Cathodoluminescence Property of ZnO Nanophosphors Prepared by Laser Ablation

Abstract

ZnO nanophosphors with a diameter of 7 -50 nm have been fabricated under an oxygen gas atmosphere at room temperature by evaporating ZnO powder or Zn targets using pulsed laser ablation. The size and uniformity of ZnO nanophosphors strongly depend on oxygen gas pressure. Results of cathodoluminescence analysis show strong ultraviolet, blue, green, and greenyellow emissions from ZnO nanophosphors excited by a $150 eV low-energy electron beam emitted from carbon nanotubes, depending upon the target material and oxygen gas pressure. Ultraviolet, blue, green, and green-yellow emissions can be attributed to the transitions from the conduction band to the valence band, the Zn i level to the V Zn level or the valence band, the V O level to the valence band, and the Zn i level to the O i level, respectively.

High-pressure synthesis and luminescent properties of cubic ZnO/MgO nanocomposites

“…The blue luminescence from ZnO NP has been usually attributed to transitions between Zn interstitial ͑Zn i ͒ and Zn vacancy ͑V Zn ͒ levels. 26 In our case rsZnO/MgO nanocomposites show the blue-shifted luminescence with lower intensity indicating the higher defect incorporation density and the higher concentration of free carriers.…”

Defect Control of ZnO Nano-particles Fabricated by Pulsed Nd:YAG Laser Ablation

“…In previous results, we reported the size of ZnO nano-particles is 11.8 nm, when oxygen pressure was less than 5 kPa. [4] In this experiment, the typical size of the ZnO particles is about 10 nm. As we can observe the size distribution of particles by measuring size of particles taken in the TEM images, the dimensions are typically in the range 10-20 nm, having a large surface to volume ratio.…”

“…The CL analysis presented in Fig. 5 shows two dominant peaks: a strong UV peak, attributed to the near band edge emission (NBGEE) [4] and a broad green-yellow peak, attributed to the deep-level emission. The luminescence intensity of the UV peak increases with raising the oxygen partial pressure from 300 to 1000 Pa, while the intensity of the defect-relates emission peak seems no obvious change.…”

“…In our previous report, the green-yellow emission has been assigned to a large number of defect centers including zinc interstitial atoms (Zn i ), oxygen vacancy (Vo) and oxygen interstitial atoms (O i ) for a structured emission. [4,27] As well known, the oxidation rate of the vaporized Zn atoms/ions is crucial to control the intrinsic defect during PLD process. In the mixture plasma, helium in 35 [3] 611-615 (2010) [32] When the oxygen pressure varies from 500 Pa to 1000 Pa, the enhanced three-body collision frequency involving oxygen atoms/ions and zinc atoms/ions gives rise to the synthesis of a better crystalline structure of ZnO.…”

“…[1][2][3][4][5] Especially ZnO nano-materials with a wide variety of structures show great promise in the field of nano-scale photo-electronic devices, because of their large surface area-to-volume ratio and ease of crystallization and anisotropic growth. [2,3,6,7] However, the surface defects of nano-size ZnO particles have been found to quench the luminescence of exciton and hinder the charge transfer between ZnO and adsorbed molecules at the interface.…”