Quantitative Assessment and Measurement of X-ray Detector Performance and Solid Angle in the Analytical Electron Microscope

Microscopy and Microanalysis ◽

10.1017/s143192762101360x ◽

2021 ◽

pp. 1-13

Author(s):

Nestor J. Zaluzec

Keyword(s):

Solid Angle ◽

Collection Efficiency ◽

Analytical Formula ◽

Individual Performance ◽

Detector Performance ◽

X Ray ◽

Wide Range ◽

Analytical Electron ◽

Scanning Transmission ◽

Electron Microscopes

A wide range of X-ray detectors and geometries are available today on transmission/scanning transmission analytical electron microscopes. While there have been numerous reports of their individual performance, no single experimentally reproducible metric has been proposed as a basis of comparison between the systems. In this paper, we detail modeling, experimental procedures, measurements, and specimens which can be used to provide a manufacturer-independent assessment of the performance of an analytical system. Using these protocols, the geometrical collection efficiency, system peaks, and minimum detection limits can be independently assessed and can be used to determine the best conditions to conduct modern hyperspectral and/or spectrally resolved tomographic analyses for an individual instrument. A simple analytical formula and specimen is presented which after suitable system calibrations can be used to experimentally determine the X-ray detector solid angle.

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Energy-dispersive x-ray detectors for analytical electron microscopy

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s042482010008924x ◽

1991 ◽

Vol 49 ◽

pp. 986-987

Author(s):

L. E. Thomas

Keyword(s):

Collection Efficiency ◽

Analytical Electron Microscopy ◽

Energy Dispersive ◽

Detector Performance ◽

X Ray ◽

Performance Improvements ◽

Transmission Electron ◽

Analytical Electron ◽

Scanning Transmission ◽

Electron Microscopes

Continuing evolution of energy-dispersive x-ray spectrometer (EDS) systems has greatly advanced x-ray detector performance in analytical electron microscopes. The latest detectors offer improved energy resolution, count rate performance, geometrical collection efficiency, durability, and efficiency for light and heavy elements. Innovative detector designs for transmission and scanning transmission electron microscopes (TEM/STEMs) include such features as liquid-nitrogen-free operation, in situ de-icing of the detector crystal, user cleanable windows, demountable windows, ultrahigh vacuum compatibility (including adaptations to allow microscope bakeouts without removing the detector), beam damage protection, and microscope interfaces with optimized collection geometries. Divergent design philosophies have produced a variety of systems with specialized features, and users may face hard choices in selecting the best detector for the job. The aim of this paper is to review the current state of EDS detector development and the importance of the performance improvements to TEM/STEM users.

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Analytical Formulae for Calculation of X-Ray Detector Solid Angles in the Scanning and Scanning/Transmission Analytical Electron Microscope

Microscopy and Microanalysis ◽

10.1017/s1431927614000956 ◽

2014 ◽

Vol 20 (4) ◽

pp. 1318-1326 ◽

Cited By ~ 34

Author(s):

Nestor J. Zaluzec

Keyword(s):

Electron Microscopy ◽

Electron Microscope ◽

Solid Angle ◽

Analytical Electron Microscopy ◽

X Ray ◽

Analytical Electron ◽

Analytical Electron Microscope ◽

Scanning Transmission ◽

Analytical Formulae ◽

Detector Configurations

AbstractClosed form analytical equations used to calculate the collection solid angle of six common geometries of solid-state X-ray detectors in scanning and scanning/transmission analytical electron microscopy are presented. Using these formulae one can make realistic comparisons of the merits of the different detector geometries in modern electron column instruments. This work updates earlier formulations and adds new detector configurations.

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Theoretical and Experimental X-Ray Peak/Background Ratios and Implications for Energy-Dispersive Spectrometry in the Next-Generation Analytical Electron Microscope

Microscopy and Microanalysis ◽

10.1017/s1431927615015755 ◽

2016 ◽

Vol 22 (1) ◽

pp. 230-236 ◽

Cited By ~ 3

Author(s):

Nestor J. Zaluzec

Keyword(s):

Theoretical Calculations ◽

Detection Sensitivity ◽

X Ray ◽

Background Ratio ◽

Exit Surface ◽

Wide Range ◽

Analytical Electron ◽

Solid Angles ◽

Electron Microscopes ◽

The Impact

AbstractModern analytical electron microscopes equipped with silicon drift detectors now allow for a wide range of geometrical configurations capable of performing quantitative X-ray spectrometry. Recent work has improved the collection solid angles of these detectors, however, the impact of increasing the solid angle on detection sensitivity as measured by the peak/background ratio has not been addressed. This work compares theoretical and experimental peak/background ratios for incident electron energies in the range of 20–200 keV, with X-ray detectors in both conventional orientations (on the electron entrance surface) as well as new geometries (the electron exit surface). The implications of these parameters on detectability limits for the next generations of “Lab-in-the-Gap” analytical microscope are also considered. It was found that theoretical calculations of the angular distribution of bremsstrahlung and their effects on the peak/background ratio match well with experimental measurements, and indicate that new geometries which can result in large solid angles provided an added benefit in addition to increased characteristic signal, namely increased sensitivity for the analyst.

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Materials science applications of a 120kV FEG TEM/STEM: Triskaidekaphilia

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s042482010008780x ◽

1991 ◽

Vol 49 ◽

pp. 698-699

Author(s):

J. Bentley ◽

A. T. Fisher ◽

E. A. Kenik ◽

Z. L. Wang

Keyword(s):

Electron Microscope ◽

Materials Science ◽

X Ray ◽

Transmission Electron ◽

Analytical Electron ◽

Analytical Electron Microscope ◽

Scanning Transmission ◽

Potential Impact ◽

Electron Microscopes ◽

Electron Energy Loss

The introduction by several manufacturers of 200kV transmission electron microscopes (TEM) equipped with field emission guns affords the opportunity to assess their potential impact on materials science by examining applications of similar 100-120kV instruments that have been in use for more than a decade. This summary is based on results from a Philips EM400T/FEG configured as an analytical electron microscope (AEM) with a 6585 scanning transmission (STEM) unit, ED AX 9100/70 or 9900 energy dispersive X-ray spectroscopy (EDS) systems, and Gatan 607 serial- or 666 parallel-detection electron energy-loss spectrometers (EELS). Examples in four areas that illustrate applications that are impossible or so difficult as to be impracticable with conventional thermionic electron guns are described below.

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Optimizing conditions for x-ray microchemical analysis in analytical electron microscopy

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100109884 ◽

1978 ◽

Vol 36 (1) ◽

pp. 548-549 ◽

Cited By ~ 2

Author(s):

N. J. Zaluzec

Keyword(s):

Solid Angle ◽

Analytical Electron Microscopy ◽

Incident Beam ◽

Thin Foil ◽

Experimental Conditions ◽

X Ray ◽

Microchemical Analysis ◽

Analytical Electron ◽

Image Position ◽

Incident Beam Energy

The ultimate sensitivity of microchemical analysis using x-ray emission rests in selecting those experimental conditions which will maximize the measured peak-to-background (P/B) ratio. This paper presents the results of calculations aimed at determining the influence of incident beam energy, detector/specimen geometry and specimen composition on the P/B ratio for ideally thin samples (i.e., the effects of scattering and absorption are considered negligible). As such it is assumed that the complications resulting from system peaks, bremsstrahlung fluorescence, electron tails and specimen contamination have been eliminated and that one needs only to consider the physics of the generation/emission process.The number of characteristic x-ray photons (Ip) emitted from a thin foil of thickness dt into the solid angle dΩ is given by the well-known equation

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High spatial resolution x-ray microanalysis of interfaces

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100137793 ◽

1995 ◽

Vol 53 ◽

pp. 284-285

Author(s):

J. R. Michael

Keyword(s):

Spatial Resolution ◽

Electron Probe ◽

Solid Angle ◽

Collection Efficiency ◽

Spatial Scales ◽

Energy Dispersive Spectrometer ◽

X Rays ◽

X Ray ◽

Probe Size ◽

Brightness Field

X-ray microanalysis in the analytical electron microscope (AEM) refers to a technique by which chemical composition can be determined on spatial scales of less than 10 nm. There are many factors that influence the quality of x-ray microanalysis. The minimum probe size with sufficient current for microanalysis that can be generated determines the ultimate spatial resolution of each individual microanalysis. However, it is also necessary to collect efficiently the x-rays generated. Modern high brightness field emission gun equipped AEMs can now generate probes that are less than 1 nm in diameter with high probe currents. Improving the x-ray collection solid angle of the solid state energy dispersive spectrometer (EDS) results in more efficient collection of x-ray generated by the interaction of the electron probe with the specimen, thus reducing the minimum detectability limit. The combination of decreased interaction volume due to smaller electron probe size and the increased collection efficiency due to larger solid angle of x-ray collection should enhance our ability to study interfacial segregation.

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The effect of small additions of Cu on precipitation in Al-Mg-Si alloys

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100135812 ◽

1990 ◽

Vol 48 (2) ◽

pp. 442-443

Author(s):

M. Tamizifar ◽

G. Cliff ◽

R.W. Devenish ◽

G.W. Lorimer

Keyword(s):

Electron Microscopy ◽

Analytical Electron Microscopy ◽

Scanning Transmission Electron Microscope ◽

Argon Atmosphere ◽

Age Hardening ◽

X Ray ◽

Transmission Electron ◽

Heat Treated ◽

Analytical Electron ◽

Scanning Transmission

Small additions of copper, <1 wt%, have a pronounced effect on the ageing response of Al-Mg-Si alloys. The object of the present investigation was to study the effect of additions of copper up to 0.5 wt% on the ageing response of a series of Al-Mg-Si alloys and to use high resolution analytical electron microscopy to determine the composition of the age hardening precipitates.The composition of the alloys investigated is given in Table 1. The alloys were heat treated in an argon atmosphere for 30m, water quenched and immediately aged either at 180°C for 15 h or given a duplex treatment of 180°C for 15 h followed by 350°C for 2 h2. The double-ageing treatment was similar to that carried out by Dumolt et al. Analyses of the precipitation were carried out with a HB 501 Scanning Transmission Electron Microscope. X-ray peak integrals were converted into weight fractions using the ratio technique of Cliff and Lorimer.

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Practical Estimation of Analytical Sensitivity for EDS in an Intermediate Voltage FEG-STEM

Microscopy and Microanalysis ◽

10.1017/s1431927600011715 ◽

1997 ◽

Vol 3 (S2) ◽

pp. 965-966

Author(s):

M. Watanabe ◽

D. W. Ackland ◽

D. B. Williams

Keyword(s):

Spatial Resolution ◽

Single Atom ◽

Acquisition Time ◽

Analytical Sensitivity ◽

X Ray ◽

Quantitative Microanalysis ◽

Analytical Electron ◽

Atom Detection ◽

Electron Microscopes ◽

Image Position

One of the ultimate objectives for energy-dispersive X-ray spectrometry (EDS) in the analytical electron microscope (AEM) is single-atom detection in thin specimens, as well as quantitative microanalysis with high accuracy approaching ±1% relative. In order to realize the single-atom analysis, the design of the AEM has to be optimized with respect to improvements in spatial resolution and detectability limits. The detectability limit, as defined by the minimum mass fraction (MMF), is given by:where P is the peak intensity of interest, (P/B) is the peak-to-background ratio for that peak, and r is the acquisition time. To improve the sensitivity for analysis, any or all of the variables P, (P/B), and τ should be increased. Intermediate-voltage analytical electron microscopes combined with high brightness field-emission gun (FEG) are expected to improve the MMF, while maintaining high spatial resolution. Additionally, the MMF should also be improved by maximizing the solid angle of X-ray collection.

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