Structural and optoelectronic properties of Al-doped zinc oxide films deposited on flexible substrates by radio frequency magnetron sputtering

Al-doped zinc oxide (AZO) thin films were deposited onto flexible polyethylene terephthalate substrates, using the radio frequency (RF) magnetron sputtering process, with an AZO ceramic target (The Al2O3 content was about 2wt.%). The effects of the argon sputtering pressure (in the range from 0.66 to 2.0Pa), thickness of the Al buffer layer (thickness of 2, 5, and 10nm) and annealing in a vacuum (6.6×10−4Pa), for 30min at 120°C, on the morphology and optoelectronic performances of AZO films were investigated. The resistivity was 9.22×10−3Ωcm, carrier concentration was 4.64×1021cm−3, Hall mobility was 2.68cm2/Vs and visible range transmittance was about 80%, at an argon sputtering pressure of 2.0Pa and an RF power of 100W. Using an Al buffer decreases the resistivity and optical transmittance of the AZO films. The crystalline and microstructure characteristics of the AZO films are improved by annealing.