Nanoporous Ag Films Prepared by Cluster-Source Sputtering as Substrates for Surface-Enhanced Raman Scattering

By mounting a cluster source on a conventional sputtering system, a new sputtering system is devised for the deposition of nanoporous metal thin films at room temperature. First, the diameter of the nozzle is fixed while the pressure inside the cluster source is kept at several hundreds of mTorr. By adjusting the length of the cluster source, nanoporous films of different thickness can be formed at room temperature. The Raman response characteristics according to the process conditions are then analyzed, and the applicability of the sputtered thin film as a substrate for surface-enhanced Raman scattering (SERS) is examined. The results show that the Raman intensity increases with increasing film thickness and reaches a saturated value at a thickness of 2 µm. Therefore, the proposed system takes advantage of an existing sputtering process, and it is possible to form a nanoporous metal film with thickness of several micrometers or more that can be used as a Raman substrate.