Structural, optical and electrical evolution of Al and Ga co-doped ZnO/SiO/glass thin film: Role of laser power density

This study investigates the characteristics of laser annealed thin films of Al-Ga co-doped zinc oxide (ZnO:Al-Ga) nanoparticles on top of SiO/glass. The samples are synthesized using simple sol-gel, spin coating and radio frequency magnetron sputtering methods. The studies on the structural, optical and electrical properties of the pre-annealed sample and samples annealed at different power densities are conducted using a variety of characterization techniques. The samples exhibit a hexagonal wurtzite structure. Spectroscopic and nano-imaging techniques confirm that by increasing the laser power density, the crystallinity of the samples is improved and the nanoparticle size is enhanced from ∼10 nm to ∼35 nm. Spectroellipsometry is employed to calculate the refractive index, extinction coefficient, and real and imaginary components of the dielectric constant. The resistivity exhibits a minimum value at 440 mJ cm. Results demonstrate that the optical band gaps of the samples are between 3.29 and 3.41 eV, which are greater than that of pure bulk ZnO (band-gap of 3.21 eV). Several vibrational modes occur as a result of the dopant combination in the ZnO lattice. A discussion on the origins of modes and their intensity changes is provided. This work suggests that a laser annealing process can be an effective tool to fabricate various thin films with enhanced crystallinity. The optical and electrical properties can also be adjusted by varying the power density.