Invited talk
Modeling vertical and lateral electron transport across heterostructures
Department of Physics, Applied Physics, and Astronomy Rensselaer Polytechnic Institute, Troy, NY 12180, USA
This talk will concentrate on recent developments for the understanding of charge transport across heterostructures between nanostructured materials, including one-dimensional and two-dimensional systems.
In the first part of my talk, I will focus on electron transport taking place along heterosctructures characterized by covalent bonding [1]. I will show how controlled doping on one side of the junction can lead to device properties that are well suited for photovoltaics and photocatalysis properties.
In the second part of my talk, I will present our recent work on the role of collective motion in the ultrafast charge transfer in van der Waals heterostructures (Figure 1). [2] Using time-dependent density functional theory molecular dynamics, we find that the collective motion of excitons at the interface lead to plasma oscillations associated with optical excitation. Application to the MoS2/WS2 heterostructure yields good agreement with experiment, indicating near complete charge transfer within a timescale of 100 fs.
Finally, I will briefly present recent theoretical developments for the understanding of electronic band gap renormalization induced by substrate polarization effects, taking adsorbate size into account.
Figure 1: Atomic and electronic structures of MoS2/WS2 heterostructures. a) Illustration of the heterostructure, where a WS2 monolayer lies on top of a MoS2 monolayer. Electron and hole carriers excited by incident light separate by hole transfer onto the WS2. b) Band structure of the heterostructure, showing an indirect bandgap from Γ to K. c) Band structure in the vicinity of K-point in the Brillouin zone.
[1] J. Cai et al., Nat. Nanot. 9, 896 (2014); A. Lherbier et al., Carbon 95, 833 (2015); L. Liang and V. Meunier, J. Phys. Chem. C 119, 775 (2015).
[2] L. Liang and V. Meunier, Nanoscale 6, 5394 (2014); S. Huang et al., Nano letters 14, 5500 (2015) H. Wang et al., Nat. Comm., in press (2016).
[3] N. Kharche and V. Meunier, unpublished (2016).