Transmission coefficients

Asked by samantha poulsen on 2018-06-20

I tried to reproduce Transmission coefficients of GeTe sandwiched between metallic electrodes. despite previously mentioned in the literature that this material has a 0.7 eV band gap the Transmission coefficients that I have calculated is not zero near the Fermi energy(band gap). can anyone guide me about the potential reason for this error? I should mention that I used proper mesh cut off, k-points, PAO basis and also relaxed the scattering region and interfaces.

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Nick Papior
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Nick Papior (nickpapior) said : #1

1) "close to zero" may be as good as "not zero". :)

2) The length of the GeTe junction is probably very important.

3) Are you sure the metallic region is big enough to have a potential profile that is smooth and converges to the bulk potential?

Dear Nick,
1- :)
2-Thank you so much. You are right the length of junction is very important. The length of centre region(GeTe) in my device is 50 A which for this length my device should definitely show band gap.
3- I used 4layer of TiN as electrode (electrode length= 8 A)and two layer of TiN was added to the centre region as electrode extension(about 4A). I doubled the electrode extension but I didn't observed any significant difference in transmission coefficient.
I guess that the problem is in my Pseudopotential(I get it from this paper: if you agree with me please guide me how can I find out that this Pseudopotential is accurate enough for my calculation.
I should mention that the Pseudopotential for Te in siesta website show ghost state for l=1 so I couldn't used it.

Best Nick Papior (nickpapior) said : #3

2) Ok.
3) You could probably try with a bit more TiN layers, it isn't alot of layers. As for the PP, I am no expert in the generation of the PP. So you will have to ask in a separate question if you have more specific details regarding this.

Thanks Nick Papior, that solved my question.