Large potential steps are observed at the interfaces between metals and novel 2D materials. They can lower the work function by more than 1 eV, even when the two parts are only weakly interacting. In this thesis the transfer and redistribution of electrons in metal|2D material heterostructures are studied by means of first principles methods and analyzed by phenomenological models. The first part of the thesis covers the charge transfer at metal-organic interfaces. A model based on an integer electron transfer is used to accurately describe the experimentally observed pinning levels. In the second part of the thesis the doping level of graphene in a metal|thininsulating-film|graphene heterostructure under an external electric field is studied. Special attention is paid to the incommensurable interface structure of hexagonal boron-nitride (h-BN) and graphene. It is shown that a small band gap is opened in graphene when the angle between the two lattices is small. Larger angles lead to electron-hole puddles. Lastly, the physical processes responsible for the large potential steps at weakly interacting metal|insulator interfaces are studied. The metal|h-BN interface is used as an archetypal interface. It is shown that Pauli exchangerepulsion is the most important effect to explain the large potential steps, but it is not the only one.
|Award date||15 Nov 2013|
|Place of Publication||Enschede|
|Publication status||Published - 15 Nov 2013|