Effect of Mn doping on the structural, morphological, optical and magnetic properties of indium tin oxide films

We report on the preparation and characterization of high purity manganese (3–9 wt.%) doped indium tin oxide (ITO, In:Sn = 90:10) films deposited by sol–gel mediated dip coating. X-ray diffraction and selected area electron diffraction showed high phase purity cubic In₂O₃ and indicated a contraction of the lattice with Mn doping. High-resolution transmission electron microscopy depicted a uniform distribution of ∼20 nm sized independent particles and particle induced x-ray emission studies confirmed the actual Mn ion concentration. UV-Vis diffuse reflectance measurements showed band gap energy of 3.75 eV and a high degree of optical transparency (90%) in the 100–500 nm thick ITO films. X-ray photoelectron spectroscopy core level binding energies for In 3d_5/2 (443.6 eV), Sn 3d_5/2 (485.6 eV) and Mn 2p_3/2 (640.2 eV) indicated the In³⁺, Sn⁴⁺ and Mn²⁺ oxidation states. Magnetic hysteresis loops recorded at 300 K yield a coercivity H_c ∼ 80 Oe and saturation magnetization M_s ∼ 0.39 μ_B/Mn²⁺ ion. High-temperature magnetometry showed a Curie temperature T _c > 600 K for the 3.2% Mn doped ITO film.