Given its intriguing band structure and unique tunable bandgap, AB-stacked bilayer graphene has great potentials in the applications of high-end electronics, optoelectronics and semiconductors. The epitaxial growth of AB-stacked single-crystal bilayer graphene films requires a strict AB-stacked lattice, identical orientations and seamless stitching of bilayer graphene islands. However, the particles inevitably present on the metal surface that produced during high temperature growth would induce random orientations, twisted stacking islands, and uncontrollable multilayers, which is a great challenge to overcome. Here, we propose a heat-resisting-box assisted strategy to produce nearly pure AB-stacked bilayer graphene single-crystal films on Cu/Ni (111) foils. With our technique, the particles on the Cu/Ni (111) surface are effectively eliminated, which greatly minimizes the occurrence of randomly twisted islands and uncontrollable multilayers. The as-grown AB-stacked bilayer graphene films show > 99% alignment and > 99% AB stacking order. Our work provides a promising method towards the growth of pure AB-stacked bilayer graphene single crystals and would accelerate its device applications.

The state-of-the-art semiconductor industry is built on the successful production of silicon ingot with extreme purity as high as 99.999999999%, or the so-called "eleven nines". The coming high-end applications of graphene in electronics and optoelectronics will inevitably need defect-free pure graphene as well. Due to its two-dimensional (2D) characteristics, graphene restricts all the defects on its surface and has the opportunity to eliminate all kinds of defects, i.e., line defects at grain boundaries and point or dot defects in grains, and produce intrinsically pure graphene. In the past decade, epitaxy growth has been adopted to grow graphene by seamlessly stitching of aligned grains and the line defects at grain boundaries were eliminated finally. However, as for the equally common dot and point defects in graphene grain, there are rare ways to detect or reduce them with high throughput and efficiency. Here, we report a methodology to realize the production of ultrapure graphene grown on copper by eliminating both the dot and point defects in graphene grains. The dot defects, proved to be caused by the silica particles shedding from quartz tube during the high-temperature growth, were excluded by a designed heat-resisting box to prevent the deposition of particles on the copper surface. The point defects were optically visualized by a mild-oxidation-assisted method and further reduced by etching-regrowth process to an ultralow level of less than 1/1, 000 μm². Our work points out an avenue for the production of intrinsically pure graphene and thus lays the foundation for the large-scale graphene applications at the integrated-circuit level.