Probing the electron-phonon coupling in ozone-doped graphene by Raman spectroscopy

TL;DR

This study uses Raman spectroscopy to analyze how ozone doping affects electron-phonon interactions in graphene, revealing doping-dependent shifts and intensity changes that inform on electron-electron and electron-phonon dynamics.

Contribution

It provides a detailed analysis of electron-phonon coupling in ozone-doped graphene and demonstrates the layer-independence of the coupling ratio up to ten layers.

Findings

Blue shift of G and 2D peaks indicates increased p-doping.

Decrease in 2D and 2D' intensities correlates with electron-electron scattering.

Electron-phonon coupling ratio remains constant across layers.

Abstract

We have investigated the effects of ozone treatment on graphene by Raman scattering. Sequential ozone short-exposure cycles resulted in increasing the $p$ doping levels as inferred from the blue shift of the 2$D$ and $G$ peak frequencies, without introducing significant disorder. The two-phonon 2$D$ and 2$D'$ Raman peak intensities show a significant decrease, while, on the contrary, the one-phonon G Raman peak intensity remains constant for the whole exposure process. The former reflects the dynamics of the photoexcited electrons (holes) and, specifically, the increase of the electron-electron scattering rate with doping. From the ratio of 2$D$ to 2$D$ intensities, which remains constant with doping, we could extract the ratio of electron-phonon coupling parameters. This ratio is found independent on the number of layers up to ten layers. Moreover, the rate of decrease of 2$D$ and 2$D'$ intensities with doping was found to slowdown inversely proportional to the number of graphene layers, revealing the increase of the electron-electron collision probability.