Study of graphene/hBN heterostructures using Raman Spectroscopy

In this work, heterostructures of graphene and hexagonal boron nitride (hBN) were built using the pick-up method and dry-transferred to an insulator substrate (glass). Then, electric contacts were made in order to control the charge carrier concentration applying a voltage between graphene and the golden contact deposited on hBN. In this way, it was possible to access charge concentrations higher than $10^{13}~cm^{-2}$. Aligned sample was desired in order to obtain a Moiré patterning such that the cloning of the Dirac cones would occur for small energy values, being accessible by voltage application. In order to check the formation of the cloning of the Dirac cones due to the Moiré patterning, Raman spectroscopy was used. It was observed a frequency reduction and width increase in the G band for three distinct values of the voltage applied in the sample. The electron-phonon coupling effect was investigated to explain such experimental observations between the different Dirac points and the G band phonons.