Sn-doping concentration dependence of electrical, optical, and magnetic properties in epitaxial Mn-doped indium tin oxide films deposited by RF magnetron sputtering

The effects of Sn doping on the structural, electrical, optical, and magnetic properties of epitaxial Mn-doped indium tin oxide (ITO) films were systematically investigated. We deposited epitaxial Mn-doped ITO films with various Sn concentrations using radio frequency magnetron sputtering. The lightly Sn-doped films exhibited the high degree of the crystalline alignment, whereas the heavy Sn doping led to the fluctuations in the crystalline alignment. The carrier concentration and optical bandgap increased with increasing Sn concentration up to about 10 at. % and then decreases at higher Sn concentrations. Room-temperature ferromagnetism was observed across all the films. Furthermore, the magnetization exhibited a strong correlation with the carrier concentration, suggesting that the ferromagnetism in Mn-doped ITO films is likely due to delocalized carrier-mediated interactions. The relatively small magnetization observed in these films may be attributed to ferromagnetic coupling between a limited number of Mn ions present in the films.