Viewing an active electronic circuit with a scanning electron microscope

I used my DIY scanning electron microscope to view a 555 timer circuit while it was powered. The circuit is a simple oscillator with a very long time constant to make the changes easy to see. My plan was to view the silicon die itself, and hopefully discern changes in its internal circuitry as the oscillations occurred. As it turns out, I was only able to "see" the charge of the electrical wires going to the chip socket. There is likely a clear oxide layer that covers the silicon die, and needs to be removed with hydrofluoric acid in order to use the SEM to inspect the die itself while powered.

DIY Scanning Electron Microscope - Operation procedure

After getting back from Maker Faire (which is always a hugely enjoyable and inspiring event), I thought that my microscope might need some repairs. As it turned out, I only had to change the filament and tighten some screws that came loose during the trip back from the Faire. The microscope works just as well as it ever has -- I didn't even need to move my alignment magnets. I made this video to show everyone what using it is really like.

Also, if you haven't been able to attend Maker Faire yet, it really is as amazing and epic as you have heard. The intelligent and inspiring people who make it happen are a large part of the motivation that I had to build and display this microscope. In turn, I hope my project inspires others to create things and share their ideas with everyone. There's no better way to have fun and celebrate accomplishment at the same time!

My Tektronix contest entry

Vote for me here: http://mytektronixscope.com/videos/

I am using my Tektronix 2246 analog oscilloscope to show the image generated by my DIY electron microscope. The 2246 is operating in X-Y mode, with the channels connected to a raster scan generator. The vertical scanning frequency is about 30Hz and the horizontal frequency is about 10KHz. The trace brightness (Z axis) is modulated with the secondary electron signal from the microscope.

DIY Scanning Electron Microscope - Sources, Costs and References

Metal aluminum window screen

Just a few linearity problems ;)

I used an oscilloscope's X and Y amplifiers for these images. It has much better linearity than my own, but not enough differential voltage or offset range.


The sum total of the big-ticket items shown in the video is $1485. This does not include hoses, wiring, raw metal, teflon, screws, a cabinet, etc. It also does not include an oscilloscope, which can be a very simple model (under $100 on eBay) as long as it has a z axis (brightness) input. Your diffusion pump or diffusion pump baffle may also require a water chiller.

Here are a list of information sources that helped me with this project:

Teralab - Homebuilt electron gun and other great projects
http://www.teralab.co.uk/Experiments/Electron_Optics/Electron_Optics_Page1.htm


Popular Mechanics video on commercial desktop SEM
http://www.popularmechanics.com/technology/gadgets/4218957


Hamamatsu - Supplier of PMTs
http://sales.hamamatsu.com/assets/applications/ETD/pmt_handbook_complete.pdf


TV to oscilloscope circuit
http://www.electronixandmore.com/project/14.html


CRT oscilloscope clock circuit
http://web.jfet.org/vclk/


Charged particle optics simulation program
http://www.electronoptics.com/

"A Simple Scanning Electron Microscope" P.J. Spreadbury -- Advances in Imaging and Electron Physics Vol 133 Chapter 2.5 (no link).


ISI SEM refurb at home
http://members.tm.net/lapointe2/Scanning_Electron_Microscope.html


Great technical info on cathodes and wehnelt cup spacing. Most of the article concerns LaB6 cathodes, but there is a short paragraph on tungsten cathodes.
https://www.kimballphysics.com/cathode/support_PDF/Cathode_ES423_LaB6_info.pdf

Numerous websites that gave background and operational information about SEMs.
Lots of web searches



Nearly all raw materials for this project were purchased from McMaster-Carr. All power supplies were purchased on eBay, or I already had them, in which case they came from a surplus store or flea market. Nearly all of the electronic components came from Jameco.