Chemical solution method for fabrication of nanocrystalline alpha-Fe2O3 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 tra nsform infrared (FTIR) spectroscopy. Basic optical and electrical investiga tions were also performed. X-ray analysis confirmed that post-deposition he at-treated material is nontextured alpha -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 wit h 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 determi ned to be 3.2 eV and 2.0 eV, respectively. The obtained alpha -Fe2O3 thin f ilms exhibit a rather high resistivity at room temperature. However, our pr eliminary qualitative investigations have shown that the room temperature r esistivity of alpha -Fe2O3 thin films is highly sensitive to moisture, indi cating their potential applicability in moisture sensing systems.