Spontaneous and self-oriented growth during chemical vapor epitaxy of single-crystalline MoS2

Conventional chemical vapor epitaxy concepts for single-crystalline molybdenum disulfide (MoS ₂ ) rely on sapphire template engineering to impart a preferred crystalline orientation. However, such epitaxy concepts may fall short to curb within-wafer statistical variance of the MoS ₂ crystal orientation when manufacturing sapphire substrates to semiconductor industry-standard specifications and wafer size. Here, we report metal-organic chemical vapor epitaxy of single-crystalline MoS ₂ without sapphire template engineering. By lowering the metal-organic precursor adsorption rate in the mass-transport-limited reaction regime, the MoS ₂ nucleation and growth rate slows down sufficiently for spontaneous and self-oriented MoS ₂ growth to proceed. During this self-oriented growth, the bulk sapphire crystallographic symmetry governs the MoS ₂ epitaxial registry, rather than the surface structure and termination of the sapphire steps and terraces. Even though 60°-oriented MoS ₂ twin crystals deposit, a single-crystalline MoS ₂ monolayer forms by annihilating the mirror twin grain boundaries through spontaneous van der Waals recrystallization during and after the coalescence of the MoS ₂ monolayer. We show a proof of concept in a 300 mm industrial pilot-line, yielding median carrier mobilities up to 30 ± 5 cm ² V ^–1 s ^–1 . Crucially, self-oriented growth alleviates the stringent requirements to pertain to a critically low and saturated areal density of MoS ₂ crystals, to develop unidirectional crystal orientation during the initial growth regime, or to minimize sapphire surface anomalies from substrate manufacturing. Hence, van der Waals recrystallization presents a vital mechanism during chemical vapor epitaxy to further modulate crystal defect structures in various transition metal dichalcogenides and substrates compatible with both bonding-to-wafer and monolithic integration approaches.