Electron Radiation Damage on thin Films of Phenylalanine

1973 ◽  
Vol 31 ◽  
pp. 484-485
Author(s):  
P. S. D. Lin
Keyword(s):  
Mass Loss ◽  
Incident Beam ◽  
Mean Free Path ◽  
Carbon Films ◽  
Specimen Thickness ◽  
Thin Carbon ◽  
Incident Beam Intensity ◽  
The Mean ◽  
Electron Energy Loss ◽  
Electron Energy Loss Spectra

Consecutive observation of the mass loss and change in electron energy loss spectra are being carried on In a simple field emission scanning mlcroscope. The specimens are prepared by slow sublimation onto thin carbon films on a copper grid.For mass loss measurement, unscattered electrons Nun are counted, W'lich Is related to Incident beam Intensity N0 by Nun = N0 exp(-(ai+ae)t), where tIs a specimen thickness, ae, ai the Inverse of the mean free path for elastic and Inelastic scattering, respectively. With 20 KeV and 12 mrad aperture angle, most of the elastically scattered electrons are stopped by the aperture. The Inelastically scattered electrons arefll tered by the spectrometer.

The influence of specimen thickness in quantitative electron energy loss spectroscopy: II

1983 ◽  
Vol 41 ◽  
pp. 388-389
Author(s):  
Nestor J. Zaluzec
Keyword(s):  
Energy Loss ◽  
Electron Energy ◽  
Electron Energy Loss Spectroscopy ◽  
Intensity Ratio ◽  
Mean Free Path ◽  
Specimen Thickness ◽  
Subsequent Work ◽  
The Mean ◽  
Plasmon Loss ◽  
Electron Energy Loss

In a previous paper it was shown that the influence of specimen thickness on quantitative electron energy loss spectroscopy (EELS) can be judged by measuring the intensity ratio of any two characteristic EEL edges as a function of thickness. If the specimen is homogeneous and thickness effects are neglegible then, one can show from Egerton’s formulation that this intensity ratio should be a constant. Any departure from a constant value indicates a breakdown of the quantitative theory due to thickness related effects. It was shown that if the ratio of Ip/IO (Ip = intensity of plasmon loss, IO = intensity of zero loss) exceeds ∼ 0.3 then quantitative analysis can be in significant error. In subsequent work Egerton showed that a better measure is the ratio of ℓn(It/IO) which is related to the ratio of t/λ. Here It is the total energy loss intensity, t the specimen thickness and λ the mean-free path for total inelastic scattering.

Comparison of Calculated and Recorded Electron Energy-Loss Spectra of Aluminium and Carbon

1990 ◽  
Vol 48 (2) ◽  
pp. 64-65
Author(s):  
L. Reimer ◽  
R. Oelgeklaus
Keyword(s):  
Fourier Transform ◽  
Energy Loss ◽  
Electron Energy ◽  
Rotational Symmetry ◽  
Mean Free Path ◽  
Single Scattering ◽  
Specimen Thickness ◽  
Two Dimensional ◽  
Image Position ◽  
Electron Energy Loss

Quantitative electron energy-loss spectroscopy (EELS) needs a correction for the limited collection aperture α and a deconvolution of recorded spectra for eliminating the influence of multiple inelastic scattering. Reversely, it is of interest to calculate the influence of multiple scattering on EELS. The distribution f(w,θ,z) of scattered electrons as a function of energy loss w, scattering angle θ and reduced specimen thickness z=t/Λ (Λ=total mean-free-path) can either be recorded by angular-resolved EELS or calculated by a convolution of a normalized single-scattering function ϕ(w,θ). For rotational symmetry in angle (amorphous or polycrystalline specimens) this can be realised by the following sequence of operations :(1)where the two-dimensional distribution in angle is reduced to a one-dimensional function by a projection P, T is a two-dimensional Fourier transform in angle θ and energy loss w and the exponent -1 indicates a deprojection and inverse Fourier transform, respectively.

Determination of Mean Free Path for Inelastic Scattering in Poly(2-Vinyl Pyridine) by Low-Loss Spectrum Imaging

2000 ◽  
Vol 6 (S2) ◽  
pp. 224-225
Author(s):  
A. Aitouchen ◽  
T. Chou ◽  
M. Libera ◽  
M. Misra
Keyword(s):  
Free Path ◽  
Free Fall ◽  
Mean Free Path ◽  
Specimen Thickness ◽  
Thickness Determination ◽  
Vinyl Pyridine ◽  
Integrated Intensity ◽  
Inelastic Mean Free Path ◽  
Electron Energy Loss

The common experimental method to determine the total inelastic mean free path i by electron energy-loss spectroscopy (EELS) is by the relation : t/λi= ln(It/IO) [1] where t is the specimen thickness, It, is the total integrated intensity, and Io is the intensity of the zero-loss peak. The accuracy of this measurement depends on the thickness determination. Model geometries like cubes, wedges, and spheres enable accurate thickness determination from transmission images.Spherical polymers with diameters of order 10-200nm can be made from a number of high-Tg polymers by solvent atomization. This research studied atomized spheres of poly(2-vinyl pyridine) [PVP]. A solution of 0.1% PVP in THF was nebulized. After solvent evaporation during free fall within the chamber atmosphere, solid spherical polymer particles with a range of diameters were collected on holey-carbon TEM grids at the bottom of the atomization chamber.

Energetic Deposition and Surface Characterization of Thin Carbon Films on Nickel

1998 ◽  
Vol 12 (10) ◽  
pp. 383-391
Author(s):  
K. P. Adhi ◽  
A. K. Sharma ◽  
S. S. Wagal ◽  
D. S. Joag ◽  
S. K. Kulkarni
Keyword(s):  
Photoelectron Spectroscopy ◽  
Surface Characterization ◽  
Carbon Films ◽  
Polycrystalline Nickel ◽  
Thin Carbon ◽  
Nickel Substrates ◽  
Phase Surface ◽  
Electron Energy Loss ◽  
Deposited Films

Thin films deposited by rapidly quenching the energetic carbon species impinging onto polycrystalline nickel substrates were studied by X-ray photoelectron spectroscopy (XPS), electron energy loss spectroscopy (EELS), and field ion microscopy (FIM). XPS and EELS of the deposited films, when compared with those recorded for graphite and synthetic diamond, indicated the growth of diamond like carbon films and amorphic diamond (a-D) phase. Surface atomic arrangement in the film is observed by FIM which magnifies the surface ~105 to 106 times. Facetting, lack of graphitic ordering, stability of the image inspite of raising or lowering the voltage about the field evaporation voltage indicate that the field ion micrograph is that of a-D.

Thickness Measurement by EELS

1985 ◽  
Vol 43 ◽  
pp. 398-399
Author(s):  
R. F. Egerton ◽  
S. C. Cheng
Keyword(s):  
Energy Loss ◽  
Electron Energy Loss Spectroscopy ◽  
Incident Energy ◽  
Mean Free Path ◽  
Thickness Measurement ◽  
Loss Peak ◽  
Wide Range ◽  
Integrated Intensity ◽  
The Mean ◽  
Electron Energy Loss

Electron energy-loss spectroscopy offers a rapid method of estimating the local thickness of a TEM specimen. The best-known procedure requires only measurement of the integrated intensity IO under the zero-loss peak and of the integral It under the whole spectrum (up to some suitable energy loss Δ). The thickness t is obtained from the formula:where λ(β) is the mean free path for inelastic scattering up to some angle β which is determined by the collection aperture (e.g. objective aperture in CTEM). In agreement with previous work we find that Eq. (1) is applicable over a wide range of thickness, typically 10-500 nm for EO = 100keV incident energy; see Fig. 1. Some deviation at large thickness might be expected as a result of the angular broadening produced by plural scattering, and because of contributions from electrons elastically scattered through angles greater than β.

Electron Energy Loss Spectroscopy at 5Å Spatial Resolution

1985 ◽  
Vol 43 ◽  
pp. 396-397
Author(s):  
M. Isaacson ◽  
M. Scheinfein
Keyword(s):  
Energy Loss ◽  
Electron Energy ◽  
Spatial Resolution ◽  
Electron Energy Loss Spectroscopy ◽  
Incident Beam ◽  
Beam Current ◽  
Different Types ◽  
Half Angle ◽  
Electron Energy Loss ◽  
Electron Energy Loss Spectra

One of the ultimate goals of electron energy loss spectroscopy within the electron microscope is to be able to obtain the electronic structure of interfaces at near atomic resolution. Though this goal has not yet been achieved, there has been considerable effort devoted to elemental composition at high spatial resolution using ELS (eg. References 1-3). In this paper we wish to present initial measurements made across different types of interfaces that show core and valence shell electron energy loss spectra changing within an 8Å spatial scale across the interface.All the measurements have been performed using a modified dedicated STEM (VG Scientific HB-5) equipped with beam blanking facilities, digital control and a wide-gap aberration connected energy loss spectrometer. The details of this instrument have been described elsewhere (4). The main point to be noted is that the incident illumination half angle was 7.5mrad for these experiments and the full width at half maximum of the probe was 4.6Å (measured). With these optical conditions, 90% of all the incident beam current is contained within a diameter of 9.0Å (5). For beam sensitive materials, the recording dose was kept to less than 1/3 the dose for observable sample degradation.

Electron Microscope Tomography (Emt): Reconstruction Algorithms, Imaging and Mass Loss of Thick Sections

1990 ◽  
Vol 48 (1) ◽  
pp. 514-515 ◽  
Author(s):  
A.L. Olins ◽  
H. A. Levy ◽  
M. B. Shah ◽  
G. G. Lamprecht ◽  
D. E. Olins
Keyword(s):  
Mass Loss ◽  
Signal To Noise Ratio ◽  
Beam Current ◽  
Specimen Thickness ◽  
Electron Spectroscopic Imaging ◽  
Reconstruction Algorithms ◽  
Mass Thickness ◽  
Beam Voltage ◽  
Carbon Coated ◽  
Electron Energy Loss

We previously reported EMT reconstructions of thick (>0.5 μm) sections using electron spectroscopic imaging at the most probable electron energy loss (ΔEp). We2 calculated values of contrast and signal-to-noise ratio (SNR) for images formed with electrons taken throughout the spectrum. We observed maximal SNR just below ΔEp, and found that changes in the electron beam voltage and mass thickness (t/λ) led to predictable changes in the EELS.We have begun a study of mass loss due to electron exposure of thick epon sections. Uranyl and lead stained sections were put on formvar covered grids and carbon coated on each side. Clear epon regions were analyzed. During each exposure series the beam was kept at crossover; the beam current was changed from its lowest value (0.5 μamp) to its highest value (55 μamp). As reported elsewhere, mass loss occurs early and plateaus. Calculations were based on EELS collected at different times during each series (Figure 1a). Measured positions of ΔEp at different times (min) of maximum beam current irradiation are shown in Figure 1 b. Mass thickness, t/λ = In (total area/zero loss area), shows a linear relationship with ΔEp (Figure 1c). Using λ = 115 nm in epon, we calculate the initial thickness of the sections to be 0.5, 0.75, 1.0 μm and the mass loss to be ∼37 nm. If mass loss is independent of the specimen thickness, then the 50% loss observed with thinner specimen becomes a trivial 4-7% loss in sections of 0.5 to 1.0 μm.

The Effects of Substrate Conditions on the Microstructural Evolution of Thin Diamond-Like Films

1990 ◽  
Vol 202 ◽  
Author(s):  
J. J. Cuomo ◽  
J. Bruley ◽  
J. P. Doyle ◽  
D. L. Pappas ◽  
K. L. Saenger ◽  
...  
Keyword(s):  
Beam Energy ◽  
Incident Beam ◽  
Ion Sputtering ◽  
Spatially Resolved ◽  
Different Temperatures ◽  
High Fraction ◽  
Incident Beam Energy ◽  
Electron Energy Loss ◽  
Electron Energy Loss Spectra ◽  
Deposition Conditions

ABSTRACTWe report on a study of hard amorphous carbon thin films prepared by condensing streams of energetic carbon species, onto a range of substrates maintained at different temperatures. The carbon vapor is generated either by ion sputtering, laser ablation or e-beam evaporation. Spatially resolved electron-energy-loss spectra reveal variations in the films′ microstructure brought about by altering the deposition conditions. We estimate that the density of the different films varies between 2.0 and 3.26 g/cm3. We observe an evolution towards denser films upon increasing incident beam energy, reducing substrate temperature, and increasing substrate thermal conductivity. Low density films contain a predominance of trigonally bonded sp2-hybridized carbon (i.e graphitic carbon) and the highest density films contain a high fraction (∽ 80%) of tetr-ahedral sp3-bonded carbon (i.e. diamond-like).

The Combined Effect of Channelling and Blocking in Electron Energy Loss Spectroscopy

1981 ◽  
Vol 39 ◽  
pp. 190-191
Author(s):  
J. Taftø ◽  
O. L. Krivanek
Keyword(s):  
Energy Loss ◽  
Electron Energy ◽  
Bragg Reflection ◽  
Incident Beam ◽  
Orientation Dependence ◽  
Planar Case ◽  
X Ray ◽  
Crystal Unit Cell ◽  
Electron Energy Loss ◽  
Electron Energy Loss Spectra

Bragg reflection of electrons gives rise to a modulation of the wavefield over the crystal unit cell. Depending on the incident beam direction the electrons may be concentrated at one or another type of atoms or between them. Localized ionization processes will therefore show an orientation dependence, and this will affect the X-ray emission intensities as well as electron energy loss spectra. The energy loss case gives more possibilities for experimental arrangements than the X-ray emission case, in that the direction of not only the incident electron beam, but also that of the exit beam to be analyzed may be selected.Natural MgAl2O4 spinel was studied. The crystals were ground in a mortar and thin areas were analyzed with a Gatan 607 spectrometer attached to a Philips 400T electron microscope operating at lOOkV. The experiments were done for the (400)-planar case where the main atomic planes contain Al2O4. The Mg-atoms are midway between the A12O4 and may be considered as interstitials in this planar case.

Parameterization of the mean free path for inelastic scattering of fast electrons

1987 ◽  
Vol 45 ◽  
pp. 122-123
Author(s):  
R. F. Egerton ◽  
S. C. Cheng ◽  
T. Malis
Keyword(s):  
Energy Loss ◽  
Free Path ◽  
Mean Free Path ◽  
Fast Electrons ◽  
Before And After ◽  
The Mean ◽  
Convergent Beam ◽  
Inelastic Mean Free Path ◽  
Electron Energy Loss ◽  
Beam Diffraction

The areas, Iz and It, under the zero-loss peak and under the entire energy-loss spectrum (of a sample of thickness t) are related by the formula:t/ƛ(β) = ln (It/Iz) (1)where ƛ(β) is the inelastic mean free path for all energy losses and for scattering into the collection aperture, of semiangle β. We have used Eq.(l) to experimentally determine ƛ(β) by electron energy-loss spectroscopy of specimens of known composition and thickness. In the case of crystalline samples, the local thickness t was measured by convergent-beam diffraction. In the case of evaporated thin-film specimens, the average thickness was obtained by accurately weighing the substrate before and after deposition. The energy-loss spectroscopy was carried out in CTEM mode with incident energies Eo between 20keV and 120keV, and with collection semiangles in the range 0.2 mrad to 100 mrad.

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