Identification of oxygen and zinc vacancy optical signals in ZnO

Abstract

Photoluminescence spectroscopy has been used to study single crystalline ZnO samples systematically annealed in inert, Zn-rich and O-rich atmospheres. A striking correlation is observed between the choice of annealing ambient and the position of the deep band emission (DBE) often detected in ZnO. In particular, annealing in O2 results in a DBE at 2.35±0.05eV, whereas annealing in the presence of metallic Zn results in DBE at 2.53±0.05eV. The authors attribute the former band to zinc vacancy (VZn) related defects and the latter to oxygen vacancy (VO) related defects. Additional confirmation for the VO and VZn peak identification comes from the observation that the effect is reversible when O- and Zn-rich annealing conditions are switched. After annealing in the presence of ZnO powder, there is no indication for the VZn- or VO-related bands, but the authors observe a low intensity yellow luminescence band peaking at 2.17eV, probably related to Li, a common impurity in hydrothermally grown ZnO.

Annealing effects on optical properties of low temperature grown ZnO nanorod arrays

“…43 Recently, this deep level emission band had been identified and at least two different defect origins ͑V O and V Zn ͒ with different optical characteristics were claimed to contribute to this deep level emission band. [44][45][46] From Figs. 3͑a͒ and 3͑b͒, it can be seen that the dependence of the PL intensity versus the annealing temperature showed similar behaviors for the ZNAs with different diameters.…”

Depth-resolved cathodoluminescence study of zinc oxide nanorods catalytically grown on p-type 4H-SiC

“…The variation in the green emission peak position is attributed to different relative contributions from, e.g. V O , V Zn , O Zn and Cu related defects caused by fluctuations in the growth conditions for different growth methods [13]. In the CL and EL spectra, the DBE has a peak at 521 ±0.04 nm we can say that this is due to V O in the ZnO nanorods due to which green light is emitted which contribute to the white light emitted from the device.…”

“…Photoluminescence (PL) is considered as an important tool for optical characteristics of ZnO-nanostructures [12]. ZnO has two main emission bands in its room temperature PL spectrum; these are a sharp UV band and deep band emission (DBE) or green emission due to deep defect states in the band gap [12,13]. Although much research on the origin of the deep band emission has been published, no consensus was reached.…”

“…The p-type SiC film was grown by conventional CVD technique on n-SiC commercial substrate [20]. The acceptor concentration in the p-SiC thin film was around 5x10 18 cm -3 and the thickness was around 1 m. The ZnO NRs were grown by the vapour-liquid-solid (VLS) technique [13]. First we cover a small portion of the p-SiC substrate for defining ohmic contacts on p-SiC.…”

“…Although much research on the origin of the deep band emission has been published, no consensus was reached. ZnO can exhibit different emissions in the visible range including violet, blue, green, yellow, and orange-red, which are associated with intrinsic as well as extrinsic defects [2,13]. The free carrier concentration, doping compensation, minority carrier lifetime, and luminescence efficiency are directly or indirectly related to the defects [14].…”