[Spm] Crisp images in tapping mode

[Don Chernoff at ASM]

Tania Rizwan asked about improving the image of a nanofiltration membrane with 100nm particles.  She reports blurry images.

Two key suggestions to improve tapping in air:
-Lower the tapping set point about 10%, because blurry images can be due to poor tracking of the surface.  There is a parameter called 'engage setpoint' which automatically adjusts the actual setpoint relative to the tapping amplitude when the tip first starts tracking the surface.  Perhaps another user has changed this value and you did not compensate by lowering the actual setpoint manually after the tip engaged.

-Change the probe, because it is easy for it to become contaminated.  For example, if a 100 nm particle becomes attached to the tip, the image resolution is greatly decreased.

I hope this helps.

regards,
Don
=============================================
Don Chernoff, Ph.D., President
Advanced Surface Microscopy, Inc.    E-Mail:  donc at asmicro.com
3250 N. Post Rd., Ste. 120           Voice:   317-895-5630
INDIANAPOLIS IN 46226  USA      Toll free: 800-374-8557 (in USA & Canada)
web:  http://www.asmicro.com         Fax:     317-895-5652
[business activities:  analytical services in AFM, AFM probes, consulting, training,
calibration and test specimens, calibration and measurement software,
 used NanoScope equipment.]
=============================================

original message:


In the past, I have been successful in obtaining crisp images using  
both tapping mode in air  and under liquid. We had our peizo replaced  
recently, and I am trying to reproduce those same results on a new set  
of membrane samples and I am unable to do so while scanning them in  
air. The images are blurry especially around the edges ( I cannot  
discern between the membrane and the particle edges) and donot show  
the details I desrire, despite the fact that the trace and retrace  
curves show good conformity. I don't have any issues with vibration (  
we have an air table) and I have tried various combinations of the  
following paramters:

Controller: Nanoscope 111a, tapping mode probe with resonant frequency  
of about 270-300KHz
Scan rate: 0.25 Hz to 1.5 Hz
Scan size: 8 by 8 micron to 20 by 20 micron
Setpoint
Frequency
Drive amplitude
Z limit: reduced from 6 microns to 3.5 microns ( this worked for me before)
And the gains

I would greatly appreciate any help regarding this matter.

Best Regards,

Tania Rizwan
University of Alberta
email: trizwan at ualberta.ca

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