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(a) The atomic structure of graphite. (b) The spectral dependence of the real ( and ) and imaginary ( and ) parts of the dielectric constants for different orientations in HOPG.
(a) Measurement of permittivity at the range of 240–400 nm and (b) reflection coefficients for incident angle from 20° to 70°.
The orientation of single crystalline graphite and the scheme of refraction as it occurs in graphite. The direction perpendicular to the carbon atomic plane is the optic axis (z-axis). (a) The single crystal of graphite is oriented such that the optic axis is parallel to the sample surface and is also perpendicular to the plane of incidence. A TM mode wave, with M-field polarized in the atomic plane of the graphite, is incident on the sample with an incident angle of and then refracted at an angle of . (b) The EFC mapped using ellipsometry at this orientation. (c) Schematic illustration of the normal refraction of ordinary light at the interface between the free space (circular black EFC) and the uniaxial media (circular blue EFC). The refracted wave vector and Poynting vector is determined by Maxwell’s equations. (d) The single crystal of graphite is oriented such that the optic axis is in the plane of the sample surface and in the plane of incidence. (e) The EFC mapped using ellipsometry at this orientation. (f) The negative refraction of extraordinary light at the interface between the free space (circular black EFC) and the uniaxial media (hyperbolic blue EFC).
Simulation results for 254 nm TM light at incident angles of 30° (a), 45° (b), and 60° (c) using HFSS. Dielectric spectra shows the indefinite permittivity ( and ) of the sample at 254 nm. The refracted wave vector (yellow arrow) and Poynting vector (green arrow) is determined by Maxwell’s theorem. The Poynting vector is negatively refracted, although the phase vector remains positive.
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