Tuning Transparent Conductive Oxides: A Comprehensive Investigation of Mn and Gd Doping in ITO Thin Films

Transparent conducting oxides (TCOs) are crucial materials in modern electronics and photonics because they uniquely combine optical transparency and electrical conductivity, a combination that is rare in nature. They have a wide band gap, and a small introduction of dopants gives them metal like conductivity. Conducting current while allowing light to pass through the screen makes them great for displays, touch screens, solar energy harvesting, and sensors. In this study, we chose Indium Tin Oxide (ITO) as a well-known TCO and doped it with Manganese (Mn) or Gadolinium (Gd), trying to exhibit magnetism + conductivity + transparency, which is potentially useful for transparent spintronics or magneto-optical devices. The goal is to investigate how doping allows tailoring of ITO’s electronic band structure, magnetic response, and optical absorption edge. A series of Mn-doped and Gd-doped ITO thin films (1um thick) with varying dopant concentrations were prepared by DC magnetron co-sputtering of ITO and dopant targets. The structural, electrical, magnetic, and optical properties of the films were systematically examined. Spectroscopic ellipsometry and photoluminescence (PL) revealed a consistent decrease in the optical bandgap with increasing concentration of either dopant. Furthermore, the Burstein–Moss effect was observed based on the measured direct/indirect and allowed/forbidden transition energies. The films’ electrical resistivity increases with concentration of either dopant. Annealing in air at 500^oC makes the films more transparent and they remain conductive. The films are subsequently studied using magnetometry, low temperature PL, transmission measurements, ellipsometry and x-ray diffraction. Initial findings indicate the potential to create a transparent, conductive thin film with paramagnetic characteristics.