Periodic array-based substrates for surface-enhanced infrared spectroscopy

At the beginning of the 1980s first reports of surface enhanced infrared spectroscopy (SEIRS) surfaced. Probably due to enhancement factors of only 101 to 103, which are modest compared to those of surface enhanced Raman spectroscopy (SERS), SEIRS did not reach the same significance up to date. However, taking the sensitivities of the underlying methods and enhancement factors together, SEIRS reaches about the same sensitivity as SERS and, due to the complementary nature of both techniques, can valuably augment information gained by SERS. For the first 20 years since its discovery, SEIRS relied completely on metal-island films, fabricated by either vapor- or electrochemical deposition. The resulting films showed a strong variance concerning their structure, which was essentially random. This strongly restricted reproducibility and hindered theoretical modelling of their plasmonic properties, a prerequisite for improving performance. Hence, only comparably marginal progress had been made concerning the further development of the substrates. In recent years, however, the development of periodic array based substrates helped SEIRS to gather momentum. This development is fueled by technological progress concerning electromagnetic field solvers, which help to understand plasmonic properties and allow targeted design. In addition, the strong progress concerning modern fabrication methods allowed to implement these designs into practice. The aim of this contribution is to critically review the development of these engineered surfaces for SEIRS, and compare the different approaches with regard to their performance among themselves and with the traditional metal island based substrates.