<!DOCTYPE html>
<html>
<head>
<meta http-equiv="content-type" content="text/html; charset=UTF-8">
</head>
<body>
<p>Folks,</p>
<p> Nick Edgington started a project with the Forge Initiative to
build an affordable scanning tunneling microscope ("STM") capable
of visualizing individual atoms. He, Jaime Johnsen, and I have
been gathering up information and doing a few initial things to
test the waters with input from Rob Mackey of the Forge and
others. Now we'd like to start organizing the project and
connecting with folks interested in becoming involved.<br>
</p>
<p> An STM is a primarily electronic device that senses quantum
tunneling current flows between individual atoms while an
electrically charged, atomically sharp probe moves at very close
range across the surface to be scanned. Commercial STMs such as at
universities are very expensive. Our goal is to make something
that can be reproduced for a few hundred dollars. Ultimately we
want a kit suitable for school children. More details of STM
operation here: <a
href="https://my.eng.utah.edu/~lzang/images/Lecture_6_STM.pdf"
class="moz-txt-link-freetext">https://my.eng.utah.edu/~lzang/images/Lecture_6_STM.pdf</a><br>
</p>
<p> Here are some key features of the project:</p>
<ul>
<li>Extremely efficient resistance to vibration. Because the probe
must move less than a nanometer from the surface to be scanned,
very efficient dampening must be used. Also the dampening must
be portable and use inexpensive materials.</li>
<li>A means of moving the probe very precisely. Piezo crystals and
precise applied voltages are the common method for hobby STMs.<br>
</li>
<li>A means of creating atomically sharp probe wires (the tip must
be a single atom!). This typically involves electrochemical
etching with gizmos to manage the process in a very repeatable
manner. Alternatively, a probe tip can be made in a much simpler
way with manual techniques for cutting the probe wire.<br>
</li>
<li>A very stable package for the probe that contains the piezo
probe actuator and the probe current front end electronics. One
of the best projects we've found uses what appears to be a
CNC-machined block of aluminum that is a thing of beauty just
asking to be used for inspiration.<br>
</li>
<li>High performance but inexpensive electronics to sense probe
current (*peak* current is a nanoampere or two) and digitize it,
arrange bias voltages between tip and target to enable quantum
tunneling, and move the probe on three axes. The power supplies
have to be excellent. Custom PC boards are a given.<br>
</li>
<li>Software to control the system, gather data and translate it
into visualization and provide a user interface. A large body of
code for the Espressif ESP32 (project Edger) can be leveraged
for a very low cost system. The software will probably be a
mixture of Python, C, and Javascript.</li>
<li>Making test systems that help detect things going right and
wrong.<br>
</li>
<li>Many supporting tasks to do with documentation, safety,
communication, coordination, sponsorship, etc.<br>
</li>
</ul>
<p> <b> An informal meeting will be held this Monday July 1st at 7pm
</b>with Jitsi using the usual TriEmbed URL :
<a class="moz-txt-link-freetext" href="https://meet.jit.si/TriEmbed">https://meet.jit.si/TriEmbed</a> .</p>
<p><b>A more formal meeting will be held in mid August</b> in a room
provided by the town of Apex (the Forge is based in Apex).<br>
</p>
<p> The various subsystems of an STM really push the envelope for
performance, and this project will be quite challenging, even
though there are many shoulders to stand on.<br>
</p>
<p> A Discord channel on the Edger project is accumulating records
while we finish setting up a GitHub repository and supporting web
resources. I'll send directions on how to hook up with it later.</p>
<p>Pete<br>
</p>
</body>
</html>