Fig. 1.

Inverse charge funnelling in strained HfS₂. a Schematic diagram of the proposed device (see Fig. 4 for the actual implementation). Compressive strain is induced in the centre of a semiconducting HfS₂ channel by controlled photo-oxidation. The compression induces tensile strain away from the HfS₂/HfO₂ interface, resulting in the spatial modulation of the bandgap. b Ab initio calculations of the valence band maximum (VBM) and conduction band minimum (CBm) of 1T-HfS₂ as a function of strain in the Γ → Γ (direct gap) and Γ → M (indirect gap) directions. c Change in bandgap as a function of strain in the two directions, with respect to the unstrained bandgap (relaxed lattice constant a₀ = 3.625 Å). Inset: calculated band structure of 1T-HfS₂