Silver alloy-based metal matrix composites: a potential material for reliable transparent thin film heaters†
In this study, a flexible Zn(3 at%)–SnOx/AgTi0.0007Cr0.0067/Zn(3 at%)–SnOx (Zn–SnOx/ATC/Zn–SnOx) multilayer transparent conducting thin film on a polyethylene terephthalate (PET) substrate was fabricated by on-axis radio frequency (RF) magnetron sputtering at room temperature to obtain a reliable and transparent thin film heater. To optimize the composition of the Ag–Ti–Cr alloy, which is more durable in high-temperature and humid conditions than the Ag thin film, we performed the constant temperature–humidity test for Ag–Ti–Cr thin films of various compositions deposited by continuous composition spread sputtering. The Zn–SnOx/Ag-0.07 at%Ti-0.67 at%Cr/Zn–SnOx multilayer thin film exhibited a higher transmittance of around 89% and enhanced durability compared with that of the Zn–SnOx/Ag/Zn–SnOx multilayer thin film. Moreover, the mechanical flexibility was confirmed through a bending test. The Zn–SnOx/ATC/Zn–SnOx multilayer thin film heater took approximately 40 s to attain a temperature of 100 °C when the voltage was 6.5 V, and it exhibited stable heating operation even after remaining in a heating state for 2 h. In addition, the durable and transparent Zn–SnOx/ATC/Zn–SnOx multilayer thin film heater exhibited uniform heat distribution and reliable thin film heater performance. Hence, the suggested reliable and transparent Zn–SnOx/ATC/Zn–SnOx multilayer thin film heater is applicable to multifunctional smart windows and anti-fogging systems.