NetNotes


Au/Pd targets are usually 60:40 or 80:20. Tis raises a few ques-


tions that are beyond my knowledge: How does the proportion of Au and Pd in the target alloy affect the efficiency of sputtering and the grain size of the coating? Is there a “eutectic” alloy composition for sputtering that is most efficient? Does the presence of Pd inhibit crystallization of Au in the coating (and so result in a finer grain size)? Kurt Friehauf friehauf@kutztown.edu


Quorumtech provides Au-Pd targets at a ratio of 80/20: https://


www.quorumtech.com/wp-content/uploads/2021/01/Q-Plus-Se- ries-options-and-configs-V1-1.pdf. You may also find 60/40 Au/ Pd targets at other manufacturers. Te elemental composition/ catalog number of a target is typically specified on its packaging. Inna Popov innap@savion.huji.ac.il


Cross-Sectional Electropolish Microscopy Listserver Can anyone recommend good references (literature or web) for


cross-sectional electropolish protocols for metals? I am imaging dice, sandwich, dimple, and then twin-jet samples looking at dislocations in ion-beam-implanted metallic samples. Te FIB leaves far too much dislocation debris behind to get the data I need. Tanks. Chad Parish parishcm@ornl.gov


The main issue may be bonding in the cross-section. Most


bonding agents (M-Bond 610, Gatan G-1, Epotek 353ND) are insulators and won’t e-polish. It is possible that a thin enough glue layer may dimple sufficiently, and the glue layer won’t be an issue. I suspect that you will not get much thinning imme- diately adjacent to the glue layer, but you should be okay a little further away. My suspicion is that mixing metal powder into the glue layer will not help. While the glue will then be macro- scopically conductive, there will still be small non-conductive regions. Also, the glue layer will likely be thicker. Henk Colijn colijn.1@osu.edu


When I worked at Monash/MCEM years ago, Xi-Ya Fang was


a pro with electropolishing. I would encourage you to reach out to her: https://www.monash.edu/researchinfrastructure/mcem/ about-us/people/dr-xi-ya-fang. Ellen Lavoie lavoie@uw.edu


SEM Imaging of Fe Nanoparticles Microscopy Listserver I am trying to determine the average particle size from a conduc-


tive film with embedded iron nanoparticles. It is very hard to get a clear image as I increase magnification. Could the nanoparticles be magnetizing and blurring the image? TIA for any advice. I don’t get many materials science samples in our facility. Best, Julian Smith III smithj@winthrop.edu


First, are the Fe nanoparticles embedded in the top of the


film, so they are sticking up out of it, or within the film and cov- ered by it? If the latter, that will make the boundaries indistinct. Second, from your post, I infer you are using secondary imaging. True? Or backscattered electron imaging (BSE)? If you are not us- ing BSE, try that. Te Z-difference between the film and the Fe particles will help clear up the edges. I would also raise the stage as close to the BSE detector as you can. Assuming it is an under-lens detector, and not off to the side. Plus, try different spot sizes and accelerating voltages. 20kV should be good, but try 25kV? Note: Try sputter-coating both surfaces of the glass substrate so that the


64


paste is applied to a conductive surface. Tis will provide a better path to ground for the electrons and better imaging than just con- necting the top surface of the film to ground. Also, I have found conductivity problems (therefore charging) with TiO, and I doubt adding Fe will help all that much. Is this substrate required? And what is the paste? What is its conductivity? Just to ensure your life is difficult enough, how are you doing stigmation? If stigma- tion correction is close but not correct, then the image will look fuzzy, but not smeared, as it is when the stigmation is obviously off. Given that beam spread is affected by depth into a sample, you can have an interesting time getting stigmation correct on an im- aging volume at some depth into the film, even if it is correct at the top surface of the film. Just to be more annoying, how accurate do the particle sizes have to be? Non-fuzzy images or not, you have a “where’s the edge” problem, and therefore a real measurement accuracy problem. Not to mention trying to get the interaction volume correct. Which is a reason to ask, are you sure the SEM is the correct instrument for this? Do you have a confocal, maybe with STED or other super-resolution feature? Tis could be more accurate. Phil Oshel oshel1pe@cmich.edu


Tanks for the responses! SEM, W gun, 20kv. Spot-size set to


35 and 10mm WD, which is what we typically use for high-res work and EDS maps. Column aligned, focus and stigmation set properly. Particles were applied in a paste to a fluorine-doped titanium ox- ide (FTO) substrate on glass, and then the substrate and film were baked overnight at 550°


C and grounded (film surface to stub) on


aluminum stubs with silver paint. I still get a carbon signal in the X-ray spectrum, so maybe the problem is that it needs to bake out longer. But I cannot get sharp images of the iron nanoparticles. Tey are quite fuzzy at the edges. Hence, I am wondering about magnetic field effects. Julian Smith III smithj@winthrop.edu


20kV acceleration voltage and using the SE detector might


bring too much signal from within the nanoparticles, hence the fuzzy edges. Also, if your specimen is mounted on a large piece of glass substrate this might add some strange effects, even when silver paint is applied on the edges. I would try to do this task with a field emission SEM and 2–5 kV. Or on your SEM with as low a kB as possible using a beam diameter as narrow as possible. Stefan Diller diller@stefan-diller.com


If the paste is carbon-based, you should be able to see the Fe


contrast using a backscatter electron detector. You may have to reduce the spot size considerably and take a prolonged exposure, but there should be good contrast. It may still give you a noisy image, but you should see the particles clearly. Carol Heckman heckman@bgsu.edu


I agree with Stefan, try reducing the keV for imaging the


nanoparticles. I would also using a short working distance, something like 4 or 5 mm. I think that magnetic effects from the nanoparticles would manifest similarly to charging (streaking in the image) as the beam moves while scanning. Brittany Cymes bacymes@gmail.com


Lowering the kV will work well if the particles are on or very


close to the film surface. Otherwise, you’ll just be imaging the film. If you have Casino or DTSA-II, you might model the beam pen- etration into the film and see what kVs best reach the particles, and how much the electrons scatter within the sample. Phil Oshel oshel1pe@cmich.edu


www.microscopy-today.com • 2022 July


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