Transmission spectra

[yangzw1985]

Hi, everyone! Now, I have two questions to ask.

First,transmission spectra for two probe model, I want to know what is the really meant if there is no of peaks or magnitude of the transmission peaks in bais window.As far as I know, if there is no transmission peaks in bias window, meaning there are no electrons can through the scattering region.I want to know  explainations exactly.

Second,if I have calculated the transmission spectra for my two probe model, Is it possible to calculate the integrated transmission for different bias windows. If it is possible, how to carry it out?

Thanks in advance!

[Nordland]

I am not certain about your first question, but if the transmission is zero in the entire bias windows, then there is no transport of electrons between the electrodes, and hence there are no current etc.

Regarding your second question - there is a function called calculateLinearReponseCurrent, that will calculate the current ( the integrated transmission spectrum ) for a whole set of different bias windows without having to perform the selfconsistent calculation.
It is quite fast for making a quick sweep to create a decent I-V curve.

I hope it helps you.

Best regards,
  Nordland.

[Anders Blom]

One can't help suspecting that the reason the transmission is zero is that the calculation converged to an unphysical state of zero charge. You'd better check the output log.

[yangzw1985]

Hi,Nordland, thanks for your reply.

if there are no electrons can transmitte through the scattering region, are these electrons being reflected or scattered? As far as i know, if the mean free path of electron is larger than the input nanostructures in two probe, there are no elastic scattering occur, the electrons can through the structures directly.  If the Fermi wavelength of the electron in semiconductor is larger than the nanostructures in all size, the scattering effects occur.

I want to know if the mean free path and the fermi wavelength of the electron are both larger than the input semiconductor nanostructures for all size in two probe model, can scattering effects occur when the electrons transmitting the central region?

thanks!

[Nordland]

Dear yangzw.

It is a bit unsafe to take the physics of the system in an unphysical state, hence talking about the mean free path of an electron is without any real sense. However if you want to force physical interpretation onto this, it would be total reflection of all incoming waves.

The mean free path of the electron is in continuum, and hence a junction/interface/device is typical not a continuum, then scattering occurs.

[yangzw1985]

Hi, Nordland! Thanks for your reply.

I am sure my calculation in physical state. Now that the scattering occur duo the interface between the contact and the nanostructures, and In the large contact the electron is carried by infinitely channels. But in ballistic nanostructures ,however, the electron is carried by a limited number of channels, i.e. of parallel transport channels. it requires a redistribution of the electron from the contact into the nanostructures.

As far as i know, with the increase of the contact, the conductance channels increase, and the resistance of the interface should be decrease. I want to know, ballistic nanostructures as input structure in two probe model, if the contact area increase, the scattering effect is increase or decrease? For my calculation, with the same length, with the increase of contact area, the current decrease,I am not sure the relationship between the contact and the scattering.

Thank you!

[zh]

I want to know, ballistic nanostructures as input structure in two probe model, if the contact area increase, the scattering effect is increase or decrease? For my calculation, with the same length, with the increase of contact area, the current decrease,I am not sure the relationship between the contact and the scattering.

The quantum size effect in your called ballistic nanostructures should be taken into account. The fundamental question in your case is which contact exists between your called ballistic nanostructure and electrodes. Is it Ohmic contact, Schottky contact, or others without contact effect? This may be your real question to be thought.

[yangzw1985]

Thank you very much!