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lens and the lens which immediately follows it. Any problem with the clarity of this image will be related to the objective lens setting and the setting of the objective lens stigmators. Problems in any other lens (other than instabilities) will not have any infl uence on the image sharpness. You say that the instrument has been serviced by a person who knows the 109, so we must expect it to be free of high voltage or lens problems. T at brings us back to the objective lens, but most of all in your case, the objective astigmatism. You note that with a through focal series the image improves, this goes hand in hand with astigmatism. At true focus the astigmatism will be minimized but as you move out of focus it will destroy the image quality. Please look into the objective stigmator, it may be a double strength system like all modern instruments, or it may be in the style of early instruments. Early instruments used a stigmator, which provided a device to change the stigmator fi eld strength, combined with the ability to change the direction of that fi eld. T is system was called strength and rotate, and it may be the style on the 109. From the point of best focus change the strength control until you see it change the image. T en change the rotate control until you fi nd the point that improves the image quality. T en back off the strength slightly, check the rotation, check the focus. Repeat this procedure until the image is satisfactory. Steve Chapman T u Sep 15

TEM: B fi eld strength in JEOL 2100FX

Do you know someone who might have measured it or have a value that is at least by 10% close to the real value? Hasan Ali hasan.ali@ T u Sep 22

See Christenson, K., & J. Eades J (1986). On “parallel” illumi- nation in the transmission electron microscope. Ultramicroscopy , 19(2): 191–194; . You could do the experiment described in this paper to measure the Larmor frequency. With near-parallel illumination, take a series of images over a large Z range, then align the images in e.g., MIDAS which is part of IMOD software ( ), this will give the image rotation per focus step used, the Larmor frequency. Once you have the Larmor frequency, you can calculate the fi eld strength in the immersion lens. T is paper from the same authors has a bit more detail: K Christenson, and J Eades, “Skew T oughts on Parallelism,” Ultramicroscopy , 26 (1988) 113–132. Wim Hagen T u Sep 22

SEM: staining Cu

We are using an older model SEM to image samples with copper structures on the surface and just a few nm below the surface at the same time (typically buried under a thin layer of glass). Since the copper layer below the surface is just covered by this very thin glass layer, even with lower acceleration voltages it is very hard to distinguish on the images whether the imaged copper structures are located on the surface or below it. As our goal would be that the copper on the surface clearly looks diff erent from the copper buried under the thin glass layer, we were wondering whether we could use a staining procedure. For instance, we are aware of a wet chemical procedure allowing to tin-plate copper. However, without trying it we don’t know if it would result in a consid- erable diff erent contrast in the SEM as the atomic mass of Sn is very close to the one of Cu. Wet chemical gold plating on the other hand involves not only expensive but also highly toxic chemicals. Are you aware of (wet chemical) staining procedures for copper that produce a considerable contrast and are preferably inexpensive as well as not highly toxic? Is


there maybe another technique we could use? Stefan Schoenleitner dev. Wed Sep 7 T ere are few things you can try to distinguish between exposed and slightly buried Cu conductors: 1. Based on your mentioning of “atomic mass of Sn is very close to the one of Cu” I am suspecting you may be using backscattered electrons for imaging - try secondary electron detector imaging at lowest acceleration you can aff ord without losing too much resolution. 2. Apply negative bias to the sample (retarding fi eld) to reduce landing energy of primary electrons. T is could work or not, depending on geometry of your instrument, stage, and your instrumentation skills/capabilities. 3. Electrolysis nickel- plating chemicals cost less than Au plating kits, though either one is safe enough to do in ordinary fume hood with gloves and common sense. 4. Exposure to iodine vapor in humid atmosphere (room air) would corrode exposed Cu fairly quickly, making it look “fl uff y” or “rough,” while buried conductors will remain intact for a while. T e tricky part would be to image/scan the sample fairly quickly - once started the corrosion would eventually consume all the Cu layers. You want to image the exposed layer once it has been just slightly corroded on the surface, and immediately polish it away to prevent damage for the underlying layers. 5. Either sulfuric or nitric acid with H2O2 should etch Cu crystallographically, making the exposed surface look diff erent than metal protected by dielectric. You would want to experiment with “disposable” devices and develop reliable procedures prior to immersing the “real” one. T e same is true for plating, by the way. 6. Image the chip, etch away Cu with FeCl3, wash-rinse, and the image same area again. Buried under dielectric Cu would be on both images, while exposed would disappear aſt er etching. You would need to develop procedures and control time/temperature/concentrations of etchants to get repeatable results. 7. Do forward-scattered imaging, or even regular SE imaging at glancing angle - it would be much more sensitive to the presence of a thin dielectric layer. Foreshortening correction would be required. Valery Ray Sun Sep 11

SEM: remote imaging

We have previously instituted remote imaging on our FEI Quanta 200 for broadcasting live demos to our local school area. We also wanted to do the same with our Hitachi S4700. Although we can load the server/ client software (TightVNC) and get a connection, the image does not port to the client pc. We get a “purple screen”. Has anyone been able to get the live (or captured) image from the Hitachi onto a network client? Wallace Ambrose Wed Oct 12 I believe you’re seeing the eff ects of hardware-acceleration with the video. What I am guessing is happening is the microscope image is transferred via DMA (direct memory access) to the video card directly, bypassing the operating system. VNC however grabs the video frame buff er from the operating system, which doesn’t have any information (because aſt er that image is transported to the video card, the DMA transaction fills in the purple section before being sent out to the monitor). What I did for an older 1990s FEI FIB 200, was to use a VGA video cable splitter: distribution-amplifi ers/vga/1x2-compact-vga-splitter.html and then a VGA2USB frame grabber: products/vga2usb/ T en get another computer, an old desktop or laptop or even a new mini-PC like an Intel NUC or compute-stick or RasperryPi (<=$40), which can stream/save the video however you like. You’ll just need to get a splitter and grabber for your specifi c video cable (I’m guessing VGA or DVI): • 2017 January

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