🚀 go-pugleaf

In article <Jan.4.22.43.27.1993.8155@planchet.rutgers.edu> gbloom@nyx.cs.du.edu (Gregory Bloom) writes:
>How hard is it to build an STM or AFM?  Does it seem like a project
>that could be made on the scale of 'The Amateur Scientist' series
>from Scientific American?  I have heard that getting the monatomic
>tipped probe is perhaps the hardest part.  Could standard
>electronics crystals, removed from their cases, be used to position
>the probe?  How noisy can the controlling current be?  How hard is 
>it to observe tunneling current?
>
>Is 'rolling your own' STM merely unlikely, or am I asking something
>more like 'how do I build a space shuttle in my backyard?'

I'm a graduate student in theoretical chemistry, and I've worked
with electron tunneling simulations in other systems (biochemical
electron transfer reactions).  I'm interested in doing some
work with scanning microscopes after I get my Ph. D. (soon, I hope!) and
so even though I've never worked with them, I've found some answers
to these questions.

About a year ago, I saw an article -- maybe in _Computers_in_Physics_ --
on constructing a scanning tunneling microscope as a semester project for an
undergraduate physics laboratory.  Unfortunately, I can't find the reference, 
but my recollection is that the only specialized pre-fab part they
used was the 3-axis piezoelectric scanning assembly.  (I think they
built their own amplifier, and used a standard PC with D/A and A/D 
boards to drive the microscope and process the data.)
I doubt that it's too difficult to make your own scanning
assembly, but unless they're very expensive, it'd probably be
better to focus on debugging the other stuff.

At the trade show at the APS March meeting, I asked a supplier how much
standard, pre-prepared scanning tips cost, and got an offhand 
answer of a dollar or so per probe.  

Burleigh Instruments (Burleigh Park, Fishers, New York, 14453, 716/924-9355)
advertised an entry-level STM for roughly $10,000.  It includes
all the specialized control electronics and software, but you need
your own Windows-capable PC-compatible to control it.

More capable STMs seem to run up to $100,000 or so, and maybe higher.
At the APS meeting, which was largely devoted to solid state physics,
the expensive ones were intended for experiments at cryogenic
temperatures in high vacuum.

There are a variety of articles in _Review_of_Scientific_Instruments_
on STM construction.  A representative recent one is Rev. Sci. Instrum.
63:3643, by M. A. Dubson and Jeeseong Huang, "Simple, variable-temperature,
scanning tunneling microscope."  The first four footnotes in this article
refer to the "several designs for variable-temperature and low-temperature
scanning microscopes (STMs) [which] have been published."  
I think plain "vanilla" STMs are no longer cutting edge enough to make
it into this journal, so if you wanted construction details for
them, you might try the same journal, several years back.

  Bill Newman
  newman@theory.tc.cornell.edu

PS: I'd appreciate e-mail from anyone who could point me to references 
about chemical physics or biochemical physics sorts of research 
with STM's.  Mostly I've seen research with a solid-state-physics bent.