Raman spectroscopy study of the charge carrier concentration and mechanical stresses in graphene transferred employing different frames

Abstract

The charge carrier concentration (n) and relative strain (ε) in graphene synthesized by chemical vapor deposition and transferred to the surface of SiO2 /Si substrate using two diff erent frames, polymethylmethacrylate (PMMA) and paraffi n, followed by complex processing were compared. The positions of Raman-active modes were analyzed using a correlation method. The charge carrier concentration in graphene was lower if paraffi n was used rather than PMMA. Further liquid-phase and heat treatment used to remove the paraffi n frame led to an increase of n up to 1.2∙10 13 cm −2 . No clear trend in the change of n was observed for graphene samples transferred using a PMMA frame, regardless of the type of processing. The scatter of ε values for graphene transferred with paraffi n followed by liquid-phase and heat treatment in vacuum was greater than for graphene transferred with PMMA and treated similarly, i.e., from −0.01875 to −0.1448% and from −0.04375 to −0.0875%. Besides the transfer frame material itself, a combination of processing methods had a decisive impact on the quality of the graphene. Optimization of these parameters made it possible to increase the effi ciency of the graphene-transfer technique with a simultaneous improvement in the performance of graphene nanoelectronic devices.