Double-layer effect on electrothermal properties of transparent heaters

Transparent double-layer heaters that consist of aluminum-doped zinc oxide and fluorine-doped tin oxide films are prepared by electron cyclotron resonance-metal organic chemical vapor deposition and RF-sputtering systems, in sequence. The double-layered transparent conducting oxide film is designed and prepared to achieve both of high conductivity and high-temperature performance. This double-layer structure has lower sheet resistance, due to the grain size increase with respect to the single-layer films. The fluorine-doped tin oxide/aluminum-doped zinc oxide double-layer film shows a sheet resistance as low as 36.7 Ω sq^-1, and an optical transmittance of ∼82%, which are suitable properties for low-voltage transparent heaters. Hall measurement results show that the double-layer film has remarkably increased conductivity and decreased resistivity. In addition, the time-versus-temperature profile shows that the performance of the fluorine-doped tin oxide/aluminum-doped zinc oxide double layer is superior to that of the aluminum-doped zinc oxide and fluorine-doped tin oxide single-layer films.