Photoluminescence properties of hexagonal indium tin oxide nanopowders prepared by solvothermal method

Abstract

Hexagonal structure indium tin oxide (ITO) nanopowders were prepared by a solvothermal process at only 175 °C for 24 h and post-annealing at 400 °C, using metal indium and SnCl4·5H2O as the raw materials. The morphology, crystal structures and structure defects of products were, respectively, analyzed by scanning electron microscopy (SEM), X-ray diffraction (XRD) and confocal microprobe Raman system, the elemental state was investigated by X-ray photoelectron spectroscopy (XPS), and the optical properties were carried out by ultraviolet–visible (UV-Vis) and photoluminescence (PL) spectrophotometers. The results show that the products are hexagonal structure with a particles size of 28–41 nm; the morphology of products consists of sphere and irregular cubic. When pH values of solution increase, the content of oxygen vacancies increases and the optical band gap varies from 3.59 to 3.78 eV. The products exhibit strong emission at 417 nm with an excitation of 370 nm, and the PL intensity of samples increases with pH values increasing. Contrasting to cubic structure ITO powder, the hexagonal structure ITO has narrower optical band gap and higher PL intensity under the same excitation wavelength.