Graphene and related single-layer materials
We probe single-layer materials such as graphene, graphene oxide, Molybdenum disulfide (MoS2) and carbon nanotubes using THz frequencies up to 30 THz after near-/mid-infrared excitation. In our studies of carbon nanotubes, we measured the transient dielectric function and conductivity of excitons in semiconducting carbon nanotubes after resonant excitation. We characterized the time scale and temperature sensitivity of bi-molecular decays, steps useful for exploiting the optoelectronic properties of carbon nanotubes for commercial application.
We explore the equilibrium and transient dynamics of chemical-vapor-deposition (CVD) grown single layer graphene transferred to a variety of substrates. The choice of substrate critically affects the optical wavelengths that can be used for study, but also affects electronic parameters such as the Fermi level and disorder. To better understand the effect of the Fermi level on electronic properties, we prepared a simple device using graphene in a field-effect transistor, where the Fermi level of the graphene can be tuned systematically by applying a voltage across the sample. This allows us to us infrared and terahertz fields to probe the optical and electronic properties of graphene while systematically tuning the Fermi energy.
We explore the equilibrium and transient dynamics of chemical-vapor-deposition (CVD) grown single layer graphene transferred to a variety of substrates. The choice of substrate critically affects the optical wavelengths that can be used for study, but also affects electronic parameters such as the Fermi level and disorder. To better understand the effect of the Fermi level on electronic properties, we prepared a simple device using graphene in a field-effect transistor, where the Fermi level of the graphene can be tuned systematically by applying a voltage across the sample. This allows us to us infrared and terahertz fields to probe the optical and electronic properties of graphene while systematically tuning the Fermi energy.