Improved infrared reflection properties of aluminum-doped zinc oxide thin films depending on sputtering pressure for low emissivity applications

Aluminum-doped zinc oxide (AZO) films were prepared on glass substrates using radio frequency (RF) magnetron sputtering technique. The sputtering pressure was varied between 10 and 80 mTorr for films with a deposition time of 30 min and between 40 and 80 mTorr for films with a deposition time of 180 min. Effects of the sputtering pressure on optical properties, crystal structure, electrical properties, microstructure and infrared reflection of the AZO films were systematically investigated by UV-VIS-NIR spectrophotometry, XRD, Hall measurement, AFM and FTIR, respectively. The prepared AZO film at PAr = 80 mTorr with 180 min deposition time exhibits the lowest electrical resistivity, highest mobility and carrier concentration as well as high average visible transmission in 400-760 nm wavelength range about 82.9%. The average infrared reflection of 63.1% in 8-14 mu m waveband makes the film a superior candidate for low-emissivity applications.