Spin -Resolved Self-Doping Tunes the Intrinsic Half- Metallicity of AlN Nanoribbons

1. CNMS Staff Science Highlight Spin-Resolved Self-Doping Tunes the Intrinsic Half-Metallicityof AlNNanoribbons Scientific Achievement Demonstrated how and why the half-metallic property of aluminum nitride (AlN) nanoribbonscan undergo a transition to fully-metallic or semiconducting behavior with application of an electric field or uniaxial strain. Significance and Impact The band structure tunability of AlN indicates the possibility of rationally designing magnetic nanoribbons with “on-demand” electronic structure. An external transverse electric field induces a full charge screening that renders the material semiconducting, while an uniaxial strain varying from compressive to tensile causes the spin-resolved, selective self-doping to increase the half-metallic character of the ribbons. Research Details Top, the real space distribution of the net-spin density corresponding to the electronic states of an AlNnanoribbon ([AlN]6(2)). The red and green isosurfaces correspond to net spin-↑ and spin-↓ electron densities respectively. Bottom, the spin-resolved band structure, within a narrow energy window around the Fermi level for different types/amount of strain. • First principles computation of molecular orientation, bonding, and spin-resolved electronic structure • Improved computational capability to study the non-equilibrium electronic structure of complex materials • Approach enables opportunities for designing new materials exhibiting tunable electronic properties. write Work was performed at the CNMS – ORNL. A. Lopez-Bezanilla, P. Ganesh, P. R. C Kent, B. G. Sumpter, Nano Res. DOI 10.1007/s12274-013-0371-1

2. Tuning Electronic Properties On Demand Scientific Achievement We demonstrated that aluminum nitride (AlN) nanoribbons have a rich variety of “on demand” tunable electronic properties due to a spin-resolved self-doping. Significance and Impact Materials exhibiting metallic behavior for electron spins with one orientation and insulating for the spins with the opposite orientation are critical for modern applications of spintronics. The results of this study provide a “materials recipe” for designing systems for exhibiting these properties by deriving edge states from elements with sufficiently different localization properties. Research Details This work enabled the development of an improved computational capability and understanding of the electronic structure of complex layered materials. The approach provides enhanced opportunities for designing new materials exhibiting tunable electronic properties, e.g., multifunctional materials by design. Left, the real space distribution of the net-spin density corresponding to the electronic states of an AlNnanoribbon ([AlN]6(2)). The red and green isosurfaces correspond to net spin-↑ and spin-↓ electron densities respectively. Right, electronic band structure for the configuration. The spin orientations for Al- and -N edge atom are given by arrows at the bottom of the band structure. Work was performed at the CNMS – ORNL. A. Lopez-Bezanilla, P. Ganesh, P. R. C Kent, B. G. Sumpter, Nano Res. DOI 10.1007/s12274-013-0371-1