Electrical and optical properties of ferric oxide thin films prepared via a sol-gel method

The sol-gel process has been employed for depositing hematite films on various substrates. These films were characterized by structural, electrical, and optical techniques. Dip coating produced films 100 nm thick comprising nanoparticles of size 20 nm with a yellow color and good adhesion to a glass substrate. Electrical conductivity measurements showed a thermal activation energy, Ea, of 0.82 eV, a hopping activation energy, w, of 0.86 eV, and a thermal activation energy of mobility, Eμ, of 0.04 eV. The optical studies demonstrated an increase in transmittance to >90%, a decrease in reflectance to <10%, and a sharp edge at ∼600 nm. An absorption coefficient, α, of 104 cm−1, an allowed direct type transition of 2.63 eV, an indirect type transition of 1.95 eV, and an absorption index, k, from 0.05 to 2 were estimated.