On exfoliated graphene, with e-beam lithography and thermal evaporation.

Measurementsproviding:-Position ofthe Fermi level-Carrier density-Carrier mobility-Band gap-Corrections tostandard conductivity model at low temperature

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CONTACT :CONTACT :

Miguel RUBIO-ROY rubioroy@cemes.fr

Coordinator: Pascale Maldivi pascale.maldivi@cea.fr

Miguel RUBIO-ROY rubioroy@cemes.fr

Coordinator: Pascale Maldivi pascale.maldivi@cea.fr

B. Kumar,1 G. Lapertot,1 F. Duclairoir,1 L. Dubois,1 G. Bidan,1 P. Maldivi,1 J.-L. Thomassin,1 F. Lefloch,1 D. Rouchon,2 D. Mariolles,2

M. Mikolasek,3 J.-L. Bantignies,3 M. Paillet,3 J.-R. Huntzinger,3 A. Tiberj,3 J.-L. Sauvajol,3 M. Rubio-Roy,4 O. Couturaud,4 E. Dujardin4

1) INAC, CEA Grenoble, 17 rue des Martyrs, 38054 Grenoble cedex 09, 2) CEA/LETI, CEA Grenoble, 17 rue des Martyrs, 38054 Grenoble cedex 09, 3) L2C, Université Montpellier II , Pl. Eugène Bataillon , 34095 Montpellier, 4) CEMES, 29 rue Jeanne Marvig, BP 94347, 31055 Toulouse Cedex 4

GRAFONICS :Graphène Fonctionnalisé pour l'électronique C-MOS hybrideP2N 2010

Journées Nationales en Nanosciences et Nanotechnologies 2012

semi-metallic graphene

semi-conducting graphene

chemical grafting

Context

Results presented on

Task 3: SiC graphene growthTask 5: bulk graphene functionalization Task 3: suspended graphene

Vacuum pump

Coil

Graphite

susceptor

Gas inlets

Quartz tube

Furnace (induction heating) key aspects: vacuum/inert gas and Ar/H2 line available

SiC graphene growth

The objectives: of the project are to:�optimize graphene fabrication�test the functionalization as a tool to tune the graphene band gap

Graphene is a material that has attracted a lot of scientific attention over the past few years as it seems to be compatible with a lot of applications. It can be obtained by various techniques and each technique will provide a graphene with properties better suited for one application rather than another. Regarding the microelectronics field, graphene is an interestingmaterial as it shows ballistic transport and very high mobility;however it is not yet compatible with CMOS-like applications as it lacks a band gap.

330nm deepTechnological steps:

�Starting substrate: SiO2 (290nm) / Si (100)�UV projection lithography

Metal marks: double resist for undercut + thermal evaporationPools: normal resist + CF4 ICP RIE

�Lift-off

The line scanned corresponds to the position of the laser spot on the background picture.In yellow, optical contrast. In cyan, G band integrated intensity.

ExperimentsCalculations

• Normalization with HOPG• True numerical apertures to be

measured probably close to 0.7

• Normalization with graphene freely suspended in air

• Numerical apertures: 0.9

G band intensity as a function ofetched depth and laser wavelength

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0.2

0.4

0.6

0.8

1.0 457 nm 476.5 nm 488 nm 514 nm 532 nm 561 nm 633 nm

IGov

er tr

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G

detch

(nm)

Raman of CoPc

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0.6

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Binding Energy (eV)

Co2p3

AFM topography

Selective grafting on monolayer

Graphene model: bilayer more electron donating than monolayer?:

HOMO

LUMO -2.87 eV

-4.83 eV

nCy(nc) 19 (54)

-4.38 eV

-2.76 eV

Eint =44 meV/C 3.31Å

Standard protocol: surface preparation = organic desorption + graphitization

Optimized protocol: surface preparation = idem + H 2 annealingAr/H2,

1600ºC (30 min)

Stage 4

1100ºC (30 min)

RT

Ar/H2 Ar/H2

Ar/H2 switched off

Stage 5Stage 3

810ºC (4 h)470ºC (1 h)

Stage 2

RT

Stage 6

1600ºC (30 min)

Study of different growth parameters:With or without annealing and under Ar or vacuum

G(Vac)

G(Ar/H2-Vac)

G(Ar/H2-Ar)

G(Ar)

1500 2000 2500Raman shift (cm -1)

G2D

Sample P(2D) FWHM P(G) FWHM

G(Vac) 2730.2 62.2 1588.9 24.2

G(Ar) 2743.1 56.4 1605 18.3

G(Ar/H2-Vac) 2737.9 46.3 1598.8 16.9

G(Ar/H2-Ar) 2718.3 31.8 1588.4 16.3

With annealNo anneal

Under vacuum

UnderAr

Each growth cycle is decomposed into a preparation step and a sublimation/graphene growth step

12-14 layers thick, 2D band shapecompatible with Bernal stacking

Phase image

AFM HeightOptical microscopy

1/3 – bilayer or more

2/3 - monolayer

mono-layer, relaxed,Good crystalline quality

2 layers, not perfect Bernal stacking, non homogeneous

strain

rough samples, small graphene domains

500

400

300

200

100

1500 2000 2500

Wavenumber (cm-1)

G

2D

Best graphene sample obtained after H2annealing and growth under Ar

Large monolayer domains

Suspended mechanically exfoliated graphene

Graphene Functionalization

Suspended graphene should not show interactions with the substrate. Such type of structure would prevent various parasitic phenomena occurring upon deposition of graphene flakes on SiO2 (strain, local doping…)

Substrate preparation

5x1 µm2 pools: Depths of 160nm, 210nm, 260nm, 340nm already measured (400nm, 480nm, 615nm upcoming)

Efficient model to simulate the G band intensity variation with pool depth and laser wavelength

Modification of SiC graphene with CoPc

Samples obtained after immersion of the sample in a CoPc solution in CHCl3 (1’ dipping time –concentrations targeted ~10-4M)

After selective molecule deposition monolayer domains appear brighter even on optical microscopy image

Other studies in progress

Theoretical calculations

Raman G band

Raman of Graphene (G band)

Device fabrication

Reflectivity / Transmission