Modified thermal evaporation process using GeO2 for growing ZnO structures

In the current work, zinc oxide (ZnO) nano/microstructures are synthesized using a modified thermal-evaporation process by introducing germanium oxide (GeO2) powder mixed with metallic Zn powder as the raw material. Without the use of any catalyst and oxygen flow in the furnace system, GeO2 is utilized to provide an oxygen source for the growth of ZnO structure. The samples are treated by different temperatures ranging from 500 to 900 degrees C. Morphology, phase structure, and photoluminescence properties are investigated by scanning electron microscopy (SEM), X-ray diffractometer (XRD) and photoluminescence (PL) spectrometer. The structures and morphologies of the samples were found to vary with growth temperature. The XRD diffraction peaks show that the films grown at temperature from 600 to 800 degrees C consist of hexagonal wurtzite ZnO structures. Room-temperature PL measurement revealed ZnO spectra representing two bands: near-band-edge emission in the ultraviolet (UV) region and broad deep-level emission centered at about 500 nm. The strong UV emission in the PL spectra indicates that the GeO2 supplies sufficient oxygen for formation of ZnO structures with few oxygen vacancies. The growth mechanism and the roles of GeO2 for formation of ZnO structures are discussed in detail. (C) 2012 Elsevier Ltd. All rights reserved.