CVD graphene-MoS2 Van der Waals heterostructures on the millimeter-scale

This study investigates the interactions between chemical vapor-deposited graphene and metal-organic chemical vapor-deposited molybdenum disulfide (MoS₂) in heterostructures assembled via wet transfer. We use Raman spectroscopy to quantitatively determine close coupling between graphene and MoS₂ based on the peak separations in graphene. Although annealing seems to be necessary after transfer to establish a close coupling, its parameters do not have a significant impact on the quality of coupling (for 100 °C < T < 400 °C and 5 min < t < 120 min). Furthermore, the method is robust against variations in graphene thickness because bilayers can be distinguished by comparing the full width at half maximum of the graphene 2D peak. We expand our study to mm²-scale areas of graphene-MoS₂ heterostructures finding that films assembled via wet-transfer technique exhibit considerable variability in terms of coupling strength. Evaluating such interactions in heterostructures on large areas is important for future practical applications in heterostructure devices.