Probing the Stress Effect on the Electronic Structure of Graphite by Resonant Raman Spectroscopy

In this work we report the dispersive behavior of the most characteristic Raman contributions of highly oriented pyrolytic graphite at biaxial stresses up to 10 GPa, using a moissanite anvil cell as a pressure device. The stress coefficients and the relative Grüneisen parameters are obtained for two different excitation wavelengths, 488.0 and 532.0 nm. We observe for some of the Raman contributions different stress slopes depending on the excitation energy (2.54 and 2.33 eV). Specifically, the stress coefficients vary with the excitation wavelength for those contributions originated by resonant processes. Additionally, we have carried out selected experiments at lower excitation energies of 2.18 and 1.96 eV. Finally, the analysis of the dispersive behavior of strained graphite allows us to qualitatively estimate the influence of the stress on the electronic structure of graphite, associating the changes in the dispersion with stress to an energy gap closure.