Why Would the Vacuum Level Vary?

Go to slide 12 of Lecture 25 : https://nanohub.org/resources/5829/download/2009.03.11-ECE606-L25.pdf (video : https://nanohub.org/resources/5749/about)

Textbooks say that the Fermi level shouldn't vary at equilibrium. Really? There's no intuitive explanation why. And with respect to what?

Then, on this slide, he's showing the Vacuum level varying. How can that be? The vacuum level should be an absolute. According to his diagram, an electron can be taken to the vacuum level on the left, so it's no free and then moved to the vacuum level on the right - for which, truly no energy should be necessary, and yet, it would now have gained kinetic energy. WT*??

Here's what I would do : make it clear in the beginning what the students should leave with, don't put bullet points saying what topics you're going to cover. In the case of Schottky barriers :

1. They are majority carrier devices - and give the intuitive explanation.
2. Remind students that the Fermi level is above the bottom of the conduction band.
3. Why does it need to be MET-n? Why not MET-p? 
4. Tell us how to think about it - why is Al-n one type (ohmic or schottky) and Al-p the other?

Slide 9 is another masterpiece - pulling a rabbit out of a hat. What the h is Nc? We've gotten used to Nd and Na and ni. Why be like this and upset the OCDs?

On the metal side - a sea of electrons. On the N-type - free electrons. When you do p-n, the electrons diffuse over to the P side and you get ionized donors on the N side. So, what happens in the case of Metal-N? Why would you have ionized donors like the the case of the classic pn junction? Explain man!! For the record, Streetman isn't any better. Now you know why Google and Apple rake it in while the Semi companies keep struggling - just poor education, due to which the researchers use trial-and-error methods to advance the state of the art.. Pity.