Structural, Morphological, Optical, and Electrical Characterization of Fluorine Doped Tin Oxide (FTO) Thin Films Synthesized by PSP

Abstract

This paper reports a study of Fluorine-doped Tin Oxide (FTO) thin films deposited by the Pneumatic Spray Pyrolysis (PSP) technique. The films were deposited on glass substrates at 450 °C with a ~125 nm thickness, using an F/Sn ratio of 0, 0.2, 0.35, 0.5, 0.65 and 0.85, respectively. The samples were characterized by X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM), UV-visible Spectroscopy and Hall Effect techniques, respectively. XRD results revealed that the FTO thin films were polycrystalline with a tetragonal rutile-type structure and had preferential orientations along (110) planes. SEM studies showed that FTO thin film morphology was totally affected by an increased F/Sn ratio. The calculated grain mean sizes were 10-35 nm. Optical transmittance spectra of the films showed a high transparency of approximately 80-90 % in the visible region. The optical gap of FTO thin films was in a 3.70-4.07 eV range. Electrical and optical properties of these films were studied as a function of the F/Sn ratio. Therefore, the optimal FTO (F/Sn = 0.5) films revealed a maximum value of the figure of merit approximately 8.05 × 10-3 (Ω-1) at λ = 400 nm. The high-conducting and transparent-elaborating FTO thin films may have several promising applications due to its multifunctional properties.