Characterization of thin films for optical sensors of food-borne pathogens

The purpose of this study is to produce a platform device with the ability to detect a variety of pathogens based upon antigen-antibody interactions. The sensor comprises a nanoporous GeSe channel waveguide fabricated on a substrate, with an intermediate cladding buffer layer [GeSe₂], which is required when the substrate does not transmit at the desired λ. The light from a laser source is then coupled through a fiber and prism into the waveguide and collected with the help of a lens into a detector. The top cladding layer is a Ge₂₈Sb₁₂Se₆₀ thin film in which biomolecules can be 'tethered' via functionalization of the surface. Therefore the surface chemistry of the thin film and the specificity of antibody to its antigen are important considerations. This paper will focus primarily on the surface characterization of the top cladding layer using XPS, AFM, ellipsometry, contact angle measurements and diffuse reflectance analysis.