Development of Spray-Coated Fluorine-Doped Tin Oxide Films for Near-Infrared Plasmonic Applications

Cost-effective plasmonic coatings are required for developing portable point of care devices for several medical applications. Development of such devices is not economical with noble metals. In this paper, fluorine doped tin oxide thin films were developed which exhibit excellent plasmonic behaviour in near infrared region. To investigate the optimum coating, the films with various dopant concentrations were prepared using the spray coating route. The effect of dopant concentration on the structural, electrical, and optical properties was investigated in the context of plasmonic properties. A thorough investigation of the electrical and optical properties revealed plasmonic properties in the films. The negative for the real part of the dielectric constant has been verified through the Drude-Lorentz theory-based fitting, by extracting the dielectric spectra and the cross-over wavelength, and this revealed the suitability of these films as an alternative material for plasmonic applications. Finally, the surface plasmon resonance has been experimentally excited in the spray coated fluorine doped tin oxide films using the Kretschman-based prism geometry with air as dielectric in wavelength interrogation.