Universal hydrogen-free synthesis and elemental doping of two-dimensional transition metal selenides

Two-dimensional transition metal selenides (TMSs) feature notable bandgap flexibility, versatile doping characteristics, and practical manufacturability, positioning them as promising candidates for next-generation electronics. However, their synthesis remains a critical bottleneck, as conventional chemical vapor deposition (CVD) routes require H2 assistance for selenization, raising safety, cost, and quality concerns and constraining elemental doping. Here we show a universal, H2-free CVD method that overcomes these limitations. Our approach produces a broad spectrum of 2D TMSs, including monolayer binaries, bilayer polytypes, alloys, and heterostructures, and is compatible with diverse substrates. Incorporating common metals (Al, Zn, Fe, Ni, Cu) into the precursor enhances growth kinetics and enables precise doping. Al-doped WSe2 exhibits markedly lower resistance, with centimeter-scale films attaining a hole mobility of 28.36 cm2 V−1 s−1 and an on/off ratio of 3.56×106, comparable to exfoliated and H2-assisted monolayers. This work establishes a safe, scalable, and tunable synthesis strategy for high-performance 2D electronics. 2D transition metal selenides (TMSs) exhibit interesting (opto-)electronic properties, but their bottom-up synthesis usually requires H2 gas, leading to safety concerns and cost implications. Here, the authors report a universal H2-free chemical vapour deposition method to grow large-scale metal-doped 2D TMSs on various substrates.