Fun With Quantum Mechanics: Scanning Tunneling Microscopes

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Credit to the Sykes Lab of Tufts University

A research-grade low pressure/temperature STM (top) and a portable laptop-capable STM (bottom)

I know what you’re thinking:  aren’t Scanning Tunneling Microscopes (STMs) hundreds of thousands or millions of dollars?  Who has that lying around, much less in grant money?     Well… almost nobody.

STMs do indeed cost a lot of money, but can tell you a whole lot of stuff about a surface.  They’re so expensive that a simple google search doesn’t yield any results for websites which sell STMs.  Going further, I found that DME-SPM sells a whole range of STMs.  However, the prices aren’t listed (kind of like an expensive restaurant, where you only get the price once the bill comes).  Not really too affordable.

However, if you have the cash, an STM can be a fun thing to have.  After all, who doesn’t want to see things on the atomic level?  One can move hydrogen atoms around under a Pd crystal or Xenon atoms on a metal surface.  This is done using an atomically sharp tip (and the electrons attached).  Using this method, Paul Weiss managed to spell out the PSU Logo on a Pd Crystal.  (He was also part of the team that wrote out the IBM Logo in Xenon atoms).

One of the coolest things about STMs is that you can get a gigantic apparatus which has space for liquid Helium and a super vacuum and can resolve images on a atomic level OR you can get a STM that can fit on your desk, plug into a laptop, and work at STP! Well, I had the chance recently to work with one of these STMs for a Quantum Mechanics lab.

Can you see individual monolayers?  Etch points?  Sections of C10 SAMs?

My very own STM image of SAMs on a Au surface!

My group made the road trip through time and space (well, really just space) to the Sykes lab of Tufts University, where we had the chance to explore the world of atoms.  This was especially fun considering my lab group consisted of myself, an undergrad interested in synthetic chemstry, and another undergrad currently researching inorganic chemistry but going to business school.  If you’ve keeping score, that equals exactly zero people who would be interested in Quantum Mechanics.  Even so, we all had a blast playing with an STM.  Predictably, we didn’t get to use the giant STM that the lab has (which uses liquid He to cool and contains a very, very strong vacuum).  Instead, we had the chance to use a portable STM that hooks right up to a laptop.  Using this setup, we analyzed surface-assembled monolayers (alkanethiols of C8 and C10 length) on a gold surface.  Pictures on the side.

If you were curious, you can get one of these desktop STMs for around $9000 (so told by a friend in the Sykes lab).  It’s on my graduation wish list for sure.  Check back soon for more posts – now that school is winding down, Chiral and I will be on CENtral Science more.  Also tune in next monday for a look at peptidomimetics!

Author: Sidechain Bob

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  1. What is a SAM?

  2. Hey Mitch! A SAM is a Surface Assembled Monolayer – basically where you have a bunch of organic molecules attached to a surface (in this case gold) by a thioester or thioether bond.