Formation of interface defects of ZnO/ZnS core-shell nanowires and its optical properties investigations
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摘要: ZnO/ZnS核壳纳米结构因具有优异的光电特性，在光电子领域极具应用前景，其依靠核壳结构界面处载流子的束缚效应可更加有效地控制载流子的产生、传输和复合过程。为讨论ZnO/ZnS核壳结构界面状态及其相应的光学特性，生长了不同程度硫粉硫化的ZnO/ZnS核壳纳米线，再利用扫描电子显微镜(SEM)、透射电子显微镜(TEM)及光致发光光谱(PL)等测试表征手段，分析并讨论经过不同程度硫粉硫化后的ZnO/ZnS核壳纳米线界面处的结构及其光学性质的变化。通过分析ZnO/ZnS核壳结构形貌发现，ZnS成功包覆ZnO纳米线。随着硫化程度的增加，ZnO核结构被破坏，并在核壳界面处引入缺陷，导致形成具有不同结晶质量的ZnO/ZnS核壳纳米线结构，从而会影响ZnO/ZnS核壳纳米线的光学性质。结果表明，ZnO/ZnS核壳界面处缺陷较少时，对载流子的产生和传输具有一定的束缚作用，可以抑制非辐射复合效应，提高材料光学性能；当界面缺陷增加时，形成的缺陷能级则会降低材料的光学性能。Abstract: ZnO/ZnS core-shell nanostructures have great application prospects in optoelectronic area due to their excellent optoelectronic properties. They rely mainly on the binding effect of carriers at the interface of the core-shell structure to more effectively control carrier generation, transmission and recombination processing. In order to discuss the interfacial state of ZnO/ZnS core-shell structure and its corresponding optical properties, ZnO/ZnS core-shell nanowires with different amounts of sulfur powder vulcanization were grown and then characterized using scanning electron microscopy(SEM), transmission electron microscopy(TEM), Photoluminescence spectroscopy(PL). Analysis and discussion were conducted for the structure and optical properties of the ZnO/ZnS core-shell nanowire interface after sulfurization with different amounts of sulfur powder. By analyzing the morphology of the ZnO/ZnS core-shell structure, it was found that ZnS successfully coated ZnO nanowires and with the increase of vulcanization degree, the ZnO core structure was destroyed and defects were introduced at the core-shell interface, resulting in forming ZnO/ZnS core-shell structure with different crystal qualities. The structure affects the optical properties of ZnO/ZnS core-shell nanowires. The results show that when few defects appear at the interface of the ZnO/ZnS core shell, they have a binding effect on the generation and transport of carriers, thus inhibiting the non-radiative composite effect and improving the optical properties of the material. When the interface defects increase, the formed defect energy level reduces the optical properties of the material.
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Key words:
- core-shell nanostructures /
- localized states /
- interface defects /
- photoluminescence
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图 1 不同剂量硫粉硫化的ZnO/ZnS核壳纳米线的SEM图像，(a)、(b)2 mg，(c)、(d)5 mg，(e)、(f)10 mg，插图为相应的直径分布图
Figure 1. SEM of ZnO/ZnS core-shell nanowires with different amounts of sulfur powder, (a)、(b)2 mg, (c)、(d)5 mg, (e)、(f)10 mg. Insets show the corresponding diameter distributions
图 2 不同剂量硫粉硫化的ZnO/ZnS核壳纳米线TEM图像(a)2 mg，(c)5 mg，(e)10 mg；(b)、(d)、(f)为相应的SAED(Selected Area Electron Diffraction)图像
Figure 2. TEM images of ZnO/ZnS core-shell nanowires with different amounts of sulfur powder (a)2 mg, (c)5 mg, (e) 10 mg and corresbodingSAED image (b), (d), (f)
图 3 纯ZnO纳米线(a)及不同剂量硫粉(b)2 mg，(c)5 mg，(d)10 mg硫化的ZnO/ZnS核壳纳米线HRTEM图像，插图为ZnO纳米线和ZnS纳米颗粒的晶格条纹间距
Figure 3. HRTEM images of(a)pure ZnO nanowires and ZnO/ZnS core-shell nanowires with different amounts of sulfur powder (b)2 mg, (c)5 mg, (d)10 mg; inset shows the lattice fringe space of ZnO nanowires and ZnS nanoparticles
图 4 (a) 10 K时ZnO纳米线及不同剂量硫粉硫化的ZnO/ZnS核壳纳米线PL光谱，(b)10 K时UV区域光谱图，(c)ZnO纳米线及经过不同剂量硫粉硫化后10 K时UV区域PL光谱强度及半峰宽，(d)ZnO/ZnS硫化过程球棍模型
Figure 4. (a)PL spectra of ZnO nanowires and ZnO/ZnS core-shell nanowires with different amounts of sulfur powder at 10 K, (b)UV region spectra at 10 K, (c)PL spectral intensities and FWHMs of ZnO nanowires and ZnO/ZnS core-shell nanowires with different amounts of sulfur powder at 10 K, (d)ZnO/ZnS ball model with different sulfurization degrees
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