Radiative defects, emission and structure of ZnO nanocrystals obtained by electrochemical method

Abstract

Radiative defects, emission and structure of ZnO nanocrystals (NCs) have been studied by means of the scanning electron microscopy (SEM), energy dispersion spectroscopy (EDS), X-ray diffraction (XRD) and photoluminescence (PL) techniques. ZnO NCs were prepared by etching Zn sheets and annealing at 200–400°C in ambient air. The NC size and volume of ZnO crystalline phase increase with annealing temperature rising from 200°C up to 400°C. Simultaneously, XRD parameters and inter-planar distances in ZnO NCs vary no monotonically: decreasing upon annealing at 200–360°C and increasing at 400°C annealing. The PL intensity variation of orange, yellow, green and blue PL bands correlates with the change of XRD parameters. The study of PL band thermal decays, within the range 10–300K, permits to estimate decay activation energies and to analyze the nature of donors and acceptors responsible for the orange, yellow and green PL bands in ZnO NCs.The electrochemical method allows varying the PL intensity of different PL bands by a controllable way that is interesting for ZnO NC film application in “white” light emitting device structures.