EPMA Analysis using samples prepared by FIB

[Joshua Silverstein]

Hello All,

Our group is interested to investigate EPMA analysis on materials prepared using focused ion beam (FIB). With the elimination of the bulk can we improve characterization and analysis of unknown materials while developing quantitative chemical maps of submicron features? Our sample materials will also be prepared using FIB techniques. Is there any information on this topic?

Cheers,

Josh

[macosta]

Hello Josh,

Here at the UO, we've been using a FIB to prepare samples for EPMA with great success. For us, the motivating reason was microcrystals of SiO2 intimately mixed with even smaller crystals of TiO2. Since we were interested in measuring Ti in the quartz lattice, secondary fluorescence was a huge issue - one *readily solved by using the FIB to either moat out regions around crystals or by extracting them as one would initially for TEM sample prep. Simply blast away the offensive phase. We did not thin the samples to the thickness desired for TEM, as that would not work for EPMA.

Are you wanting a workflow that looks like FIB --> EPMA --> TEM ? I think there would need to be a second FIB step between EPMA and TEM where you thinned the sample. Also, if your samples are susceptible to beam damage, thinning would be a way to get rid of the beam damage before going to the TEM ( I found this out the hard way by looking at a quartz crystal that had undergone beam-induced amorphization during EPMA - which actually looked kind of cool). 

Overall, I think that there is a lot of potential to be had in the FIB-EPMA-TEM combo , though there is a lot of trial and error to be had before it reaches full potential.

Best,
Marisa

[Philippe Pinard]

A few papers that might help:

Pinard, P. T. & Richter, S.
Improving the quantification at high spatial resolution using a field emission electron microprobe
IOP Conference Series: Materials Science and Engineering, 2014, 55, 012016
https://iopscience.iop.org/article/10.1088/1757-899X/55/1/012016
See section 4.2

Y Kubo
Focussed ion beam thin sample microanalysis using a field emission gun electron probe microanalyser
IOP Conference Series: Materials Science and Engineering, 2018, 304, 012007
https://iopscience.iop.org/article/10.1088/1757-899X/304/1/012007

Ehle et al.
IDENTIFICATION OF CRYSTAL STRUCTURES AND ELEMENTAL COMPOSITION OF REACTIVE AIR BRAZED Ba0.5Sr0.5Co0.8Fe0.2O3-Δ-Ag-14CuO JOINTS BY EBSD, EPMA AND ANALYTICAL TEM
EMAS 2019 Proceedings
See attached

When we did this work (Pinard/Richter, 2014), it was important to:

• avoid occlusion of the WD spectrometer by the sample holder and TEM grid
• have a carbon liner below the sample to minimize stray X-rays produced by transmitted electrons