Effect of fluorine doping on the structural, optical and electrical properties of SnO2 thin films prepared by spray ultrasonic

Abstract

Abstract The undoped and fluorine doped tin oxide (SnO2) thin films are synthesized by using cost-effective spray ultrasonic technique; the films are sprayed on heated glass substrates at 480 °C. The dependence of structural, optical and electrical properties of SnO2 films on the concentration of fluorine is investigated. X-ray diffraction, Optical absorption, four-point probe and Hall Effect studies have been performed on undoped and fluorine doped SnO2 (FTO) films. X-ray diffraction pattern reveals the presence of cassiterite structure with (2 0 0) as preferential orientation for FTO films. The crystallite size varies from 10.3 to 27.12 nm and was affected by F concentration which was lying between 0 and 12 wt.%. All films exhibit optical transmission T(λ) more than 83.9% in visible region; the optically estimated film thickness varies from 700 to 975 nm for the same given time (3 min deposition) and band gap (Eg) varies from 3.651 to 3.902 eV. The electrical study reveals that the films have n-type electrical conductivity and depend upon fluorine concentration too. The sprayed FTO film doped at 6 wt.% has the minimum resistivity of 1.47 × 10−3 Ω cm and minimum resistance sheet (Rsh) of 21 Ω/cm2 whereas the carrier concentration and mobility were about 2.04 × 1019 cm−3 and 208.4 cm2 V−1 s−1 respectively.