A method for obtaining flat n-graphene sheets

using reverse exfoliation process

V. Huc, IPCMO, OrsayN. Bendiab, LSP-UJF, Grenoble

T. Ebbesen, U .Pasteur, StrasbourgC. Delacour, V. Bouchiat, Institut Néel, CNRS- Grenoble

Deposited Graphene layers exhibits defects : pleats and folds

Novoselov, Geim group

lowered carrier mobility and suppression ofweak localization in graphene-based devices have beenattributed to corrugation of the graphene.

Masa Ishigami, et al. Nano Lett. ASAP paper 11-May-2007

Novoselov, Geim group

Meyer, J. C.; et al. On the roughness of single- and bi-layer graphenemembranes. Preprint archive, xxx.lanl.gov, cond-mat/0703033, 2007.

Step 1 : Bulk HOPG Bonding (upside down)

Oxidized Silicon chipFreshsly cleaved

Bulk HOPG

Epoxy glue

Epoxy glue

Reverse Exfoliation Process

Reverse Exfoliation Process

Epoxy glue

Epoxy glue

Step 1 : Bulk HOPG Bonding (upside down)

Adhesive wafer bondingF. Niklaus et al. Appl. Phys. 99, 031101 , 2006

Molding of the top Graphite surface into the epoxy

Step 2 : epoxy curing under screw press

Reverse Exfoliation Process

Oxidized Silicon chip

Epoxy glue

Epoxy glue

Reverse Exfoliation Process

Bulk HOPG

Step 3 : Bulk HOPG Scalpel Cleaving

Oxidized Silicon chip

Epoxy glue

Epoxy glue

Bulk HOPG

Step 4 : Scotch™ tape exfoliation

K.S. Novoselov et al;, Science 306, 666 , (2004).

Coupe au niveau d’une bulle

Si

EpoxyGlue

grapheneÉpaisseurÉpaisseurColle = 3µmColle = 3µm

A process reminiscent from the Smart-cut ® process

Atomic scalpel

US Patent 5,882,987, published 1999

A process reminiscent from the Smart-cut ® process

Atomic scalpel

US Patent 5,882,987, published 1999

Bernin

Image d’une fissure de contrainte (colle dans la fissure)

pleats defects

SEM zoom on Pleats defects

Graphene on epi SiC (GaTech U.) :

same kind of pleats

1µm

Effective surface potentialSonde de Kelvin

Scanning Potential Microscopy

Lift height = 5 nm Tip bias = 2V 6 µm Scan

Raman Probing The Raman spectrum of graphite is composed of a strong band at 1582 cm-1, which has been assigned to the in-plane E2g zone centre mode (G band).

Gupta et al. Nano Lett., Vol. 6, No. 12, 2006 p.2668

Raman Probing The Raman spectrum of graphite is composed of a strong band at 1582 cm-1, which has been assigned to the in-plane E2g zone centre mode (G band).

G-band clearly downshifts with increasing n

Gupta et al. Nano Lett., Vol. 6, No. 12, 2006 p.2668

Raman Probing The Raman spectrum of graphite is composed of a strong band at 1582 cm-1, which has been assigned to the in-plane E2g zone centre mode (G band).

G-band clearly downshifts with increasing n

Gupta et al. Nano Lett., Vol. 6, No. 12, p.2668 2006A. C. Ferrari, et al. Phys. Rev. Lett. 97, 187401 (2006).

Raman as a way to assess single graphene layers

Gupta et al. Nano Lett., Vol. 6, No. 12, 2006 p.2668

Raman micro-spectroscopy

MicroRaman spectra are collected using a X100 objective with a spot size of 1m using 514.5 nm excitation under ambient conditions at low laser power (<1mW).

• Marche monocouche

• Colle ? Bulle

AFM sur Zone Raman Monocouche (2)

AFM sur Zone Raman Monocouche (2)

1 µm

Fissure de contrainte ?

2 µm

Reconnection using Pd

100 µm

Contacts Pd/Graphene

5 µm

Conclusion :

Reverse exfoliation make possible the realization of flat graphene sheets

PRL98,166802(2007)