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I am still having problems with AFM tip damage during approach (in tapping mode).
Would you offer all the tips to avoid this?? I know to start with small scan area (like 1 nm) and low scan speed. Added to this, I ahve a basic question: What is "drive amplitude'??
Also, I can not get rid of the noise when I scan in 'phase' mode. What will help reducing the noise ? It seems oscillation, but reducing the feedback does not help.
I am scanning Moly surface.
Regards,
Hi Jay,
I forgot which instrument and software version you are using? That would greatly help pointing you in the right direction. Some general remarks and questions:
Best,
Stefan
scanning in air. The tip is TESP (standard). Nanoprobe IIIa is the model.
Basically, I have to replace the tip after couple scans. I am never able to reuse the tip for the 2nd sample. The substrate is Moly sputtered film on glass. It is polycrystaline, with RMS roughness of 10 nm. I was told if I buy a better tip, I would have better luck. So, I purchased TESPA. I am getting very small (30 mV) drive amplitude setting after I do auto-tune. I am guessing it auto adjusts based on the laser intensity. Everything was good until I approached. The tip would crash into the film and when I look at the tip under the optical microscope, the tip is gone !!! This happened twice in a row, and I don't want to lose another tip until I know what I am doing wrong...
To add a bit more info, the problem I have with TESP tip is that it wears out like crazy on the Moly surface.
I can scan couple nice images, then pull back, put in a 2nd sample. But the tip will never ever work on a 2nd sample. This I do not get. Is it wear, or is the tip crashing every time it approaches, ending up with a mangled tip it approaches on the 2nd sample ???
Now, for the TESPA, I cannot even get the tip to engage (see my post above)....
Jay,
TESP and TESPA are the exact same tips. Both levers are made from silicon following the same manufacturing process. The 'A" denotes that the backside of the cantilever is coated with Aluminum to increase the reflectivity which in turns will give you higher sensitivity (higher sum signal) and reduce laser interference.
You are saying now that you can take a few scans before you have to replace the tip. That means that you probably did not crash the tip during approach as this would mean that you wouldn' be able to get a single scan. That hints that you maybe have a setpoint that is too low causing excessive wear, your scan speed may be too high, or your feedback loop is not responding fast enough. It could also mean that maybe your airtable is not floating or other things in your environment not being the way they should. It is very difficult troubleshooting the problem further here and I strongly suggest that you get into contact with Bruker technical support to work with you directly. If you like and send me your address I can put you directly in contact with Tech Support.
Before I talk to tech support, would you elaborate on "too low set point" ?? What is this doing and how would too low set point cause 'excessive wear' ??
Your setpoint determines the amount of damping that you are looking for. The lower your setpoint the more damping of the initial oscillation and consequently the more energy dissipated. So a very low setpoint will be a bit more harsh on the tip-sample. If you go to the "Application Notes" section and download Application Note #133 (PeakForce Tapping) you will find a more detailled description of the situation.
When you talk to our Tech Support department keep in mind that besides troubleshooting they also offer other things such as training classes on the Bruker AFMs.
Best regards,
I read your #133 note, and also the AFM manual. Now I understand the "set point" and "drive frequency" concept. I still am not clear on "drive amplitude". Would you explain on this, or suggest a "better" manual ??
How does this Drive Amplitude affect my AFM scanning ?? Is this in any way, tied into how I would set the 'set point' or feedback parameters ???
Please see my explanation fro "drive amplitude" in my first answer to your query: "
The higher the drive ampliutde, assuming the same setpoint, the higher the force between tip and sample. The use of higher drive amplitudes may sometimes be dictated by sample properties. If, e.g. your sample exhibits quite some adhesion you have to choose a higher drive amplitude to make sure that your tip does not get stuck on the surface permantly. Again, there should be no reason a TESP tip works and a TESPA does not.