Structural and electrical characterization of TiO2 films grown by spray pyrolysis

The sol–gel spray pyrolysis method was used to grow TiO2 thin films onto silicon wafers at substrate temperatures between 315 and 500 °C using pulsed spray solution feed followed by annealing in the temperature interval from 500 to 800 °C in air. According to FTIR, XRD, and Raman, the anatase/rutile phase transformation temperature was found to depend on the film deposition temperature. Film thickness and refractive index were determined by Ellipsometry, giving the refractive indexes of 2.1–2.3 and 2.2–2.6 for anatase and rutile, respectively. According to AFM, film roughness increases with annealing temperature from 700 to 800 °C from 0.60 to 1.10 nm and from 0.35 to 0.70 nm for the films deposited at 375 and 435 °C, respectively. The effective dielectric constant values were in the range of 36 to 46 for anatase and 53 to 70 for rutile at 10 kHz. The conductivity activation energy for TiO2 films with anatase and rutile structure was found to be 100 and 60 meV, respectively.