Paper NS-ThM9
Self-Assembled Double Strand DNA Monolayers as Spin Filters

Thursday, November 3, 2011, 10:40 am, Room 203

Spin control provides new and interesting opportunities for control and study of the factors governing electron transport. Recent work by Naaman and co-workers has shown that self-assembled monolayers of double stranded DNA (ds-DNA) can act as a spin filter for electrons photoemitted from a gold substrate.[1,2] This phenomenon depends on the helicity of the ds-DNA, which leads to spin polarization and consequent capture of filtered electrons that tunnel back to the substrate. In this work, this effect is investigated for electron flow between two electrodes, a bottom Ni electrode to which one strand of the DNA is bound, and a top gold nanoparticle electrode which serves to identify the ds-DNA and provide good electrical contact through binding to the complementary strand. The current characteristics are measured by conductive scanning probe microscopy, as applied in a previous study of electron transport in DNA monolayers.[3] A magnetic field of approximately 0.3 T at the surface is provided by a permanent magnet placed below the sample. The results are consistent with the photoemission work, namely marked differences in the current flow depending on magnetic field alignment. Furthermore, the effect depends on length of DNA chain, with longer chains providing a more significant effect relative to shorter ones.These experimental findings, together with a physical model will be presented.

[1] Goehler, et al, Science 331, p. 894 (2011).

[2] Ray, et al, Phys. Rev. Lett., 96, 03101 (2006).

[3] Nogues et al, J. Phys. Chem. B 110, 8910 (2006).