Abstract
In the past, high-κ dielectrics gained much attention because of the constant demand for increasingly smaller semiconductors. At the same time, in the field of optical sensing, high-κ dielectrics are key materials. This study presents the experimental investigations on a lossy mode resonance-based optical planar waveguide (LMROPW) sensor coated with a high-κdielectric of an indium tin oxide (ITO) layer. Two types of sensing structures were fabricated by coating (i) only a single-layer ITO (or bared LMROPW) and (ii) an ITO layer with glucose probes onto the optical planar waveguide (or boronic LMROPW) to detect glucose molecules. The sensing characteristics of these two types of sensors toward the surrounding analyte were determined using different concentrations of glucose solutions. It was found that the bared LMROPW sensor is only suitable for a higher concentration of glucose; the boronic LMROPW sensor with glucose probes on ITO could be applied to a lower-concentration solution to monitor glucose adsorption onto the sensing surface. Furthermore, with the advantages of a simple structure, easy alignment, and suitable production, the LMROPW sensor with a high-κ dielectric surface could be applied in clinical testing and diagnostics.
Highlights
Silicon dioxide (SiO2 ) has been widely used as a gate oxide material for the past few decades.It is well known that metal-oxide-semiconductor field-effect transistors (MOSFETs) with 100 nm gate lengths require a thinner SiO2 gate oxide
To experimentally verify that indium tin oxide (ITO) acts as an LMR active material, we fabricated the lossy mode resonance-based optical planar waveguide (LMROPW)
We mounted the LMROPW sensor in the experiment setup, allowed the white light from the halogen lamp to enter from one end of the fiber, and started recording the transmission spectra from the output end
Summary
Silicon dioxide (SiO2 ) has been widely used as a gate oxide material for the past few decades. The application of metal as a dielectric material was mainly presented in the surface plasmon resonance (SPR) [14,15], while the application of the ITO as a dielectric layer had been investigated mainly in the LMR, such as in refractive index sensors [16] or monitoring devices [9,17]. Since the ITO deposition has been widely used as a mature coating technology in the fabrication of transparent conductive thin films, here we made use of ITO as the high-κ dielectric material for the LMR sensor. Another aim of this work was to confirm the suitability of the LMROPW to perform in two types of glucose sensors. To the researchers’ best knowledge, no study has been published on combining the advantages of LMR and OPW to evaluate a glucose sensor
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