Example: Thin film resistance

Thin films Introduction This model shows the approach that can be used in COMSOL Multiphysics in order to model very thin films in diffusion and conductions problems. The example compares a high-fidelity model, where the physical extension of the film is taken into account, with a much less computationally demanding thin-film approximation. The example makes use of COMSOL Multiphysics’ ability to activate and deactivate dependent variables in different subdomains.

Geometry and problem definition for the two cases This films – Problem definition Geometry and problem definition for the two cases High fidelity model This example treats the conduction of a direct current through a metallic conductor. The blue-colored layer is of a much poorer conductor. The thin layer creates a large number of elements and nodes. Analogous problems are found in diffusion and heat conduction models. Approximation

Model Equations Thin film – Problem Definition Main flow of current Implemented in the boundary conditions for both f1 and f2 Main flow of current

Potential distribution, comparison Thin films – Results Potential distribution, comparison High fidelity model Approximation

Potential distribution, cross-section Thin films – Results Potential distribution, cross-section High fidelity model Approximation

Thin films Concluding remarks The results from the high fidelity and the approximation are almost identical. The computational time for the approximation is an order of magnitude smaller than that of th detailed model. The modeling approach has been used for current conduction, diffusion, heat conduction, and porous media flow using Darcy’s law.