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The combination of extraordinary strength and stiffness in conjunction with exceptional electronic and thermal properties in lightweight two-dimensional materials has propelled graphene research toward a wide array of applications including flexible electronics and functional structural components. Tailoring graphene's properties toward a selected application requires precise control of the atomic layer growth process, transfer, and postprocessing procedures. To date, the mechanical properties of graphene are largely controlled through postprocess defect engineering techniques. In this work, we demonstrate the role of varied catalytic surface morphologies on the tailorability of subsequent graphene film quality and breaking strength, providing a mechanism to tailor the physical, electrical, and mechanical properties at the growth stage. A new surface planarization methodology that results in over a 99% reduction in Cu surface roughness allows for smoothness parameters beyond that reported to date in literature and clearly demonstrates the role of Cu smoothness toward a decrease in the formation of bilayer graphene defects, altered domain sizes, monolayer graphene sheet resistance values down to 120 Ω/□ and a 78% improvement in breaking strength. The combined electrical and mechanical enhancements achieved through this methodology allows for the direct growth of application quality flexible transparent conductive films with monolayer graphene.

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3D transition metal nitrides are well recognized for their good electrical conductivity, superior mechanical properties and high chemical stability. Recently, 2D transition metal nitrides have been successfully prepared in the form of nanosheets and show potential application in energy storage. However, the synthesis of highly crystalline and well-shaped 2D nitrides layers is still in demand for the investigation of their intrinsic physical properties. Here we report the growth of ultrathin tungsten nitride crystals on SiO 2 /Si substrates by a salt-assisted chemical vapor deposition (CVD) method. High-resolution transmission microscopy verifies the as-grown samples are highly crystalline WN. The stiffness of ultrathin WN is investigated by atomic force microscopy based nanoindentation with the film suspended on circular holes. The 3D Young's modulus of few-layer (4.5 nm thick or more) WN is determined to be 3.9 × 10 2 ± 1.6 × 10 2 GPa, which is comparable with the best experimental reported values in 2D family except graphene and h-BN. The synthesis approach presented in this paper offers possibilities of producing and utilizing other highly crystalline 2D transition-metal nitride crystals.Received: ((will be filled in by the editorial staff))Revised: ((will be filled in by the editorial staff))