3d Printed Scanning Electron Microscope

The goal is to build a DIY Scanning Electron Microscope (DIY SEM) with commonly available materials

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A lot of people have the hobby to investigate the micro world with light based microscopes. With a scanning electron microscope (SEM) it is possible to investigate the nano world.

Unfortunately, SEM cost several thousand to some hundred thousand of dollars. However, a SEM consists actually only of few components:

a electron beam source
electronic or magnetic lenses
an electron detector and
a control unit

I reviewed the different components and I think it could be possible either to print or to buy the different components. I think that the housing could be printed with conductive and non- conductive material. For the lens, small super magnets could be suitable and for the control unit, an Arduino based platform could be used.

I am impressed about the impact of open source projects like 3d printer and microcontroller platforms. With this project, I hope to start something impressive too.


A Simulation is available since the  Log 07/13/2017

Magnetic lens system Vacuum and electron beam


Electron detector

Not Started yet

High voltage shield for Arduino

In progress see the last Logs

Overview and Introduction of SEM

1965 was the first Scanning Electron Microscope (SEM) commercially available (wiki). 2011 Ben build the first SEM at home. He used special equipment to build it. Now 2017 I start to build the first SEM with common available components. I would like to create imanges like these.

I will not explain the principles of a SEM because the explanation on the homepage of is great and I can't do it better.

Also the overview video from Ben is great for the introduction. But for a deep understanding I recommend the book Physical Principles of Electron Microscopy from author Ray F. Egerton.

My plan is to go ahead with the following steps:

  • Simulation
  • Vacuum and electron beam
  • Housing
  • Magnetic lens system
  • Electron detector
  • High voltage shield for Arduino

1. Build a simulation with a magnetic field simulation tool to determine the dimensions

I want use the tool FEMM 4.2. This tool is free and it is possible to create code based on Lua 4.0.

2. Build a suitable vacuum and an electron beam

My internet search shows that common SEM uses a ultra high vacuum (UHV). This is required for function of the electron beam source. For the creation of the UHV a diffusion pump can be used. I plan to avoid a UHV be using approach developed by Delft University of Technology. They have shown...

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  • Electronic PCB

    Chris.deerleg7 days ago 1 comment

    On the image above it the PCB shown which I made. I right lower corner of the PCB are the Femto ampere amplifier placed . The plain area surrounded with vias are the guard ring as I describe in the  last log entry. On the guard ring is the solder mask removed to get the bare resistance of the FR4 base material and don't "short" the FR4 resistance by the solder mask . The square pattern around the Femto ampere amplifiers are for a EMI Gaskets to improve the shielding for the case that I run in to EMC issues. In the square pattern above the Femto ampere ampere amplifiers are placed the secondary amplification stage with the MAX4450. 

  • Detectorelectronic

    Chris.deerleg02/21/2018 at 03:11 0 comments

    The image above gives an overview how the electrons are collected and detected. The incoming electron beam triggers two types of electrons: the Back Scatter Electrons (BSE), which fly backwards along the beam and the Secondary Electrons (SE), which stay close to the target and don't move. Charged plates are located both above and alongside the target.  The image below shows how a picture looks with BSE compared to SE.

    I expect that the BSE and the SE current to be measured will be quite low. Therefore, I had to look for an amplifier with a very low leakage current of the inputs. I am glad that I now found femto ampere amplifiers for an affordable price. The LMP7721 from Texas Instruments and the ADA4530 from Analog devices.  Both companies have several application notes which explain how to use these amplifiers.

    Above is shown the whole schematic I created to measure the BSE and SE. In the next paragraphs I explain each part in more detail:

    A: This section shows the Femto ampere amplifier. The opamp is configured as a non-inverted amplifier. The reason is that with a configuration as a inverted amplifier it is hard to get a broad band width. For example a 1 GOhm resistor with a 1p capacitor in parallel would result in a cutoff frequency of 160Hz (f=1/(2*PI*1G*1p). Further The amplification is set to 2.48 (8.2k/3.3k=2.48) for stay in a comfortable area of the GBW (Gain Band Width) of the opamp.  The 10p capacitor set the low pass cutoff frequency to 1.94MHz (f=1/(2*PI*8.3k*10pF). The virtual ground (VirGnd=3.3V/2=1.65V) is set to the half supply voltage of the micro controller. The applied VirGnd voltage appear at the +input  of the opamp and make it possible to measure even negative current with just a single supply of the opamp. The 6k8 resistor in the input line limits the current in the case of activating the opamp internal ESD dioses. The 6k8 builds with the opamp internal capacity a low pass with a cutoff frequency of 2.12MHz ((f=1/(2*PI*6k8*11pF)) .

    B: This section shows the secondary amplifier. The Max4450 is a high speed opamp and has a band width of 175MHz. This make it possible to get amplification of 14,4 (Av=56k/3.9k) at 1MHz. The high bais current of 6.5µA requires to configure the opamp as a inverted amplifier, because in the configuration as non-inverted amplifier is it challenging to get a stable virtual ground. The low pass cutoff frequency of each opamp stage is set 2.4MHz ((f=1/(2*PI*56k*1.2pF)) . The 10µF input line creates a high pass with a cutoff frequency of  0.27Hz (f=1/(2*PI*{56k+3.9k}*10µF). This high pass blocks the DC voltage of each previous stage.

    The image above shows a bode plot over the whole amplifiers. The blue line is the signal at the +Input at the LMP7721  of section A and the green line is the output at the last MAX4450 amplifier of section B. The plot illustrate the whole schematic creates a amplification of 80dB. This mean that a 1 Femto ampere make a output of 10mV (U=I*R*Av=1fA*1G*10000).

    C: This section shows the guard amplifier. For measuring Femto ampere is a addition shielding required, which is in chapter 8.1.1 of datasheet of the LMP7721 described. The approach for this shielding is to surround the high impedance input of the femto ampere amplifier with a signal which has a equal potential but lower impedance. Analog Devices gives in the chapter Layout Guidelines of datasheet ADA4530 a good overview. The actual guard amplifier is a non-inverting amplifier connected to the -input of the Femto ampera amplifier.

    D: This section are just symbolizing the power supplies . The 5V power supply is for the amplifiers and the 3.3V for the virtual grounds.

    E: This section shows the generation of the virtual ground for the secondary amplifier. The resistors...

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  • Vacuum Chamber

    Chris.deerleg12/28/2017 at 17:31 0 comments

    Thanks the Danbury Hackerspace I have now access to a laser cutter.

    I decided to make a new chamber because I need more space in the chamber that I can begin to build the electron detector. In the image above are the single parts of the chamber shown. The parts are made of 3mm acrylic sheet. The 5mm golden pogo pins are from Ebay and the black rubber rings are from sealing kit from Amazon.

    In the Image above are the assembled chamber shown.  The white round disk in the chamber is a Zinc Sulfide screen to visualize the electron beam.

    On the image above are the connections in side the chamber shown. The black tube is the connection to the vacuum pump. The clear tube below is the entrance for the electron beam. Left to the tubes are the pogo pins and a nut. These elements should connect the electron detector to the outside. On right side are three pegs visible. With these pegs I want to measure the vacuum because I had a lot of trouble with the vacuum in the past.

    On the image above is electron beam in the chamber made of acrylic plastic shown.

  • STM32 Hello World

    Chris.deerleg12/15/2017 at 21:10 0 comments

    I started with the microcontroller. I programmed already several, but it is still the same. Its a pain in the neck until the tool chain is running and the "Hello World" led is blinking. I decided to use a STM32F103C8 because of the high clock frequency 72MHz and the 32Bit architecture. On the image above is my setup shown. Between the PC and the hub is USB isolatora from Ebay. Just for the case of something goes very wrong to protect my PC. The hub has the nice buttons to turn off each USB connector. The blue USB programmer is a  ST-Link V2 from Ebay too.

    One remarkable thing is that you need a additional rest cable which wasn't delivered with the programmer. 

    As IDE I use the pre-configurated eclipse version from AC6 which is available for download at toolchain .

    The video above shows how to use the USB of the STM32.

  • Beam Deflection

    Chris.deerleg11/29/2017 at 22:18 0 comments

    The images above show the movement of the electron beam. It is necessary to apply two magnetic fields. One magnetic field is much faster as the other. The fast one causes the red line and the slower one causes a rotation of the line.

    The image above shows the deflection system of a scope's CRT . On the right side is a original one and on the left side is the version out of the 3D printer. The black plastic is conductive and the white plastic build a isolation. The approach from a scope doesn't worked for me, because of the high acceleration voltage. The voltage at the deflector plates should be in the same rage as the acceleration voltage.

    In the my CRT tube is the accelerations voltage  about  3000V and the plasma ignition starts at approx. 400V. Therefor a plasma appear if the accelerations voltage is applied to the deflector plates. This plasma is a electron source and make it impossible to have a sharp electron beam. The right approach for the deflection is similar as the deflection in a TV tube. Two magnetic fields applied for different directions make it possible to deflect the beam.

    DIY CRT tube by Nyle Steiner K7NS Oct 2007

    The image above shows the set up from Nyle Steiner who demonstrated on his homage how he made it.

  • Magnetic Lens

    Chris.deerleg11/06/2017 at 23:11 0 comments

    I was able to find some magnets (Ring-Magnets) that have the right shape to work as a magnetic lens. On the image above is the magnet arrangement show which produced the smallest and brightest spot. Two magnets are close together. The distance between the both magnets is approximately 1mm. The third magnet has a distance of approximate 35 mm to the double magnet.

    The small red spot is approximately 20 mm away from the third magnet. On the image above is shown how the focus is changed by moving the double magnet. From left to right moves the double magnet closer to the third magnet. The consequence is that the red spot becomes more blurred.

    I got a sharper and brighter spot. On the  image above from left to right the dual magnet move from up to down.

    The reason for the blurry spot was a uptight connection form the tubing to the vacuum pump. I glued a push connector with epoxy direct to the pump. An now it seams to work.

  • Vacuum Chamber

    Chris.deerleg10/20/2017 at 16:17 0 comments

    Now I know one reason more why I had trouble to see a electron beam. The vacuum was too bad.

    I figured out that electron beam disappear if I place a wire with 0.3mm between the rubber plug and the gals wall.

    Further I figured out that by changing the spark gap from the anode side to the cathode side I could remove the aluminum strip from the bottom of the glass. Also I changed the screen material from glowing in the dark powder to pure zinc sulfide.

  • Electron Gun

    Chris.deerleg09/25/2017 at 22:05 0 comments

    Whole setup

    I needed  one month. However I saw my first self made electron beam. I have had to over come multiple challenges.

    pure zinc sulfide glows red by electron detection

    First of all I wasn't sure what the right material was to make an electron beam visible. I thought that I needed a type of phosphor because the most web pages speak about a phosphor screen for the visualization of an election beam. Luckily, I found some pages that mentioned zinc sulfide is the right material.

    glowing in the dark powder also called zinc sulfide with copper (ZnS:Cu) glows green A very common and good available mixture is zinc sulfide with copper (ZnS:Cu) or also called glowing in the dark powder. It has a long after glow effect even on light. To build a screen mix zinc sulfide powder with water and a little bit of glue and let it dry on the bottom of the chamber. I recommend glue because without it the screen isn't stable. Otherwise it could happen that the screen blows away by returning air when the vacuum is released.

    glowing caused by light

    Unfortunately, I thought a long time that I see electrons even if I saw just light. The effect that the spot didn’t move either by an electrical or by a magnetical field made me distrustful.

    Spark gap

    The second main issue was that the voltage collapses from 6kV to 500V by applying it to the plasma tube. Whereas the high voltage is required to accelerate the elections enough to build a beam.  Maybe the reason that the voltage collapsed was a non-suitable vacuum or not strong enough power supply. Anyway, I solved this issue by including a spark gap in the circuit of the plasma tube. This spark gap let the voltage rise until it's big enough to create a spark. Once the spark appears, the high volt is applied and accelerate the electrons properly. The spark gap is made by a piece of the LDPE vacuum tube and two spikes.

    Discharge rings made of aluminum foil

    A third issue was that the out part of the tube need a anode to discharge the chamber. I putted just a little bit of aluminum foil around the chamber and connected it to the anode.

    The video show the whole set-up and further more what happens if

    •    The Discharge ring isn’t connected to the anode?
    •    How adjust the voltage?
    •     What happens without a spark gap?
    •     What happens with a wrong polarity?
    •     What do the plasma in a magnetic field?

  • HV Supply

    Chris.deerleg08/02/2017 at 21:02 0 comments

    For my first experiments I use a 7kV china high voltage supply.  (the black box on the right top). To get a impression of the capabilities of the HV Supply. I build a 200Meg Ohm voltage divider to measure the the voltage. I putted the resistor to connect the multi meter in the middle of the divider, just in case of a short circuit. The voltage divider has a ratio of 2001  =  (200M+0.1M) / 0.1M. Each voltage on the multi meter multiplied with 2001 is the voltage over the voltage divider .

    The image above shows the test setup. The variable resistor RL I realized severl 10Meg Ohm resistors connected parallel.

    The table above shows the measured values.

    The diagram above show the voltage and the current of the HV supply.  The calculation of the internal resistor Ri is shown below.

  • Vacuum Chamber

    Chris.deerleg08/01/2017 at 19:40 0 comments

    I got my vacuum pump and started to build the vacuum chamber.

    I started with a marmalade glas, LDPE pressure tube and a quick connector.

    With the first printed vacuum chamber cap, the achievable vacuum was quite bad with 120mBar.

    I putted colored glue on the cap, closed the vacuum chamber and started the vacuum pump. After a while I could see on the bottom of the cap the colored glue. Therefor the root cause for the bad vacuum were some small gaps in the printed cap.

    Above you can see the CAD model of the cap. In this version the quick connector is replaced by a barb connection, similar to the connection between the vacuum pump and the tube.

    The video above shows an accelerated print, it visible that the filling factor is 100% of the print.

    To get a strong connection between the cap made of PLA and the tube made of LDPE I used a special 2K glue. The special at this glue is, that it is suitable for PE. The most other 2K glues are explicit not recommended for PE or PP gluing.

    The image above proofs it, now all looks tight.

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Enjoy this project?



Saidurga Karthikeyan wrote 11/15/2017 at 06:19 point

Even I am working on to build a Scanning Electron Microscope from scratch. Hope this serves as a good source for me.

  Are you sure? yes | no

Chris.deerleg wrote 07/27/2017 at 19:01 point

Thanks for you explanation. I will have you thoughts in mind and maybe it reconsider in a later stage once the first real particles fly.

  Are you sure? yes | no

ballsystemlord wrote 07/03/2017 at 20:32 point

I joined hackaday just to follow awesome projects like these!

Perhaps you are currently having troubles with vibrations and that is why your formulas are off?

  Are you sure? yes | no

Chris.deerleg wrote 07/04/2017 at 07:33 point

Thanks for joining. What do you mean exactly with vibrations?

  Are you sure? yes | no

ballsystemlord wrote 07/22/2017 at 02:10 point

(Sorry for the late reply, I can't get online often.)

Not that I'm an expert in the field, but if you are firing electrons (atomic particles), and then a vibration strikes the machine, all that that vibration has to do is to knock the machine at an atomic level to the point where is sends the electron in an unanticipated trajectory thus causing you to think that there is something wrong with your calculations.

Mind, I can't prove this to be the case. It could be that the magnetic fields compensate for the vibrations (that is to say, when the device moves as a result of a vibration the magnetic field remains in the same place and just changes in intensity slightly, due to the proximity to the magnet).

  Are you sure? yes | no

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