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We were getting nice height, current images and IV curves with SCM PIC tips on polymer semiconductors. We changed from PIT tips to conform to material hardness.
But suddenly the same tips stopped working on the very same samples. We consulted with your support group people and even ordered RMN tips. The problem now is the PIC tips do not yield current ( at low or high sensitivity), whereas the height image in PIT and RMN probes ( even with the lowest spring constants ) at the lowest possible setpoint is not acceptable.
We do not have PF TUNA mode to ensure that force is optimized during the CAFM scans. Would appreciate any help in resolving this matter. Thanks. Mithun
Mithun,
The softest RMN (solid metal wire) probes is 0.3N/m which is not much more than the PIC probes whcih are rated 0.2N/m. I am surprised that you see such a big difference. I assume you did try minimizing the setpoint after engaging?
If your PIC probes worked and then stopped working you may have either i) removed the conductive coating or ii) a problem in your conductive path. Did you check the probes afterward by plaing e.g. an SMD resistor in between probe and sample chuck to see if they still work? The somewhat fragile nature of the coating may be what prompted Tech Support to suggest using solid metal probes (RMN) which do not exhibit that behaviour.
If you do not have TR mode or PFT available you may have to live with a compromise and that is to get the best Height imaging using a regular tapping mode tip and the conductivity image using the RMN tip.
Stefan
Stefan,
I did lower the setpoint after engaging, till almost the point where it would withdraw from the surface. We ordered a box of the softest RMN tips you mentioned but they turned out to be very bad investment as both the height and current images are nto comparabel to any of the original Bruker tips - PIC or PIT. The same sample when imaged with these tips result in wavy , unstable images with intermittent scan lines. Do you have any suggestions, any settings that need ot be changed for these special tips? What about their positioning in the holder and the laser alignment?
I did check voltage on puck, continuity between cantilever holder and the wire. I did not understand " Did you check the probes afterward by plaing e.g. an SMD resistor in between probe and sample chuck to see if they still work?" Would appreciate if you were to have a SOP for this .
Regards
Mithun
I do not have SOP for this. My suggestion when a measurement like yours suddenly does not work as expected is to test the whole 'loop" If you mount e.g. a resisitor on the sample puck and you touch the other end with your tip you should be able to measure the current flow as determined by the resistor selected.
I am not sure why your images using the RMN are different and what the difference is. Have you contacted tech support and discussed the results with them?
Thanks. I will try that out. It had not been used that much to wear out the coating though, I would think. But certainly that is probable.
One of my colleague had sent out a mail with the images (screen shots of settings, images and force curves) attached to AFMSupport@bruker-nano.com .. but has not heard back. Is there anyone specific we should send it to?