Towards intrinsically pure graphene grown on copper

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 μm^(2).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.