Transport properties of atomic-size aluminum chains: first principles and nonequilibrium Green's function studies

Abstract

Structures at the atomic scale may display novel phenomena. In particular, transport properties of these systems are important for technological applications. In this work we present aluminum chains transport properties in four different geometries: a linear monoatomic chain, two double-atomic chains with a ladder and zigzag configurations, and double zigzag structures. The atomic structures have been optimized using first principles total energy calculations within the density functional theory. It is found that the monoatomic chain is unstable, and using larger unit cells, the double atomic and the ladder chains transform in to the zigzag structure. However, we have studied the transport properties of all four chains, since normally, these systems are grown on a surface and they may be stabilized by the substrate. The current versus voltage characteristic have been determined using the nonequilibrium Green's function approach. Results show that all four aluminum chains have different current–voltage (I–V_b) behaviour. The ladder structure displays a negative differential resistance (NDR) mechanism and the double zigzag configuration also shows the NDR effect with an abnormal performance due to structural instability. These aluminum atomic scale wires are fully metallic in the ground state with half-filled energy bands crossing the Fermi level.