|Title||Polarization-Controlled Directional Multiphoton Photoemission from Hot Spots on Single Au Nanoshells|
|Publication Type||Journal Article|
|Year of Publication||2018|
|Authors||Pettine, J, Grubisic, A, Nesbitt, DJ|
|Journal||The Journal of Physical Chemistry C|
Directional photoemission from single Au nanoshells is demonstrated in the low-intensity, multiphoton regime. This directionality is shown to be due to the plasmonic excitation of highly photoemissive, nanometer scale surface regions, which are characterized by correlated momentum mapping, scanning electron microscopy (SEM), and laser polarization-dependence studies. Furthermore, the photoelectron flux from a single nanoshell can be systematically rotated by over 90° in momentum space simply by polarization-controlled coupling to different hotspots. Photoelectron distributions are directly characterized in momentum space via velocity map imaging (VMI) of the two-dimensional transverse (px, py) momentum components for singlenanoshells. For the majority of nanoshells studied, the photoemission is directionally orthogonal to the laser polarization, which implicates nanoscale crevice-shaped “hot spots” clearly observed in the correlated SEM/VMI studies, with the near-field plasmonic nature of these crevices clarified further via finite-element simulations. These results rationalize the large photoemissionenhancements observed in previous Au nanoshell studies, but more importantly provide a novel experimental access to directionally tunable electron emission from nanoscale sources. The ability to control photoemission/photocurrent angular distributions at the nanoscale with only modest optical fields indicates a new parameter for optimizing nanoplasmonic system performance and suggests new plasmonic applications such as ultrafast, polarization-controlledphotoelectric/photovoltaic switches.
|Short Title||J. Phys. Chem. C|