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.

范围广泛的过渡金属二硫族化物 (TMDC) 半导体可作为单层 (ML) 晶体使用，因此将每种类型精确集成到范德华 (vdW) 超晶格 (SL) 中可以实现具有以前未开发功能的新型结构。在这里，我们报告了具有可编程堆叠周期的 vdW SL 的原子逐层外延生长，由两种以上不同的 TMDC ML 组成，例如 MoS ₂、WS ₂和 WSe ₂. 通过金属有机化学气相沉积在近平衡极限下使用动力学控制的 vdW 外延，我们实现了精确的 ML-by-ML 堆叠，没有层间原子混合，从而产生可调谐的二维 vdW 电子系统。例如，通过在相干二维 vdW 异质界面上利用一系列 II 型带排列，我们展示了谷极化载流子激发——vdW ML 半导体中最独特的电子特征之一——它与我们的堆栈数n成比例(MoS ₂ /WS ₂ ) _n光学激发的 SL。