Controlling the aspect ratio of Zn(1−x)Eu(x)O nanostructures obtained by a statistical experimental design involving atomic layer deposition and microwave-assisted hydrothermal methods

Different aspect ratio nanostructures of pure ZnO and Zn(1−x)EuxO were produced through the application of a statistical factorial design 23. The procedure consisted of two stages. First, the growth of ZnO thin films by atomic layer deposition on silicon (111) substrates, by decomposition of the metal precursor, diethyl zinc, at 190 °C and 0.25 Torr. In the next stage, those films were processed using the microwave-assisted hydrothermal method to promote the growing of ZnO nanostructured compounds, using a precursor solution of Zn(NO3)2·6H2O and hexamethylene tetramine, acting as a bi-dentate ligand capable of bridging two Zn2+ ions in solution. In addition, europium-doped ZnO (Zn(1−x)EuxO) and ZnO nanostructures were produced using Zn(NO3)2·6H2O and Eu(NO3)3·5H2O. The experimental levels (values) considered for every factor were Eu3+ concentration (0.02 and 0.06, atomic, %), temperature (80° and 120 °C) and time (30 and 50 min). The synthesis products were characterized through X-ray diffraction, scanning electron microscopy, X-ray photoelectron spectroscopy and photoluminescence measurements. Our results demonstrate that it is possible to produce nanostructures with specific size, morphology and physical properties depending on the specific synthesis based on our proposed experimental design.