[Spm] different deflection sensitivity in two phases

[R Lartius]

Dear Sam,
You wrote "My questions are (1) why the deflection sensitivity of the
cantilever is changing from one phase to another phase?"

Just to briefly add to Yan's comments on optical lever sensitivity
(OLS).  OLS is of course related to shape of the laser spot reflecting off
of the cantilever among other things (please see this excellent reference
from Jan Hoh's lab discussing this point and a non-contact method for
estimating lever sensitivity - D'Costa, N. P, and J. H. Hoh. 1995.
Calibration of optical lever sensitivity for atomic force microscopy. *Rev.
Sci. Instr.* 66:5096-5097)...

For the past few years AFM probes from some manufacturers have become
increasing inconsistant with rough reflective surfaces leading to poor lever
sensitivities. In addition some of the lever coatings are actually
delaminating after short periods of use under the right conditions. As a
result the lever sensitivity with these probes can and do change over time.
If the reflective lever coatings are done properly this of course shouldn't
be an issue. In case you have some of these probes, however, you might check
your OLS before and after your experiments using the contact method that Yan
mentioned or the non-contact method described in the D'Costa paper above.

Best of Luck,

Raj
~~~~~~~~~~~~~~~~~~~~~~~~~
Raj Lartius, PhD
Novascan Technologies, Inc.
Ames, Iowa 50010

Voice: 515-233-5400
Email: rlartius at novascan.com
Web: www.novascan.com
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