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Hi, we are using a veeco multimode AFM with conductive afm application module to investigate the surface electrical properties of our sample. The signal we got is in picoampere range (appro. 30 - 70 pA) and it shows a very strong correlation between the current image and the deflection image when we ran the test with relatively low feedback gain. The current image is almost identical to the inverted deflection image and the signal disappeared when we ran the test in constant height mode (gains value = 0). Hence, we wonder if this is due the interference between the piezo-scanner feedback system and the C-AFM signal? If this is possible.
Thanks!
Hi Weil,
I am not exactly sure what you are saying. Are you saying that your current image somehow mirrors the topography? If so then this might simply due to higher conductivity there but maybe you can clarify it a bit.
Thanks,
Stefan
Hi,
Thanks for the prompt reply. The image below is a section analysis of the image. As you can see, the current image mirrors the deflection image, but not the height image(although there is certain relationship between the height image and current image as well). However, when I zero the proportional gain and integral gain of the feedback system, the current image shows no apparent signal accept background noise (we believe the cantilever was still touching the surface since the magnitude of the deflection of the cantilever is similar to height image when the feedback gains were optimized.) We are puzzled by the source of the signal and we are not sure if the current signal is actually came from the sample.
Weil
Just to add to the previous post, we observed the same signal even when we did not apply sample bias.