Strontium doping effect on characteristics of ultrasonically sprayed zinc oxide thin films

Abstract

In the present work, Sr-doped ZnO (SZO) thin films were grown on heated glass substrates (250 °C) by the ultrasonic spray technique. The effect of strontium concentration on the structural and physical characteristics was studied. The molar ratio of strontium in the ultrasonically sprayed solution was varied from 0 to 5 at.%. Several characterization techniques have been investigated to analyze the SZO thin films. The X-ray diffraction results showed that the SZO thin films exhibited the hexagonal wurtzite structure of ZnO with a preferential orientation along (002) plane. Scanning electron microscope indicated that the surface morphology of the SZO thin films changed with the increase in Sr concentration. No impurity was present in all the SZO films which was confirmed by the elemental composition analysis. Moreover, Fourier transform infrared spectroscopy showed the chemical bonding of zinc oxide (ZnO) and confirmed the incorporation of the dopant into the ZnO lattice. From the UV–Vis studies, it was found that the optical band gap decreased from 3.34 to 3.04 eV by increasing Sr doping concentration. Measurements of the Hall Effect indicated that all the elaborated samples exhibited n type conductivity. From all the films studied, SZO (1 at.%) was the most suitable for applications in optoelectronic devices, where a large figure of merit was required.