A spin polarized He metastable beam investigation of the adsorption of l-cysteine on magnetic surfaces

We report first results on the deposition of l-cysteine (Cys), a fundamental amino-acid, on a magnetic substrate. Molecules have been deposited under ultra-high vacuum conditions on Fe(1 0 0) films. Electronic and magnetic properties of adsorbed molecules have been investigated by spin polarized metastable deexcitation spectroscopy (SPMDS). The spectra show a growth dynamics apparently similar to the one already reported on coinage metal surfaces with the formation of a strongly-bound thiolate species (SFe bond) and weakly-bound second-layer molecules. SPMDS revealed the spin-polarized character of an Auger (Penning) deexcitation peak related to a Cys molecular orbital. Interestingly, these spin-polarization effects, ascribed to the interaction with the magnetized substrate, vanish before the first layer completion, suggesting a possible correlation with the SAM assembly properties.