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My Icon false engages using the default engage set point in QNM mode in air. My sample is a 100-nm-thick layer of Ti e-beam deposited on a silicon wafer, though the false-engage problem seems to be sample independent. If I set the engage set point high enough, I can eventually engage on the surface, but I get nothing but noise and destroy the tip.
My theory is a repulsive force between the tip and the surface due to static-charge buildup. The system is grounded, Ti is conductive, and Si is a semiconductor, so I have no idea why my samples would charge up, but that's the best I can come up with.
Has anyone had a similar experience? Is it static-charge buildup? If so, how do you get rid of it?
System specs: Dimension Icon, Nanoscope V controller.
Hi Fosterrn
Static charge could definitely be an issue, especially in winter when everything is dried out by heating systems. What type of probes are you using? are they conductive? Also, how conductive is the Si? Is it doped? We often use radioactive alpha sources to help eliminate static charge -- they are available from photography stores, but you can find stronger ones online if you look.
This type of problem more commonly results from excessive optical interference. Better alignment of the laser (maximize the sum), or using probes with a better reflective coating may help. Have you tried working with a fresh ScanAsyst-Air probe?
--Bede
Bede,
Thanks for the quick response. I'm actually using ScanAsyst Air probes. And from the couple images I've been able to take of these samples, I don't see the typical optical-interference wave pattern in any of the data channels.
The Si is a typical 4" wafer. It's not doped with anything.
I've ordered a radiation source. Hopefully it works. If not, I'll be back!
Thanks,
-Rami
Be sure to place the alpha source in direct line-of-sight to the probe. I often use a piece of tape to attach it directly to the scan head.
Good luck!