Quantitative assessment of a parallel detection system for energy‐loss spectrometry

Serial detection systems that are standardly employed in electron energy loss spectrometry (EELS) only examine one energy channel at a time and are therefore inherently inefficient. Parallel detection systems using either photodiode arrays or charge-coupled devices (CCDs) promise to remove this inefficiency. However, to completely replace the serial detection systems, they will need 1) a detective quantum efficiency (DQE) approaching 100%, 2) a dynamic range sufficient to cover the range of intensities encountered in the energy loss spectra (about 106), and 3) ability to operate without any loss in energy resolution.We have constructed and tested a parallel detection system which incorporates three quadrupole lenses placed after the magnetic sector prism of the Gatan 607 spectrometer, a single crystal YAG scintillator, and a fiber-optically coupled linear photodiode array. The quadrupoles magnify the small dispersion (1.8μm per eV at 100kV primary voltage) of the spectrum produced by the magnetic sector to as high as 1 mm per eV without producing any spectrum rotation and with small power requirements.

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A Photodiode, Parallel Detection System for Energy Loss Spectrometry

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100098356 ◽

1981 ◽

Vol 39 ◽

pp. 370-371

Author(s):

D.E. Johnson ◽

S. Csillag ◽

K.L. Monson ◽

E.A. Stern

Keyword(s):

Energy Loss ◽

Detection System ◽

Image Intensifier ◽

Beam Axis ◽

Depth Of Focus ◽

Parallel Detection ◽

Detection Systems ◽

Photodiode Array ◽

Simple Film ◽

Dispersion Plane

The advantages of parallel detection systems for energy loss spectometry are certainly clear. A variety of approaches are possible ranging from simple film recording to elaborate intensified television cameras. We are in the process of evaluating one approach to such a parallel detection system, which consists of; a magnetic post-spectrometer lens to increase dispersion, a phosphor conversion plate, glass coupling lenses, a dual channeltron image intensifier, and a cooled photodiode array (Reticon RL256C/17). A schematic diagram of the system is shown in Fig. 1.The post-spectrometer lens is an RCA-3G intermediate lens which typically magnifies (∼15x) the dispersion to ∼25μm/ev with a rotation of ∼90°. Although the dispersion plane of the straight edge sector magnet used is tilted at 30° from the beam axis, pre-spectrometer optics reduce the angular divergence of the beam entering and leaving the spectrometer to ∼1 mr and the consequently large depth of focus assures that the dispersed beam is in focus across the conversion plate, perpendicular to the beam axis.

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Data Acquisition and Handling Unit for a Quantitative Use of Electron Energy Loss Spectroscopy

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100078699 ◽

1977 ◽

Vol 35 ◽

pp. 232-233 ◽

Cited By ~ 1

Author(s):

P. Trebbia ◽

P. Ballongue ◽

C. Colliex

Keyword(s):

Electron Microscope ◽

Energy Loss ◽

Electron Energy ◽

Electron Energy Loss Spectroscopy ◽

Single Channel ◽

Detection System ◽

Surface Barrier ◽

Solid State Detector ◽

Electrostatic Mirror ◽

Electron Energy Loss

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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Probing the Chemistry and Spectroscopy of Radiation-Sensitive Polymers by Parallel-Detection EELS

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s042482010013376x ◽

1990 ◽

Vol 48 (2) ◽

pp. 34-35

Author(s):

E. G. Rightor ◽

G. P. Young

Keyword(s):

Electron Beam ◽

Bisphenol A ◽

Energy Loss ◽

Parallel Detection ◽

Commercial Grade ◽

Incident Electron Beam ◽

Ptfe Sample ◽

Spectroscopic Information ◽

Edge Features ◽

Electron Energy Loss

Investigation of neat polymers by TEM is often thwarted by their sensitivity to the incident electron beam, which also limits the usefulness of chemical and spectroscopic information available by electron energy loss spectroscopy (EELS) for these materials. However, parallel-detection EELS systems allow reduced radiation damage, due to their far greater efficiency, thereby promoting their use to obtain this information for polymers. This is evident in qualitative identification of beam sensitive components in polymer blends and detailed investigations of near-edge features of homopolymers.Spectra were obtained for a poly(bisphenol-A carbonate) (BPAC) blend containing poly(tetrafluoroethylene) (PTFE) using a parallel-EELS and a serial-EELS (Gatan 666, 607) for comparison. A series of homopolymers was also examined using parallel-EELS on a JEOL 2000FX TEM employing a LaB6 filament at 100 kV. Pure homopolymers were obtained from Scientific Polymer Products. The PTFE sample was commercial grade. Polymers were microtomed on a Reichert-Jung Ultracut E and placed on holey carbon grids.

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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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Acquisition of EELS spectra for high-resolution spectroscopy

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100148721 ◽

1993 ◽

Vol 51 ◽

pp. 578-579

Author(s):

Maoxu Qian ◽

Mehmet Sarikaya ◽

Edward A. Stern

Keyword(s):

Energy Loss ◽

Detection System ◽

High Resolution Spectroscopy ◽

High Signal ◽

Short Report ◽

Edge Structure ◽

High Background ◽

Gain Variation ◽

Sufficient Energy ◽

On Line

It is difficult, in general, to perform quantitative EELS to determine, for example, relative or absolute compositions of elements with relatively high atomic numbers (using, e.g., K edge energies from 500 eV to 2000 eV), to study ELNES (energy loss near edge structure) signal using the white lines to determine oxidation states, and to analyze EXELFS (extended energy loss fine structure) to study short range ordering. In all these cases, it is essential to have high signal-to-noise (S/N) ratio (low systematical error) with high overall counts, and sufficient energy resolution (∽ 1 eV), requirements which are, in general, difficult to attain. The reason is mainly due to three important inherent limitations in spectrum acquisition with EELS in the TEM. These are (i) large intrinsic background in EELS spectra, (ii) channel-to-channel gain variation (CCGV) in the parallel detection system, and (iii) difficulties in obtaining statistically high total counts (∽106) per channel (CH). Except the high background in the EELS spectrum, the last two limitations may be circumvented, and the S/N ratio may be attained by the improvement in the on-line acquisition procedures. This short report addresses such procedures.

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