From Self-Assembly Hierarchical h-BN Patterns to Centimeter-Scale Uniform Monolayer h-BN Film

The self-assembly into highly ordered pattern is a universal phenomenon with unprecedented natural properties. However, the nonequilibrium processes in complex systems demand rigorous molecular formation mechanism, which are highly important for fundamental research. Herein, a large-scale formation of highly self-assembly hierarchical hexagonal boron nitride (h-BN) superordered structures on a liquid Cu surface by the chemical vapor deposition (CVD) method is demonstrated. The hierarchical h-BN superordered structure is found to be composed of two vertical stacking parts: one part is underneath h-BN film and the other part is top orientated branched h-BN patterns. In addition, the size, orientation, and morphology of the h-BN superordered structures can be precisely tuned by varying the gas flow rate and growth time. A kinetics-limited growth mechanism is proposed to elucidate the formation process, owing a well consistency with experimental results. Further, by mechanically peeling off the top few-layer h-BN, centimeter-scale uniform monolayer h-BN film is produced, demonstrating a direct and facile top-down fabrication method. This synthesis of highly ordered hierarchical h-BN patterns and following uniform monolayer h-BN film can be applied to other 2D materials, paving way for great potential in the investigation of growth mechanism and construction of homo- and heterostructures.