Production of metalo-dielectric nano-composite films that show plasmonic behavior with atomic layer deposition method and characterization

Recently, surface plasmon resonance is frequently utilized for molecular sensing. Sensors are made up of simply a very thin metallic layer which is supported by glass or crystal. The molecules close by the sensor surface, interacts with the surface plasmon zone. This interaction causes angular, spectral and phase related changes in the reflection and scattering of the light which is exposed to the surface. These changes can be read and recorded by means of the electro-optical components which are attached to the optical sensor. The sensors of today's technology are not adequate for observing the behaviors of tiny amount of molecules accurately. Besides this, undesirable losses of the light (scattering) occur due to the defects on the smoothness of the produced films and the pinhole and impurity inside the films and this scattering, as a source of noise, effects the measurements of the sensors negatively. In this study, metallo-dielectric nano composite films, were produced by using Atomic Layer Deposition (ALD) which is a deposition method for very thin and high quality films which were composed of gold-silver-alumina layers for more sensitive plasmonic sensor applications. Besides this, optical characterization was carried out. Firstly, metal and dielectric layers were optimized by using Winspall simulation program which is based on Fresnel equations as geometrical and spectral. Moreover, the film layer thicknesses of the most suitable nano-composite film configuration were calculated as 24 nm gold-34 nm silver-142 nm alumina for the best response of the sensor (high sensitivity). The most suitable wavelength was found to be 632,3 nm. Gold and silver layers were deposited using sputtering method whereas alumina layer was deposited using the ALD method. In additional studies, alumina and gold nano structures were produced by utilizing thermal processing and sputtering methods on the obtained nano composite films. The increase in the light intensity and the operability at various wavelengths were accomplished by means of the nanostructures produced as mentioned. SEM was used for characterization of the surfaces and the cross sectional areas and AFM was used for characterization of surface roughness of all the produced structures. Total reflection, backscattering, transmission behaviors were analyzed at UV/Vis/NIR spectrometry for optical characterization. The absorption curves were obtained using the reflection and transmission curves. In Addition, reflection behaviors of alumina nano-structured and gold nano-structured sensors were determined at different environments (air, deionized water, glycerin-water) which have different refractive indices.