Near-Infrared Plasmonic Planar Films: Advancements in Aluminum-Doped Zinc Oxide for Sensing and Telecommunications Applications

Heavily doped metal oxides are considered to be efficient plasmonic materials for near infrared (NIR) applications due to their lower carrier density compared to noble metals such as gold and silver, which are traditionally used in the visible region. However, the development of real-world low-loss plasmonic materials for applications well below the telecommunication wavelength in near-infrared remained a challenge. In this work, we demonstrate the tunability of carrier concentration and the tunability of the negative dielectric constant of planar aluminum-doped zinc oxide (AZO) films coated on low-cost microscopic glass slides via precise engineering of material properties and film thickness, to perform as suitable plasmonic material in the near-IR-wavelength region. We evaluated the low-loss nature of the films and then showed the surface plasmon resonance (SPR) of these films in near IR for wavelengths >1300 nm using Kretschmann-type prism configuration. We also portrayed the sensing behavior of these films at different refractive index media to ensure their applicability in device applications. This demonstration would be a breakthrough in the history of near-IR surface plasmon phenomena in the context of portable and point-of-care healthcare devices, where the film developed on glass substrates can be used as a disposable sensing chip with suitable functionalization.