The Electrical, Optical, Heating Property and Electromagnetic Wave Shield Effect of TiO₂/Ag/TiO₂ Thin Films

Transparent TiO₂ single layer and TiO₂/Ag/TiO₂(TAT) tri-layer films were deposited by DC and RF magnetron sputter on a polyimide substrate at room temperature. During the TAT deposition, the thickness of the TiO₂ layer was kept at 20 nm, while the Ag interlayer was varied as 10, 15, 20 nm to investigate the effect of Ag thickness on the figure of merit value which is decided by the visible transmittance and sheet resistance of the films. The compared FOM values revealed that the TiO₂ films with a 15 nm thick Ag interlayer had an ideal tri-layer structure with a higher figure of merit of 8.96×10⁻³ Ω⁻¹. In a planar heater test, when the bias voltage of 15 V was applied to the TiO₂ 20 nm/Ag 15 nm/TiO₂ 20 nm films, their steady state temperature increased to 108.1 o C. After the heat radiation test, the films retained constantly stable optical and electrical properties. In addition, the TAT films showed superior electromagnetic interference shielding effectiveness up to 45 db, which is above the specifications grade of commercial electromagnetic interference shielding products. From the observed experimental results, it is supposed that TAT films with an optimal Ag interlayer of 15 nm deposited on PI films can be applied as transparent electrodes for rollable display devices and as planar heating elements, as well as electromagnetic shielding glass in future autonomous cars.