A New Era of 2D Semiconductors: From Lab to Fab
The pursuit of atomically thin semiconductors has long promised a new era in nanoelectronics. Among them, two-dimensional (2D) transition metal dichalcogenides (TMDCs), such as MoS2 and WSe2, have emerged as leading candidates for sub-1 nm transistor channels due to their ability to mitigate short-channel effects, positioning them as promising contenders for sustaining Moore's Law. However, industrial-scale application of these 2D semiconductors remains limited by a fundamental bottleneck: the scalable growth of high-quality single-crystal TMDC wafers. Conventional chemical vapor deposition (CVD) methods typically produce polycrystalline films containing mirror-twin domains and grain boundaries, which induce non-uniform carrier scattering and severely degrade electronic performance. Consequently, achieving precise control over grain boundaries and realizing wafer-scale single-crystalline 2D films is essential for the development of next-generation integrated circuits and high-performance electronic devices. Very recently, Wang and his collaborators reported a universal and robust epitaxial strategy that realizes wafer-scale growth of single-crystal TMDCs, specifically MoS2, WS2, MoSe2, and WSe2 semiconductors, on 150-mm wafers for the first time. This remarkable achievement bridges the long-standing gap between laboratory-scale synthesis and semiconductor foundry compatibility, marking a historic milestone in the evolution of 2D semiconductors 'from lab to fab'. The core innovation lies in atomic-scale interface engineering. Conventional c-plane sapphire (α-Al2O3) substrates possess a near-central-inversion symmetric surface, leading to two energetically degenerate, antiparallel orientations of TMDC domains. This symmetry inevitably causes twin boundaries. Wang's team overcame this symmetry constraint by introducing a monolayer of lanthanum (La) to passivate the sapphire surface. The La atoms induce surface reconstruction, reducing the symmetry from P3 to P1, and amplify the energy difference between antiparallel domains by nearly two orders of magnitude, thereby enabling unidirectional epitaxial alignment and the elimination of grain boundaries across the entire 150-mm wafer. Using this strategy, Wang's group successfully achieved 150-mm single-crystal wafers of MoS2, WS2, MoSe2, and WSe2 semiconductors grown by both thermal CVD and metal-organic CVD (MOCVD) methods. Wafer-scale second-harmonic generation (SHG), Raman, and photoluminescence (PL) mappings confirmed the excellent uniformity and quality of the films.