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Dear AFM specialists,
I am using a Multimode V/Nanoscope 7.3 with tapping mode in liquid using a standard liquid cell with SNL probes. In the software, there are a bunch of engage parameters for tapping engage (Tools>Enage Settings>Tapping...; Page 91 in Nanoscope 7.3 Rev G User Guide).
My problem is that I do not find the right parameters which allow me to engage without crashing into the surface. I tried with the standard parameters and also with very conservative ones. But it ends always in the same way: as soon as the probe gets into contact, the deflection jumps up to about 7V (causing the software to stop the engage process by throwing an error that the deflection is >5V). Then I have to increase the setpoint in such a way that the pizeo completely retracts and by slightly increasing again go into normal feedback (usually this setpoint is about 50% higher than the end-setpoint after the engage process). But at this point, the tip is already damaged.
This happens with the J and A scanner. I use mica as the support with various buffers (mainly PBS pH 7.2 or with 250mM monovalent salt pH 8).
I know that the amplitude increases a lot while getting closer to the surface, but I do not know any way to go very close to the surface where the amplitude is already near max without crashing.
If somebody uses the same system, it would already help me a lot if I could know the used engage settings and even better some tips and tricks.
Cheers, Raphi
Hi, Raphi
Do you think you can shoot me an email: james.shaw@bruker-nano.com
Let me see if I can help you offline.
Best,
James
Hi Raphi,
please contact me for Web meeting:http://confocal-manawatu.pbworks.com/w/page/23665663/Dmitry%20Sokolov
Cheers,DmitryMIAWiki for Real-Time Collaboration
Hi, Raphi,
Your engage problem could be due to wrong tuning, what were your tuning parameters and what probe and frequency you used?
LA
Hi Raphael,
Normally the defaut Tapping engage parameters should allow you engaging normally.
In Air, it should look like something like this:
- sew tip = triggered
- sewing trigger = 98%
- Engage = 1.05 (for soft approach and 0.95 for a standard approach)
- delta setpoint = -0.06
- final delta setpoint = 0.06
- test treshold slope = 25
- test treshold slope delta z = 25 nm
- engage minimum setpoint = 25
- TM engage gain = 1.00
In liquid, it should be the same except that the TM engage gain should be much lower, like 0.2
In air, even a 0 setpoint is enough to engage. In liquid, you might have to go up to 1, 2 or even 2.5 but never higher.
You can also have the problem you describe when the laser is misaligned: instead of being at the very end of the cantilever, you're aligned on the chip. Did you check that.
Good luck,
Alex.
Hi Alex,
my default tapping engage parameters looks quite the same:
- Delta Setpoint = -0.0600
-Final Delta Setpoint = 0.0600
-Test threshold slope = 25.0
-Test treshold dZ = 25.0 nm
-Engage min setpt [%] = 25
-TM engage gain = 1.00
-Sew tip = Yes (here the only options I have are YES and NO. There is no TRIGGERED option)
-Sewing trigger [%] = 98 (this field is inactive)
-Pre engage setpoint [%] = 90
-Engage Setpoint = 0.85
I do not know what you mean by Setpoint of 0 in air and in liquid 1, 2 or <2.5. I assume you mean the Engage Setpoint... (somehow this option is not explained in the Guide).
The laser is well aligned. I can also measure without any problems after engage... just that the tip hit the surface and I can see the hole of the tip in the substrate.
If I use these values:
- Delta Setpoint = -0.2
-Final Delta Setpoint = 0.01
-Test threshold slope = 600
-Test treshold dZ = 40.0 nm
-Engage min setpt [%] = 85
-TM engage gain = 7.5
-Sew tip = Yes
-Sewing trigger [%] = 98
-Pre engage setpoint [%] = 95
-Engage Setpoint = 0.95
then I can avoid the ">5V deflection error" but it ends up with a false engage error where the amplitude setpoint is smaller than allowed (if this happends, the deflection jumps up to about 3V and I am engaged and can measure). Sometimes it is a real false engage and when I continue with the approach I get the >5V-error and the deflection jumps again to ~7V.
With a high engage gains (>4) at least after jumping to ~7V the deflection goes back to 0...
Until now I did not play with the Engage Setpoint because I had no idea about the range at what it is exactly. Maybe this is the key-value.
Cheers,
Raphi
Hey Ang,
I use SNL-C at 6.9-7.2kHz, 500-800mV drive amp resulting in 200-300mV amplitude.
Dmitry Sokolov: Hi Raphi, please contact me for Web meeting:http://confocal-manawatu.pbworks.com/w/page/23665663/Dmitry%20Sokolov Cheers,DmitryMIAWiki for Real-Time Collaboration
Hi Dmitry,
thank you very much for your offer. I will contact you as soon as I have time!
Hi, Raphael
I think all of them are possible variables for engagement problems for Tapping in fluid.
I will summarize my experience
1. Mica substrate lifting: when the mica detach from the metal puck or single layer lifting can cause problem in engagement. Usually the defl go positive and out of range
2. Tuning to the wrong peak. For the cantilever you use, the thermal resonance is about 6 or 7 khz. However I found sometime it requires you to go higher resonance peak to engage. I can’t explain it why it does that.
3. Engagement setting:
- Delta Setpoint = -0.0600 ß--------- change this to -0.02
Stage Engage
SPM engage step: ~ 300 nm (instead the default could be 0.972 um)
Please let us know if the issue is solved.
Dear all, thanks for the support!
After a few emails with James, the problem is more or less solved. If I want to approach the surface in tapping mode without crashing I have to choose a higher frequency. Because I am using an old liquid cell I first have to heavily increase the driving amplitude (~1800mV) to see peaks of about 150mV around 15-17kHz. With a peak in this frequency range approach works quite fine. After engage, I go to frequency sweep mode with an offset of 150nm and change to the 6-8kHz peak with a driving amplitude of about 500-800mV, resulting in an amplitude of about 200-300mV.
Raphael