Optical Thickness Monitoring as a Strategic Element for the Development of SPR Sensing Applications.

Donato Luna-Moreno,Melissa Rodríguez-Delgado,Araceli Sánchez-Álvarez

doi:10.3390/s20071807

Abstract

The importance of the monitoring of thickness and rate deposition is indispensable for the fabrication of thin film sensors, such as SPR sensors. The sensitivity of SPR responses varies with the thickness of the film, as well as the linear range. Thus, in the present work, we presented an experimental study of the plasmonic response of Cr/Au thin films deposited onto glass slides by evaporation, based on both a rotation and no-rotation system. The results show that the thickness of the gold film varies from 240 to 620 Å, depending on the glass slide position. The SPR response curves obtained experimentally were compared with simulated plasmonic responses and different parameters such as resonance angle, and the depth, slope and half-width of the SPR curve were analysed.

Highlights

The surface plasmon resonance (SPR) technique has become an active field of research due to the constant development of devices capable of detecting chemical and biological substances for a broad range of applications, from biomedical to food industries
The SPR response curves obtained experimentally were compared with simulated plasmonic responses, and further analyzed to extract different parameters such as resonance angle, and the depth, slope and half-width of the curves
The theoretical reflectance of a multilayer thin film was expressed by R = rr∗, where r is the amplitude reflectance calculated by the expression r =

Summary

Introduction

The surface plasmon resonance (SPR) technique has become an active field of research due to the constant development of devices capable of detecting chemical and biological substances for a broad range of applications, from biomedical to food industries. SPR devices are based on the interaction of the electromagnetic excitations of surface plasmons (charge density oscillations) at an interface between a thin metallic layer (~50 nm of Au or Ag) and a dielectric medium [1]. This phenomenon highly depends on the thickness of the multilayer structure, and any factor that causes variations in it could generate significant changes in the plasmon dispersion, altering the SPR curve. The analysis of the SPR response curve provides specific information related to sensing applications. The width of the curve gives information about effects related to the absorption process in the metal layer [2,3]

Methods

Results

Conclusion