Effects of energetic irradiation on materials and devices based on graphene and topological insulators

This report focuses on the optical and electronic properties of graphene and topological insulators and how these Dirac fermion systems interact with energetic irradiation. We first present data exploring the effects of electron-beam and oxygen plasma induced disorder on the electronic properties and Raman spectra of graphene. These initial investigations were important for relating Raman peak intensities and weak localization features to each other and to an average disorder length in graphene, LD. We then integrate gate-effect measurements into the Raman spectroscopy study to fully explore the relationships between carrier density, disorder and Raman spectrum signatures. We find significant a dependence in the Raman spectra on both disorder and carrier density and extract an electron-phonon coupling strength as a function of disorder, which could prove valuable for understanding electron-phonon physics in doped and disordered graphene. We conclude the report with smaller chapters covering other investigations undertaken during the period of study encompassed by this dissertation. This includes our work investigating the use of graphene to modulate the intensity of perpendicular laser light through changes in carrier density, as well as our work using graphene field-effect devices as radiation sensors. We also investigate the etching rates and Raman spectra of various topological insulators