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 regarding setting Z height between two geometries		  New Topic  Reply to Topic
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thasnimolus@gmail.com

3 Posts
Posted - Jan 02 2024 :  06:51:14  Show Profile  Reply with Quote
Hi I want to set distance between a tip apex (sphere made by spheregen command) to a disc. When I give the distance between them, it is measuring from the center of sphere to the disc. This is giving me wrong values. Is there any way I can set the Z height w.rt. surface (apex) of the sphere.
The code is as follows.
C tipradius50nm.txt 1.0 5.0e-9 5.0e-9 52.253e-9

C discnewaroundfive.f 1.0 0.0e-9 0.0e-9 1.5e-9.

Now, the Z = 52.253-1.5, what I actually want the distance to be say, sphere, just 1nm above disc. How do I eliminate the contribution from radius of the sphere?

Enrico

545 Posts
Posted - Jan 03 2024 :  00:20:57  Show Profile  Reply with Quote
If you are using FasterCap, you may use a hierarchical file structure: in the first you reference your sphere and offset it by the radius, and then you reference the second file and offset it only by the distance you need.

However in general I find it simpler just to consider the radius plus the distance and offset the sphere by that value; but of course it depends on what you are trying to achieve (if this is part of a more complex structure, it may be difficult to keep track of all the offsets).

Hope this helps,
Best,
Enrico
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thasnimolus@gmail.com

3 Posts
Posted - Jan 10 2024 :  18:42:57  Show Profile  Reply with Quote
Hi Enrico,

Thanks for your quick reply. I could not follow the method of offsetting. Can you please tell me how can I do that?

The device geometry I am making is Scanning probe tip-defect, so the distance is very sensitive. When I offset with radius+distance, my results are very different. I need the Z<1nm between tip and defect. Even if I make a sphere (tip) with radius=1nm, for a distance 0.5nm from tip apex to the defect, i need to set Z= 1+0.5nm, which is causing error. Please let me know any suggestions to try out
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Enrico

545 Posts
Posted - Jan 15 2024 :  19:15:05  Show Profile  Reply with Quote
Let's use the 'sphere2.txt' example in the 'Samples' folder. This is a unit radius sphere centered at the origin. Then we'll use also the 'plate.txt' in the same folder to define a reference.

Let's define the 'sphere2_offset.txt' file as:

* offset conductive sphere
*

C sphere2.txt   1.0  0.0 0.0 2.0


This actually shifts the sphere of two units in the Z direction.

Then using the new file as e.g. in a file 'spheres_over_plane.lst' defined as:

* Spheres over plate
*

C sphere2_offset.txt   1.0  2.0 2.0 0.0
C sphere2_offset.txt   1.0  2.0 -2.0 0.0
C sphere2_offset.txt   1.0  -2.0 2.0 0.0
C sphere2_offset.txt   1.0  -2.0 -2.0 0.0
C plate.txt 1.0 0.0 0.0 0.0


You are actually positioning four spheres that will hover on top of the plate instead of having the plate intersect them.

You may visualize the output by flagging the -o option when running FasterCap and then loading up the resulting 'spheres_over_plane_ref.lst' file in FastModel.

Best,
Enrico
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