IV-Voltage Drop

[kh]

Hello,

I do have a question regarding voltage drops and atomic configurations. Basically it is an SiO2 type structure with n doped leads. I calculated the voltage drop and see what is depicted in the attachment. The calculation is done with densitymatrix and equivalent bulk initial density. I am a little bit confused, because the voltage drop is ok for the left lead and the dielectric. But at the right lead I see a huge drop which should not be there because of metallic like leads due to high doping.
The structure is like:
n-Si|n-Si|SiO2|n-Si|n-Si
Does somebody have an explanation to this and maybe a solution? Do I have to use larger screening layers or electrodes?

Regards,
K.

[Nordland]

If you could give me a little more information I might have some ideas on what to try.

On the X-axis of your plot what is the unit? It is the grid index? or it is the coordinate?

Also what are the length for your electrodes?

[kh]

It is coordinate in Bohr. y-axis in Rydberg.
The electrode length is about 5.5Angstrom.

[Nordland]

Have you tried with the opposite sign of the voltage? Making the voltage drop going in the other direction?
The result is similar?

[nori]

Your voltage drop seems alright at least computationally.
(I don't know this result is right physically though...)

I guess the current flow is from left to right(electron flow is from right to left) and the value of current is quite small.
Is this right?
In ATK, non-equilibrium density matrix is included in finite bias calculation, which may be important to understand your voltage drop.
At left electrode, there is almost no transmitted electron because of high resistance of SiO2, so that the electronic structure doesn't change
from equilibrium one.
On the other hand, at right electrode, the electronic structure could be dramatically changed from equilibrium one because there are incident electron and reflected electron.

If you want to obtain a voltage drop more smoothly connected to reservoir at right electrode, it may be good prescription to increase surface layers of right electrode.

[kh]

The opposite sign of voltage has the nearly same effect.

Current flow is from left to right and very small. Tunnelingspectrum shows me minima around fermi energy of ~10^-15 which is somehow correct compared to experimental results.

I will try to use more surface layers.