Influence of Thickness and Number of Silver Layers in the Electrical and Optical Properties of ZnO/Ag/ZnO/Ag/ZnO ultra-Thin Films Deposited on the Glass for Low-Emissivity Applications

We report on transparent ZnO/Ag/ZnO and ZnO/Ag/ZnO/Ag/ZnO thin-films were deposited on the glass substrate by RF and DC sputtering for ZnO and Ag targets, respectively. The electrical and optical properties of the single and double Low Emissivity coatings were investigated with respect to the deposition time of Ag mid layer. The visible transmittance remains about 65% for single and 45% for double Low-E coatings as the Ag deposition time increases. Besides, the decrement of sheet resistance makes lower thermal emissivity of the coatings. In agreement with the optical performance, lower thermal emissivity can strongly increase NIR reflectance as the Ag layer thickness increases. The carrier concentration increases gradually as the sheet resistance decreases and the increase of the free carriers and conductivity of the coatings lead to a sharp rise of the NIR reflectance. The results show that the characteristics of Low-E coatings depend on both the continuity of the metal layer and the metal thickness.