Two-dimensional (2D) materials, such as graphene, transition metal dichalcogenides (TMDs), and hBN, exhibit intriguing properties that are sensitive to their atomic-scale structures and can be further enriched through van der Waals (vdW) integration. However, the precise synthesis and clean integration of 2D materials remain challenging. Here, using graphene or hBN as a vdW capping layer, we create a nano-confined environment that directs the growth kinetics of 2D TMDs (e.g., NbSe2 and MoS2), enabling precise formation of TMD monolayers with tailored morphologies, from isolated monolayer domains to large-scale continuous films and intrinsically-patterned rings. Moreover, Janus S-Mo-Se monolayers are synthesized with atomic precision via vdW-protected bottom-plane chalcogen substitution. Importantly, our approach simultaneously produces ultraclean vdW interfaces. This in situ encapsulation reliably preserves air-sensitive materials, as evidenced by the enhanced superconductivity of nano-confined NbSe2 monolayers. Altogether, our study establishes a versatile platform for the controlled synthesis and integration of 2D TMDs for advanced applications.
@article{arxiv.2512.15518,
title = {Atomically-precise synthesis and simultaneous integration of 2D transition metal dichalcogenides enabled by nano-confinement},
author = {Ce Bian and Yifan Zhao and Roger Guzman and Hongtao Liu and Hao Hu and Qi Qi and Ke Zhu and Hao Wang and Kang Wu and Hui Guo and Wanzhen He and Zhaoqing Wang and Peng Peng and Zhiping Xu and Wu Zhou and Feng Ding and Haitao Yang and Hong-Jun Gao},
journal= {arXiv preprint arXiv:2512.15518},
year = {2026}
}