Statistical analysis of the temperature dependence of the phonon properties in supported CVD graphene

Existing literature reports on the dependence of phonon properties on temperature rarely use statistical analysis. The lack of uncertainty assessment, which takes into account changes in the parameter value within the sample, substantially hinders comparison among the data reported so far. Moreover, it is impossible to determine whether these results display discrepancies between themselves due to sample- and technology-dependent issues, manifestations of statistical noise, or a deeper cause that has not yet been grasped. Here, we show the distributions of the phonon properties at temperatures in the range of 300 K-500 K, which were used to calculate the temperature derivatives of the phonon energies χ. These can be used in the procedure of the extraction of graphene thermal conductivity κ but are also related to the anharmonic part of the graphene crystal lattice potential and/or nonadiabatic effects. Finally, we show that the correlation analyses revealed the existence of an unknown physical cause of differences between χ values, showing that the thermal properties of phonons in graphene are still not fully understood and further studies on the contribution of doping, stress, defects and interaction with the substrate, including its thermal expansion, are required to explain the observed parameter variability.

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