First principles investigation of electronic structure, magnetic properties and spin polarized conductance of self assembled molecular monolayers (SAMs) on Ni(111) substrate

摘要

Using first principles gradient corrected density functional theory and supercell approach we have investigated electronic structures, magnetic properties, and density of states for self assembled CH_3S monolayer on a magnetic Ni(11) substrate. Three fold hollow sites are found to be energetically more favorable sites for CH_3S adsorption with a binding energy of 2.6 eV and C-S axis making an angle 32~0 normal to the surface plane, which is consistent with the results obtained from angle resolved X-ray measurements. The magnetic moment of adsorbed substrate is reduced to 0.68 mu_B compared to 0.71 MU_B found for the free surface. In order to determine an optimum separation between a scanning tunneling microscope tip and SAM surface for tunneling measurement, we have also performed electron tunneling distance dependent calculations at zero bias for C_2HS monolayers on Ni(111) surface. The optimum electron tunneling distance between the tip and SAMs surface is found to be percent 3 A.