Chemical doping tunes the half-metallic properties of A1N nanoribbons
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Chemical doping tunes the half-metallic properties of AlN nanoribbons Alejandro Lopez-Bezanilla1 1 Materials Science Division, Argonne National Laboratory, 9700 South Cass Avenue, Lemont, Illinois, United States ABSTRACT Spin-polarized first-principles calculations have been conducted to study the electronic structures and magnetic properties of O and S functionalized zigzag aluminium nitride (AlN) nanoribbons. Chemical functionalization with O atoms at the edges strengthens the half-metallic properties of the AlN by adding new electronic states at the Fermi level for one spin-channel and widening the gap of the other. On the contrary, edge-termination with S atoms renders the AlN ribbon a semiconductor. Peierls instabilities towards the dimerization and trimerization of the doping atoms were observed.
INTRODUCTION Numerous experiments with graphene have stimulated a revolution in materials science related with mono-layered materials. One-atom-thick materials such as BN, silicene, and graphene [1] have gained a great interest as potential cheap replacements for the current oxide electrodes used in organic solar cells, and also for the silicon-based transistors currently implemented in electronic devices. In a previous study [2] we reported that extended onedimensional monolayered AlN ribbons exhibit half-metalicity when their edges are arranged in a zigzagged geometry. A half-metallic material is required to realize spin polarized currents, where one of the material’s spin channels exhibits metallic behavior while the other owns an electronic band gap, displaying an insulating behavior [3]. We showed that the half-metallic property of AlN ribbons can undergo a transition into semiconducting behavior upon application of an external electric field, which induces a full charge screening and opens a band gap shifting the energy states to higher and lower energies. In contrast, a uniaxial strain varying from compressive to tensile induces a spin-resolved self-doping process that increases the halfmetallic character of the ribbons. AlN ribbons could be synthesized by unfolding AlN nanotubes, similarly to BN nanotubes[4]. However, due to the high reactivity of the sigma-electrons at the bare AlN ribbon edges it is expected that foreign atoms will passivate the dangling bonds in the etching process. Therefore edge-terminated AlN nanoribbons must be considered and the possibility of an alteration of their electronic properties expected. In this article the half-metallic and semiconducting properties of chemically modified AlN ribbons with O and S atoms are described by means of density functional theory based calculations. Edge termination with these atoms modifies the density of states at the Fermi level of pristine AlN zigzag ribbons in a selected manner. Whereas O atoms are predicted to increase the number of states in the vicinity of the Fermi level for one spin-channel, for the other spin channel the number of states at the same energy range is observed to decrease. On the contrary, S
atoms remove the half-filled ele
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