Graphene has initiated intensive research efforts on 2D crystalline materials due to its extraordinary set of properties and the resulting host of possible applications. Here the authors report on the controllable large-scale synthesis of C N, a 2D crystalline, hole-free extension of graphene, its structural characterization, and some of its unique properties. C N is fabricated by polymerization of 2,3-diaminophenazine. It consists of a 2D honeycomb lattice with a homogeneous distribution of nitrogen atoms, where both N and C atoms show a D -symmetry. C N is a semiconductor with an indirect bandgap of 0.39 eV that can be tuned to cover the entire visible range by fabrication of quantum dots with different diameters. Back-gated field-effect transistors made of single-layer C N display an on-off current ratio reaching 5.5 × 10 . Surprisingly, C N exhibits a ferromagnetic order at low temperatures (<96 K) when doped with hydrogen. This new member of the graphene family opens the door for both fundamental basic research and possible future applications.

We demonstrate a graphene-based electro-absorption modulator achieving extraordinary control of terahertz reflectance. By concentrating the electric field intensity in an active layer of graphene, an extraordinary modulation depth of 64% is achieved while simultaneously exhibiting low insertion loss (∼2 dB), which is remarkable since the active region of the device is atomically thin. This modulator performance, among the best reported to date, indicates the enormous potential of graphene for terahertz reconfigurable optoelectronic devices.