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No current image in CAFM using SCM PIC

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Mithun Bhattacharya posted on Fri, May 11 2012 11:00 AM

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

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replied on Mon, May 14 2012 4:41 PM

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

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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

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replied on Tue, May 15 2012 12:38 PM

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?

Stefan

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Stefan,

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?

Mithun

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