[Leica] [Off Topic] Atomic Force Microscopy...

[Alexey Merz <alexey@webcom.com>]

Alexey Merz alexey@webcom.com wrote:

<< ... AFM's are NOT "basically high resolution microscopes" as they
>>can probe *many* properties of an object, including electical and
>>mechanical properties. What's more, AFMs can be used (as I already
>>pointed out) to manipulate, move, and place on substrates single
>>molecules or even single atoms. They are not simply passive viewing
>>devices, as you (parhaps not intentionally) imply.

Berg Na <bergna@yahoo.com> replied:
>Not true. In addition to normal surface topography imaging, AFM may
>also be used to measure interatomic or intermolecular forces but it
>CANNOT be used to deposit materials or pattern surfaces on the atomic
>scale as you described. Such tasks, as demonstrated by IBM, require a
>scanning tunneling microscope (STM). I also want to point out that AFM
>may yield structural information on a sample but provides no clues
>about its electrical properties.

Berg is correct about AFM vs. STM. I was too sloppily using the term
AFM to refer to the whole class of scanning probe microscopes. In my
earlier post (now clipped) I more carefully referred to "AFMs and 
their relatives". 

>I also want to point out that AFM may yield structural information
>on a sample but provides no clues about its electrical properties.

Actually, that depends on *how* the AFM is used. Consider the 
following paper by my college housemate Eric and his colleagues; 
I would certainly not say that their AFM data "provide no clues
about electrical properties":

- ----------------------
Probing Electrical Transport in Nanomaterials: Conductivity 
of Individual Carbon Nanotubes.

Hongjie Dai, * Eric W. Wong, * Charles M. Lieber 
[1996] _Science_ 272:523

A general approach has been developed to determine the
conductivity of individual nanostructures while simultaneously
recording their structure. Conventional lithography has been 
used to contact electrically single ends of nanomaterials, and 
a force microscope equipped with a conducting probe tip has been 
used to map simultaneously the structure and resistance of the 
portion of the material protruding from the macroscopic contact. 
Studies of individual carbon nanotubes demonstrate that the 
structurally most perfect nanotubes have resistivities an order 
of magnitude lower than those found previously and that defects 
in the nanotube structure cause substantial increases in the 
resistivity.
- -----------------------

Regards, 
Alexey
..........................................................................
Alexey Merz | URL: http://www.webcom.com/alexey | email: alexey@webcom.com
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