Calibration, Maintenance, Troubleshooting and Warranty
TappingMode AFM Troubleshooting
Rev. B
MultiMode SPM Instruction Manual
319
15.12
TappingMode AFM Troubleshooting
Depending on the operating mode being used, the symptoms and subsequent resolution may vary.
For this reason, problems listed in this section are divided into Contact Mode (see
)
and TappingMode (see
). STM problems are described in
Some of the problems and cures associated with contact AFM are also relevant to TappingMode. If
problems occur, it may be helpful to read through the Contact AFM problems and vice-versa. The
most common problem while operating in TappingMode is due to unusual resonance peaks in the
Realtime
>
View
>
Cantilever Tune
command. Double peaks in the resonance curve can be
caused by improper seating of the cantilever or a fracture in the cantilever. In general, bad
cantilevers produce strange resonance curves, so the
fi
rst thing to do when an unusual resonance
curve occurs is to clean the groove on the cantilever mount and reseat the cantilever. If this does not
improve the resonance curve, install a new cantilever.
15.12.1
Streaks on the trailing edge of surface features
Streaks are an indication of the tip not tracking the surface due to either: 1) insuf
fi
cient tapping
force; 2) an excessively fast scan rate; or, 3) gain values set too low. Streaking may also result from
any combination of these factors (see
Try the following procedures to eliminate this condition:
•
Reduce the setpoint voltage. This increases the amount of tapping force on the surface.
This is probably the thing that will be most effective. Be careful when doing this on soft
samples. The sample surface can still be disturbed even though the forces are very small.
•
Reduce the scan rate. The scan rate needs to be slower in TappingMode than in contact
AFM. Typically it should be around 1-3Hz.
•
Increase the integral and proportional gains. This will speed up the response time of the
Z piezo transducer.
