A method for obtaining flat n-graphene sheets using reverse exfoliation process V. Huc, IPCMO, Orsay N. Bendiab, LSP-UJF, Grenoble T. Ebbesen, U .Pasteur, Strasbourg C. Delacour, V. Bouchiat, Institut Néel, CNRS- Grenoble

Deposited Graphene layers exhibits defects : pleats and folds Novoselov, Geim group lowered carrier mobility and suppression of weak localization in graphene-based devices have been attributed to corrugation of the graphene.

Masa Ishigami, et al. Nano Lett. ASAP paper 11-May-2007 Meyer, J. C.; et al. On the roughness of single- and bi-layer graphene membranes. Preprint archive, xxx.lanl.gov, cond-mat/0703033, 2007. Novoselov, Geim group

Reverse Exfoliation Process Epoxy glue Freshsly cleaved Bulk HOPG Oxidized Silicon chip Step 1 : Bulk HOPG Bonding (upside down)

Reverse Exfoliation Process Epoxy glue Step 1 : Bulk HOPG Bonding (upside down) Adhesive wafer bonding F. Niklaus et al. Appl. Phys. 99, 031101 , 2006

Molding of the top Graphite surface into the epoxy

Reverse Exfoliation Process Step 2 : epoxy curing under screw press

Reverse Exfoliation Process Bulk HOPG Epoxy glue Oxidized Silicon chip Step 3 : Bulk HOPG Scalpel Cleaving

Step 4 : Scotch™ tape exfoliation Bulk HOPG Epoxy glue Oxidized Silicon chip Step 4 : Scotch™ tape exfoliation K.S. Novoselov et al;, Science 306, 666 , (2004).

Coupe au niveau d’une bulle Epoxy Glue Épaisseur Colle = 3µm graphene Si

A process reminiscent from the Smart-cut ® process US Patent 5,882,987, published 1999 Atomic scalpel

A process reminiscent from the Smart-cut ® process US Patent 5,882,987, published 1999 Bernin Atomic scalpel

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

Effective surface potential Scanning Potential Microscopy Effective surface potential Sonde de Kelvin

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 2006 A. 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 1m using 514.5 nm excitation under ambient conditions at low laser power (<1mW).

AFM sur Zone Raman Monocouche (2) Marche monocouche Colle ? Bulle

AFM sur Zone Raman Monocouche (2)

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