Forums
Bruker Media
Community Media
Bruker AFM Probes
SPM Digest
Application Notes
NanoTheater
Website
中文
Brochures & Datasheets
Publications
Probes Catalog
Events
Manuals & Documentation
Presentations
Guide to AFM Modes
News
Journal Club
Webinars & Video
Nanovations
Other
Hello,
I'm using a dimension 3100 and aimed to analyse chrystal growth on zinc surfaces. My problem is, that the RMS Amplitude is never above 0.6mV. As a result the AFM isn't able to generate pictures of the rough zinc surfaces. I already enabled the z-modulation and tuned it to those parameters given in the manual. This gave a slight increase but unfortunately not enough. I also checked if the probe is fixed firmly and it is. The sum signal is about 4V, which shouldn't be too bad.
So I really don't have a clue, which factor causes my problem. I would be very pleased if somebody could give me solution or a hint, which helps me.
Thank you very much
Marvin
Hi Marvin,
it is not completly clear to me what exactly you are doing. To get a start it would be helpful to know which liquid holder are you using and what kind of tips you aligned? I assume you are using tapping mode. What is the frequency you tune at? I am not sure where you are located but it may be easier to just arrange a tech support call so that we could walk you through it using a remote instrument control session.
Thanks, Stefan
Hi Stefan,
I'm using Micro Cantilever from Olympus with the Name OMCL-AC160TS-W2. They have their resonance frequency between 287.5 and 368.3 kHz. The liquid holder used, is the standard liquid holder made for the dimension 3100. I try to get more information concerning the holder. But my suspicion is, that the cantilever itself may not be appropriate for this application. I do get resonace at about 8.5 kHz in destilled water, but the Amplitude is never stable above 0.5 V. It even often decreases, for some reason, while approaching the surface.
Thanks and Regards
I doubt that you will have any chance of success using those tips in fluids. The levers may be suited well for tapping mode applications in air but not in fluids. They are way too stiff to be excited properly in fluids. I suggest using a much softer cantilever. The DNP/SNL c-type lever (veecoprobes.com) with a spring constant 0.32 N/m and a resonance of 40-7 kHz (air) work just perfectly in fluids. They should work at either <10kHz or <20 kHz in liquid. There is a sample spectrum in the manual. We do have a new direct drive fluid cell for Dimension systems which significantly simplifies the Tapping operation in fluids if you are interested. The other thing you could do is to simply invoke a thermal tune in fluids to find the resonance and that use that value.
Thank you very much for the information. I have to discuss now whether I can get those cantilever or not. Otherwise I try working in contact mode.
Regards
If you send me an email with your address I can have a few samples mailed to you.
Best,
Stefan (skaemmer@veeco.com)
Hello Stefan,
I sent you the address where you can send the cantilever to. As I told, I tried working in contact mode. But for some reason I still have the same problem, that the AFM is unable to recognize the position in which it has contact to the surface. I drove it manually down and supervised the movement. At some point I could see the deflection myself through the camera and had to abort the movement in order to save the cantilever. I assume that the laser isn't properly reflected by the cantilever. The detection system, which recognizes the laser, works without a problem in dry surroundings. If you have an idea what else could cause this problem I would be thankful if you could tell it to me. Meanwhile I clean the cantilever holder for fluid again and change the position of the cantilever and hope this already solves my problem.
Regards,
I contacted our German offfice and asked them to get in touch with you directly. The cantilevers for liquid imaging are also on their way.
Stefan
Some additional input from my colleague Hartmut Stadler:
From first glance, I can see the following causes:
(1) Z modulation does not work. A check would be, just to record a cantilever spectrum on the typical DNP-probe (short, thin) in fluid between 0 and 20kHz (without autotuning) with different drive amplitudes, to see if there are peaks. If not, it can be some hardware problem (controller, cable connection etc.)
(2) Z modulation works, but laser alignment is wrong, and some intensive false reflection is recorded. On a Dimension, the laser spot shifts, when immersing the probe in fluid. Both laser position (move the laser along the cantilever axis) and photodiode adjustment needs to be updated.
(3) Z modulation works, but the tuning was done in a wrong manner (no peak at the chosen frequency). In that case, the solution is easier, he just needs to choose the right frequency.