Au-Si Diffusion Effects on Surface Plasmon Resonance Sensor Using Internal Photoemission at Metal/Si Schottky Barrier

Area of Science:

• Materials Science
• Nanotechnology
• Sensor Technology

Background:

• Surface plasmon resonance (SPR) sensors based on Schottky barriers offer potential for compact chemical sensing.
• These sensors use gold nanostructures on n-type silicon to generate electrical signals via internal photoemission at the gold/silicon (Au/Si) interface.
• A key challenge is the long-term stability and performance degradation of these SPR sensors.

Purpose of the Study:

• To investigate the mechanisms of performance degradation in Au/Si Schottky barrier SPR sensors.
• To identify the role of atomic diffusion at the Au/Si interface in sensor instability.
• To evaluate the effectiveness of a molybdenum diffusion barrier in enhancing sensor stability.

Main Methods:

• Continuous 10-day measurements of a conventional Au/Si SPR sensor.
• Spectroscopy analysis to study atomic diffusion and interface changes.
• SPR response measurements of sensors with and without a molybdenum diffusion barrier.

Main Results:

• Silicon atom migration to the gold surface was observed in conventional Au/Si sensors, causing a >46% drop in responsivity.
• This silicon diffusion was identified as a primary cause of performance degradation and SPR angle shifts.
• The molybdenum diffusion barrier effectively suppressed Si diffusion, preventing SPR angle shifts and responsivity loss.

Conclusions:

• Atomic diffusion, specifically silicon migration, is a critical factor limiting the stability of Au/Si Schottky barrier SPR sensors.
• Incorporating a molybdenum diffusion barrier layer is a viable strategy to mitigate atomic diffusion and enhance sensor longevity.
• These findings provide crucial insights for designing more robust and reliable SPR sensing devices.