Atomic Layer Deposition of Molybdenum Oxides with Tunable Stoichiometry Enables Controllable Doping of MoS₂

A study demonstrates two new low-temperature atomic layer deposition (ALD) processes and use them to deposit molybdenum oxides with controlled molybdenum oxidation states. The optical bandgaps and resistivities increase with increasing oxygen content, following the same trends as crystalline molybdenum oxides. The study dopes MoS₂ by depositing a MoO_x overlayer and tune the threshold voltage shift in thin film transistors (TFTs) from positive (p-type) to negative (n-type) by tuning the oxide composition. Low hysteresis in sweeps of the transistor gate voltage, an absence of strain, and reversibility upon oxide etching together suggest that this process maintains the van der Waals interface without significant chemical changes, and should be applicable as a doping strategy for 2D systems.