Very low energy electron microscopy of graphene flakes

Mikmeková, Eliška; Bouyanfif, H.; Lejeune, Martine; Müllerová, Ilona; Hovorka, Miloš; Unčovský, Marek; Frank, L.

doi:10.1111/jmi.12049

Cited by 11 publications

(6 citation statements)

References 15 publications

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“…Scatter in the data at 2.3 eV is due to the plasmon gain phenomenon in the Au substrate [36]. The electron transmissivity of graphene exhibits a maximum at 5 eV, which is consistent with that of Mikmekova et al [37] for a suspended monolayer sample using LEEM in a scanning transmission electron microscope. The 50-60% intensities over the range 10-50 eV agree well with previous results [38] from a suspended graphene sample.…”

Section: Low-energy Electron Transmissivity 343supporting

confidence: 80%

Measurement of the Low-Energy Electron Inelastic Mean Free Path in Monolayer Graphene

Sun

Hou

et al. 2020

Phys. Rev. Applied

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Measuring electron transport properties of substrate-supported nanomaterials with the traditional 27 two-point comparison method is difficult at electron energies below 50 eV, where core-level 28 signals are too feeble to be detected against the strong secondary-electron background. Herein, a data-driven spectral analysis technique is used to study the low-energy electron transport properties of substrate-supported target nanomaterials while eliminating the influence from the substrate signal. Applying this technique, the electron transport properties of the effective attenuation length and the inelastic mean free path (IMFP) can be determined with extremely high efficiency over the entire measured energy range of 6-600 eV. Further, these results show excellent agreement with other experimental and theoretical results. Significant differences are observed between monolayer graphene and bulk graphite IMFP, which illustrates the importance of the nanometer effect in the electron transport properties of the material. Furthermore, this technique is readily applicable to any ultrathin material that can be transferred onto a polycrystalline gold substrate.Recently, X-ray absorption fine structure techniques have been used to determine the IMFPs of

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Section: Low-energy Electron Transmissivity 343supporting

confidence: 80%

Measurement of the Low-Energy Electron Inelastic Mean Free Path in Monolayer Graphene

Sun

Hou

et al. 2020

Phys. Rev. Applied

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“…The enhanced electron interaction cross-section and surface sensitivity of such imaging conditions are advantageous for discriminating between clean and contaminated regions on the Gr layer. 29, 30 …”

Section: Resultsmentioning

confidence: 99%

Toward clean suspended CVD graphene

et al. 2016

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The application of suspended graphene as electron transparent supporting media in electron microscopy, vacuum electronics, and micromechanical devices requires the least destructive and maximally clean transfer from their original growth substrate to the target of interest. Here, we use thermally evaporated anthracene films as the sacrificial layer for graphene transfer onto an arbitrary substrate. We show that clean suspended graphene can be achieved via desorbing the anthracene layer at temperatures in the 100 °C to 150 °C range, followed by two sequential annealing steps for the final cleaning, using Pt catalyst and activated carbon. The cleanliness of the suspended graphene membranes was analyzed employing the high surface sensitivity of low energy scanning electron microscopy and x-ray photoelectron spectroscopy. A quantitative comparison with two other commonly used transfer methods revealed the superiority of the anthracene approach to obtain larger area of clean, suspended CVD graphene. Our graphene transfer method based on anthracene paves the way for integrating cleaner graphene in various types of complex devices, including the ones that are heat and humidity sensitive.

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“…For this reason, ultralow-energy STEM with the cathode lens mode has been applied to 2D crystals, firstly to graphene. The first results were achieved when comparing the Raman spectroscopy identification of flakes of a certain thickness with STEM observation [46]. Even flakes exhibiting a Raman spectrum corresponding to single-layer graphene were found to be composed of tiny flakes of various thicknesses and small holes.…”

Section: D Crystalsmentioning

confidence: 99%

Scanning Electron Microscopy with a Retarded Primary Beam

Frank¹

2016

Modern Electron Microscopy in Physical and Life Sciences

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The general trend for reducing the energies of primary electrons in electron microscopy has been faced with a gradual deterioration of the image resolution. Biasing the sample to a high negative voltage and making the electrons arbitrarily slow solely on and inside the sample has shown itself to be far more feasible than originally expected. The fundamental aberration coefficients (spherical and chromatic) of a combination of an objective lens and an immersion electrostatic lens formed by the biased sample decrease with the decreasing landing energy of the electrons. As a result, the spot size in scanning systems may become nearly independent of the landing energy of the electrons. The requirements placed on samples are strict but feasible, and detection of signal electrons is greatly facilitated by the acceleration of both reflected and transmitted electrons in the field of the biased sample and their collimation toward the optical axis. The interaction of slow electrons is not only more intensive than that at standard energies but even scattering phenomena appear which are not otherwise observed. Several application examples are presented. The benefits of very low energy EM are still being uncovered after its having been in routine use for several years.

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Very low energy electron microscopy of graphene flakes

Cited by 11 publications

References 15 publications

Measurement of the Low-Energy Electron Inelastic Mean Free Path in Monolayer Graphene

Measurement of the Low-Energy Electron Inelastic Mean Free Path in Monolayer Graphene

Toward clean suspended CVD graphene

Scanning Electron Microscopy with a Retarded Primary Beam

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