Solution-processable zinc oxide based thin films with different aluminum doping concentrations

Abstract

Al doped zinc oxide (AZO) thin films are attempted to be formed on glass substrates via solution processing with 0, 0.5, 1, 2, 3, and 4 at% Al doping concentrations. Analysis of X-ray diffraction patterns and scanning electron microscopy micrographs indicate that the AZO thin films belong to the wurtzite hexagonal structure with (100), (002), (101), (102), (110), (103), (112) and (201) orientations, and show that the grain size of AZO thin films decreases with higher Al doping concentrations. Optical and electrical properties of the AZO thin films are characterized from using a UV/vis spectrometer and a four-probe measurement system, respectively. The AZO thin films obtained have a minimum sheet resistance of 30.41 Ω/sq for the dopant concentration of 1 at%, and a bandgap energy varying from 3.26 eV to 3.16 eV as the Al doping concentration increases from 0 to 4 at%. The maximum figure of merit value of 7.48 × 10−3 (Ω/sq)−1 corresponds to the deposition of the AZO thin film with 2 at% Al doping.