Sol–gel-based single and multilayer nanoparticle thin films on low-temperature substrate poly-methyl methacrylate for optical applications

Abstract

Single and multilayer (SiO2, TiO2, SiO2–TiO2, TiO2/SiO2–TiO2/SiO2) films were deposited on polymer substrate poly-methyl methacrylate (PMMA) at room temperature by sol–gel method. Optical micrographs show that spin-coated nanoparticle thin films have homogeneous surface with good adhesion with PMMA substrate. Scanning electron microscope results show good incorporation of silica and titania particles as composites with small grain size within range of 0.2–1.28 µm. The structural characterization was carried out by X-ray diffraction, which shows an amorphous pattern for SiO2, SiO2–TiO2 and TiO2/SiO2–TiO2/SiO2 samples but shows semicrystalline behavior in TiO2 sample. From UV–visible spectroscopy, it is found that coated films have a good optical transparency with tunable refractive index of 1.39–2.14. So, these films can be useful for various potential optical applications.