The spectra of optical constants, index of refraction ͑n͒, and extinction coefficient ͑k͒ of graphene and graphite are obtained in the wavelength range of 190-1000 nm ͑6.53-1.24 eV͒ using broadband optical spectrophotometry in conjunction with the Forouhi-Bloomer dispersion relations for n and k. Measurement is made possible by the use of a multilayer substrate consisting of bulk Si and a 3000 Å SiO 2 film. The effect of multiple internal reflections between the Si/ SiO 2 and SiO 2 /graphene interfaces amplifies the attenuating effect of the graphene layer, thereby improving the sensitivity of the reflectance measurement by a factor of 27 in the deep ultraviolet region of the spectrum. Maximum sensitivity is observed in the deep ultraviolet region of the spectrum, where a strong peak in the spectrum of the extinction coefficient of graphene is identified. The proposed method enables fast nondestructive angstrom-level thickness measurements of graphene and graphite. In this work, layers ranging in thickness between 3.8 Å ͑graphene͒ and 792.8 Å are detected, measured, and characterized. Reflectance spectra of graphene and graphite on Ni, Co, and Fe substrates are calculated. Differences of 1.1%-2.0% between the bare substrate and the graphene on the substrate are predicted in the deep ultraviolet region of the spectrum, which makes graphene detectable and measurable on these substrates.
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