Characteristic Electron Energy Loss Measurements at Low Temperatures

An effective use of electron energy loss spectroscopy for chemical characterization of selected areas in the electron microscope can only be achieved with the development of quantitative measurements capabilities.The experimental assembly, which is sketched in Fig.l, has therefore been carried out. It comprises four main elements.The analytical transmission electron microscope is a conventional microscope fitted with a Castaing and Henry dispersive unit (magnetic prism and electrostatic mirror). Recent modifications include the improvement of the vacuum in the specimen chamber (below 10-6 torr) and the adaptation of a new electrostatic mirror.The detection system, similar to the one described by Hermann et al (1), is located in a separate chamber below the fluorescent screen which visualizes the energy loss spectrum. Variable apertures select the electrons, which have lost an energy AE within an energy window smaller than 1 eV, in front of a surface barrier solid state detector RTC BPY 52 100 S.Q. The saw tooth signal delivered by a charge sensitive preamplifier (decay time of 5.10-5 S) is amplified, shaped into a gaussian profile through an active filter and counted by a single channel analyser.

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Trends in Electron Energy Loss Spectroscopy

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100078675 ◽

1977 ◽

Vol 35 ◽

pp. 228-229

Author(s):

C. Colliex ◽

P. Trebbia

Keyword(s):

Energy Loss ◽

Electron Energy ◽

Electron Energy Loss Spectroscopy ◽

Materials Science ◽

Analytical Technique ◽

Recent Developments ◽

Quantitative Results ◽

Electron Microscopes ◽

Electron Energy Loss ◽

Primary Electrons

The physical foundations for the use of electron energy loss spectroscopy towards analytical purposes, seem now rather well established and have been extensively discussed through recent publications. In this brief review we intend only to mention most recent developments in this field, which became available to our knowledge. We derive also some lines of discussion to define more clearly the limits of this analytical technique in materials science problems.The spectral information carried in both low ( 0<ΔE<100eV ) and high ( >100eV ) energy regions of the loss spectrum, is capable to provide quantitative results. Spectrometers have therefore been designed to work with all kinds of electron microscopes and to cover large energy ranges for the detection of inelastically scattered electrons (for instance the L-edge of molybdenum at 2500eV has been measured by van Zuylen with primary electrons of 80 kV). It is rather easy to fix a post-specimen magnetic optics on a STEM, but Crewe has recently underlined that great care should be devoted to optimize the collecting power and the energy resolution of the whole system.

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Signal/Noise Ratio and Elemental Detectivity by Eels

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100054893 ◽

1982 ◽

Vol 40 ◽

pp. 488-489

Author(s):

R. F. Egerton

Keyword(s):

Energy Loss ◽

Electron Energy ◽

Elemental Analysis ◽

Electron Energy Loss Spectroscopy ◽

Emission Spectroscopy ◽

X Ray ◽

Signal Noise ◽

Characteristic Signal ◽

Noise Ratio ◽

Electron Energy Loss

An important parameter governing the sensitivity and accuracy of elemental analysis by electron energy-loss spectroscopy (EELS) or by X-ray emission spectroscopy is the signal/noise ratio of the characteristic signal.

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Quantitative Electron Energy Loss Mapping

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100118898 ◽

1985 ◽

Vol 43 ◽

pp. 404-405

Author(s):

R.D. Leapman ◽

C.R. Swyt

Keyword(s):

Energy Loss ◽

Electron Energy ◽

Electron Energy Loss Spectroscopy ◽

Elemental Concentration ◽

Core Loss ◽

Elemental Distribution ◽

Electron Energy Loss

The intensity of a characteristic electron energy loss spectroscopy (EELS) image does not, in general, directly reflect the elemental concentration. In fact, the raw core loss image can give a misleading impression of the elemental distribution. This is because the measured core edge signal depends on the amount of plural scattering which can vary significantly from region to region in a sample. Here, we show how the method for quantifying spectra due to Egerton et al. can be extended to maps.

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

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100133916 ◽

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.

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Parallel Detection of Electron Energy Loss Spectra in Direct Mode

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100134004 ◽

1990 ◽

Vol 48 (2) ◽

pp. 82-83

Author(s):

Eckhard Quandt ◽

Stephan laBarré ◽

Andreas Hartmann ◽

Heinz Niedrig

Keyword(s):

Energy Loss ◽

Electron Energy ◽

Energy Resolution ◽

Large Angle ◽

Maximum Energy ◽

Semiconductor Detectors ◽

Parallel Detection ◽

Photodiode Arrays ◽

Electron Energy Loss ◽

Electron Energy Loss Spectra

Due to the development of semiconductor detectors with high spatial resolution -- e.g. charge coupled devices (CCDs) or photodiode arrays (PDAs) -- the parallel detection of electron energy loss spectra (EELS) has become an important alternative to serial registration. Using parallel detection for recording of energy spectroscopic large angle convergent beam patterns (LACBPs) special selected scattering vectors and small detection apertures lead to very low intensities. Therefore the very sensitive direct irradiation of a cooled linear PDA instead of the common combination of scintillator, fibre optic, and semiconductor has been investigated. In order to obtain a sufficient energy resolution the spectra are optionally magnified by a quadrupole-lens system.The detector used is a Hamamatsu S2304-512Q linear PDA with 512 diodes and removed quartz-glas window. The sensor size is 13 μm ∗ 2.5 mm with an element spacing of 25 μm. Along with the dispersion of 3.5 μm/eV at 40 keV the maximum energy resolution is limited to about 7 eV, so that a magnification system should be attached for experiments requiring a better resolution.

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