GRAFONICS : Graphène Fonctionnalisé pour … · On exfoliated graphene, with e-beam lithography...
Transcript of GRAFONICS : Graphène Fonctionnalisé pour … · On exfoliated graphene, with e-beam lithography...
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 [email protected]
Coordinator: Pascale Maldivi [email protected]
Miguel RUBIO-ROY [email protected]
Coordinator: Pascale Maldivi [email protected]
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
0 50 100 150 200 250 300 3500.0
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
ench
/IGH
OP
G
detch
(nm)
Raman of CoPc
0.0
0.2
0.4
0.6
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1.0
770780790800810
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