Focused Ion Beam Assisted Interface Detection for Fabricating Functional Plasmonic Nanostructures

Plasmonic nanoscale devices/structures have gained more attention from researchers due to their promising functions and/or applications. One important technical focus on this rapidly growing optical device technology is how to precisely control and fabricate nanostructures for different functions or applications (i.e., patterning end points should locate at/near the interface while fabricating these plasmonic nanostructures), which needs a systematic methodology for nanoscale machining, patterning, and fabrication when using the versatile nanoprecision tool focused ion beam (FIB), that is, the FIB-assisted interface detection for fabricating functional plasmonic nanostructures. Accordingly, in this work, the FIB-assisted interface detection was proposed and then successfully carried out using the sample-absorbed current as the detection signal, and the real-time patterning depth control for plasmonic structure fabrication was achieved via controlling machining time. Besides, quantitative models for the sample-absorbed currents and the ion beam current were also established. In addition, some nanostructures for localized surface plasmon resonance biosensing applications were developed based on the proposed interface detection methodology for FIB nanofabrication of functional plasmonic nanostructures. It was shown that the achieved methodology can be conveniently used for real-time control and precise fabrication of different functional plasmonic nanostructures with different geometries and dimensions.