Nanocomposite Bi/TiO2 multilayer thin flms deposited by a crossed beam laser ablation confguration

Abstract

A crossed beam pulsed laser deposition confguration was used to prepare nanocomposites Bi/TiO2 thin flms on two different substrates. The multilayered system was formed by depositing TiO2 and Bi layers alternately. In order to embed the Bi nanostructures in TiO2, the subsequent TiO2 layers were synthesized using a constant number of laser pulses (3000) corresponding to a thickness of approximately 21 nm. The Bi nanostructures were deposited on the TiO2 layers alternately by irradiating the Bi target with 30, 100, 200, and 300 laser pulses. In this way, the Bi nanostructures were embedded inside the TiO2 matrix. A total of 8 samples with bismuth and one reference, with TiO2 only, were produced. Transmission Electron Microscopy (TEM) showed that nearly spherical nanoparticles (NPs) were obtained at lower number of pulses, whereas at 300 pulses a quasi-percolated nanostructured Bi flm was obtained. X-Ray Photoelectron Spectroscopy (XPS) revealed that the TiO2 layers were not afected due to the bismuth presence. Raman Spectroscopy showed vibrational features characteristic of the rutile phase for the titania layer. The Raman spectrum of the multilayer prepared using 300 laser pulses on the bismuth, suggests that the Bi layer is formed by a mixture of metallic Bi, and α-Bi2O3. The Ultraviolet–Visible Spectroscopy reveals that no substantial changes are presented in the transmittance spectra indicating similar optical properties of the diferent deposits. Finally, the photoluminescence emission spectra indicate that the substrate position in the deposition chamber afects the electronic structure of the material.