Temperature dependence of Raman spectra of graphene on copper foil substrate
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We investigate the temperature dependence of the phonon frequencies of the G and 2D modes in the Raman spectra of monolayer graphene grown on copper foil by chemical vapor deposition. The Raman spectroscopy is carried out under a 532.16 nm laser excitation over the temperature range from 150 to 390 K. Both the G and 2D modes exhibit significant red shift as temperature increases, and the extracted values of temperature coefficients of G and 2D modes are −0.101 and −0.180 cm−1 K−1, respectively, different from that of graphene on SiO2 substrate. The obtained results shed light on the anharmonic property of graphene, the complex interfacial interactions between graphene and the underlying copper foil substrate as temperature changes, and also proposes a new routine to estimate the thermal expansion coefficient of graphene on copper substrate rather than on SiO2 and SiN substrates. Furthermore, our work is instructive to study the similar temperature dependent mechanical properties, and the interfacial interactions between the other emerging two dimensional materials and their underlying substrates by temperature dependent Raman scatterings.
This work is supported by Basic Research (973) from Ministry of Science and Technology with Contract Number of 2011CB309504. Authors are also grateful to the Analytical and Testing Center, Huazhong University of Science and Technology for technical assistances.