40
JPK Instruments NanoWizard
®
Handbook Version 2.2
Reducing drift and vibration
Mechanical drift and vibration isolation are critical factors in the design of most
types of SPM, and these are important aspects of AFM design. The signals from
the measurement and control systems are
interpreted as being caused by either
the interaction that is being studied, or the topography of the surface. Any
differential movements of the tip and sample arising from vibrations or longer term
changes due to different thermal expansion coefficients,
for example, can not be
separated from the desired interaction and topography information.
Good AFM design will therefore include minimizing
the vibrational coupling to the
environment, as well as reducing the potential for mechanical drift from thermal
or
other effects. The general approach is usually to construct AFMs from small, light,
rigid components that will have high resonant frequencies. The AFM is then
located on a large, heavy, damped table that will have a much lower resonant
frequency (gen
erally designed to be around 1 Hz). This should lead to mechanical
filtering of the environmental vibrations to only include the low frequency
components, which will not be able to couple strongly into the SPM tip-
separation
The location and use
of the AFM is also important in reducing the effects of drift
and vibration. Even a the best AFMs need a good location and environment.
Acoustic noise, vibrations from air conditioning or other airflow, and large
variations in room temperature are all t
hings that will cause problems for AFM
imaging. It is best to locate an AFM in a relatively small room, where there are not
many people passing through, in a stable environment.
To Next Page
Loading...