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An novel approach to
the combination of AFM with optical spectroscopy —
May 18, 2005
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During recent years a novel trend in optical spectroscopy techniques
has emerged that makes use of the particular properties of nanometer
scale objects. Of particular interest is the interaction of an
AFM tip with a sample within an external optical field. Special
attention has been devoted to surface (tip) enhanced Raman spectroscopy
and to the manipulation of single molecules and particles with
simultaneous single molecule fluorescence. JPK Instruments addresses
this matter introducing the Tip Assisted Optics (TAO) module as
an add-on to the NanoWizard® AFM.
The NanoWizard® AFM is especially designed for the combination
with optical techniques on the basis of inverted optical microscopes.
As a three-axis closed loop system it allows the sample to stay
fixed within the optical focus at all times. Furthermore, the
use of an infrared light source (850nm) and special filters eliminates
cross talk between optical experiment and AFM .
The TAO system consists of an additional 100x100µm X-Y-scanner
for the sample, which can be used independently and simultaneously
to the AFM. This allows the precise compensation of the inevitable
offset between confocal optical image obtained with the sample
scanner and the simultaneous AFM topography. The tip can be positioned
exactly into the optical focus while the user can still navigate
within the AFM image. Thus, the tip-enhancement effect can be
maximized or it becomes possible to do single molecule manipulation
experiments within the focus of a confocal optical image.
First applications are in the area of Raman spectroscopy of biological
materials with highest spatial resolution and the manipulation
of quantum dots and dye molecules with single molecule fluorescence.
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