Molecular charge transfer via π-π interaction: An effective approach to realize the half-metallicity and spin-gapless-semiconductor in zigzag graphene nanoribbon

On the basis of first-principles computations, we have proposed a simple and effective strategy through the molecular charge transfer via noncovalent π-π interaction to tune the electronic and magnetic behaviors of zigzag graphene nanoribbons (zGNRs). This charge transfer is induced by depositing the electron-donating/withdrawing tetrathiafulvalene (TTF) or tetracyanoquinodimethane (TCNQ) molecules on the surface of the pristine zGNRs. When solely adsorbing the electron-donating TTF molecule, all the modified zGNRs systems can be uniformly the antiferromagnetic (AFM) semiconductor with a small band gap, while merely adsorbing the electron-withdrawing TCNQ can endow the combined zGNRs systems with intriguing ferromagnetic (FM) half-metallicity with a large magnetic moment (ca. 4.0 μB), regardless of the adsorption site and ribbon width. Comparatively, when synchronously adsorbing TTF and TCNQ molecules, this cooperative molecular charge transfer can not only make the FM half-metallic but also induce AFM spin gapless semiconducting (SGS) behaviors in the joint TTF-zGNR-TCNQ systems. Moreover, it is revealed that all the TCNQ/TTF-modified zGNRs systems can exhibit considerable adsorption energies, implying their high structural stabilities. These intriguing findings will be advantageous for promoting carbon-based nanomaterials in the application of spintronics and multifunctional nanodevices in the near future.