Dielectric

[kesh]

Professor, I would like to know, what kind of dielectric was used in the tutorial "Graphene junction device - a nanoscale transistor". Also, is it possible to use a different dielectric of your choice for other FETs? Thank you

[Anders Blom]

The dielectric in this kind of setup is not a particular material, it's just a region in space with a particular dielectric constant. The specific value was chosen to match SiO2, just to pick a number. Thus you can in principle enter any value you prefer to see what the effect of at least the dielectric constant has on the electrostatic control of the system. In other cases it's important to actually simulate the specific dielectric material, in which case it's necessary to include it atom by atom.

[kesh]

Thank you for your reply but in order to simulate the specific dielectric material, how do you include it atom by atom? Thank you.

[Anders Blom]

Just like you would any other material. For instance use the database to pick the material, make a supercell to get sufficient size, and instead of the dielectric region you place the "lump" of atoms you have made there. Take care to match the lattice constant/cell size to keep the dielectric reasonable in directions with periodic boundary conditions.

[kesh]

Thank you.