Scanning electron microscopy is one of the niche instruments that most of us don’t always need, but we still hope to use it occasionally. Although we have discussed some attempts in family building before, many attempts have failed, except for the projects that ended this day. The IO of user vini lab seems to be still under active development. The principle of SEM is very simple; A specially prepared sample is bombarded with a focused electron beam, which is manipulated in a grating mode. One of a variety of techniques is used to obtain the signal, such as secondary electron (SE) backscattered electron (BSE) or simply input the transmitted current into the sample. The signal can then be used to form an image of the sample or collect other characteristics.
Condenser assembly
The project is obviously at an early stage. As the author said, it is a very expensive construction, but there are some processed parts ready for assembly. The work of driving electronic equipment for condensing cylindrical lens has begun. This part of the instrument receives the central part of the rapidly divergent original electron beam, passes it through the anode, and uses two sets of octupole coil groups and one or two apertures to select only the central part of the beam and correct any astigmatism in the beam. By adjusting the relative current through each coil, a quadrupole magnetic field is generated, which offsets the asymmetry of the beam.
Scanning control and signal acquisition are processed by a special card, which uses the PIO function of raspberry PI Pico module. Pico can drive scanning operation and use external ftdi usb3. 0 device to send the four synchronous channels of the collected sample data back to the host. Using PCIe connectors and matching edge connectors on cards can provide robust and cost-effective physical connections. As can be seen from the project page, many mechanical designs have been completed and processing has begun, so this is a project that needs to be paid attention to in the coming months or even years!
We have seen some SEM hackers, here is a small power SEM hacker from [Ben krasno], here is another attempt. For such a simple concept and huge use of equipment, it seems a little negligent that there are no more such projects.