?Zur Pr�fung des �quivalentgesetzes an Trockenplatten?

Eggert, J.; Noddack, W.

doi:10.1007/bf01328272

Cited by 5 publications

(8 citation statements)

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“…The calculation of the bremsstrahlung distribution for background approximations follows Kramer's law [4], using the modification by Lifshin [5], and was substituted by a quick calculation of the absorption terms  E and A E [6]: ( 1 ) with: N E br number of bremsstrahlung counts measured in spectrum-channel with related energy E   E detector efficiency with photon energy E  (the fraction which is detected) A E absorption correction with photons of energy E  (the fraction which is not absorbed) a, b empirical coefficients for spectra fit (if b= 0, then a represents absolute adjustment only) E 0 primary electron energy. It is possible to use as many fit-regions as desired to get the best background fit.…”

Section: Methodsmentioning

confidence: 99%

“…For SEM spectra evaluation, it is possible to describe the absorption part of (1) with  E A E with only a single absorption formula [6]:…”

Section: Methodsmentioning

confidence: 99%

“…They are calculated before the bremsstrahlung computation process. In the case of specimen element edges the formula is [6]: ( 4 ) where L is a numerical value which considers geometry (ratio between absorption path and X-ray emission depth), E 0 is the primary electron energy, k b is a constant, c i is the mass fraction of the element in specimen and (μ/ρ) diff is the difference between mass absorption coefficient after and before the regarded edge energy E i (all values in keV). Described differently, eq.…”

Section: Methodsmentioning

confidence: 99%

“…Following the model derivations in [6], a basic estimation of a mean generation depth of photons in the specimen was made, based on the Thomson-Whiddington law [7]. The self-absorption is then calculated based on the assumption of a mean emission depth of X-rays with specific energies.…”

Section: Methodsmentioning

confidence: 99%

“…The used bremsstrahlung background calculation is briefly described in the next section and is based on an earlier publication [6]. There were improvements of the basis method, published in [8], and the dedicated application for TEM spectra was investigated and published in [3].…”

Section: Introductionmentioning

confidence: 99%

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Benefits from bremsstrahlung distribution evaluation to get unknown information from specimen in SEM and TEM

Eggert¹,

Camus²,

Schleifer³

et al. 2018

IOP Conf. Ser.: Mater. Sci. Eng.

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Abstract. The energy-dispersive X-ray spectrometer (EDS or EDX) is a commonly used device to characterise the composition of investigated material in scanning and transmission electron microscopes (SEM and TEM). One major benefit compared to wavelength-dispersive X-ray spectrometers (WDS) is that EDS systems collect the entire spectrum simultaneously. Therefore, not only are all emitted characteristic X-ray lines in the spectrum, but also the complete bremsstrahlung distribution is included. It is possible to get information about the specimen even from this radiation, which is usually perceived more as a disturbing background. This is possible by using theoretical model knowledge about bremsstrahlung excitation and absorption in the specimen in comparison to the actual measured spectrum. The core aim of this investigation is to present a method for better bremsstrahlung fitting in unknown geometry cases by variation of the geometry parameters and to utilise this knowledge also for characteristic radiation evaluation. A method is described, which allows the parameterisation of the true X-ray absorption conditions during spectrum acquisition. An 'effective tilt' angle parameter is determined by evaluation of the bremsstrahlung shape of the measured SEM spectra. It is useful for bremsstrahlung background approximation, with exact calculations of the absorption edges below the characteristic peaks, required for P/B-ZAF model based quantification methods. It can even be used for ZAF based quantification models as a variable input parameter. The analytical results are then much more reliable for the different absorption effects from irregular specimen surfaces because the unknown absorption dependency is considered. Finally, the method is also applied for evaluation of TEM spectra. In this case, the real physical parameter optimisation is with sample thickness (mass thickness), which is influencing the emitted and measured spectrum due to different absorption with TEM measurements. The effects are in the very low energy part of the spectrum, and are much more visible with most recent windowless TEM detectors. The thickness of the sample can be determined in this way from the measured bremsstrahlung spectrum shape. IntroductionThe energy-dispersive X-ray spectrometer (EDS) spectrum depends on both the material elements and the measurement geometry of the excited specimen area. The emission intensity of low energy X-rays is influenced significantly both by self-absorption of the generated X-rays inside the specimen and by the surface topography at the analysed point. For example, self-absorption exceeds 70 % for aluminium X-rays in the high absorption case versus 35 % with low absorption (example almandine, electron excitation energy 15 keV, scanning electron microscope (SEM)). It is well known that

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