Transparent and high infrared reflection film having sandwich structure of SiO2/Al:ZnO/SiO2

New transparent and high infrared reflection films having the sandwich structure of SiO2/Al:ZnO(AZO)/SiO2 were deposited on the soda-lime silicate glass at room temperature by radio frequency (R.F.) magnetron sputtering. The optical and electrical properties of SiO2 (110 nm)/AZO (860 nm)/SiO2 (110 nm) sandwich films were compared with those of single layer AZO (860 nm) films and double layer SiO2 (110 nm)/AZO (860 nm) films. The results show that these sandwich films exhibit high transmittance of over 85% in the visible light range (380–760 nm), and low reflection rate of below 4.5% in the wavelength range of 350–525 nm, which is not shown in the conventional single layer AZO (860 nm) films and double layer SiO2 (110 nm)/AZO (860 nm) films. Further these sandwich films display a low sheet resistance of 20 Ω/sq by sheet resistance formula and high infrared reflection rate of above 80% in the wavelength range of 15–25 μm. In addition, the infrared reflection property of these sandwich films is determined mainly by the AZO film. The outer SiO2 film can diminish the interference coloring and increase transparency; the inner SiO2 film improves the adhesion of the coating to the glass substrate and prevents Ca2+ and Na+ in the glass substrate from entering the AZO film.