Use of Multilayer Oxide Films Prepared by RF-Magnetron Sputtering as Transparent IR-Reflector

摘要

A transparent-conducting indium tin oxide (ITO)/Titanium di-oxide (TiO_2) multilayer optical filter has been developed using conducting and transparent ITO and transparent insulating TiO_2 films grown by RF-magnetron sputtering. The objective is to cut off the infrared portion of the solar spectrum to avoid the heating effect. The electrical resistivity of ITO film is 1.2 x 10~(-4) Ω·cm, the sheet resistance is below 8 Ω/□ and the visible optical transmission is above 85%. The refractive index of this film is 1.9. On the other hand, TiO_2 is highly resistive (resistivity is of the order of 10~(10) Ω·cm), and has 85% visible optical transmission and very low absorption in the visible and infrared regions. The refractive index of TiO_2 film is 2.6 at a substrate temperature 250℃ and 2.9 at 450℃. At 450℃, the rutile titanium dioxide structure was formed which was confirmed on the basis of diffraction rings. In the multilayered ITO/TiO_2 structure ITO and TiO_2 layers were alternately deposited. Thicknesses of the ITO and TiO_2 layers were optimized to achieve the best result. The multilayer has the same sheet resistance as that of ITO film and about 92% visible transmission with the plasma resonant frequency at 840 nm. The X-ray diffraction (XRD) pattern of the ITO/TiO_2 multilayer indicates a the random orientation of crystal growth.