This work reports the self-limiting synthesis of an atomically thin, two dimensional transition metal dichalcogenides (2D TMDCs) in the form of MoS 2. The layer controllability and large area uniformity essential for electronic and optical device applications is achieved through atomic layer deposition in what is named self-limiting layer synthesis (SLS); a process in which the number of layers is determined by temperature rather than process cycles due to the chemically inactive nature of 2D MoS 2. Through spectroscopic and microscopic investigation it is demonstrated that SLS is capable of producing MoS 2 with a wafer-scale (∼10 cm) layer-number uniformity of more than 90%, which when used as the active layer in a top-gated field-effect transistor, produces an on/off ratio as high as 10 8. This process is also shown to be applicable to WSe 2, with a PN diode fabricated from a MoS 2 /WSe 2 heterostructure exhibiting gate-tunable rectifying characteristics.
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