Modelling ferroic functional elements

The modelling concepts of a nanoscale organic field effect transistor on a ferroelectric substrate are presented. The device consists of a ferroelectric substrate with a switchable, macroscopic electric polarisation, an electric-field-sensitive organic molecule, and suitable connectors. The structural and electronic properties of the single components and the major interactions between them are modelled by first-priciples electronic structure calculations. For the influence of the electric field on the optical and the conductivity properties of the larger organic molecules, a related density-functional-based tight-binding scheme was employed, which focusses on the salient features of the electronic system. For the self-assembly of the transistor building blocks, mesoscale approaches based on atomistic pair potentials and on a supramolecular Ising-type modelling have been developped and successfully applied.