Fabrication and Characterization of Ultraviolet Visible and Near infrared Filters for Smart Applications

Abstract

produced by the more advanced methods include chemical vapor deposition, physical vapor deposition, glancing angle deposition; molecular beam epitaxy, etc. are expensive. The dielectric filter or reflector usually has a number of layers of two distinct materials with their distinct refractive indices and thicknesses. To achieve the high reflection or wave prohibition band, we should fabricate a reflector with certain number of layers. The sophisticated fabrication methods involve high fabrication cost along with their complex procedures. Further, the cost of such dielectric reflectors in mass-scale industrial processes are challenging. Thus, this has brought the attention of the researchers to an alternative fabrication approach which can help to reduce the manufacturing costs with the simple process. Accordingly, other methods such as spin-coating, dip-coating, and spray pyrolysis, which are recognized as the cost-effective ones but the requirement of number of layers of dielectric reflector is still more. In addition, the dip coating approach involves the wastage of solution whereas the spray pyrolysis method is rather complicate as compared to the spin coating and dip-coating approaches. In this doctoral study, we focus on the fabrication of multilayer dielectric reflectors with the minimum number of TiO2/SiO2 stacks/bilayers. Using the combined sol-gel spin-coating method, it is possible to overcome the issues of high-cost fabrication of dielectric reflectors. Sol-gel spin-coating method offers tunability in process parameters including precursor concentration, catalyst concentration, choice of solvent, spin rate/speed, and annealing temperature. With this, we address the process optimization for the low-cost and rapid fabrication of ultraviolet (UV), visible (Vis) and near-Infrared (NIR) dielectric reflectors with of 100% reflectance. We have carried out numerous studies to explore the structural, morphological, and optical characteristics of the reflectors. newline