Effect of RF power on physical and electrical properties of Al-doped ZnO thin films

We deposited Al-doped zinc oxide (AZO) thin films on PTFE flexible substrate by RF sputtering with respect to the power in the range 125-155 W. XRD-pattern showed the preferred c-axis (002) orientation regardless the rf-power, which confirmed the hexagonal wurtzite crystal structure. The dislocation density (δ), and strain (ε) of AZO thin films were determined to be 1.86×10¹⁵-0.74×10¹⁵ m^-2, and 85.6×10^-3-54.0×10^-3, respectively. The AZO film deposited at 135 W showed the smooth and uniform microstructure, which is the highest intensity of XRD-pattern due to smaller grain size. The refractive index (n) increased from 2.24 to 2.34, while the bandgap (Eg), and urbach tail (Eu) decreased from 3.66 to 3.31 eV and 0.33 to 0.22 eV as the RF power increased from 125 to 155 W. The sheet resistance and figure of merit (FOM) of AZO thin films were observed to be the lowest 53.36 Ω/cm and 5.17×10^-10Ω^-1 for the sample 135 W. (author)