2D materials hold great promise for a variety of electronic devices including transistors, photovoltaics and light-emitting diodes, particularly since heterostructures can be formed by simply stacking layers of different 2DMs. The properties, and hence functionalities, of such devices depend on the electronic structure at the interface between layers, which is intrinsically difficult to measure directly. In work recently published in Science Advances, Neil Wilson et al, in collaboration with researchers at the University of Washington, uses spatially-resolved Angle Resolved Photoemission Spectroscopy (micro-ARPES) with carefully-designed samples to probe the electronic structure of stacks of MoSe₂, WSe₂ and graphene, in monolayer, bilayer, heterobilayer and bulk forms. This allows key electronic structure parameters to be extracted, such as the effective mass, spin-orbit coupling, and band widths, as well as band alignments relative to graphene, and in particular, the interaction effects in semiconductor heterobilayers. Nicholas Hine and Gabriel Constantinescu were then able to compare these experimental results to large-scale density functional theory simulations of model heterostructures, enabled by the ONETEP LS-DFT code. This enabled interpretation of the results in terms of intermixed commensurate-incommensurate regions of the aligned MoSe₂/WSe₂ interface.

N. R. Wilson, P.V. Nguyen, K. Seyler, P. Rivera, A. J. Marsden, Zachary P. L. Laker, Gabriel C. Constantinescu,V. Kandyba, A. Barinov, N. D. M. Hine, X. Xu, D. H. Cobden, "Determination of band offsets, hybridization and exciton binding in 2D semiconductor heterostructures", Science Advances 3, e1601832

DOI: 10.1126/sciadv.1601832