Chemical vapor deposition (CVD) can produce wafer-scale transition-metal dichalcogenide (TMD) monolayers for the integration of electronic and optoelectronic devices. Nonetheless, the material quality of the CVD-grown TMDs still remains controversial. Here, we compare the quality of representative WSe2 monolayers grown by CVD compared to that obtained by other synthesis methods: bulk-grown-chemical vapor transport (CVT) and flux. Through the use of a deep-learning–based algorithm to analyze atomic-resolution scanning transmission electron microscopy images, we confirm that Se vacancies (VSe) are the primary defects in WSe2, with a defect density of ∼5.3 × 1013 cm−2 in the CVD-grown sample, within the same order of magnitude of other methods (∼3.9 × 1013 cm−2 from CVT-grown samples and ∼2.7 × 1013 cm−2 from flux-grown samples). The carrier concentration in field-effect transistors at room temperature is ∼5.84 × 1012 cm−2 from a CVD-grown sample, comparable to other methods (6–7 × 1012 cm−2). The field-effect mobility of the CVD-grown sample is slightly lower than that of other synthesis methods, together with similar trends in on-current. While the difference in photoluminescence intensity is not appreciable at room temperature, different intensities of defect-related localized states appear below 60 K. We conclude that the wafer-scale CVD-grown samples can be utilized without loss of generality in the integration of electronic/optoelectronic devices.

Combining the synthetic tunability of molecular compounds with the optical selection rules of transition metal dichalcogenides (TMDCs) that derive from spin-valley coupling could provide interesting opportunities for the readout of quantum information. However, little is known about the electronic and spin interactions at such interfaces and the influence on spin-valley relaxation. In this work, vanadyl phthalocyanine (VOPc) molecular layers are thermally evaporated on WSe2 to explore the effect of molecular layer thickness on excited-state spin-valley polarization. The thinnest molecular layer supports an interfacial state which destroys the spin-valley polarization almost instantaneously, whereas a thicker molecular layer results in longer-lived spin-valley polarization than the WSe2 monolayer alone. The mechanism appears to involve a tightly bound species at the molecule/TMDC interface that strengthens exchange interactions and is largely avoided in thicker VOPc layers that isolate electrons from WSe2 holes.