Localized oblique-angle deposition: Ag nanorods on microstructured surfaces and their SERS characteristics

In this paper, we demonstrate a simple and convenient method of depositing Ag nanorods on a substrate inside a standard evaporation chamber with the substrate resting on a leveled stage. Microstructuring the substrate prior to the deposition imparts a large incidence angle (>70°) between the collimated vapor atoms and the local surface normal, which is essential to induce the shadowing effect. Thereby, a localized oblique-angle deposition (LOAD) is realized, forming nanorods selectively on the steep sidewalls of surface microcavities patterned via standard photolithography and silicon dry etching. We also demonstrate that these nanorods can boost SERS activity of the underlying substrate and thus perform comparable to those fabricated via advanced patterning techniques or conventional OAD whereby the entire substrate has to be tilted with respect to the incident vapor atoms. Our results suggest the viability of decorating microchannel sidewalls with SERS-active nanorods for integrated sample processing and SERS detection.