Study on the effect of Ti layer on the stability of electrical measuring surface plasmon resonance sensors with ITO/aSi:H/Ti/Au structure

Abstract

Surface plasmon resonance-based sensors, or surface plasmon resonance (SPR) sensors, have been demonstrated to possess high sensitivity in detecting refractive index changes in the medium occurring near the surface of the sensor. However, current SPR sensors must be coupled with an external optical system, including photodetectors and precise displacement systems, to measure changes in both the intensity and position of the reflected light. This is the main disadvantage of current SPR sensors, rendering them non-portable and challenging to apply in on-site experiments. In this study, we have overcome this limitation by integrating a thin-film photodiode directly beneath the plasmonic material layer. Specifically, the SPR sensors we propose have a structure of glass substrate/indium tin oxide (ITO) layer (200 nm)/hydrogenated amorphous Si layer (100 nm)/Ti (10 nm)/Au (50 nm), which can operate similarly to conventional SPR sensors based on the Kretschmann configuration. The operating principle of our proposed SPR sensor and the impact of the Ti layer on the sensor's stability will be discussed in this article.