Sculptured thin films: Overcoming the limitations of surface-enhanced Raman scattering substrates

Abstract

Surface-enhanced Raman spectroscopy (SERS) has developed as a feasible method for chemical and biological applications, unifying the precision of molecular fingerprinting with the potential sensitivity of single molecules. SERS has shown promise as a chemical and biological detection tool, but like all other methods, it has some limitations. These include brittle and fragile SERS substrates, poor adhesion of the thin film to the substrates, limited reusability of the substrates, and inhomogeneity and irreproducibility of signals within a substrate. Recently, sculptured thin films fabricated by glancing angle deposition (GLAD) have attracted considerable interest due to their potential use in plasmonics and the fabrication of highly uniform and sensitive SERS substrates. Using GLAD, the structure of the nanocolumns can be customized by changing the deposition parameters (such as gas pressure, tilt angle, and substrate rotation), resulting in a range of different properties. Recently, GLAD has become an important approach for fabricating nanocolumnar and aligned structures for SERS. Moreover, because the GLAD process is simple, inexpensive, and easy to produce on a large scale, it can expand the use of these substrates. The main objective of this review is to explain the fabrication and application of various SERS substrates using GLAD and to discuss how SERS substrates prepared using GLAD have overcome some of the limitations of SERS substrates. We begin with a brief overview of SERS and the SERS amplification process. We shall then briefly discuss the GLAD technique. Finally, we will discuss how various nanostructured SERS substrates by GLAD overcome the limitations of SERS substrates.