Abstract
In this paper, ZnO/MgO core-shell nanowires are synthesized based on a one-step chemical vapor deposition (CVD) method. The scanning electron microscopy (SEM) images of core-shell nanowires indicate that Mg addition has little influence on the morphology of the synthesizing products. High crystalline quality ZnO/MgO core-shell nanowires instead of ZnMgO ternary compounds are identified by X-ray diffraction (XRD) patterns, transmission electron microscopy (TEM) images, selected area electron diffraction (SAED) pattern and photoluminescence (PL) spectra. The experimental results show that the ultraviolet (UV) emission of these samples with MgO shell is 12 times higher than that of the corresponding bare ZnO nanowires, and the suppression of the green emission is only 1/45 of the bare ZnO nanowires. It is also found that PL properties are proportional to Mg ratio. The UV emission enhancement and green emission suppression are due to the passivation of surface defects and the improvement of ZnO crystalline quality. The results are very useful for the development of optical devices based on nanowires.
Highlights
ZnO has widely been used as the material for transparent electrode, photodetector, laser and photodiode.[1,2] Compared to ZnO film and bulk material, ZnO nanowires have better performance in the photoelectric conversion and the transmission for the quantum confinement effect.[3]
High crystalline quality ZnO/MgO coreshell nanowires instead of ZnMgO ternary compounds are identified by X-ray diffraction (XRD) patterns, transmission electron microscopy (TEM) images, selected area electron diffraction (SAED) pattern and photoluminescence (PL) spectra
We proposed a one-step method for the fabrication of ZnO/MgO core-shell nanowires with good morphology and advanced photoluminescence performance by one-step chemical vapor deposition (CVD) method
Summary
ZnO has widely been used as the material for transparent electrode, photodetector, laser and photodiode.[1,2] Compared to ZnO film and bulk material, ZnO nanowires have better performance in the photoelectric conversion and the transmission for the quantum confinement effect.[3]. The properties including photoluminescence (PL) performance of the core are improved.[6] ZnO/MgO core-shell nanowires can be post-annealed to produce ZnMgO structure,[7] and the core-shell structure has higher photoluminescence performance over bare ZnO nanowires.[8] Due to MgO coating, the improved performance can significantly passivate the surface defects of ZnO nanowires.[9] Nanoscale heterojunction has higher carrier injection efficiency compared with ZnO/MgO film structure.[10] Yang et al.[11] has reported electrically pumped near-ultraviolet lasing from ZnO/MgO core shell structure. There several methods have been developed to synthesize ZnO/MgO core-shell nanostructures. Most of these methods are carried out by a two-step process in which the preparation of ZnO core and MgO shell are conducted separately.[12,13,14,15] Hydrothermal growth methods are the common way of preparing MgO shell.
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