Why does Hafnium or Zirconium result in high k dielectrics?

[Suspicious-Teach8788]

I understand the fundamentals of why we need high-k, and even from a EE perspective too. I know that we want a wide band gap, high-k, and material that has a decent band offset with the Si wafer.

But anything specific about hafnium that gives it its high-k properties? I know that hafnium and zirconium are in the same column on the periodic table. Perhaps there's something on the molecular orbital level? Like similar to why certain elements are paramagnetic, etc?

 

[TecHNooB]

I don't know the answer, but if I were attempting to look for one, I'd start by thinking about how atoms that are not conductors polarize. Then I'd try to figure out the relation between number of protons/electrons and how easy it is to polarize various configurations with the same electric field.

my 2 cents.

 

[Suspicious-Teach8788]

That's freaking it. I took a final for some class 2 days ago and it seems I've already washed my knowledge away with alcohol. Thank you for mentioning polarization.

There's the electronic polarization where an electric field will push the electrons from the nucleus. Larger atoms like Hf or Zr will be more easily polarized. However, most materials will experience this like SiO2.

What separates Hf and Zr from SiO2 is the fact that Hf and Zr are metals, and their oxides would be more polar than an SiO2 molecule. The result is that there's also an ionic factor of polarization where the bonds are stretched and the molecule is oriented so the positively charged ion is pushed one way and the negatively charged ion is pushed the other way.

This is a big I *THINK* but I think this might be just what I was looking for.