Boundary condition of device configuration with gate

[Bobby]

Hello Sir/Madam,

I would like to simulate a FET device made of graphene sheet (Please see the first picture attached).


Q1: when I repeat my device configuration in A&B direction for 2*2 times to check how it looks like, I found the gate is not repeated like the graphene sheet (Please see the second attached picture).

But in this topic: http://quantumwise.com/forum/index.php?topic=2204.0#.U0CjBfldX54 , Anders said the gate should be repeated too. So what is the problem?

Q2: Since the central region is graphene sheet (not graphene nanoribbon, which means there is no bandgap), I used periodic boundary condition for multi-grid poisson solver in the B direction without any additional vacuum area (please see the third attached picture for the whole boundary condition settings), is it correct? Should I use Neumann boundary condition for both A and B direction in this device configuration with a gate?

Thanks in advance and looking forward to your reply.

Regards

[Bobby]

Could someone please give me some help on this problem? Thanks

[Anders Blom]

It's correct the gates are not repeated if you repeat the structure in the Builder (the old post indicated to repeat in the Viewer, which was supported on older ATK and will be again enabled in ATK 2014). However, in the computation it would be, effectively, due to the periodic boundary conditions.

Neumann is fine.

[Bobby]

Thanks very much, Anders.