NetNotes
How flat is the surface? What is the phase distribution on a micro-scale? If the Pb is present as a second phase it might well be preferentially polished away changing the volume (and mass) fraction and skewing the results. Also, EDS correction routines are written to process intensities from homogeneous analysis volumes. If you are trying to lower the magnification and scan an area, you will present the sum of the phase intensities to the analyzer. However, Pb probably had nothing to do in determining the interaction volume in the regions where the Cu and Sn are, nor did the Cu and Sn x-rays undergo absorption by Pb atoms. Once in a while, EDS might give the right answer in such cases, but I would not count on it being the right. BTW, the same issue would be true of WDS too. The matrix corrections are much the same. They assume a homogenous sample volume. Warren Straszheim
wesaia@iastate.edu Fri Jan 30
I would not use the Pb in glass standard for this analysis. You should try to use a standard as close to your unknown composition. Pb in SiO 2 is not close. I would try using one of your CuSnPb standards as the standard and see how the results turn out. You say you “use the default internal calibration (leaded glass) to calibrate Pb element.” Did you use the same operating conditions? kV, take-off angle? Also which lines for each element did you use? K L M? Be careful of background too. David Hull drhull@zoomin-
ternet.net Fri Jan 30
EDS: calibration
I have performed EDS analysis of Au Nanoparticles on Copper TEM grids using an Oxford EDS. I am getting a lot of Cu peaks instead of an Au peak. I am using INCA microanalysis suite version 4.15.
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Could anybody suggest to me how to do a calibration and what kind of standard reference sample should be used for calibration? Ravi T akkar
ravi.thakkar369@
gmail.com Wed Feb 4
You are always going to see Cu under those circumstances. T e amount of Cu metal in the grid is vast compared to the size of an Au nanoparticle. As your electron beam passes through the Au nanoparticle, some electrons will scatter and hit the grid producing fl uorescence. T ere can also be electrons scattered from electron microscope components such as apertures as well — though this is less a problem these days than it used to be (depends on the age of your microscope). If you aren’t interested in Cu, I suggest you just ignore the peak. If you are interested in Cu in your nanoparticle, then producers such as EMS, Ted Pella and Ladd make a variety of grids out of a variety of elements and compounds so that you can almost certainly fi nd some element you don’t care about. When avoiding Cu, I’ve had luck using beryllium, and silicon nitride. For general calibration, a simple and very common approach is to use the Cliff -Lorimer method of k-factors: Cliff , G. & Lorimer, G. W. (1975). “T e Quantitative Analysis of T in Specimens,” Journal of Microscopy 103(2) 203–07. T e Oxford soſt ware has this method built in and allows you to defi ne those k-factors once you measure them (using the method from the paper above). T e Oxford soſt ware also has some good guesses built in if you don’t need very much accuracy. I have also found it useful to extract peak areas from TEM/EDS spectra and process them myself. I fi rst use fi tyk, Python, or the Oxford/Bruker soſt ware to fi t peak areas. T en I use k-factors and apply a thickness correction using some soſt ware I wrote for myself (
https://github.com/ZGainsforth/StoichiometryFitter/blob/ master/
Stoichiometry%20Fitter%20Screenshot.png). You might like a solution like this if you want to control every aspect of the analysis. Zack Gainsforth
zackg@berkeley.edu Wed Feb 4
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