Spatially resolved luminescence properties of ZnO tetrapods

ZnO tetrapods were prepared by Zn-vapour deposition at 740 degrees C in Argon and subsequent oxidation in air for 1-30 min. The photoluminescence (PL) and cathodoluminescence (CL) spectra were measured from ZnO particles collected at various distances from the Zn source representing decreasing dimensions. The ZnO tetrapods showed a green emission centred at 516 nm (2.40 eV) band and the exciton emission at 387 nm (3.20 eV). The measured data suggested that the green emission is strongly increased for particle sizes below 500 nm, whereas the exciton emission is dominant for particle size larger than 500 nm. Spatially resolved CL-measurement on individual tetrapod legs showed, that the green emission increases with decreasing ZnO leg diameter. To our knowledge, the local CL spectroscopic measurements were correlated with the dimensions of the individual ZnO tetrapods for the first time.