The effect of cooling rate during hydrothermal synthesis of ZnO nanorods

Abstract

The hydrothermal method was employed in order to obtain zinc oxide nanorods directly on Si/SiO2/Ti/Zn substrates forming brush-like layers. In the final stages of synthesis, the reaction vessel was naturally cooled or submitted to a quenching process. X-ray diffraction results showed that all the nanostructures grew [0001] oriented perpendicular to the substrate. The influence of the cooling process over the morphology and dimensions of the nanorods was studied by Scanning Electron Microscopy. High Resolution Transmission Electron Microscopy images of the quenched samples showed that the ZnO crystal surfaces exhibit a thin layered coating surrounding the crystal with a high degree of defects, as confirmed by Raman spectroscopy results. Photodetectors made from these samples exhibited enhanced UV photoresponses when compared to the ones based on naturally cooled nanorods.