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We just got a new Icon system and are learning how to use it, and had some issues on tip approach.
From what I understand Scan Asyst and QNM work with a similar principle of working in the off resonance so tip frequency response should make no difference. Aside from the obvious that QNM produces more data output I could find very little differences between the two methods (Comparing all the parameters side by side) except…..
We were using Scanasyst-air probes and some have with horrible frequency responses (Frequency tune, low slope and overlapping frequency peaks). The Scan-Asyst-air experiment crashed the poor resonance tips into the surface on approach, and the QNM did not. I could switch back and forth just changing the factory set experiment and reproduce it every time. The system would drive and never make it to the sewing action, just drive till the system sensed that something was wrong. The system knew the correct tip in the setup; it was selected from the tip database.
I was able to prevent most of the crashes in ScanAsyst-air by changing the engage SPM Safety from 100nm to 150nm, and Fast engage Threshold from 85% to 100%. QNM worked fine with the standard factory settings.
This did not happen with the Tap150, RTESP, or Tap525, and they had nice resonance curves. So my question is, what is the difference between ScanAsyst-air , and Nano Mechanical-QNM, and how can I make the Scan-Asyst more careful on approach like the QNM? Why does a clean frequency curve seem to matter for peak force or is this just a coincidence ?
Thanks for your help in advance.
Mac
Hi Mac,
If you are using the factory setting for ScanAsyst and PeakForce QNM, they may have different engage settings. Go to the Engage Settings under the Microscope pull down menu, and check the Engage Mode parameter under the Smart Engage list. There are two possible settings for this parameter - Smart and Standard.
ScanAsyst is set to Smart in the factory workspace. This will find the resonance frequency of the probe by automatically conducting a cantilever tune (Autotune) before engaging. For this to work properly, you will need to set the proper cantilever type in the Setup menu, otherwise it may sweep through the wrong resonance frequency range. The ScanAsyst-air probes typically have a resonance at around 70kHz or so. Is this what you are seeing?
PeakForce QNM is set to Standard in the factory workspace. This engagement is based setting the distance of the SPM Clearance parameter (usually 1mm) by focusing on the tip and then sample. It will move quickly toward the sample until it reaches the SPM safety distance, and then start the slow engagement. This method is not based on the resonant behavior of the cantilever, so would work better if the cantilever is having oscillation problems at resonance.
So, if you are going back and forth between modes with the factory settings this would explain the differences that you are seeing. You can always change the ScanAsyst workspace to a Standard engagement, and it should work fine.
Smart engage usually works pretty well however. The ScanAsyst-air probes are softer and do not oscillate at resonance as nicely as the other probes that you have mentioned, but they do have a pretty well defined resonance peak and usually engage fine with the Smart engage.
Also, what sofware version are you using? I am describing version 8.15.
I hope this helps. Let me know if you need further help with this.
Thanks,John
Yes we are using version 8.15, and yes the frequency is within the range listed on the box, of ~70kHz.
For some reason my mind never thought to click that item to see if that was a changeable item.
We have made the change over here. Our Scan Asyst mode approaches are several seconds longer, and we now have consistantly safe approaches that preserve the tip sharpness.
Thank you for all your help,