What I'm trying to do: I'm using the static current conduction equation to model current in very thin two layer metal/oxide film stack where the metal film is in a special pattern. This is a 3d problem because current enters the film stack normal to the plane and gets carried out by thin metal "highways" laterally. I'd like to accurately account for the electrical loss (joule heating) in the film stack. I'm designing solar cells in academia.
What I've done so far:
I've made a step file model of my film stack and meshed it with gmsh. The thin film stack I'm trying to simulate here is two layers: a 60nm thick layer where the current enters up from below on almost the whole surface, then on top of that, there's a 100nm thick layer of patterned metal, the whole thing is centimeters in the X and Y directions. I drawn the step file model in mm units in x and y, but in the z direction, I thickened the films up by a factor of 10000 to make meshing possible. I load my mesh up into Elmer and set up the boundary conditions (a current injection surface at z=0 & a ground surface on one side are the only ones I need) and the materials and equations. If I run the simulation without correcting for the 1000x too thick z scaling i have in my model, everything seems to work mostly fine with the default solver settings (elmergui 9.0). It converges in like 60 iterations or something, done in a few seconds. Some of the data is a tiny bit splotchy/non-uniform, but for the most part, the results show me that the physics is correct (the bad z-scaling ruins the analysis): I got this result with
Code: Select all
Coordinate Scaling(3) = 1e-3 1e-3 1e-3
The problem is when I set
Code: Select all
Coordinate Scaling(3) = 1e-3 1e-3 1e-7
I've tried playing with the solver settings for a pretty long time, but nothing I do seems to help (there's a lot there, so maybe I've missed the right combo). If anyone can offer any tips on how to get this system to behave, I'm all ears.
Thanks in advance for any help anyone can offer!
Cheers,
¬grey