Structural, Optical and Electrical Properties of Hydrothermally Synthesized Fe₂O₃ Thin Films for Optoelectronic Applications

Abstract

Thin films of α-Fe₂O₃ (hematite) are desirable materials for optoelectronic, sensing, photocatalytic and photoelectrochemical applications. Fe₂O₃ thin film was deposited on glass using hydrothermal method using concentration of FeCl₃.6H₂O 0.25 M at PH 3.0, treated at 160 °C for 4 h and annealed at 500 °C for 5 h. XRD, SEM, EDS and current-voltage measurements were used to characterize the films. XRD peak matching resulted in the presence of characteristic peaks of α-Fe₂O₃. The SEM images showed a densely compacted granular structure with grains having a faceted shape and dimensions of around 1.5–2.5 µm. The major elements detected by EDS analysis were iron (54.08 wt%) and oxygen (45.92 wt%). The absorbance value for the UV-Visible reading ranged in the 370–1100 nm range between 0.82850 to 1.16931, with the maximum reading obtained at 838 nm. The Tauc analysis resulted in an apparent optical band gap of ~1.29 eV. This value however, should be interpreted with caution as it is based on results obtained from a film thickness measurement and no validated bare-glass reference. Current response was measured over the range of 0-14 V, and it was observed that the current response increased in this range, which shows a highly resistive film. Linear regression gave the result of I = 0.1179V − 0.0250 (I in pA), with a coefficient of determination (R²) of 0.9871, which is basically linear. However, it is not possible to calculate an intrinsic conductivity or resistivity reliably because of the unknown geometry of the electrodes and the thickness of the film.