Chemical solution method for fabrication of nanocrystalline iron(III) oxide thin films

A chemical solution technique for preparation of nanocrystalline iron(III) oxide thin films is developed. The deposition process is essentially based on the thermal decomposition of urea. The as-deposited and post-deposition heat-treated materials were characterized by X-ray analysis and Fourier transform infrared (FTIR) spectroscopy. Basic optical and electrical investigations were also performed. X-ray analysis confirmed that post-deposition heat-treated material is nontextured -iron(III) oxide, with an average crystal size of 22 nm. The optical investigations show that the absorption of films (as-deposited and post-deposition treated) gradually decreases with an increase of the wavelength in the 390–820 nm region. The optical band gap for the as-deposited and post-deposition heat-treated films was determined to be 3.2 eV and 2.0 eV, respectively. The obtained -Fe₂O₃ thin films exhibit a rather high resistivity at room temperature. However, our preliminary qualitative investigations have shown that the room temperature resistivity of -Fe₂O₃ thin films is highly sensitive to moisture, indicating their potential applicability in moisture sensing systems.