MOCVD-Grown MoS₂ Wafers as a Transfer-Free Platform for Top-Gate Devices via Dry Interface Engineering

We uncover the electronic origin of hidden interfacial doping in monolayer MoS₂ single-crystal wafers grown on sapphire by metal-organic chemical vapor deposition (MOCVD) and establish a transfer-free top-gate device platform. Despite structural perfection, as-fabricated devices exhibit degenerate electron doping and lack a clear off state. Hall measurements quantify an interfacial electron density of 2.7 × 10¹² cm^-2, evidencing substantial charge transfer across the nominal van der Waals interface. Interface-sensitive spectroscopy, lateral force microscopy, and thermal desorption analysis reveal a buried sulfate-derived layer accompanied by a water-like interfacial structure that acts as an intrinsic electron donor. A purely dry H₂/Ar annealing process selectively removes these species, suppressing charge transfer and restoring intrinsic FET characteristics without transfer or wet processing. Through this dry interface engineering approach, we demonstrate MOCVD-grown single-crystal MoS₂ wafers as a robust, transfer-free platform for the reliable evaluation of intrinsic gate stacks and device performance.