How to calculate band gap energy of semiconductor electrodes in two probe system

[Jin-Kyu Choi]

Dear all,

I'm studying charge transport properties of a single molecule in a junction with various kinds of electrodes (not only metallic).

I want to draw the schematic energy diagram for a molecular junction with semiconducting electrodes, for example, as shown in the Figure.

By the MPSH calculation in the ATK package, I can determine the molecular orbital energies but, I can not draw the simple band diagram for the semiconducting electrode (band gap).

In ATK package, is it possible to calculate band gap (conduction band minimum - valence band maximum) of the electrode in the molecular junction?? Not bulk case. For a simple bulk case, I can find the tutorial in the QW website.

Please give me any comments.

Thank you very much.

[Anders Blom]

The band structure of the electrode is not different from bulk - it is by definition exactly like in the simple bulk case.

[Jin-Kyu Choi]

So... there is no changes in the band structure of the electrode due to interaction with the centered molecule?
The interaction between the electrode and the molecule (self-energy) is just affecting on the molecule? not electrode?

And, there is no way to directly extract the information about electronic structure of the electrode in the molecular junction?
(I have already performed the calculations on the transmission spectrum and current-voltage)

[Anders Blom]

Not exactly. The molecule also affects the layers of metal (or whatever the electrode is made of) that are inside the central region. But outside the central region, the system (i.e. the electrodes) is assumed to be bulk-like and repeated bulk-like to infinite on either side. The central region is however never repeated in Z.