From Theoretical Understanding on the Growth Mechanisms to the Synthesis of Wafer-scale Single Crystalline 2D Materials

In compare with the 3D materials, graphene and most 2D materials owns the unique properties of the ultra-high flexibility and weak interaction with a substrate, which distinguish its growth mechanism from those of the homoepitaxial growth of 3D crystals and heteroepitaxial growth of thin films. The weak van der Waals interaction between graphene and a substrate allows a single crystalline graphene island to across a grain boundary (GB) of the substrate without changing its single crystallinity. Based on this theoretical prediction, we propose that wafer scale graphene single crystal could be synthesized on a polycrystalline substrate via nucleation suppression. [1] Such a strategy was realized by the method of feedstock local feeding during graphene CVD growth. [2]The preferential alignment of nucleated graphene islands on a transition metal surface allows us to grow single crystalline graphene on a symmetry matching substrate and, therefore, wafer scale graphene single crystal growth might be achieved on a large single crystalline substrate.[1,3,4] Experimentally, large area single crystalline Cu (111) foils was synthesized for the growth of wafer scale graphene single crystal.[5,6] Besides the (111) surfaces of fcc crystals, our theoretical analysis predicts that unidirectional growth of hexagonal boron nitride or other 2D materials could be realized on a high-index single crystalline metal foil.[7]References:[1] X Zhang, et al, (2012), The Journal of Physical Chemistry Letters 3, 2822-2827[2] T Wu, et al, (2016), Nature materials 15, 43[3] J Gao, et al, (2011), Journal of the American Chemical Society 133, 5009-5015[4] Q Yuan, et al, (2014), The journal of physical chemistry letters, 5, 3093-3099[5] S Jin, et al,(2018), Science 362, 1021-1025[6] X Xu, et al, (2017), Science Bulletin 62, 1074-1080[7] L Wang, et al, (2019) Nature 570, 91-95