Sub-10 nm Graphene Nanoribbon Arrays are fabricated over large areas by etching CVD-grown graphene. A mask is used made by the directed self-assembly of a cylindrical PS-b-PDMS block copolymer under solvent annealing guided by a removable template. The optimized solvent annealing process, surface-modified removable polymeric templates, and high Flory-Huggins interaction parameters of the block copolymer enable a highly aligned array of nanoribbons with low line edge roughness to be formed. This leads to a higher on/off ratio and stronger temperature dependence of the current for nanoribbon FETs, and a photocurrent which is 30 times larger compared to unpatterned graphene.