Kelvin Probe: ´Potential´signal is alternating.

stsolong posted on Tue, Jul 10 2012 4:23 AM

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Hi Friends,

I found the signal of ´potential´ is alternating while I increases the lift distance or drive phase.

For example, I measured the surface potential difference on the edge of Pt coating and isolator. I set the ´drive amplitude´ 1800mv, ´drive phase´ 105° and lift distance 150 nm. When I changed the lift distance to 200nm (other parameters kept constant), the data center of  ´potential´ shifted from 5V to -5V, and then back to 5V, -5V, 5V...

This happened as well when I only increased the ´drive phase´ 5° upper (other parameters kept constant).

What is the reason for this phenomenon?

Any reply will be appreciated.

Solong