Does anybody know the most reliable way to measure the bandgap and band edge level of dielectric films? My sample is ~10 nm thick SiO2, SiNx, Al2O3, HfO2 film on highly doped n-type Si wafer (100).
Dear Jeongse:
The thickness of your films is too small to use Uv-vis Spectroscopy.
Can I ask you: what deposition methods did you use to grow the films ... ?
Probably you are gonna need to use XPS and UPS... (X Ray and UV Photoelectron Espectroscopy),
Combining these two techniques you can build up the Bands Diagram of your junction(s) (i.e. the Work Function, Electron Afinity, Valance and Conduction Bands Edges and the Electrical and Optical Bandgaps).
Although I don't know how to do it, nor the specific technique/methodology for obtaining these characterizations, but I'm sure you can find plenty of articles presenting these studies for dielectric, semiconductor, metal, etc thin films...
Try to use the search words: 'measuring the optical bandgap with ultraviolet photoelectron spectroscopy, UPS' or 'Measuring the Work Function of thin films with UPS, XPS' ...
I'm sure you will be able to find the information
Regards ! :)
The most accurate technique to measure this, is UPS (Ultra violet photoelectron spectroscopy), but you need to have a very clean surface to do this kind of measurement without interferences.
To Franklin
SiO2 by dry oxidation at 900 C, SiNx by LPCVD
Al2O3 and HfO2 by ALD
Dear Jeongse:
Trying to elaborate a little bit more on your question, although I have never done these measurements ..
I know that is possible to determine the Ionization Energy of your material with UPS, since UPS interacts with the Valence Levels Shells of the atom.
Therefore, the definition of I.E. : "Is the Energy needed to rip one Electron from the Valence Shell of an atom" ... ore more formaly: "Is the Energy needed to bring one Electron from the Valence Shell of an Atom to the Vacuum Level".
So, since UPS is a technique which involves photons knocking off Valence's Shell Electrons, if you have someone who knows well how to perform this technique, it shoud n't be difficult to detirmine the I.E. of your material.
Then, you would have to determine the Electron Afinity as well , I would think you can do it with UPS to, or by combining both techniques (UPS and XPS), but I don't know how.
Once you have determined both, just compute: Eg = E.A. - I.E. , and thats it.
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