Effect of Zn<SUP>2+</SUP> Source Concentration on Hydrothermally Grown ZnO Nanorods

Abstract

We studied the effect of Zn2+ source concentration on the structural and optical properties of hydrothermally grown ZnO nanorods. The nanorods were grown on ZnO/p-Si(111) substrate using by a hydrothermal process in various concentrations of reagent at a low temperature (approximately 95 degrees C) and the structural and optical characteristics of ZnO nanorods were subsequently investigated by X-ray diffraction, field-emission scanning electron microscopy, and room temperature photoluminescence. The results demonstrate that the morphology and crystallinity of ZnO nanorods are influenced by the overall concentration of the precursor. The density and diameter of ZnO nanorods with a hexagonal structure are especially sensitivite to concentration of reactants. Furthermore, the structural transition is shown by increasing concentration. At the lowest concentration of Zn2+, the ZnO nanorods grow as single crystals with a low density and variable orientations. On the contrary, at the highest concentration, the nanorods grow as polycrystas due to the supersaturated Zn2+ source.

Cu-doped ZnO nanorod arrays: the effects of copper precursor and concentration

“…It is evident that there is a slight lattice deformation in the Cu-ZnO lattice, which may be assigned to the diminishing Cu Zn -O bonds [32]. In this study, with up to 2% Cu concentration from the two precursors, neither the Cu nor CuO phases are observed in the XRD measurements, which indicates that the Cu impurities are dissolved completely in the ZnO crystal lattice [26,30]. …”

“…This shift is more significant for sample S3. On the other hand, previous research showed that at low concentrations (<1.5 at.%) of Cu, the peak position is not significantly affected by Cu doping, while at high concentration, a slight shift towards higher angles is reported due to the substitution of Zn 2+ (ionic radii = 0.074 nm) by Cu 2+ (ionic radii = 0.057 nm) [30,31]. Additionally, these changes in crystallinity might be due to the changes in the atomic environment as a result of Cu incorporation into the ZnO lattice.…”

“…This result suggests that the samples doped with Cu(CH 3 COO) 2 (S2 and S3) have a low concentration of crystallographic defects. The decrease in the crystal quality of the samples doped with Cu(NO 3 ) 2 (S4 and S5) might be attributed to (i) the formation of [Cu Zn -Zn i ] x complexes and/or (ii) the lack of hydrolysis process in ${\mathrm{NO}}_3^{-}$, which could increase the anion vacancies in the ZnO lattice [29,30]. However, the strong (002) peaks' positions of the Cu-doped nanorods showed a slight shift toward a lower angle relative to the undoped nanorods.…”

Synthesis, Characterization, and Applications of ZnO Nanowires

“…However, a continuous increase in the solution concentration may not increase the density of the nanowires when its density is larger than the saturation density. Kim et al [84] reported that the density and diameter of ZnO nanorods are especially sensitive to the concentration of the reactants. Furthermore, the structural transition is shown by increasing the concentration.…”

Influence of OH−Ion Concentration on the Surface Morphology of ZnO-SiO2Nanostructure

“…Tailoring the morphology, shape, and size of ZnO could be a way of expanding its potential especially in solar cell and sensor technologies where reaction at the surface is very crucial. Works have been reported for controlling size and shape of ZnO nanostructures like varying the initial zinc and hydroxyl ion concentrations [5,6] and also by introducing silica (SiO 2 ) to ZnO as a concept of composite material [7,8]. With good mechanical resistance and high dielectric strength, SiO 2 is likely to be an ideal component to enhance the properties of ZnO.…”