Raman spectroscopy of large-area graphene by wet transfer method

In this letter, Raman spectroscopy was used to study the variation of transfer graphene. First, the Raman spectroscopy of chemical vapor deposition (CVD)-grown monolayer graphene was compared with that of mechanical exfoliated graphene, the 2D Raman band frequency of monolayer graphene grown on copper foils by CVD showed a blue shift upto 12 cm^-1 . Then, the CVD-grown graphene on copper substrates was transferred to SiO₂(300nm)/Si by wet transfer method, that caused a 2D-band redshift by 15cm^-1 compared with the graphene before transferred, besides, the defects appeared in some regions. According to the changes of Raman spectrum, the strain was confirmed as the most important reason in the letter. The observation of the Raman shifts helps us to gain more physical insights into the transfer of graphene.