Influence of hydrophobicity on the chemical treatments of graphene

The defect-free transfer of graphene grown by using chemical vapor deposition is essential for its applications to electronic devices. For the reduction of inevitable chemical residues, such as polar molecules and ionized impurities resulting from the transfer process, a hydrophobic polydimethyl-siloxane (PDMS) film was coated on a SiO2/Si wafer. The hydrophobic PDMS film resulted in fewer defects in graphene in comparison to a bare SiO2/Si wafer, as measured with Raman spectroscopy. We also studied the influence of the hydrophobic PDMS film on the chemical doping of graphene. Here, nitric acid (HNO3) was used to make p-type graphene. When graphene was transferred onto a SiO2/Si wafer coated with the hydrophobic PDMS film, fewer defects, compared to those in graphene transferred onto a bare SiO2/Si wafer, were created in grapheme by HNO3 as measured with Raman spectroscopy. The experiments suggest that when graphene is transferred onto a hydrophobic film, the number of defects created by chemical molecules can be reduced.