Atmospheric pulsed laser deposition and thermal annealing of plasmonic silver nanoparticle films.

A new method for pulsed laser deposition of plasmonic silver nanoparticle (NP) films in flowing gas at atmospheric pressure is described. The ablation was done using an excimer laser at 248 nm. Fast optical imaging shows that the ablation plume is captured by the flowing gas, and is expected to form a NP aerosol, which is carried 5-20 mm to the substrate. The dependence of the deposition rate on laser fluence, gas flow velocity, and target-substrate distance was investigated using electron microscopy and absorption spectroscopy of the deposited films. The NP films were annealed in argon and hydrogen at 400 °C, and in air for temperatures in the range 200 °C-900 °C, leading to strong enhancement, and narrowing of the surface plasmon resonance. The films were used for surface enhanced Raman spectroscopy of a 10-5 molar solution of Rhodamine 6G; films annealed in air at 400 °C were five times more sensitive than the as-deposited films.