Tunnel resistane between dissimilar electrodes

[ali.awarke]

Hi,

I would like to evaluate roughly the tunneling resistance (Ohm.cm2) between an Al-aC (amorphous carbon)junction separated by a thin layer of PVDF polymer. I use the model developed by Simmons (Journal of Applied Physics, vol 34. N9, p 2581), and assume that aC is a metal (since the band gap was found to go to zero with increasing aC cluster sizes).
the model needs as parameters the barrier heights (offset between the Fermi Levels and the lower end of the conduction gap of the PVDF insulator, see fig.) at each of the Al-PVDF aC-PVDF interfaces.
Since I am not an expert on this field, I am asking if the following way to get the barrier heights is roughly valid.

from [Europhys. Lett., 61 (1), pp. 81–87 (2003)] it was found that the PVDF gap is 6eV. Assume the Fermi level of pvdf is in the middle of the gap, so that when the fermi level at the first contact are aligned, the first barrier height would be 3eV. the second barrier height is offset from 3eV by 0.82ev which is the work potential difference of Al (4.28eV) and aC(5.1eV) (see fig).

if the above looks weird to an expert, how can one obtain the barrier heights? any known parameters relevant to my system (Al, PVDF, aC)?

your help and comments are very much appreciated

 

[eljose79]

Hello,

The approach you have described for obtaining the barrier heights in your system seems reasonable. However, there are a few factors that you may want to consider in order to get a more accurate estimate of the tunneling resistance.

Firstly, the band gap of PVDF can vary depending on its crystallinity and processing conditions. Therefore, it would be best to find the specific band gap value for the PVDF polymer that you are using in your experiment.

Secondly, the Fermi level of PVDF may not necessarily be in the middle of the band gap. It is possible that the Fermi level is closer to the conduction band edge, which would affect the barrier height calculations.

Thirdly, the work function difference between Al and aC may also vary depending on the surface conditions and the specific polymorph of aC. It would be helpful to determine the exact work function values for your materials in order to get a more accurate estimation of the barrier heights.

Additionally, it is important to consider the influence of defects and impurities at the interfaces on the barrier heights. These can significantly affect the tunneling resistance and should be taken into account in your calculations.

In terms of known parameters relevant to your system, you can also consider the dielectric constant of the PVDF polymer and the thickness of the polymer layer. These parameters can also have an impact on the tunneling resistance.

I hope this helps and please feel free to reach out with any further questions or clarifications. Good luck with your experiment!