From the equations derived from the background section, a groove in the surface will have the following evolution:

 

 

 

 

However, if the groove depth is deep enough, as the surface diffuses, a void will form inside the material, as show in the figures below:

 

 

 

 

 

We based the distance that the nodes of the sides of the groove must come within each other to form a void on the bonding length of Si, which is 233pm.