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Synthesis of few layer single crystal graphene grains on platinum by chemical vapour deposition

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2015-08-01
Karamat, S.
Sonusen, S.
ÇELİK, ÜMİT
UYSALLI, YİĞİT
Ozgonul, EKİN
Oral, Ahmet
The present competition of graphene electronics demands an efficient route which produces high quality and large area graphene. Chemical vapour deposition technique, where hydrocarbons dissociate in to active carbon species and form graphene layer on the desired metal catalyst via nucleation is considered as the most suitable method. In this study, single layer graphene with the presence of few layer single crystal graphene grains were grown on Pt foil via chemical vapour deposition. The higher growth temperature changes the surface morphology of the Pt foil so a delicate process of hydrogen bubbling was used to peel off graphene from Pt foil samples with the mechanical support of photoresist and further transferred to Si02/Si substrates for analysis. Optical microscopy of the graphene transferred samples showed the regions of single layer along with different oriented graphene domains. Two type of interlayer stacking sequences. Bernal and twisted, were observed in the graphene grains. The presence of different stacking sequences in the graphene layers influence the electronic and optical properties; in Bernal stacking the band gap can be tunable and in twisted stacking the overall sheet resistance can be reduced. Grain boundaries of Pt provides low energy sites to the carbon species, therefore the nucleation of grains are more at the boundaries. The stacking order and the number of layers in grains were seen more clearly with scanning electron microscopy. Raman spectroscopy showed high quality graphene samples due to very small D peak. 2D Raman peak for single layer graphene showed full width half maximum (FWEIM) value of 30 cm(-1). At points A. B and C, Bernal stacked grain showed FWIIM values of 51.22, 58.45 and 64.72 cm(-1), while twisted stacked grain showed the FWIIM values of 27.26, 28.83 and 20.99 cm(-1), respectively. FWHM values of 2D peak of Bernal stacked grain showed an increase of 20-30 cm(-1) as compare to single layer graphene which showed its dispersive nature and confirmed Bernal sequence. On the other hand, the slightest decrease in FWHM values of 2D peak in twisted grain comparing to single layer confirmed the twisted sequence of grains. Atomic force microscopy analysis showed an increasing trend in grain height profile with an increase in the number of layers. (C) 2015 Chinese Materials Research Society. Published by Elsevier GmbH.