13 May 2015 Characterization of the role of oxide spacers in multilayer-enhanced SERS probes
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Surface enhanced Raman spectroscopy (SERS) has several advantages as a transduction method for many types of optical sensors, due to its sensitivity and potential for multiplexed detection. Over the years, SERS probes have been developed to be capable of extreme sensitivities, with single molecule SERS having been achieved in randomly located hot-spots of colloidal aggregates. However, these structures suffer from significant irreproducibility, due to the randomness of the aggregation. Alternatively, strategies such as ordered 2D arrays or enhancement based on single probes (e.g. immunno-nanosensors, nanostars) have high reproducibilities but limited enhancement factors. In our laboratory a widely applicable enhancing geometry based on metal thin films interleaved with dielectric spacers that takes advantage of interaction into the volume of the probe (perpendicularly to the surface) to enhance the signal independently from the underlying structure has been developed. Preliminary evidence into the mechanism of this enhancement suggests that the dielectric spacer material and thickness play a key role in the magnitude of the resulting enhancement. In this paper we investigate the thickness dependence of the multilayer enhancement using substrates fabricated using ultrathin oxide deposited by atomic layer deposition as spacers. The SERS enhancement measured for substrates based on semiconductor and dielectric materials have been characterized in order to understand the origin of this dependence. In addition a model to describe the mechanism by which the spacer properties influence the multilayer enhancement will also be discussed.
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Pietro Strobbia, Pietro Strobbia, Alex Henegar, Alex Henegar, Theodosia Gougousi, Theodosia Gougousi, Brian M. Cullum, Brian M. Cullum, "Characterization of the role of oxide spacers in multilayer-enhanced SERS probes", Proc. SPIE 9487, Smart Biomedical and Physiological Sensor Technology XII, 94870P (13 May 2015); doi: 10.1117/12.2177467; https://doi.org/10.1117/12.2177467

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