Enhanced electrical and optical properties based on stress reduced graded structure of Al-doped ZnO thin films

Graded structures of aluminum-doped zinc oxide (AZO) multilayered thin film were prepared on quartz glass substrate by sol-gel process, and then sequentially annealed by raped thermal annealing(RTA) and UV laser annealing technologies for transparent conducting oxide (TCO) applications. Different Al mol% (0, 0.17, 0.33,0.5, 0.66, 0.83, 1) doped ZnO graded structures of multilayer thin films were prepared to optimize the lattice parameter to reduce stress, and then the annealing processes were sequentially performed. Introducing graded multilayered thin films, reduced the stress between the layers. The AZO graded structures of multilayer thin films were annealed by RTA followed by a 350 nm nanosecond pulsed UV laser annealing method. The graded structures of multilayered AZO thin films were investigated and analyzed by X-ray diffraction (XRD), field emission scanning electron microscope (FE-SEM), four-point probe, and UV-vis spectrophotometer, respectively. These results show that multilayered graded thin films were well grown with decreased stress, and well crystallized along the c-axis. The optical transmittance of the films is around 94.8% at 400-800 nm wavelength, and the energy band-gap is around 3.27 eV, respectively. The sheet resistance value of 13.2 kΩ/sq shows a 30% improvement.