Electrostatics
Add terminal and ground features to the model to apply boundary conditions for the electrostatics parts of the model.
1
In the Model Builder window, under Component 1 (comp1) click Electrostatics (es) .
2
In the Settings window for Electrostatics, locate the Domain Selection section. From the Selection list, choose Electrostatics.
Charge Conservation in Solids I
In the Model Builder window, Under Component 1 (comp1) > Electrostatics (es) right-click Charge Conservation in Solids 1 and choose Delete.
With the assumption that the silicon membrane is a good conductor, use the Domain Terminal feature to set a bias voltage on the domain.
Note: The Domain Terminal feature will be very handy for a conducting domain with a complex shape and many exterior boundaries – instead of selecting all the boundaries to set up the Ground, Terminal, or Electric Potential boundary condition, we only need to select the domain to specify the Domain Terminal with the same effect. In addition, the computation load is reduced, because the electrostatic degrees of freedom within the Domain Terminal do not need to be solved for.
Terminal 1
1
In the Physics toolbar click Domains  and choose Terminal .
2
Select Domain 4 only.
3
In the Settings window for Terminal, locate the Terminal section. From the Terminal type list, choose Voltage.
The default value of 1 V is fine in this instance.
Ground 1
1
In the Physics toolbar click Boundaries  and choose Ground .
2
Select Boundary 9 only.