Ion beam sputtered ultra-thin and nanostructured Ag films for surface plasmon applications

The growth of ultra-thin (10−17 nm) Ag films by ion beam sputtering with controlled morphology suitable for surface plasmon applications is demonstrated. A growth rate of 0.02 nm/s, by employing Ar ion energies as low as 150 eV, is achieved. These conditions result in a surface morphology that consists of oblate particles of size 10-30 nm, depending on the ion energy, with surface roughness of 1-3 nm. The aspect ratio of the grains decreases from 77 to 20 with increase in incident ion energy. The morphology-induced changes are manifested in the shift of the surface plasmon resonance peak from 440 to 480 nm.