# DEVICE: Two contacts are adjacent, modeling several materials in metal contact

#1

I wanted to simulate a stack of metals contacts with Ti/TiN/AlCu/TiN and am wondering what is the proper way to do this?
I did:
Attempt 1:
I made 4 rectangles for cathode and anode( named them cathode0, cathod1, etc), and added contacts in the boundary conditions for the top cathode and anode. This resulted in error saying that some conductors did not have contacts defined. so then I did:

Attempt 2:
grouped the rectangles into a Structure Group, so 1 structure group for cathode side and one for anode side, then set the contacts to apply to the cathode/anode structure groups instead of just the top cathode/anode. This gave error: “Two contacts are adjacent”. The cathode(or anode) stack defines the layers as zmin0=0 to zmax0=thickness1; then the next rectangle structure is zmin1= thickness1, zmax1=thickness1+thickness2, so one starts at the coordinate where the other ends.

Is this the wrong way/ how do I address the “two contacts are adjacent” issue?

#2

Hi. DEVICE is designed to calculate carrier transport in semiconductors. It uses a complex model for semiconductor materials to achieve this. However, contacts (metals) are always treated as perfect electrical conductors (PEC) in DEVICE. Even if you stack multiple metals in one structure group, the whole stack is going to behave like a single block of perfect conductor.

he reason you are getting this error is because you have the two contacts touching each other. This is not allowed because then at the boundary of the two contacts, the solver will have two different voltage boundary conditions which is not possible.

Can you tell me what sort of behavior you are trying to model here?

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