It is an interesting challenge.  Not an immediate answer, just a comment:
Carbon nanotubes have been
promising for etching deep trenches and I would guess that if the sample
were tilted, some fraction of the
side wall could be etched with such an extremely thin, high aspect ratio,
structure.  One problem, though,
is the flexibility of CNTs...they tend to "snap to" the sidewalls if they
are too long, because they bend
relatively easily.  In this regard, there are other options on the horizon
that really should be explored by
the SPM imaging community.  These include directly growing silicon
nanowhiskers on each standard AFM tip; and using the "other"
nanotubes like the WS2, WSe2 NTs discovered by Reshef Tenne and his group
(they are significantly
stiffer than CNTs, for the same diameter), etc. In short, there is no lack
of interesting nanostructures that likely could be directly
grown on each AFM commercial tip during production (what, they sell these
in batches of 400 per wafer, right?).

There was also work by Bustamante and colleagues on making "hooked tips"
like Randall discusses below,
back in the 1980's.  A small carbon spire was grown by focussing a STEM
beam onto a tight spot, and deliberately
introducing a small hydrocarbon impurity, like xylene. The e-beam
dissociates the xylene, and a hard carbon deposit
(with some hydrogen likely present) is formed.  By tilting the substrate at
a certain time during growth, the direction
of growth relative to the angle of the substrate was changed.  This type of
tip seemed to hold promise for imaging
side walls, but I am guessing that they moved away from this rather complex
method of making tips, when the CNTs were discovered. Since their primary
goal was simply high aspect ratio, thin tips for imaging, without a hook
present.

Feel free to fire this off to the SPM companies or tip-making companies and
agitate them a bit. For example,  if they funded my group, we could make
very rapid
progress on some of the above! I would also be willing to join with them,
and pursue SBIR opportunities or leverage their industrial support
with federal support to work towards the commercial introduction of a wide
host of tip types to the community.

Rod Ruoff
[email protected]
Dept of Mechanical Engineering

At 12:35 PM 1/24/2002 +0800, Randall Cha (Dr) wrote:
>Dear Emer,
>
>Sometime back, IBM developed a kind of AFM tip that looks like hammer-head,
>which can be used to measure sidewall roughness quantitatively. If my memory
>do not fail me, it supposes to read measurements in 2-axis. However, now I do
>not know whether they make that kind of tips anymore, and whether any company
>is making some eqt that house the tip.
>
>You may like to check out Veeco.
>
>By the way, how deep are you going to check the sidewall profile? If it's
>deeper than 6um, then you might have a problem.....
>
>Randall
>
>-----Original Message-----
>From: Emer O'Reilly [mailto:[email protected]]
>Sent: Wednesday, January 23, 2002 4:01 AM
>To: [email protected]
>Subject: [mems-talk] measurement of sidewall roughness
>
>
>Dear all,
>
>I hope someone can help me with my query. If I get enough responses, I will
>collate answers and sent to the message board.
>I am interested in carrying out sidewall roughness measurements on my
>samples, using AFM. My samples are polymer tracks of various thickness on
>silicon and are as yet uncleaved. Has anyone carried out this type of work?
>If so I would be grateful to learn about the do's and don'ts.
>
>Thanks in advance.
>
>Emer.
>
>
>****************************************************************************
>***
>Research Engineer, Nanotechnology Group,
>NMRC, University College Cork, Ireland.
>
>Direct line: +353 (0)21 4904182
>Fax: +353 (0)21 4270271
>www.nmrc.ie
>****************************************************************************
>***
>
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>name of winmail.dat]
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Prof. Rod Ruoff
Dept of Mechanical Engineering
2145 Sheridan Road
Northwestern University
Evanston, IL 60208-3111

phone 847 467 6596
fax 847 491 3915
[email protected]
http://bucky-central.mech.nwu.edu/recentpublications.html (downloadable
Ruoff group articles, last 3 years)

Note: interest in student or postdoc positions in the Ruoff group should
please be directed to Ms. Charlotte Gill, my program assistant. Her email is
Charlotte Gill  . She organizes files for me and I
read them weekly. Thank you for your interest in my group and our research.