The feature-rich electronic and magnetic properties of fluorine-doped graphene nanoribbons are investigated by the first-principles calculations. They arise from the cooperative or competitive relations among the significant chemical bonds, finite-size quantum confinement and edge structure. There exist C-C, C-F, and F-F bonds with multi-orbital hybridizations. Fluorine adatoms can create p-type metals or concentration- and distribution-dependent semiconductors, depending on whether the π bonding is seriously suppressed by the top-site chemical bonding. Furthermore, five kinds of spin-dependent electronic and magnetic properties cover the non-magnetic and ferromagnetic metals, non-magnetic semiconductors, and anti-ferromagnetic semiconductors with/without spin splitting. The diverse essential properties are clearly revealed in the spatial charge distribution, spin density, and orbital-projected density of states.

The geometric and electronic properties of passivated armchair graphene nanoribbons, enriched by strong chemical bonding between edge-carbons and various adatoms, are investigated by first-principle calculations. Adatom arrangements, bond lengths, charge distributions, and energy dispersions are dramatically changed by edge passivation. Elements with an atomic number of less than 20 are classified into three types depending on the optimal geometric structures: planar and non-planar structures, the latter of which are associated with specific arrangements and stacked configurations of adatoms. Especially, the nitrogen passivated nanoribbon is the most stable one with a heptagon-pentagon structure at the edges. The low-lying band structures are drastically varied, exhibiting non-monotonous energy dispersions and adatom-dominated bands. A relationship between energy gaps and ribbon widths no longer exists, and some adatoms further induce a semiconductor-metal transition. All the main characteristics are directly reflected in the density of states, revealing dip structures, plateaus, symmetric peaks, and square-root divergent asymmetric peaks.

The alkali-adsorbed graphene nanoribbons exhibit the feature-rich electronic and magnetic properties. From the first-principles calculations, there are only few adatom-dominated conduction bands, and the other conduction and valence bands are caused by carbon atoms. A lot of free electrons are revealed in the occupied alkali- and carbon-dependent conduction bands. Energy bands are sensitive to the concentration, distribution and kind of adatom and the edge structure, while the total linear free carrier density only relies on the first one. These mainly arise from a single s − 2p z orbital hybridization in the adatom-carbon bond. Specifically, zigzag systems can present the anti-ferromagnetic ordering across two edges, ferromagnetic ordering along one edge and non-magnetism, being reflected in the edge-localized energy bands with or without spin splitting. The diverse energy dispersions contribute many special peaks in density of states. The critical chemical bonding and the distinct spin configuration could be verified from the experimental measurements.

The electronic properties of graphene oxides enriched by strong chemical bonding are investigated using first-principles calculations. They are very sensitive to the changes in the number of graphene layers, stacking configuration, and distribution of oxygen. The feature-rich electronic structures exhibit destruction or distortion of the Dirac cone, opening of a band gap, anisotropic energy dispersions, O- and (C,O)-dominated energy dispersions, and extra critical points. All of the few-layer graphene oxides are semi-metals except for the semiconducting monolayer ones. For the former, the distorted Dirac-cone structures and the O-dominated energy bands near the Fermi level are revealed simultaneously. The orbital-projected density of states (DOS) has many special structures mainly coming from a composite energy band, the parabolic and partially flat ones. The DOS and spatial charge distributions clearly indicate the critical orbital hybridizations in O-O, C-O and C-C bonds, being responsible for the diversified properties.