time Monitoring by Ellipsometry

Challenging goal:

To growth graphene of large scale with uniform thickness

How to achieve this?

We have uniquely developed a Real-Time Graphene Metrology





Objectives

Characterisation


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Graphene on Copper Foil by CVD

Since the growth was first demonstrated on Copper foil, there is a tendency to use the same foil:

Impurities affect not only quality but also the catalytic decomposition of CH4 and

therefore the thickness (Single or bi-layer)

[Z. Luo et al. Adv. Funct. Mater. 2011, 21, 911–917]

Kinetic factors, such as the surface reaction rate, play a critical role on the uniformity of thickness of CVD

graphene layers by limiting the deposition of carbon atoms on Cu surface.

The higher the impurities (e.g. Cu 99.8%), the faster surface reaction rate, the lower the thickness uniformity.

The dopants or impurities could effectively enhance the catalytic activity of the Cu surface

No growth of bilayer even after 120min

1500 2000 2500

Wavenumber (cm-1)

D

G 2D

Bi-L G grown on 99.5%Cu

(800°C 50min)

Impact of Copper foil impurities





Objectives

Characterisation


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Graphene by CVD on Copper Films

Graphene on Cu/SiO2/Si

0

100

200

300

400

500

600

700

800

900

1 000

1 100

1 200

1 300

1 400

Inte

nsi

ty (

cn

t/sec

)

1 200 1 400 1 600 1 800 2 000 2 200 2 400 2 600 2 800 3 000

Raman Shift (cm-1)

500

1 000

1 500

2 000

2 500

3 000

3 500

4 000

4 500

5 000

5 500

6 000

6 500

7 000

7 500

Inte

nsi

ty (

cn

t/sec

)

1 200 1 400 1 600 1 800 2 000 2 200 2 400 2 600 2 800 3 000

Raman Shift (cm-1)

FWHM=

33cm-1

FWHM=

60cm-1

IG/I2D=0.6

1581 26981595 2699

G

2D

T=1200°CT=1100°C

0

50

100

150

200

250

300

350

400

450

500

550

Inte

nsi

ty (cnt/

sec

)

1 200 1 400 1 600 1 800 2 000 2 200 2 400 2 600 2 800 3 000

Raman Shift (cm-1)

FWHM=

50cm-1

T=1000°C

Single Loretnzian peak mark of monolayer graphene

Impact of Growth temperature

D

G 2D

D

G2D

1593 2700

Three regimes of temperature have been identified that can be exploited for improving processes

grapheneResidual Cu





Objectives

Characterisation


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Graphene by CVD on Copper Films @ T>1200 C

Taking benefit of Cu dewetting (Tmelting =1084 C), graphene can be obtained on any

substrate avoiding the tedious etching/transferring/PMMA steps

Substrate engineering

30

0

mx3

00

m

Graphene directly on SiO2 and Al2O3

(residual copper-white strips can be removed by 5min HCl etching)





Objectives

Characterisation


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Graphene on Polycrystalline Nickel

2D FWHM=50cm-1

[A.J. Pollard et al. J. Phys. Chem. C,

113, 2009, 16565]

[A.Reina et al , Nanotechnology 21

(2010) 015601]

State-of-the-art[A. Reina et al. Nano Lett., 9,1, 2009]

Typically growth on polycrystalline Ni results in a

non-homogeneous mixture of few-layers graphene

We are able to achieve on polycrystalline Ni results similar to what obrained on single crystalline Ni

On Single crystal Ni(111)

CNR-IMIP

On poly-Ni





Objectives

Characterisation


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Graphene by CVD on Nickel

30

40

50

60

70

80

90

100

110

120

130

Inte

nsi

ty (

cn

t/se

c)

1 200 1 400 1 600 1 800 2 000 2 200 2 400 2 600 2 800

Raman Shift (cm-1)

30

40

50

60

70

80

90

100

110

120

130

140

150

160

170

180

190

Inte

nsi

ty (cnt/

sec)

1 200 1 400 1 600 1 800 2 000 2 200 2 400 2 600 2 800

Raman Shift (cm-1)

•Non homogeneity mainly depends on pre-treatment of Ni, CH4/H2 ratio and deposition time

•Noteworthy, absence of the D peak indicative of defects

(we started from here-heterogeneous) We can get this-more homogeneous

G

2D

I2D/IG0.9

I2D/IG2.1

1200 1400 1600 1800 2000 2200 2400 2600 2800

2D

G

Wavenumber (cm-1)

1587cm-1

2705cm-1

39cm-1

31cm-1

I2D/IG=2.8

G2D

59cm-1

48cm-1

Progress Beyond the State-of-the-art





Objectives

Characterisation


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1200 1400 1600 1800 2000 2200 2400 2600 2800

Wavenumber (cm-1)

Graphene transferred from Ni to SiO2Progress Beyond the State-of-the-art

700mx700m

Starting from typical non-homogeneous

43cm-1

I2D/IG=0.92695cm-1

1593cm-1

D

G

2D

D

G

2D

1200 1400 1600 1800 2000 2200 2400 2600 2800

Wavenumber (cm-1)

1587cm-1

30cm-1

I2D/IG=2.1 2696cm-1

39cm-1





Objectives

Characterisation

Improvement is achieved by enhancement of catalysts substrate treatments


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Real Time Monitoring of CVD process

0 500 1000 1500 2000 2500 3000 3500

-1.0

-0.5

0.0

0.5

1.0

1.5

2.0G21

G19

G15

< 1

>

Time (s)

0 500 1000 1500 2000 2500 3000 3500

1.0

1.5

2.0

<K

>

Time (s)

A

BB’

C’

B’’

C”

5mx5m

0 500 1000-1.0

-0.5

0.0

0.5

1.0

1.5

2.0

< 1

>

Time (s)

0 500 1000

1.4

1.5

1.6

1.7

1.8

1.9

2.0

2.1

2.2

<k>

Time (s)

CH4 off

CH4 off

Ni ref

Ni ref

D

Ni substrate crystallization Graphene deposition

D

A

C’

C

CH4 in

CH4 offCH4 in

CH4 offCH4 in

C

D

C’

A

C

A

C’

D

CH4 in

G15

cooling

G19

G21

G21

G19

G15

G19

G21

G15

G19

1200 1400 1600 1800 2000 2200 2400 2600 2800

Wavenumber (cm-1)

1200 1400 1600 1800 2000 2200 2400 2600 2800

1200 1400 1600 1800 2000 2200 2400 2600 2800

Wavenumber (cm-1)

DG

2D

I2D/IG3

39cm-1

I2D/IG0.9

51cm-1

I2D/IG0.78

80cm-1

Real Time Monitoring

Growth

kinetics

100mx100m

Ex-situ Raman mapping In-situ Real-Time Ellipsometry and We have set a correlation between that allows us to monitor and control the whole CVD process from substrate preparation to

graphene thickness and quality




Conclusions

Objectives

Characterisation


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Hydrogen in CVD Graphene

When the angle of incidence is increased the C-H stretching band increases.

This suggests that the C-H bonds are out-of-plane

IR Reflection spectra run at BESSY Synchrotron

Intrinsic Hydrogen is the main difference between CVD and exfoliated graphene





Objectives

Characterisation


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Roadmap for Progress in Graphene Synthesis

The electron mobility within the graphene is effected by the substrate.

finding better substrates for future graphene devices in order to reduce the

effects of charged impurity scattering and remote interfacial phonon

scattering

There are still many chemical routes to synthesis of graphene and a lot of

room for improving the exploited ones.

Challenging the growth of large area graphene with controlled thickness

Substrate Engineering

Conclusions

Real Time Monitoring vs Parametric Trials

Finding technological solution to optimize processes

Structuring GrapheneConsortium Graphene for Metamaterials

Real Time Monitoring

Objectives

CharacterisationSynthesis of Graphene


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We will be pleased to take any question/curiosityCoordinator: Iris Bergmair

Nanoimprint Lithography of NIMs

Maria Losurdo, Giovanni Bruno

Synthesis and Characterisation of Large area Graphene

Rados Gajic

Exfoliation and characterisation of graphene

Costas Soukoulis

Simulation of Different Design of NIMs

Markus Oppel, C. Helgert,

Nanoimprint Litography stamps

Kurt Hingerl

Modelling Optical properties in the IR and UV-VIS

Karsten Hinrichs, Tom Oates

Ellipsometry measurements in the IR and UV-VIS

Lars Reissmann, Michael Arens

Ellipsometry, Plasma Etching

Hakan Atasoy, S. Herrndorf

Resists for Nanoimprint Litography

Ingolf Reischel, Lars Dick

Master Fabrication

maria losurdo nim nil - european commission · pdf filemaria losurdo nim_nil laurea cum laude...

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