Structural and optical properties of Iodine doped zinc oxide nanoparticles

Abstract

Iodine-doped zinc oxide (viz., ZnO1-xIx) nanoparticles were prepared using the sol-gel method. The samples were treated at 700 degrees C in air for 1h. The structural, morphological, and optical properties were measured using an X-ray diffractometer (XRD), a field emission scanning electron microscope (FE-SEM), UV-visible spectroscopy (UV/vis), and Raman spectroscopy, respectively. XRD results showed that the pure and doped samples have a wurtzite hexagonal structure, indicating the presence of some impurities in doped samples. The lattice parameters a and c were observed to be closer to the reported values for pure ZnO. The average crystalline size values of samples were calculated and found to be between 84 +/- 18 and 177 +/- 53 nm. The FE-SEM micrographs reveal that the particle sizes decreased from 77 to 57 nm with an increasing I concentration from x = 0.0 to x = 0.4, respectively. The morphologies of the samples were changed from particle to flask shape at higher I concentrations of 0.6 and 0.8 with average diameters of 213 and 427 nm. The increasing I concentration from 0.0 to 0.8 narrows the optical energy gap (Eg) from 3.271 to 3.242 eV due to the presence of oxygen vacancies or the lattice expansion caused by doping. Raman spectra of samples consist of the E2(high) mode, which confirmed the wurtzite hexagonal structure and it is located between 435 and 436 cm-1 except for x = 0.6, where the E2(high) mode was shifted to the higher wavenumber could be due to defects or anisotropic internal strains consistent to different growth directions.