Raman Spectroscopy Study of the Charge Carrier Concentration and Mechanical Stresses in Graphene Transferred Employing Different Frames

The charge carrier concentration ( n ) and relative strain (ε) in graphene synthesized by chemical vapor deposition and transferred to the surface of SiO 2 /Si substrate using two different frames, polymethylmethacrylate (PMMA) and paraffin, 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 paraffin was used rather than PMMA. Further liquid-phase and heat treatment used to remove the paraffin 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 paraffin 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 efficiency of the graphene-transfer technique with a simultaneous improvement in the performance of graphene nanoelectronic devices.