▎ 摘　　要

Present methods for producing semiconducting-metallic graphene networks suffer from stringent lithographic demands, process-induced disorder in the graphene, and scalability issues. Here we demonstrate a one-dimensional metallic-semiconducting-metallic junction made entirely from graphene. Our technique takes advantage of the inherent, atomically ordered, substrate-graphene interaction when graphene is grown on SiC, in this case patterned SiC steps, and does not rely on chemical functionalization or finite-size patterning. This scalable bottom-up approach allows us to produce a semiconducting graphene strip whose width is precisely defined to within a few graphene lattice constants, a level of precision beyond modern lithographic limits, and which is robust enough that there is little variation in the electronic band structure across thousands of ribbons. The semiconducting graphene has a topographically defined few-nanometre-wide region with an energy gap greater than 0.5 eV in an otherwise continuous metallic graphene sheet.