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Definition of labels for a Silicon(111)-Boron surface (or really any surface with the same reconstruction). I have always found these labels to be a bit confusing when dealing with the Silicon-Boron surface. The S labels tend to have additional labels like S_3B(Si) or S_3B(B). Essentially of the two atoms in the reconstruction, two of the three letters S,I,B are used in both the atoms and the labels.
The a small amplitude approximation for the frequency shift in frequency-modulated atomic force microscopy is easier to work with but typically not applicable. This figure attempts to show the difference between two very different oscillation amplitudes: a constant force gradient is reasonable at this point of the force curve for amplitude A1, but it is not reasonable for amplitude A2.
A submission from twitter (@CiaraBRoche). The submission is titled "conference drawings part II" and came along with the hashtags " #drones #Foucault #panopticon " This submission was put in front of the Friday Physics Drawings panel this morning and a decision about its suitability was delivered in under three hours.
The panel is intrigued by the use of a lighthouse. Is this drawing from a lighthouse conference? We assumed lighthouse development had slowed of late, but who are we to judge that? (We can only judge the drawing itself). It would seem that the artist has also drawn a very windy bridge leading away from the lighthouse. Does the old man that lives in the lighthouse have to walk this lonely path every morning and night? Or perhaps this is more of a visual metaphor for his/her journey through life. The presence of some kind of many-bladed pizza box has one judge intrigued: "Is this what amazon is planning for our futures?".
It is possible that this drawing is actually related Panopticism, a social theory originally developed by French philosopher Michel Foucault in his book, Discipline and Punish? That might make the lighthouse some kind of watch tower and the bridge and stairwell to many cells. Could the pizza box be a #hashtag #drone? It is almost impossible to know.
As the drawing says "always visible but never unverifiable" which makes almost no sense.
Wiring diagram for Iso, the scanning tunneling microscope. This is supposed to be what is connected during scanning, which means almost everything is unplugged from the vacuum chamber.
If you do not create spring mounting points that are equidistant from the center of mass of your microscope, you may get into some trouble when hanging a scanning probe microscope. If we consider the torque acting on at the center of masss of the microscope:
T = SUM_i R_i x Fi = SUM_i Ri x kx
where Ri are the vectors from the center of mass to the mounting point, k is the spring constant and x is the extension of the spring. Thus if we want a microscope that hangs with its walls parallel to the copper can, then we must have equal R_i.
This is achievable by changing the k_i as well, or even the x_i but this introduces less symmtery and will likely lead to more complications in different temperature conditions.
Another in the early versions of thesis figures series. I am trying a bit harder these days to get things wrapped up. This figure likely needs more words to give it some context. I think there will also be at least three other panels, directly beneath the current three panels that will allow the figure to make more sense without explanatory text.
The idea for this drawing is to explain how a scanning probe microscope image is created, from a single measurement at a point to building up an entire image. I am trying to write a section I am calling "anatomy of a scan." While it is maybe a bit odd and abstract for a thing that is sort of simple, it is a worthwhile exercise for me, and I think there is some measure of usefulness to it.
We start with a measurement of some signal Vi(xi,yi) at a point in space. This signal is the result of some tip-sample interaction, either directly (i.e current) or indirectly (topography, as dictated by feedback). A fast scan axis is then chosen and a series of m (likely equally-spaced) measurements along said axis. For a fast scan axis of length W, each pixel is dx = W/m wide. At each point a value of the signal Vi is measured. This measured value is displayed in the drawing as both an one-dimenional intensity map and a two dimensional line profile.
The scan is then moved to a new line in the slow scan (likely orthogonal to the fast scan axis) direction. Here the slow scan axis of length H can be divided in n parts, leading to H = ndy. We then have m x n pixels each with a value of Vi, leading to a map of intensities. The image in the drawing is trying to reproduce a simple hill-type feature (perhaps an atom).
An overhead view of one of the meeting rooms, drawn during a meeting. Next time I will include more items. Today was all about the layout.
What is the resonant frequency of the vibration isolation springs in Iso? The natural frequency of the undamped system is about 4 Hz. This is not totally ideal. Getting commercial springs with a small enough spring constant was a pain for this microscope configuration. A design constraint placed on the length of the springs limited the options for springs. The spring constant was taken from extension of the springs and the known of the microscope. Known dimensions of the microscope were used to calibrate the image.
Trying to keep up with a new image every day to get through more of this thesis stuff. This one might not be complete. The basic idea here is that there are two main design changes I have made since the last time the lab built microscope, Iso, was presented.
So, B and C in the figure are the new parts. B is a spring suspension connector that moves the attachment points of the spring suspension and allows the microscope to hang from three springs which are equidistant from the center of mass of the microscope. Previously, the spring attachment points were simply equidistant from eachother (i.e. 2pi/3 apart on a circle). The issue being that the center of mass of the microscope is towards the back of the microscope. If we wish to use three equal springs to hang the microscope evenly, then the attachment points had to be fixed.
The part in C is a wire/pin interface. It allows for simpler wire replacements as well as acting as stress-relief for wires which attach to the sensitive piezoelectric scanner tube.
Revamped chamber diagram. Moved the valve/pump layout to a different diagram.
An overly-busy figure with different representations of the UHV chamber that is used in my thesis. The diagram in (A) has some valves and tubing that do not exist (green) in the renderings of the chamber in (B) and (C).
I used Autodesk Inventor 2014's illustration mode in Inventor studio to make the images.
Back to making some figures. This one is just traces from a simulation of a circuit I use to move my scanning tunneling microscope. The simualtions were done using CircuitLab (http://www.circuitlab.com/). Not the most hardcore version of a simulation of a circuit, but not a bad tool for a quick simulation.
Iso's UHV chamber in all of its glory. I used the weird little software depth of field thing on the google camera app. You get the main object in the frame and then move the camera vertically. I think it then figures out what does not move much and blurs the rest. Fun.
I spent almost 22 hours repairing things this weekend, but right around then end of it I had it all re-assembled and things seem okay (for now).
Approach help for a scanning tunneling microscope, or really any scanning probe microscope. I don't think I have posted this one yet. Again, this diagram may straddle the boundary between useful and dumb.
When a scanning probe microscope approaches a surface, there is often a two-stage approach system. The scanning unit can extend the tip some distance L in an attempt to reach the surface. If the surface is not found, then a coarse approach unit can advance a step of distance M, which is less than L. This process continues until the surface is found.
In case you are wondering, I do have a normal process flow-type diagram (what are those normally called?) for this process as well. I can post it tomorrow.
A simple fix to the low frequency vibration issue in my STM design. Essentially it boiled down to adding four walls instead of having the microscope frame so open. The 3600 Hz is the lowest frequency of the microscope body.
Iso hangs from three springs. Magnets on the bottom of the microscope interact with the copper walls of the can to provide damping for the spring-mass system. The drawing in A is supposed to be the microscope hanging in the can sitting on a vibration isolation table. In B, there are two photos: one photo with the entire UHV chamber and one with the microscope inside the cans.
Block diagram of the scanning tunneling microscope that I worked with during my PhD research. Not sure this is my favorite diagram, but I also like how simple it looks. Diagrams from my chamber often become too complicated too quickly.
Blue and red signals are output and input and all are done with BNC connectors over RG-59 coaxial cable. The green signal is a USB connector.