Fluid Operation
Troubleshooting Tips
138
MultiMode SPM Instruction Manual
Rev. B
8.4
Troubleshooting Tips
8.4.1 Cantilever Tune Plot Looks Poor: Loose Probetip
The
Cantilever Tune
plot can be used as a diagnostic tool. Become familiar with its characteristics
when good images are obtained. If the plot looks substantially different from previous successful
experiments, there may be a problem with the
fl
uid cell. For example, the probe may be loose in its
holder.
Check the clip which holds the probe in place, and verify the probe is not loose. Contact Veeco for
assistance if needed.
8.4.2 Laser Sum Signal Absent or Weak: Air Bubbles
Verify that all bubbles are removed from the probe. Bubbles may attach themselves to the probe,
causing the laser beam to be diffracted. While bubbles can sometimes be removed by forcing
fl
uid
through the
fl
uid cell, it is often necessary to dry the
fl
uid cell with absorbent paper (e.g.,
Kimwipe).
Degassing your imaging
fl
uid prior to use in the AFM reduces bubble problems.
8.4.3 Poor Image Quality
Contaminated Tip
Some types of samples (e.g., certain proteins) may adhere to the cantilever or tip. This reduces
resolution, resulting in blurred images.
If tip contamination is a problem, it is necessary to protect the tip against contamination. There are
two ways this may be accomplished:
1. If the sample is adhered to a surface through absorption (e.g., diffusion of protein onto mica):
a. Diffuse the sample substance into the substrate, then rinse with buffer.
b. Lower the tip into a fluid containing little or no stray substances which may adhere to
the tip.
2. If the sample is short-lived and must be imaged quickly, it may be possible to mask the tip
against contamination by bringing the tip into gentle contact with an uncontaminated
substrate surface:
a. Put the MultiMode into Contact Mode: set
Other Controls
>
Microscope mode
to
Contact
and engage the substrate surface using a
0
Scan size
.