Characteristics of ITO/Ag/ITO Hybrid Layers Prepared by Magnetron Sputtering for Transparent Film Heaters

Transparent film heaters (TFHs) based on Joule heating are currently an active research area. However, TFHs based on an indium tin oxide (ITO) monolayer have a number of problems. For example, heating is concentrated in only part of the device. Also, heating efficiency is low because it has high sheet resistance (R-s). To address these problems, this study introduced hybrid layers of ITO/Ag/ITO deposited by magnetron sputtering, and the electrical, optical, and thermal properties were estimated for various thicknesses of the metal interlayer. The R-s, of ITO(40)/Ag/ITO(40 nm) hybrid TFHs were 5.33, 3.29 and 2.15 Omega/rectangle for Ag thicknesses of 10, 15, and 20 nm, respectively, while the R-s, of an ITO monolayer (95 nm) was 59.58 Omega/rectangle. The maximum temperatures of these hybrid TFHs were 92, 131, and 145 degrees C, respectively, under a voltage of 3 V. And that of the ITO monolayer was only 32 degrees C. For the same total thickness of 95 nm, the heat generation rate (HGR) of the hybrid produced a temperature approximately 100 degrees C higher than the ITO monolayer. It was confirmed that the film with the lowest R-s, of the samples had the highest HGR for the same applied voltage. Overall, hybrid layers of ITO/Ag/ITO showed excellent performance for HGR, uniformity of heat distribution, and thermal response time.