Spin-dependent electron transport along a molecular wire in a metal (probe)-vacuum-molecule-metal system: the effect of the size and the shape of the probe tip

We present the results of a first-principles quantum mechanical study of spin-dependent electron transport along a molecular wire investigating the effects of the size and the shape of the probe tip on the tunneling current. A periodic, gradient-corrected density functional method together with Bardeen, Tersoff and Hamann formalism is employed in this study. The electron tunneling through a self-assembled monolayer of benzene 1,4-dithiol on the Ni(111) substrate is found to be strongly dependent on both shape and size of the probe tip.