A new technique for direct-write ablation at the 100nm scale was used, together with photon scanning tunnelling microscopy, to study surface plasmon scattering by individual surface defects whose sizes and shapes were varied. It was found that, within a certain range of sizes, a hill on an otherwise flat surface could be the source of a micron-wide plasmon beam. It was noted that the effective cross-section of a defect could be appreciably larger than its apparent geometrical size.

I.I.Smolyaninov, D.L.Mazzoni, C.C.Davis: Physical Review Letters, 1996, 77[18], 3877-80