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Calculation of dielectric constant of buffer layer graphene on SiC substrate measured by Spectroscopic Ellipsometry using Gauss-Newton inversion method has been done. The data obtained from spectroscopic ellipsometry measurement are amplitude ratio (Ψ) and phase difference (Δ). The results show that Gauss-Newton numerical inversion method can be used to extract the dielectric constant of nanostructured graphene on SiC substrates (in this case buffer layer graphene). Through the Gauss-Newton numerical inversion method, we obtain the thickness of buffer layer is around 0.5 to 1 ML and has different dielectric constant value as compared to that of graphene films. [ABSTRACT FROM AUTHOR]

We report on the procedure for determining the dielectric constant of multilayer epitaxial graphene (MEG) film grown epitaxially on the carbon face (C-face) of SiC substrate. The dielectric constant is determined by fitting the reflectance spectra of C-face MEG film measured from synchrotron radiation over a broad wavenumber from 5000 - 165000 cm-1 by using Drude-Lorentz (DL) model. To calculate the dielectric constants of C-face MEG, the system is modeled with Fresnel coefficient for an optically stratified multilayer film system. The model is composed of the air, a layer that represents C-face MEG film, and a layer that represents SiC substrate. We have used forty DL oscillators and have found all parameters that give the best match to the reflectance data. Of those forty oscillators, we find five oscillators (i.e., at 5000 cm-1, 40000 cm-1, 45000 cm-1, 50000 cm-1, and 90000 cm-1) that contribute dominantly in the dielectric constant of MEG Film. Those dominant oscillators that appear at low wavenumbers (i.e., 5000 cm-1 and 40000 cm-1) related to the intraband transitions and many-body effects that have been observed and reported by earlier study while those at higher wavenumbers probably may come from the electronic transitions involving higher energy states. The results show that DL model can be used to determine the dielectric constant of MEG. [ABSTRACT FROM AUTHOR]

Calculation of the refractive index of Multilayer Epitaxial Graphene (MEG) on C-face SiC using Kramers-Kronig and Newton-Raphson method has been done. Calculation of complex refractive index performed through the reflectance data from Synchrotron radiation measurement with the incident angle of 17.5 °. The result of Kramers-Kronig transformation of is phase shift (δ), and the equations that are used in the extracting refractive index of MEG on C-face SiC involve Fresnel and Snell's equations. The problem in determining the root of Fresnel equation is resolved by using Newton-Raphson method. The results show that Kramers-Kronig and Newton-Raphson method can be used to extract the complex refractive index of nanostructure material, i.e., MEG on C-face SiC substrate. At lower wavenumber (up to 40000 cm-1), the complex refractive index resembles that of graphene on SiO2 and epitaxial graphene on Si-Face obtained using low energy spectroscopic ellipsometry and absorption spectroscopy, in which the refractive index is nearly constant at this particular wavenumber range indicating the transparency of MEG film on SiC substrate. we observed no difference in the value of the resulting complex refractive index of MEG films on SiC for difference Newton-Raphson tolerance, step size h, and initial guess used indicating that the resulting complex refractive index calculated using Newton-Raphson method converge very fast. [ABSTRACT FROM AUTHOR]

Graphene oxide (GO)/Poly (3,4-Ethylenedioxytriophene): Poly (styrene Sulfonate) (PEDOT:PSS) nanofibers have been successfully fabricated by a simple electrospinning technique to develop conductive nanofibers with polyvinyl alcohol (PVA) act as a carrier solution. Graphene oxide has been synthesized by Hummer's method and has been confirmed by Raman Spectroscopy, FTIR, and UV-Vis Spectroscopy. The structural and morphological properties of GO/PEDOT:PSS composite nanofibers were characterized by Scanning Electron Microscopy (SEM). The result of SEM showed that GO/PEDOT:PSS nanofibers have a relatively uniform morphology nanofiber with a diameter of 180 nm - 340 nm with smooth nanofiber surface. The produced nanofibers from this study can be utilized for various applications such as a flexible, conductive and transparent electrode. [ABSTRACT FROM AUTHOR]