Scanning tunneling microscopes, physics lab

diffusion

This may be a bit of a silly question, but I'm wondering if it is feasible to design a freshman level lab experiment using a STM? For example, lets say the lab is simply intended to give the students a better appreciation of how a STM operates within the framework of quantum mechanics, with the "cool" factor being that the students will produce an image of some material at the atomic level on the lab PC. Is such an experiment feasible? I suppose I'm asking in terms of time requirements - how long does it take to produce a coherent image on a PC using a STM? Say the students have 3 hours of lab time - what sort of simple experiments could be performed in this amount of time?

Andy Resnick

A freshman level lab? I don't know about your school, but here that means we would need at least 8 (plus a couple spares). The cost of the instruments (and instrument repair), combined with the level of manpower needed to maintain those instruments would seem to make it infeasible. And besides, the students would not likely learn a thing.

diffusion

It would be possible to design the lab so that only one STM is required. The bulk of the lab could consist of some other component, and at the end all the students could gather around while the teacher demonstrates its use, or something to that effect. There would be some way around it.

Could you elaborate on the instrument repair and manpower? Are STMs fairly problematic?

Andy Resnick

Then it's not a lab, it's a demo.

ZapperZ

I kinda agree with Andy. That is more of a demo, not a lab. A lab is where you are doing a particular investigation of something, and the instrument (in this case, the STM) is the tool you use to investigate that something. What you are proposing is a lesson in using a STM, which in itself isn't trivial (i.e. can someone teach the difference between the imaging aspect and the spectroscopy aspect that a STM can do?)

Zz.

f95toli

I actually remember using a fairly simple STM in a lab during my last year as an undergraduate student (it was in a course called "Advanced Experimental Physics"), we prepared (scotch tape!) and scanned a graphite surface and imaged the atoms.
As far as I recall we were working in groups of 4 or 5 students.
Note, however, that it was a fairly basic STM; not a proper research instrument and it has already been set up before we arrived.
But it was a lot of fun (and I still remember doing it, more than ten years later)

The "STM part" of an STM isn't very complicated (the same is true for all SPMs), the tricky (and expensive) bits are the PLLs which requires some skill to set up.
However, there are a number of products out there intended for teaching that aren't very expensive compared to a "proper" STM so it is certainly possible to use STMs in labs.

Math Jeans

Getting a demonstration with an STM machine would probably be much easier by taking the class to the machine itself.

Usually there are quite a few of them around the physics buildings at most universities, and you could probably convince someone to give you guys a demonstration. You would probably need to find one in a big room because all of the ones that I have had experience with (AFM specifically) are in small rooms. It really depends on how small the class is.

f95toli

The system we used was similar to this one:
http://www.nanoscience.com/products/...Scan2_STM.html

I.e. very simple system that does not require vibrational isolation or anything like that.

diffusion

Lab, demo, doesn't matter at this point. I've given zero thought as to the actual lab itself, all I'm asking is if something along those lines would be feasible.

Here's why I'm asking: I thought it might be a good idea for our SPS chapter (physics society, for those unaware) to get together and build a STM as sort of a medium-term project. But rather than just have it sit there and collect dust, I thought it might also be a good idea to then incorporate the STM into a freshman lab somehow, which could be taught by a couple of the senior SPS students (at my university, 4th year students routinely teach labs). Quantum mechanics and electromagnetism make up one semester of the first year physics class, so I thought it would be a good way to incorporate a bit of both into a fun little lab class.