Very Low Energy Scanning Electron Microscopy of Free-Standing Ultrathin Films

Müllerová, Ilona; Hovorka, Miloš; Hanzlíková, Renata; Frank, L.

doi:10.2320/matertrans.mc200915

Cited by 16 publications

(3 citation statements)

References 26 publications

(26 reference statements)

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“…With recent advances in the large-scale fabrication of high-quality single and multilayer graphene (and graphene derivatives) [25][26][27][28] along with its comprehensive characterization and the development of high-yield transfer methods [29][30][31] this 2D material appears to be a new prospective window platform for membrane based E-cells. In particular, graphene has a unique combination of properties, excelling in mechanical strength [32,33] and electron transparency [34][35][36][37] as well as being impermeable to liquids and gases [38][39][40]. Very recently the successful implementation of graphene and graphene oxide (GO) based membranes in liquid enclosed E-cells for SEM [41], HRTEM [42] and x-ray photoelectron microscopy has been demonstrated [43].…”

Section: Introductionmentioning

confidence: 99%

Electron transparent graphene windows for environmental scanning electron microscopy in liquids and dense gases

Stoll

Kolmakov

2012

Nanotechnology

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Due to its ultrahigh electron transmissivity in a wide electron energy range, molecular impermeability, high electrical conductivity and excellent mechanical stiffness, suspended graphene membranes appear to be a nearly ideal window material for in situ (in vivo) environmental electron microscopy of nano- and mesoscopic objects (including bio-medical samples) immersed in liquids and/or in dense gaseous media. In this paper, taking advantage of a small modification of the graphene transfer protocol onto metallic and SiN supporting orifices, reusable environmental cells with exchangeable graphene windows have been designed. Using colloidal gold nanoparticles (50 nm) dispersed in water as model objects for scanning electron microscopy in liquids as proof of concept, different conditions for imaging through the graphene membrane were tested. Limiting factors for electron microscopy in liquids, such as electron beam induced water radiolysis and damage of the graphene membrane at high electron doses, are discussed.

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Section: Introductionmentioning

confidence: 99%

Electron transparent graphene windows for environmental scanning electron microscopy in liquids and dense gases

Stoll

Kolmakov

2012

Nanotechnology

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“…Pilot experiments with the VLESTEM mode [54] revealed high thickness contrast on a 3 nm Au foil and pointed out that the electric field in the sample vicinity accelerates also the SE released near the bottom surface of the sample, generating in this way an “incoherent” contribution to the transmitted electron (TE) signal and apparently increasing the sample transmissivity to above 100% at the landing energies in hundreds of eV. Fortunately, in this energy range the SE are collimated to near the optical axis so their impact may be restricted to the bright field detector only, while the transmitted electrons should be acquired in the dark field channel as a pure signal [55].…”

Section: Resultsmentioning

confidence: 99%

Scanning Electron Microscopy with Samples in an Electric Field

et al. 2012

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The high negative bias of a sample in a scanning electron microscope constitutes the “cathode lens” with a strong electric field just above the sample surface. This mode offers a convenient tool for controlling the landing energy of electrons down to units or even fractions of electronvolts with only slight readjustments of the column. Moreover, the field accelerates and collimates the signal electrons to earthed detectors above and below the sample, thereby assuring high collection efficiency and high amplification of the image signal. One important feature is the ability to acquire the complete emission of the backscattered electrons, including those emitted at high angles with respect to the surface normal. The cathode lens aberrations are proportional to the landing energy of electrons so the spot size becomes nearly constant throughout the full energy scale. At low energies and with their complete angular distribution acquired, the backscattered electron images offer enhanced information about crystalline and electronic structures thanks to contrast mechanisms that are otherwise unavailable. Examples from various areas of materials science are presented.

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“…The spectra were acquired using a novel time-of-flight technique. Scanning Low Energy Electron Microscopy (SLEEM) was used to lower the energy of the electrons before they were transmitted through the material [9]. Transmission spectra using low energy electrons have been obtained from polymer films [10], molecular solids [11], and biomolecular solids [12].…”

Section: Introductionmentioning

confidence: 99%

Monte Carlo Simulation of Free-standing Thin Films under Low Energy Electron Bombardment: Electron Inelastic Mean Free Path (IMFP) Determination Using Elastic Peak of the Transmitted Electrons

2023

JJP

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The electron energy spectra of transmitted scattered electrons from free-standing films are simulated using a Monte Carlo computational approach. Elastic scattering is simulated using Mott cross-sections and inelastic scattering via discrete processes determined from dielectric function data. This allows one to simulate the secondary electrons as well as the loss peaks near the elastic (zero-loss) peak. The current study suggested a directed approach for determining the electron inelastic mean free path (IMFP) of materials at low primary electron energies. The IMFP of the reference material is not necessary for the suggested technique. The suggested technique uses the ratio between the transmitted elastic peak intensity and the background intensity of backscattered electrons. Free-standing films of Si, Cu, and Au were studied with thicknesses varying from 2 to 12 nm. Primary electron energies of 1, 3, and 5 keV were applied. The results appeared very good, with the percentage error range being between 5% and 25%. We also investigated the proportion of the first and second plasmon peak intensities to the elastic peak intensity. We believe that the latter could provide a directed method of measuring the IMFP of materials. Keywords: Inelastic mean free path, Monte Carlo simulation, Geant4, Free-standing film, Zero-loss peak.

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Very Low Energy Scanning Electron Microscopy of Free-Standing Ultrathin Films

Cited by 16 publications

References 26 publications

Electron transparent graphene windows for environmental scanning electron microscopy in liquids and dense gases

Electron transparent graphene windows for environmental scanning electron microscopy in liquids and dense gases

Scanning Electron Microscopy with Samples in an Electric Field

Monte Carlo Simulation of Free-standing Thin Films under Low Energy Electron Bombardment: Electron Inelastic Mean Free Path (IMFP) Determination Using Elastic Peak of the Transmitted Electrons

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