Fluid Operation
Troubleshooting Tips
Rev. B
MultiMode SPM Instruction Manual
139
b. While the tip is kept in gentle contact with the substrate surface, add the sample
substance to be imaged and allow it to diffuse/settle onto the substrate.
c. After a diffusion/settling period has lapsed, quickly lift the tip from the substrate
surface.
d. Switch
Other Controls
>
Microscope mode
to
Tapping
and image the sample before
it becomes contaminated.
Dull Tip
Change to a new probe. AFM probe tips can become dull during use and some unused tips may be
defective. Check the probe type being used. Oxide sharpened silicon nitride probes are usually
much sharper than standard silicon nitride probes.
Multiple Tip
Change or clean the AFM tip. Probes can have multiple protrusions at the apex of the tip, which
result in image artifacts. Features on the surface appear two or more times in an image, usually
separated by several nanometers.
8.4.4 Lost Particulate Samples: Attracted to Cantilever
Some particulate samples such as proteins may prove dif
fi
cult to
fi
nd directly beneath a cantilever if
the cantilever has remained stationary during a diffusion or settling period. This may be due to the
fact that some types of particulates are more attracted to the cantilever than to the substrate intended
to support them. The result is a “shadow” on the substrate directly beneath the cantilever where
fewer sample individuals can be located; they are stuck to the cantilever instead. If you suspect this
problem, shift the imaging site to a new location away from where the probe had remained
motionless.
8.4.5 Drift in AFM Image Because O-ring Slid Across Sample Surface
Note:
This problem is eliminated by the new “S” shaped O-ring design.
Set up the
fl
uid cell so there is minimal lateral movement of the optical head with respect to the
sample once the O-ring is installed. Keep the head level while positioning the tip close to the
surface, to minimize tip lateral motion during engagement. Other countermeasures:
•
Unlike three-point supports, the vertical engage scanner allows the tip to approach
samples without lateral offset, eliminating stress on the O-ring during engagement. For
more detail, contact Veeco.
•
Lightly coating the area of the O-ring which contacts the sample surface with white
petrolatum or vacuum grease allows the O-ring to slide across the surface, minimizing
