Effect of charge transfer on band alignment in 2D|3D heterostructures: A study of HfS 2 | HfO 2 interfaces (article)

Abstract

HfS 2 | HfO 2 interfaces present a uniquely interesting study in band alignment. The band alignment between materials determines the viability of many electronic devices. We have modeled a variety of two-dimensional|three-dimensional (2D|3D) interfaces HfS 2 | HfO 2 interfaces, showing that the band alignment can change substantially depending on the geometric alignment. Our results have shown that there exists almost no electronic reconstruction when layers of HfS 2 are placed on a HfO 2 substrate. Conversely, when the in-plane connection between HfS 2 and HfO 2 is made (lateral), there is a more significant interface reconstruction present. In the latter case, all examples considered yielded a type I alignment, whereas in the case that layers were parallel to the HfO 2 substrate (stacked) we found that the alignment was either type I or type II with a very small difference between the valance band offsets of the two constituents. We show that the range in the barrier heights between these two systems can vary by up to 2.46 eV. This variation is driven by the amount of charge transfer across the interface and indicate that 2D|3D interfaces have considerably more tunability in their band alignment than 2D|2D or 3D|3D interfaces.