[Spm] Re: [a] Re: Crisp images in tapping mode

[Don Chernoff at ASM]

Dear Tania,
If you have adjusted the setpoint and changed the tip and you are still having difficulties, you should make sure that the integral gain is at least 0.3.  You should also consider whether the sample is held securely.  

You asked whether contaminants on the tip will change the resonant frequency of the cantilever.  The answer is, yes, of course the frequency is changed, but whether cantilever tune is sensitive enough to measure the change is a separate question.  I have detected frequency shifts more than 10 hz only in a few cases.

Another suggestion is to put an easy sample in the AFM, such as the calibration grating.  You should review the procedures for tuning the tapping mode image that are given in the Veeco/DI SPM Training Notebook and make sure that you understand the bad effects of:  too low gain, too fast scanning and too light tapping setpoint. 

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 ----- 
  From: trizwan at ualberta.ca 
  To: Don Chernoff at ASM 
  Cc: SPM List 
  Sent: Thursday, June 14, 2007 3:38 PM
  Subject: [a] Re: Crisp images in tapping mode


  Thanks Don for your response. I have tried lowering the engage  
  setpoint and also changed the probe thinking the tip could be  
  contaminated. But I get the same results, even when I scan a clean  
  membrane where no particles are deposited. Another quick question...if  
  a tip did get contaminated say with a particle attached to the tip,  
  wouldn't it change the resonant frequency of the probe when I tune it  
  again?

  Thanks!



  _________________________________
  Tania Rizwan

  University of Alberta
  email: trizwan at ualberta.ca


  Quoting Don Chernoff at ASM <donc at asmicro.com>:

  > 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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