Modulation on electronic doping of graphene nanoribbons using alkali and oxygen atoms adsorption.

Adopting the first-principles calculation method based on density functional theory, we investigate the electronic and optical properties of alkali atoms (Li, Na and K) and oxygen (O) atoms adsorption of doped graphene nanoribbons. We further inspected the differential charge density, energy band structure, partial state density, electron energy loss spectrum, as well as the valence electron state of impurity atoms. The results revealed the significant effect of Li, Na and K atoms on the graphene nanoribbons, presenting n-type direct band gap degenerate semiconductors with the band gap values of 0.438, 0.529 and 0.494 eV, respectively. An increase in the adsorption of O in turn changed the materials into p-type direct band gap degenerate semiconductors with the band gap values of 0.573, 1.011 and 0.967 eV, respectively. Partial charge density demonstrated a charge migration between the atoms, resulting in a certain change in the electronic properties of the materials. Additionally, the hybridization and local effects of the adsorbed atoms and C atoms resulted in the promotion of the electronic properties near the Fermi level to be significantly modulated. [ABSTRACT FROM AUTHOR]