Few layer hBN was mechanically exfoliated from bulk hBN via PDMS and transferred onto a Si/SiO2 wafer. Monolayer graphene was mechanically exfoliated from bulk graphite via PDMS and transferred onto the few layers hBN flakes. According to the transfer method reported previously, the transfer process was carried out under a microscope equipped with a self-built transfer stage. The thicknesses of the exfoliated samples were determined by optical contrast, Raman spectroscopy and AFM measurement. After every transfer step, the sample was mildly annealed in vacuum at 150 °C for 2 h to remove water and contaminations from the transfer process.