Structural, optical and electronic properties of Ag–TiO2 nanocomposite thin film

Abstract

Nanocomposite thin films of Ag nanoparticles in TiO2 matrices were synthesised by RF magnetron co-sputtering and characterised by X-ray diffraction (XRD), Rutherford back scattering (RBS) spectrometry, UV–Vis, high-resolution transmission electron microscopy (HR-TEM) and X-ray photoelectron spectroscopy (XPS). The composition of Ag was varied from 0 to 45 at.%. The thickness and the concentrations of Ag in the nanocomposite thin film were revealed by RBS. XRD analysis confirmed that the TiO2 matrix is in anatase phase and shows change in phase with Ag concentration. The UV–visible absorption spectroscopy revealed low-intense and broad surface plasmon resonance (SPR) peak at ~500 nm for the thin film with 33 at.% Ag content that was red-shifted to ~525 nm with increasing its intensity for 45 at.% of Ag. The red shift in SPR peak understood by Maxwell–Garnett theory and explained further nonexistence of SPR by interparticle separation from HR-TEM images and crystallinity. This HR-TEM image analysis confirmed the formation of Ag nanoparticles, and average radii were ~5, 12, 15 nm. The Tauc plot reveals reduction in band gap from 3.05 to 2.25 eV with increase in Ag content. Above results are understood based on the XPS analysis which shows a strong interaction between the Ag nanoparticle and TiO2. This decrease in band gap was advantageous to enhance the properties like photocatalytic and bioactivities through SPR.