Spatial Regions: Inclusion of an Oxide Layer

[Dipankar Saha]

Sir
If I have to see the effect of changing the Oxide layer in case of any device.... then simply changing it, using the "spatial regions" interface, will do the job(reflecting the effect of the alternation in the transmission)?? / or, I need to make an interfacing between the oxide and the transport layer material....?? 

[Nordland]

I think it all comes down your system.

If you are modelling some device that is deposited on top of a oxygen layers, and you want to model effect of having a gate voltage - then I would use a spatial region. However
if you are interested in modelling the effect of the interaction between the device and layers, then I would add the oxygen-layers.

[Dipankar Saha]

I got your point ......Thanks ....
______________________
Now one more thing I wanted to ask.....that is _________

for an unit cell...we provide spacing...in X,Y Z direction..../now suppose in X-direction it is the thickness..../ when we add a spatial region, we generally don't enter into that unit cell box.... Say. a .5 nm around gap is being maintained in between the material layer and spatial region layer(oxide)... Will it make the material layer suspended???...What if I lift the spatial region up(X-direction) into the unit cell such that it just touches below the material layer........ 

[kstokbro]

The spatial region needs to be inside your unit cell, only the part of the spatial region which is inside will have an effect.

The distance from the spatial region to the device, should model the real atomic-scale distances. Forinstance, for a siO2 dielectric we use the dielectric constant of 3.8 and place the edge of the dielectric 1Å from the center of the outermost atoms in the device.

This 1 Å is used since,
a) The typical device-SiO2 distance is ~2 Å
b) the image  surface plane of the dielectric, (corresponding to the edge of the dielectric region) is typically 1Å away from the SiO2 atom positions.

[Dipankar Saha]

Thank you kstokbro.... / This is exactly what I wanted to know....

[Dipankar Saha]

Sir, in Transmission Analyzer, under the general properties...I find the value of current and voltage values, where the voltage is actually the electrode voltage that I set explicitly....but, how the value of the current has been found? Is it on the basis of simple Ohm's law...i.e. I=GV ? Then what will be the case, if I provide no voltage gradient at the electrodes, but keep the two contacts at diff. temp. values....??

[Dipankar Saha]

Dr. Blom

Sir, in transmission spectrum analyzer...where should I set the energy value pointer...so that the eigen value and the corresponding eigen states...may lead to a complete visualization of the of the entire transmission scenario of the system.....??

[Anders Blom]

The complete picture is made up of pieces. For each energy, and for that energy for each k-point, you can visualize the transmission eigenvalues and the corresponding eigenstates, but extracting information from these quantities requires that you know what you are looking for. It's very hard to give general instructions for this, as it depends on the system, and indeed what particular phenomena you are trying to explain.

[Dipankar Saha]

Dr. A. Blom

Sir, for the sake of a better understanding, say I want to see the how a perturbation hampers the overall transmission in case of any electrical transport (from one port to the other)........ then, where should I set the energy value pointer...??  Should I set it to the point...for which I'm getting the max. transmission??