Ultrasmooth Gold Films via Pulsed Laser Deposition

A simple, one step technique for depositing ultrasmooth gold films using pulsed laser deposition is demonstrated by optimizing process para meters. The smoothest film having a root-mean-square roughness of 0.17 nm (including the substrate roughness of 0.11 nm) for a 35 nm thick film on a silicon substrate are obtained by introducing a nitrogen flow in the chamber during deposition. We postulate that the reduction in surface roughness caused by nitrogen gas pressure in the chamber is due to the force of the gas flow acting against the flow of the plasma plume containing Au atoms. The gas acts as a filter that reduces the kinetic energy of the gold adatoms. This is the best result reported so far for a single step deposition of gold. It is a step towards low-loss planar gold films for surface plasmon applications.