Hydrothermal Synthesis and Spectroscopic Properties of Crystalline ZnO Powders and Films

Abstract

Polycrystalline zinc oxide is synthesized under mild hydrothermal conditions (150–250°C). The phase composition, morphology, and pulsed cathodoluminescence (PCL) spectra of ZnO powders, polycrystalline films, and single crystals are studied as a function of synthesis conditions (the nature of the precursor, the type and concentration of the solvent, solution temperature, and the redox potential of the system). The crystallite size in the resultant materials varies from ∼100 nm to 10 μm, depending on the synthesis conditions. The PCL spectra measured under pulsed electron-beam (τ ∼ 2 ns) or laser (Nd:YAG, fourth harmonic, λ = 266 nm, τ ∼ 10 ns) excitation show two bands in the UV and visible spectral regions. The intensity ratio between these bands depends on the ZnO preparation conditions. The influence of the precursor and solvent on the PCL spectrum of ZnO is studied. The redox potential of the system is shown to have a strong effect on the luminescent properties of the resultant material.