Variable Angle Spectroscopic Ellipsometry investigation of CVD-grown monolayer graphene

Castriota, Marco; Politano, Grazia Giuseppina; Vena, Carlo; Santo, Maria Penelope De; Desiderio, Giovanni; Davoli, Mariano; Cazzanelli, E.; Versace, C.

doi:10.1016/j.apsusc.2018.10.161

Cited by 38 publications

(31 citation statements)

References 64 publications

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“…The optical properties and the thickness of thin film structures can be derived from (Ψ,∆) values measured by spectroscopic ellipsometry (SE), where Ψ and ∆ describe the relative amplitude and relative phase change, respectively [8]. SE is the primary tool to determine the optical properties and structure of materials [9], in many cases utilizing the in situ capabilities [10,11]. Concerning amorphous Ge (a-Ge) films, papers dealing with the optical and structural characterization of evaporated Ge layers can be found in the literature [12][13][14][15][16], and only a few papers discuss the optical and structural characterization of a-Ge layers obtained by low energy (0.5-1.0 keV) ion bombardment [17,18].…”

Section: Introductionmentioning

confidence: 99%

Determination of the Complex Dielectric Function of Ion-Implanted Amorphous Germanium by Spectroscopic Ellipsometry

et al. 2020

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Accurate reference dielectric functions play an important role in the research and development of optical materials. Libraries of such data are required in many applications in which amorphous semiconductors are gaining increasing interest, such as in integrated optics, optoelectronics or photovoltaics. The preparation of materials of high optical quality in a reproducible way is crucial in device fabrication. In this work, amorphous Ge (a-Ge) was created in single-crystalline Ge by ion implantation. It was shown that high optical density is available when implanting low-mass Al ions using a dual-energy approach. The optical properties were measured by multiple angle of incidence spectroscopic ellipsometry identifying the Cody-Lorentz dispersion model as the most suitable, that was capable of describing the dielectric function by a few parameters in the wavelength range from 210 to 1690 nm. The results of the optical measurements were consistent with the high material quality revealed by complementary Rutherford backscattering spectrometry and cross-sectional electron microscopy measurements, including the agreement of the layer thickness within experimental uncertainty.

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Section: Introductionmentioning

confidence: 99%

Determination of the Complex Dielectric Function of Ion-Implanted Amorphous Germanium by Spectroscopic Ellipsometry

et al. 2020

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“…In addition to Raman, other characterization techniques were proposed in the literature to determine the quality of graphene/SiO 2 substrates. Castriota et al used the Angle Spectroscopic Ellipsometry (VASE) technique to study the optical properties of monolayer CVD graphene transferred from native copper substrate onto SiO 2 (287 nm thick)/Si substrates [25]. The graphene was modeled as the sum of Lorentz oscillators with parameters estimated experimentally at different angles of incidence in the broad energy range from 0.38 eV to 6.2 eV.…”

Section: Resultsmentioning

confidence: 99%

Graphene Synthesis by Inductively Heated Copper Foils: Reactor Design and Operation

Pashova,

Dhaouadi,

Hinkov

et al. 2020

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We report on the design of a reactor to grow graphene via inductively heating of copper foils by radio frequency (RF) magnetic fields. A nearly uniform magnetic field induced by Helmholtz-like coils penetrates the copper foil generating eddy currents. While the frequency of the current is being rapidly varied, the substrate temperature increases from room temperature to ~1050 °C in 60 s. This temperature is maintained under Ar/H2 flow to reduce the copper, and under Ar/H2/CH4 to nucleate and grow the graphene over the entire copper foil. After the power cut-off, the temperature decreases rapidly to room temperature, stopping graphene secondary nucleation. Good quality graphene was obtained and transferred onto silicon, and coated with a 300 nm layer of SiO2 by chemical etching of the copper foil. After synthesis, samples were characterized by Raman spectroscopy. The design of the coils and the total power requirements for the graphene induction heating system were first estimated. Then, the effect of the process parameters on the temperature distribution in the copper foil was performed by solving the transient and steady-state coupled electromagnetic and thermal problem in the 2D domain. The quantitative effects of these process parameters were investigated, and the optimization analysis results are reported providing a root toward a scalable process for large-sized graphene.

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“…A precise method for determining refractive indices and extinction coefficients is spectroscopic ellipsometry, which allows for extracting the dielectric function in a broad wavelength range directly from the raw data [ 16 , 17 ]. The previous works report ellipsometric studies of the optical constants of exfoliated graphene [ 18 , 19 , 20 , 21 , 22 ], epitaxial graphene [ 23 , 24 , 25 ], and CVD graphene [ 26 , 27 , 28 , 29 , 30 , 31 ], also transferred onto various substrates such as optical glass [ 26 ], silicon oxide [ 18 , 20 , 31 ], or fused silica [ 18 , 19 , 29 , 30 ]. However, the measured dielectric functions show more than 20% differences, caused not only by the graphene production technique, the effect of the substrate, or the quality of graphene but also by the use of different ellipsometric models and respective initial assumptions.…”

Section: Introductionmentioning

confidence: 99%

“…However, the measured dielectric functions show more than 20% differences, caused not only by the graphene production technique, the effect of the substrate, or the quality of graphene but also by the use of different ellipsometric models and respective initial assumptions. For instance, in the analysis of optical properties, one can take into account the adsorption of water [ 18 , 28 , 30 , 31 , 32 ] and polymer residues [ 18 , 19 ] on graphene used for the transfer of both CVD and exfoliated graphene. Therefore, despite extensive research efforts devoted to studying monolayer graphene’s optical response, optical constants’ choice remains challenging due to the lack of consensus in the field.…”

Section: Introductionmentioning

confidence: 99%

Optical Constants of Chemical Vapor Deposited Graphene for Photonic Applications

et al. 2021

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Graphene is a promising building block material for developing novel photonic and optoelectronic devices. Here, we report a comprehensive experimental study of chemical-vapor deposited (CVD) monolayer graphene’s optical properties on three different substrates for ultraviolet, visible, and near-infrared spectral ranges (from 240 to 1000 nm). Importantly, our ellipsometric measurements are free from the assumptions of additional nanometer-thick layers of water or other media. This issue is critical for practical applications since otherwise, these additional layers must be included in the design models of various graphene photonic, plasmonic, and optoelectronic devices. We observe a slight difference (not exceeding 5%) in the optical constants of graphene on different substrates. Further, the optical constants reported here are very close to those of graphite, which hints on their applicability to multilayer graphene structures. This work provides reliable data on monolayer graphene’s optical properties, which should be useful for modeling and designing photonic devices with graphene.

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Variable Angle Spectroscopic Ellipsometry investigation of CVD-grown monolayer graphene

Cited by 38 publications

References 64 publications

Determination of the Complex Dielectric Function of Ion-Implanted Amorphous Germanium by Spectroscopic Ellipsometry

Determination of the Complex Dielectric Function of Ion-Implanted Amorphous Germanium by Spectroscopic Ellipsometry

Graphene Synthesis by Inductively Heated Copper Foils: Reactor Design and Operation

Optical Constants of Chemical Vapor Deposited Graphene for Photonic Applications

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