DIY Scanning Electron Microscope | Hacker News Reader

DIY Scanning Electron Microscope

hackaday.com

87 pointspoindontcare17 comments

I built this electron microscope. Let me know if you have any questions.

Do you have any problems with ambient vibrations e.g. truck driving by?

No. The resolution of this (primitive) device is 10's of microns, which is too large to be disturbed by normal vibrations. Most SEM vibrations in simple machines are caused by insufficient damping from its own vacuum pumps.

At that resolution, is there an application for which you think your microscope is better than an optical one?

Not that it really matters, I'm impressed even if there isn't such an application.

The "f number" of the SEM is about 200, so it's depth of field is much larger than an optical microscope or camera. Also, the SEM signal of bright and dark areas is made of electrons, which can travel in curved paths and around corners. This gives the SEM image an appearance that is distinct from light images, and is helpful when viewing 3d objects for ease of feature recognition as well as aesthetic quality. Even at low magnification, SEM is often more useful. Thanks!

An SEM with a backscatter detector can be used to image changes in material. Backscatter is proportional to atomic number. A common sample to measure is the solder diffusion depth into the copper on a pcb. The first time I imaged such a sample was mind opening in the sense of understanding why you can't remove all the solder from copper, some of the solder is in the copper.

Considering you now have another electron microscope, would you ever consider building another version of this?

No. Even when I started the homebuilt SEM, I considered it a learning opportunity and wanted the thrill and satisfaction of having built a working machine. I didn't have any SEM research to do, and suspected correctly that the image quality is not better than a light microscope.

Looks like this article is from 2011 -- what tweaks and improvements have you made since then?

Not much. I've redirected my efforts toward making animations and other unusual visualizations with a commercial SEM.

It's been a while since you've posted a new video, are you still making videos?

Thanks, I enjoy your channel.

Thank you! Yes, I'm still making new videos, just more slowly than in the past. My "new" job at Verily (Google Life Sciences) is very compelling and rewarding, so I've been focusing on that.

About a zillion :-) Building one has been one of my "wouldn't it be neat to do ..." projects for a long time.

Can you say a bit more about the lenses? The Heathkit oscilloscope I built as a kid had electrostatic plates that were used to focus the beam rather than anything lens like.

Have you considered using bits of lead type as your test target, they have the advantage of being asymmetric and recognizable, could help with linearity measurements.

The SEM I used at Intel a couple of times had the electrons coming in at an angle and the detector at an angle. have you considered something like that to improve the signal pickup of your optical tube?

Most commercial SEMs use electromagnetic lenses because they provide higher power (more drastically change the path of electrons) in a smaller space. The problem is that they require custom iron pole pieces. It's easier to build electroststatic lenses, which are just metal conductors and the geometry is not extremely critical. Search for Einzel lens for details. The condenser and objective lens in my scope are Einzel lenses made from copper pipe from the hardware store. I like the idea of looking at lead type with the SEM!

The angle of the incoming electrons toward the specimen is what creates the viewing angle in the image. The angle of the secondary electron detector is what creates the apparent illumination direction. It's true that setting the specimen to split the beam and detector angles will provide a good image, similar to having a good key light in photography.

Hey great work. Electron beam technology has quite an interesting history and has been used for many applications.

I work at an atomic physics research institute and am currently building an electron beam ion trap. We use a compressed electron beam to ionize atoms into a highly charged state and then use these ions to observe things like electronic structure of the atom and quantum electrodynamic effects. We have an electron gun that can be biased up to 60 kV and we have a 7 Tesla superconducting coil combined with some einzel lenses to guide and compress the electron beam into the trapping area where we ionize the atoms.

I've never thought to bring my work home with me but this would be a really really cool project to undertake. Thanks for sharing.

Apologies if this is in the video, I am not in a location where I can view it. How much did building that machine cost in total? And how long did it take?

I used lots of surplus parts from eBay, collected over 5-6 years. The actual build process took a few months of pretty focused night/weekend work (10-20 hours per week). Total cost was around $1500. Details here: https://www.youtube.com/watch?v=L6HxTk9tfQk

Reply on news.ycombinator.com