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Electric Field / Potential distribution

Posted 10.05.2013, 20:31 GMT-4 Low-Frequency Electromagnetics Version 4.3a 3 Replies

Aidar Kemelbay
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Dear all,

I am trying to simulate a structure which consists of different material layers. I would like to see Electric field and Electric Potential distributions of a certain potential applied to the boundaries of substrate (poly-Si). My multilayer structure includes two different metall layers. When I press compute, Comsol asks me to enter Relative Permittivity values for these metals, which is actually incorrect. I set them to 0.01 but also set all boundaries of metal layers to 0V potential. Is this approach is correct?

After computing Electric Potentials (image is attached), instead of V I type sqrt(es.Ex*es.Ex+es.Ey*es.Ey+es.Ez*es.Ez) in Expression field to get Electric Field distribution, however I am getting an error (image is attached), which says "Failed to evaluate variable ... Domain 1, 10". Material of Domain 1 and 10 is Air.
Does anyone can explain what am I doing wrong?
Thanks in advance.

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3 Replies Last Post 13.05.2013, 05:04 GMT-4
Aidar Kemelbay
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Posted: 1 decade ago 11.05.2013, 08:57 GMT-4
Update: Space geometry I am using is - 2D axisymmetric.
When I am drawing the same geometry but in 2D (without symmetry) I do not have an error described above and COMSOL plots Electric field without problems.

Any ideas?
Update: Space geometry I am using is - 2D axisymmetric. When I am drawing the same geometry but in 2D (without symmetry) I do not have an error described above and COMSOL plots Electric field without problems. Any ideas?
Edgar J. Kaiser Certified Consultant
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Posted: 1 decade ago 11.05.2013, 11:26 GMT-4

In axial symmetry the spatial components are r, phi and z.

Cheers
Edgar

--
Edgar J. Kaiser
www.emphys.com
In axial symmetry the spatial components are r, phi and z. Cheers Edgar -- Edgar J. Kaiser http://www.emphys.com
Sven Friedel COMSOL Employee

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Posted: 1 decade ago 13.05.2013, 05:04 GMT-4
Hi Aidar,

That metals have no permittivity is a inappropriate generalization, it depends on the time-scale you are looking at.

We highly recommend to exclude metal domains in electrostatic computations (es) in the first place.
The charge relaxation time in metals is typically so short that the complete domain is at
homogeneous potential for all the time. Set fixed of floating potentials instead on the boundaries.

Positive side effects:
- reduced number of DOFs (faster, smaller)
- reduced condition number of the system matrix (more stable)

Have a look at the electrostatic tutorials in the model library where this is done by convention.

Best regards,
Sven
Hi Aidar, That metals have no permittivity is a inappropriate generalization, it depends on the time-scale you are looking at. We highly recommend to exclude metal domains in electrostatic computations (es) in the first place. The charge relaxation time in metals is typically so short that the complete domain is at homogeneous potential for all the time. Set fixed of floating potentials instead on the boundaries. Positive side effects: - reduced number of DOFs (faster, smaller) - reduced condition number of the system matrix (more stable) Have a look at the electrostatic tutorials in the model library where this is done by convention. Best regards, Sven

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