Modeling the silicon-hafnia interface

We report first-principles calculations of the structure and electronic properties of several different silicon-hafnia interfaces. The structures have been obtained by growing HfO _x layers of different stoichiometry on Si(1 0 0) and by repeated annealing of the system using molecular dynamics. The interfaces are characterised via their electronic and geometric properties. Moreover, electronic transport through the interfaces has been calculated using finite-element-based Green's function methods. We find that oxygen always diffuses towards the interface to form a silicon dioxide layer. This results in the formation of dangling Hf bonds in the oxide, saturated by either Hf diffusion or formation of Hf-Si bonds. The generally poor performance of the interfaces suggests that it is important to stabilise the system with respect to oxygen lattice diffusion.