Abstract
A broad range of transition metal dichalcogenide (TMDC) semiconductors are available as monolayer (ML) crystals, so the precise integration of each kind into van der Waals (vdW) superlattices (SLs) could enable the realization of novel structures with previously unexplored functionalities. Here we report the atomic layer-by-layer epitaxial growth of vdW SLs with programmable stacking periodicities, composed of more than two kinds of dissimilar TMDC MLs, such as MoS2, WS2 and WSe2. Using kinetics-controlled vdW epitaxy in the near-equilibrium limit by metal-organic chemical vapour depositions, we achieved precise ML-by-ML stacking, free of interlayer atomic mixing, which resulted in tunable two-dimensional vdW electronic systems. As an example, by exploiting the series of type II band alignments at coherent two-dimensional vdW heterointerfaces, we demonstrated valley-polarized carrier excitations-one of the most distinctive electronic features in vdW ML semiconductors-which scale with the stack numbers n in our (MoS2/WS2)n SLs on optical excitations.
Highlights
Semiconductor superlattices (SLs), periodically layered structures of two alternating semiconductors in the atomic thickness regime, have served as the material platform of various heterojunction devices in modern electronics, photonics and display technology[1,2]
We report atomic layer-by-layer epitaxial growth of van der Waals semiconductor superlattices (SLs) with programmable stacking periodicities, composed of more than two kinds of dissimilar transition-metal dichalcogenide monolayers (MLs), such as MoS2, WS2 and WSe2
We identified coherent atomic stacking orders at the van der Waals (vdW) heterointerfaces, and present scaling valley polarized optical excitations that only pertain to a series of 2D type II band alignments
Summary
Semiconductor superlattices (SLs), periodically layered structures of two alternating semiconductors in the atomic thickness regime, have served as the material platform of various heterojunction devices in modern electronics, photonics and display technology[1,2]. We report atomic layer-by-layer epitaxial growth of van der Waals (vdW) semiconductor superlattices (SLs) with programmable stacking periodicities, composed of more than two kinds of dissimilar transition-metal dichalcogenide monolayers (MLs), such as MoS2, WS2 and WSe2.
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