The limitations of quantitative EDS analysis at low voltage

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100164842 ◽

1996 ◽

Vol 54 ◽

pp. 476-477

Author(s):

C. E. Nockolds

Keyword(s):

Quantitative Analysis ◽

Low Voltage ◽

Low Energy ◽

X Rays ◽

Considerable Effort ◽

Beam Voltage ◽

Absorption Correction ◽

Transition Series ◽

Very High ◽

High Absorption

There are several reasons for carrying out x-ray microanalysis at low beam energies. In conventional electron probe microanalysis with wavelength dispersive spectrometers (WDS) there has been a considerable effort in recent years to improve the accuracy of quantitative analysis of the “light” elements B, C, N and O. The shapes of the low energy K x-rays and the L x-rays of the first transition series metals are also being studied with the aim of determining the chemical environments of the atoms in a sample. In most materials these soft x-rays suffer from very high absorption, and reducing the depth of the interaction volume by lowering the beam voltage to 5kV or below leads to a much reduced absorption correction. In scanning electron microscopy the introduction of thin window energy dispersive spectrometers (EDS) has made it possible to look at low energy x-rays and here the main interest in working at low voltages is in the improvement of the resolution of analysis.In this paper the limitations of SEM/EDS low voltage analysis will be examined, and possible solutions to some of the problems explored. It will be assumed that the aims are to achieve quantitative analysis at the best possible spatial resolution.

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Low-voltage SEM update

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100144693 ◽

1986 ◽

Vol 44 ◽

pp. 654-657

Author(s):

J.B. Pawley ◽

W.R. Scala

Keyword(s):

High Resolution ◽

Low Voltage ◽

Low Energy ◽

Special Issue ◽

Significant Progress ◽

Beam Voltage ◽

Signal Collection ◽

Upper Stage ◽

Micro Lens ◽

Made In

The advantages of operating an SEM at low beam voltage (Vo) are now widely recognized and significant progress has been made in overcoming the practical limitations to high resolution operation with Vo = 1-2 kV. A Symposium on Low Voltage SEM (LVSEM) was held at the 1984 EMSA meeting and several of the papers presented there were later collected for a special issue of the Journal of Microscopy. The purpose of this contribution is to outline three developments in instrumentation for LVSEM that have recently appeared. These include: 1) The new pole-pieces on the upper stage of the ISI DS-130c which permit it to produce very low aberration coefficients with low energy beams. 2) The replacement of the final lens of the Hitachi S-800, field emission SEM with an immersion lens to create the new S-900; 3) The development of the micro-lens for mounting in the chamber on a conventional’ SEM to produce both low aberration coefficients and a favorable geometry for signal collection.

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Prospects for X-Ray Analysis of Rough Surfaces in the SEM

Microscopy and Microanalysis ◽

10.1017/s1431927600037089 ◽

2000 ◽

Vol 6 (S2) ◽

pp. 918-919

Author(s):

P.J. Statham

Keyword(s):

Rough Surface ◽

Beam Current ◽

Low Energy ◽

X Rays ◽

X Ray ◽

Beam Voltage ◽

Gradual Loss ◽

Characteristic Lines ◽

Lower Beam ◽

Key Aspects

Some of the key aspects affecting analysis of a rough surface are described in Fig. 1. If a hypothetical sample consisting of 96% Si, 1% O, 1% Na, 1% Al and 1% Fe is analysed at 20kV at constant beam current with an x-ray detector elevated at 30deg from horizontal then the measured intensities of the various characteristic lines will vary with tilt. While absorption of low energy x-rays is reduced as the sample tilts towards the detector, there is also a gradual loss of intensity due to increased backscatter. At the lower beam voltage of 5kV, absorption of x-rays at zero tilt is already small and Fig.2 shows that variation in intensity with positive tilts is substantially reduced, although absorption still becomes significant if the sample is tilted away from the detector.

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SEM at Low Beam Voltage

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100112245 ◽

1984 ◽

Vol 42 ◽

pp. 440-443

Author(s):

James Pawley

Keyword(s):

Low Voltage ◽

Probe Diameter ◽

Small Probe ◽

Beam Voltage ◽

Practical Constraints

Operation of the SEM with V0 = l-3kV (LVSEM) was early recognized to reduce charging artefacts and increase topographic contrast. This early promise was not pursued because several theoretical and practical considerations made it difficult to produce a small probe diameter (d0) at low voltage. Recently, the necessity of using low V0 to image uncoated semiconductors without damaging them has prompted a re-evaluation of LVSEM. This re-evaluation has taken the form of efforts to eliminate the practical constraints and to alleviate the theoretical ones. In the process, some heretofore neglected theoretical advantages of LVSEM have emerged. These problems and possibilities will now be discussed in more detail.

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Low-voltage EDS of magnesium ferrite Dendrites in a FEG-SEM

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100164854 ◽

1996 ◽

Vol 54 ◽

pp. 478-479

Author(s):

Matthew T. Johnson ◽

Ian M. Anderson ◽

Jim Bentley ◽

C. Barry Carter

Keyword(s):

Monte Carlo ◽

Quantitative Analysis ◽

Monte Carlo Simulations ◽

Cross Section ◽

Spatial Resolution ◽

Low Voltage ◽

Magnesium Ferrite ◽

X Ray ◽

Interaction Volume ◽

Ferrite Spinel

Energy-dispersive X-ray spectrometry (EDS) performed at low (≤ 5 kV) accelerating voltages in the SEM has the potential for providing quantitative microanalytical information with a spatial resolution of ∼100 nm. In the present work, EDS analyses were performed on magnesium ferrite spinel [(MgxFe1−x)Fe2O4] dendrites embedded in a MgO matrix, as shown in Fig. 1. spatial resolution of X-ray microanalysis at conventional accelerating voltages is insufficient for the quantitative analysis of these dendrites, which have widths of the order of a few hundred nanometers, without deconvolution of contributions from the MgO matrix. However, Monte Carlo simulations indicate that the interaction volume for MgFe2O4 is ∼150 nm at 3 kV accelerating voltage and therefore sufficient to analyze the dendrites without matrix contributions.Single-crystal {001}-oriented MgO was reacted with hematite (Fe2O3) powder for 6 h at 1450°C in air and furnace cooled. The specimen was then cleaved to expose a clean cross-section suitable for microanalysis.

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Comparison of high-angle take-off and low-angle take-off EDX detector geometry of the HF-2000 FE-TEM

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100147107 ◽

1993 ◽

Vol 51 ◽

pp. 252-253

Author(s):

Y. Sato ◽

T. Hashimoto ◽

M. Ichihashi ◽

Y. Ueki ◽

K. Hirose ◽

...

Keyword(s):

Quantitative Analysis ◽

Field Emission ◽

Solid Angle ◽

Energy Dispersive ◽

Objective Lens ◽

X Rays ◽

High Angle ◽

X Ray ◽

Detector Geometry

Analytical TEMs have two variations in x-ray detector geometry, high and low angle take off. The high take off angle is advantageous for accuracy of quantitative analysis, because the x rays are less absorbed when they go through the sample. The low take off angle geometry enables better sensitivity because of larger detector solid angle.Hitachi HF-2000 cold field emission TEM has two versions; high angle take off and low angle take off. The former allows an energy dispersive x-ray detector above the objective lens. The latter allows the detector beside the objective lens. The x-ray take off angle is 68° for the high take off angle with the specimen held at right angles to the beam, and 22° for the low angle take off. The solid angle is 0.037 sr for the high angle take off, and 0.12 sr for the low angle take off, using a 30 mm2 detector.

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Evaluation of the mechanical properties of Inconel 718 to SCM 440 dissimilar friction welding through real-time monitoring of the acoustic emission system

Proceedings of the Institution of Mechanical Engineers Part L Journal of Materials Design and Applications ◽

10.1177/1464420721993838 ◽

2021 ◽

pp. 146442072199383

Author(s):

Yu Sik Kong ◽

Muralimohan Cheepu ◽

Jin-Kyung Lee

Keyword(s):

Acoustic Emission ◽

Friction Welding ◽

Inconel 718 ◽

Low Voltage ◽

Dissimilar Materials ◽

Average Frequency ◽

Very High Frequency ◽

Cumulative Count ◽

Emission System ◽

Very High

Friction welding was chosen for its versatility in the joining of dissimilar materials with high quality. The aim of this study is to determine the optimal welding conditions for attaining quality joints by using online monitoring of acoustic emission system signals. During friction welding, the formation of cracks, defects, or any abnormalities in the joining process which have a detrimental effect on the joints quality was identified. The most widely used materials in the aerospace industry—Inconel 718 and molybdenum steel—were joined by friction welding. The precision of the joints, internal defects, and quality are major concerns for aerospace parts. The results of the present research determined the optimal welding conditions for high tensile strength by nondestructively inducing acoustic emission signals. During friction time and upset time periods, the typical waveforms and frequency spectrum of the acoustic emission signals were recorded, and their energy level, average frequency, cumulative count, and amplitude were analyzed. Both cumulative count and amplitude were found to be useful parameters for deriving the optimal welding conditions. In the initial stage of friction welding, a very high voltage of continuous form was generated with frequency characteristics of 0.44 MHz and 0.54 MHz. The signals generated during the upset stage had a low voltage, but a very high frequency of 1.56 MHz and 1.74 MHz with a burst-type signal. The amplitude of the signal generated for the optimally welded joints was about 100 dB at the friction time and about 45 dB at the upset time.

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