Introduction of an Al Seed Layer for Facile Adsorption of MoCl₅ during Atomic Layer Deposition of MoS₂

A low-temperature one-step growth method for few-layer MoS₂ using an atomic layer deposition scheme with MoCl₅ and H₂S precursors is systematically studied by introducing an ultrathin Al seed layer. First, to optimize the deposition conditions, the effects of the deposition (200–420 °C) and MoCl₅ canister (100–160 °C) temperatures on the MoS₂ growth behavior are investigated. On the SiO₂ surface, increasing the deposition temperature reduces the growth rate while favoring more lateral growth. However, an increase in the MoCl₅ sublimating temperature, which is beneficial to improve the film quality, sharply reduces the growth rate, probably owing to the pronounced self-etching effect of MoCl₅. To compensate for the reduced deposition rate while maintaining the MoS₂ quality, an ultrathin Al seed layer (≈5 nm) is introduced, which promotes the surface adsorption of MoCl₅ molecules at an early growth stage according to density functional theory calculations. Thus, a polycrystalline mono-to-bilayer MoS₂ film with negligible amounts of residual contaminants (particularly Cl and Al) is successfully synthesized using the proposed Al seeding approach.