Tri-band transparent conductive coating of indium tin oxide

A tri-band transparent conductive indium tin oxide (In2O3:Sn, ITO) film for the visible, near-infrared (NIR) and mid-infrared (MIR) was deposited on a sapphire substrate by radio frequency (RF) magnetron sputtering. Deposition parameters, including RF power, substrate temperature, and oxygen flow rate, were optimized to improve the optical property without reducing the conductivity of the film by maximizing the Hall mobility and minimizing the carrier concentration. Films deposited at optimized conditions exhibit a Hall mobility of ∼20 cm2 V-1 s-1, a carrier concentration of ∼4.99×1020 cm-3, and a sheet resistance of 61.2 Ω/sq. Average transmissions of these films are 81.40% in the 0.4-1.6 μm region and 60.81% in the 3.0-5.0 μm region. An index-matching stack of MgF2 was developed, improving the transmittance to 90.55% and 73.20% in the regions above, respectively. These results make ITO film a promising alternative material to conventional metal mesh for missile domes shielding electromagnetic waves.