Vapor-solid interfacial reaction and polymerization for wafer-scale uniform and ultrathin two-dimensional organic films

Chemical vapor deposition is a conventional synthesis method for growing large-scale and high-quality two-dimensional materials, such as graphene, hexagonal boron nitride, and transition-metal dichalcogenides. For organic films, solution-based methods, such as inkjet printing, spin coating, and drop and micro-contact printing, are commonly used. Herein, we demonstrate a general method for growing wafer-scale continuous, uniform, and ultrathin (2-5 nm) organic films. This method is based on a copper (Cu) surface-mediated reaction and polymerization of several equivalent bromine (Br)-containing pi-conjugated small molecules (C12S3Br6, C24H4O2Br2, and C24H12Br2N4), in which local surface-mediated polymerization and internal pi-pi interactions among organic molecules are responsible for the dimension and uniformity control of the thin films. Specifically, the growth rate and morphology of thin films were found to be Cu-facet-dependent, and single-crystal Cu(111) surfaces could improve the uniformity of thin films. In addition, the number of Br groups and size of organic molecules were critical for crystallinity and thin-film formation. This method can be used to fabricate heterostructures, such as organic film/graphene, giving room for various functional materials and device applications.