Processing optimization of SiO2-capped aluminum-doped ZnO thin films for transparent heater and near-infrared reflecting applications

In this study, a series of optimization steps were performed in the production of Al-doped ZnO (AZO) thin films to tailor their properties as efficient transparent heaters and for near-infrared (NIR) reflectance. The films were produced on 50 x 75 mm(2) glass substrates via magnetron sputtering and capped with a protective SiO2 layer. Processing parameters such as deposition temperature, film thickness, and annealing conditions were all optimized in terms of structure, morphology, optical/electrical properties, and heating/deicing behavior. Electro-thermal characteristics of the films were investigated using a thermal imaging infrared camera under various input voltages. The optimized AZO/SiO2 coatings displayed impressive room-temperature electrical conductivity (sigma) of nearly 3774 S/cm with a sheet resistance (R-s) of 3.53 Omega/square, carrier concentration (eta) of 1.14 x 10(21), and Hall mobility (mu) of 20.48 cm(2)/Vs. These films exhibited very high optical transmittance (above 96%) in the visible range and reflectance (73% at 2500 nm) in the NIR region. The highest figure of merit (FOM) was achieved as 237 (x 10(-3) omega(-1)). Deicing tests were performed with samples cooled to - 40 degrees C and resulted with complete removal of ice/water only within 3 min. In addition, the heater exhibited a high surface temperature of 161 degrees C (12 V), a good thermal resistance value (219 degrees C cm(2)/Watts) with stable and reversible heating behavior. More importantly, these results reveal the potential of optimized AZO/SiO2 coatings as alternatives to transparent tin-doped indium oxide heaters and NIR reflecting mirrors for vehicular applications. [GRAPHICS]

Automated summary

Optimized AZO/SiO2 coatings showed impressive room-temperature electrical conductivity and high transparency in the visible range, as well as strong NIR reflectance. Deicing tests at low temperatures demonstrated their powerful heating performance. These results reveal the potential of optimized AZO/SiO2 coatings as alternatives to transparent tin-doped indium oxide heaters and NIR reflecting mirrors.