Diamagnetic and plasmonic properties of graphene.
Niu_Planar Alignment of Graphene Sheets by a Rotating Magnetic Field for Full Exploitation of Graphene as a 2D Material.pdf (319.6Kb)
Niu_Orientation Control of Graphene Flakes by Magnetic Field Broad Device Applications of Macroscopically Aligned Graphene.pdf (319.5Kb)
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Niu, Chao, 1988-
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Graphene is a two-dimensional (2D) material, and it has many applications in electronics and photonics due to its unique properties. We study diamagnetism of graphene and demonstrate applications of graphene in sensing, display, and polarizing optics. Graphene is also commonly used on top of a metal surface, which generates surface plasmon waves. Surface plasmons have drawn lots of attention due to a wide spectrum of potential applications, including integrated photonic circuits, light emitting diodes (LEDs), lasers, surface enhanced Raman spectroscopy (SERS), solar cells, and biosensors. The combination of graphene and plasmonic structures can lead to plenty of new applications.This dissertation studies diamagnetic properties of graphene and surface plasmons at graphene-metal interface. First, we show the magnetic response and alignment of graphene flakes. Orientation control and alignment could be achieved with a weak magnetic field. Second, a rotating magnetic field generated by a pair of small NdFeB magnets is used to realize planar alignment of suspended graphene sheets. Compared to partially aligned sheets with a static magnetic field, planar aligned graphene suspensions exhibit a much higher birefringence, order parameter, and anisotropic transmission. Third, we study physics for graphene orientation control using a magnetic field. The torques in all three spatial directions induced by diamagnetic forces are used to predict stable conditions for different shapes of graphite plates. Fourth, we study the impact of graphene on the surface plasmon resonance (SPR) of gold films, which leads to a large shift in resonance angle of SPR between the cases with and without graphene layer. We attribute this large shift to the intrinsic wrinkle structure of graphene and its near-field interaction with the Au film according to our models. Fifth, we study the resonant condition of metal-dielectric interface and related applications as a refractive index sensor. We found that the resonant wavelength oscillates as the thickness of the thin dielectric layer increases due to the cavity formed by the dielectric layer. At the end, we give a summary and discuss the future work.