Au-Al thin films and their potential in surface plasmon resonance sensors
Molly Kate Kreider
Small changes in the concentration of some substance in a medium slightly change the medium’s optical response. Surface plasmon resonance (SPR) sensors utilize metals like Au with a well-defined SPR reponse to quantify this change in concentration. An ideal material for an SPR sensor would have a reflected intensity dip with a small full width at half maximum (FWHM) and large peak height, while being highly sensitive to changes in the sensing medium. We analyzed these three metrics for Au-Al thin films, which were fabricated using the co-sputtering method and given a temperature treatment, for two sensor types (fixed incident wavelength and fixed incident angle), four film thicknesses, and three sensing media. While many alloys showed improved sensitivity, Au0.85Al0.15 was more sensitive than pure Au for every sensor type and configuration while maintaining a relatively comparable FWHM, suggesting it may have promise for application in SPR sensors.