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Greetings;
I was wondering if someone could help me on this. Thanks a lot in advance.
I am using PFQNM on a Dimension Icon using normal tapping probes with a k around 40 N/m. After having followed the typical calibration steps I can not finalize the calibration on the PS thin film reference sample. Technically, the initial modulus values on this sample are too low (around 200 MPa) which makes it impossible to arrive to the expected value of 2.7 GPa (or even anything close to this value)via changing the tip radius value. In other words, the expected situation is to get 2.7 GPa on the PS sample, after having an indentation depth of a few nanometers with a realistic tip radius of few nanometers! This is not at all what I can have!
Thanks a gain for your considerations.
Cheers
Amir
This movie is a good start at least to check if you are doing everything ok https://vimeo.com/user15273673/review/119890124/ec51c428e4
Thanks a lot Joop; I will check it out.
The first thing that can help, probably your sc is to high for the polimers. according to the PFQNM manual it should be mesured with scan asist air witch is around 0.4 N/m
another one....... did you check if there was not a protecting thin sheet over your callibration sample?
another one....... did you check if there was not a protecting thin sheet over your callibration sample? Do you have the PFQNM manual ( PEAKFORCE QNM USERS GUIDE-C (004-1036-000) ) If not give me your mail adres, i can sent it
Dear Joop, I will take into account your recommandations when next week I will be running some tests, I will let you know the result. Thanks a lot though for the comments and suggestions.
Hi; finally the main problem was the deflection sensitivity calibration (too high or too low sensivities). Now I am obtaining reasonable results. Thanks again for helps.
Hey Amir,
I am having the same kind of problems, can I ask how you determined whether the deflection sensitivity was too high/low and how you got a good calibration for this in the end?
Cheers,
Mark
Let me post some resources here. Please pay attention to the last link where you can find all many online training. The PFQNM are the first two training videos. If you need immediate AFM help, please dial the 800 number. Bruker Support website has many training and troubleshooting documents.
Bruker Atomic Force Microscope Technical Support Group
Phone: +1 800-873-9750
E-mail: afmsupport@bruker.com
Website: www.bruker.com
Bruker Support: http://brukersupport.com/
Resources: www.nanoscaleworld.bruker-axs.com
Bruker Probes: www.brukerafmprobes.com
Expert Training: http://www.bruker.com/service/education-training/training-courses/afm-optical-training-courses.html
Hey Mark; I am sorry for the late reply, been away for a while.
As you know the value of the deflection sensitivity is strongly dependent on the machine, on the position of the laser spot on the cantilever,.... which makes it impossible to give a general reference value for this parameter. Yet, here is the way I do it, and I hope it helps you:
1.Perform the ramping on Sapphire.
2.The ramping parameters: ~300 nm ramp size, at leat 512 point, 0.25 Hz rapt rate, relative trigger with trigger threshod of 0.1 or 0.2 V (for soft probes 0.2 and the harder the probe the lower the trigger, e.g. 0.1)
3. Your criteria for having a good calibration should be "a smooth and well defined ramp curve with a good linear portion", where you will zoom to measure the slope
4. Then measure the deflection sensitivity and withdraw the probe. Repeat the calibration 3 times on three areas to make sure that the value is reproducible.
5.You can change the trigger threshod and ramp size a bit in each trial to see if the result is still the same (a bit of differene is normal though)
6. After all, try to image the PS or PSLDPE reference sample. If your deflection calibration is good and the value of your deflection sensitivity is not too high or too low, the measured deformation on these samples will be in expented orders and in turn the final results will be good. But if, on the contrary you have got a problem in calibration, you may se negative deformation or too high deformation (few tens of nm) while imaging.
7. Finally, here are the typical values that I have: on a DimensionIcon, using TESPA tapping mode probes, the measured deflection sensitivity varies between 60 and 90 nm/V and I have a deformation of aroun 3 to 5 nm on PS while applying a force of ~100 nN.
I hope I could help you.
cheers
Greetings Teddy; I appreciate the suggestions, very helpful.