Novel rare earth Gd and Al co-doped ZnO thin films prepared by nebulizer spray method for optoelectronic applications

In this study, for the first time, rare earth element gadolinium and aluminum co-doped zinc oxide (Gd:AZO) films were prepared on insulating glass plates using cost-effective nebulizer spray method with various Gd co-doping levels (0, 0.5, 1 and 1.5 at.%). The deposited films were characterized using X-ray diffraction, FT-Raman, AFM, EDAX, UV-VIS spectroscopy, Photoluminescence (PL) spectrum and Hall Effect measurement at room temperature. From XRD study, it is confirmed that the Gd and Al ions are incorporated into ZnO lattice. Film crystallinity is slightly reduced due to Gd content by increasing lattice defects. Topology of AFM images displays a slight increase of Gd:AZO thin film roughness from 20 nm to 36 nm, with an increase of thickness from 232 to 324 nm respectively. Elemental mapping and EDAX studies confirmed the existence of Zn, O, Al and Gd elements in the prepared Gd:AZO thin films. Spray deposited pristine AZO films showed maximum optical transmittance similar to 91% in entire wavelength spectrum and energy gap value similar to 3.31eV. The observed PL spectra showed as a UV emission at 387 nm for deposited films. The obtained minimum resistivity and maximum figure of merit values are 3.42 x 10(-4) Omega cm, and 18.68 x 10(-3) (Omega/sq)(-1), respectively for 1.5 at.% Gd co-doped AZO thin film. Both values are decent enough for opto-electronic devices.