This tutorial will discuss basics of creating a meshed sample, including generating a mesh. We aim to make generating a mesh as pain-free as possible, but as of now, SimuSEM can not automatically adjust the sample to deal with meshing conflicts.
For our first meshed sample, we will create a sample of silicon dioxide lines on a silicon substrate:
1. Start with a new meshed project. My project name is sio2_lines
2. Add an SiO2 Trapezoidal Line
3. Next add an SiO2 Cylinder. Note that the cylinder is rotated 90 degrees, so the height of the original unrotated cylinder is the same as the line length. The dimensions refer to the original unrotated shape for cylinders, cones and spheres.
4. Now your sample should look like this:
5. We would like to align the cylinder on top of the trapezoidal line. To do that, select the line, and choose Cursor To Top on the left side of the 3D View/
If we want to align a whole cylinder with the 3D cursor that is now centered on the top of the line, we can just choose "center" and check x,y and z and then click on OK to create a curved top to the line. In my picture, I did not choose the radius of the circle correctly to get a smooth transition from line to curved top, so I changed the x-dimension to 27nm to get a smooth profile with an elliptical top.
7. Note that we have a cylinder overlapping another the line. In general, it is important to define how the shapes overlap so that the simulation will know apply the correct material model in the overlapping region. In this case since the two shapes are the same material, so for a non meshed sample overlapping shapes of the same material is usually acceptable. For a meshed sample, the mesh generation sometimes has trouble with overlapping shapes or shapes with a shared boundary. In this case, the cylinder on top could be defined as a union (if the material of the shape are the same) with the line or a Difference Filled Hole.
In this case, it turns out that a union of the cylinder with the line will mesh correctly.
So, to change the cylinder, press the Get Props button, make the cylinder a Union with the Trapezoidal Line.
Then press Modify Cylinder at the bottom of the panel.
8. Finally. press Generate Mesh. If the mesh generation is successful, the bottom of the panel will say "Mesh File Saved" and indicate the number of volumes and elements in the mesh. The number of volumes is greater than the number of shapes because the number of volumes includes a meshed vacuum region around the sample and often shapes are split into 2 or more volumes during the meshing process. We recommend keeping the number of elements under around 2 million to keep the simulation time manageable.
If the mesh generation is not successful, either the number of volumes and elements will be zero or the panel will give a list of shapes that gave problems during the meshing process.
If problems occur with the union of the cylinder and the line, we could use a half cylinder instead.
Coming soon: tutorials about 1. using a half cylinder on top of the line and creating multiple lines using Array and 2. dealing with error messages from gmsh, the mesh generation program.
9. Now that a mesh has been generated, I like to check it. If you have installed gmsh, press View in GMSH below Generate Mesh.
When gmsh opens, you will see the top of the vacuum mesh boundary around the sample:
Rotate the sample by pressing the left mouse button while moving the mouse pointer. Pan the view by pressing the right mouse button while moving the mouse pointer.
Look at individual shapes using Tools -- Visibility. Then you can check out individual shapes by highlighting the shapes in the Visibility window and press Apply.
