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Standard Sample with built in Work Function Difference

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Daveostrowski posted on Wed, Jun 1 2011 10:27 AM

I'm working on KFM and measuring a known bias across interdigitated electrodes to test my measurement, but I'm interested also in a sample with built in work function differences. Does the SCMsample from Bruker work for this, and/or does anyone know of a different sample available with this criteria?

Again, key is to have patterned work function differences that can be resolved with KFM within a typical image size of ~ 30-70 microns?


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You can see surface potential variation arising from the different doping levels on the SCM sample (SRAM), but it is not an ideal sample to check/calibrate KPFM. The problem with semiconductor samples in general is that some surface states can inevitably appear in the bandgap which can mask the fermi-energy level of the semiconductor and dictate the KPFM result. For instance, in theory, you should observe nearly 1V difference between highly doped n-Si and highly doped p-Si, but usu. you can only see a difference of 200mv~300mV at maximum.

We do not have a patterned sample with materials of different work functions, except the EFM sample with Cr stripes on Si. If you could, you can deposit 100nm Aluminum on a Si wafer, then pattern with 10um wide stripes of Au (100nm thick) on top, so you end up having alternative Au and Al stripes, with a work function difference in the vicinity of 0.8V. You can also run KPFM separately on Au and Al (al foil for example) to see the difference.




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