Abstract
Hexagonal c-axis oriented zinc oxide (ZnO) nanorods (NRs) with 120-300 nm diameters are synthesized via the low temperature aqueous chemical route at 80 °C on silver-coated glass substrates. The influence of varying the precursor solutions stirring durations on the concentration and spatial distributions of deep level defects in ZnO NRs is investigated. Room temperature micro-photoluminesnce (μ-PL) spectra were collected for all samples. Cathodoluminescence (CL) spectra of the as-synthesized NRs reveal a significant change in the intensity ratio of the near band edge emission (NBE) to the deep-level emission (DLE) peaks with increasing stirring durations. This is attributed to the variation in the concentration of the oxygen-deficiency with increasing stirring durations as suggested from the X-ray photoelectron spectroscopy analysis. Spatially resolved CL spectra taken along individual NRs revealed that stirring the precursor solutions for relatively short duration (1-3 h), which likely induced high super saturation under thermodynamic equilibrium during the synthesis process, is observed to favor the formation of point defects moving towards the tip of the NRs. In contrary, stirring for longer duration (5-15 h) will induce low super saturation favoring the formation of point defects located at the bottom of the NRs. These findings demonstrate that it is possible to control the concentration and spatial distribution of deep level defects in ZnO NRs by varying the stirring durations of the precursor solutions.
Highlights
INTRODUCTIONzinc oxide (ZnO) nanostructures synthesized by the low temperature solution approach are sensitive to synthesis parameters and conditions, i.e. pH, precursor concentration, temperature, and reaction time.[8,21]
The X-ray diffraction (XRD) patterns of all the as-synthesized zinc oxide (ZnO) NRs prepared under different stirring durations show peaks, which can be indexed to the hexagonal wurtzite structure of ZnO (JCPDS Card No.36-1451)
We have investigated the influence of the stirring durations of the precursor solutions on the concentration and spatial distributions of deep-level emission (DLE) in ZnO NRs
Summary
ZnO nanostructures synthesized by the low temperature solution approach are sensitive to synthesis parameters and conditions, i.e. pH, precursor concentration, temperature, and reaction time.[8,21]. The effect of the stirring durations on the concentration and spatial distributions of the radiative deep level defects in as-synthesized ZnO NRs is investigated
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