Influence of Al doping on the structure and properties of Fe 2 O 3 thin films: high transparency, wide band gap, ferromagnetic behavior

This paper presents a detailed study of structural, morphological, optical, transport and magnetic properties of aluminum (Al) doped ferric oxide (Fe 2 O 3 ) thin films deposited onto glass substrates at 350 °C by spray pyrolysis technique. Al concentration was varied from 0 to 10 atomic percentages (at%). The x-ray diffraction patterns of Al doped Fe 2 O 3 thin films showed the corundum structure with the predominant (104) peak. In scanning electron micrographs, the surfaces of the Al doped Fe 2 O 3 thin films were observed to be formed of nanoparticles. Al doped Fe 2 O 3 thin films were transparent in the visible to near infrared region. Transmittance and optical band gap of Al doped Fe 2 O 3 thin films increased with the rise of Al concentration up to 6 at% and then decreased for the 8 and 10 at% Al concentrations. Al doped Fe 2 O 3 thin films showed n-type electrical conductivity with high mobility and Hall coefficient. Electrical resistivity of Al doped Fe 2 O 3 thin films varied from 5.67 × 10 5 to 8.92 × 10 5 Ω-cm and carrier concentration was found between 1.56 × 10 17 and 8.64 × 10 17 cm −3 . Hysteresis loops of Al doped Fe 2 O 3 thin films recorded at room temperature matched with the nature of soft ferromagnetic materials and the saturation magnetization decreased with Al concentration in Fe 2 O 3 thin films.