Kelvin probe setup for measuring work function difference. In this case the two materials have a voltage bias (Fermi level difference) applied such that the vacuum electric field is zeroed.
<a href="//commons.wikimedia.org/wiki/User:Nanite" title="User:Nanite">Nanite</a>
2013-06-17 21:30:46
<span class="int-own-work" lang="en">Own work</span>