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arXiv 2005.14704cond-mat.mtrl-sci
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Si(001)衬底上化学气相输运生长的ZnO纳米线的聚结、晶向和发光

Coalescence, crystallographic orientation and luminescence of ZnO nanowires grown on Si(001) by chemical vapour transport

S. Fernández-Garrido, C. Pisador, J. Lähnemann, S. Lazić, A. Ruiz, A. Redondo-Cubero

摘要:

我们分析了在Si(001)衬底上用化学气相输运法生长的自组装ZnO纳米线的形貌、结构和发光特性。通过扫描电子显微镜检查的纳米线合奏揭示,不可忽略的部分的纳米线合并在一起,形成合并的聚集体在生长过程中。我们表明,聚结度可以明确量化的纳米线的横截面形状的统计分析。通过X射线衍射的结构性能的检查的证据表明,纳米线结晶在纤锌矿相,沿c轴伸长,并在平面内随机取向。通过光致发光和阴极发光光谱研究了ZnO纳米线的发光,发现ZnO纳米线的发光主要由两个带组成,即近带边发射和ZnO缺陷相关的特征绿光。扫描电子显微镜和单色阴极发光强度图的互相关表明:(i)聚结关节作为非辐射复合的来源,和(ii)ZnO纳米线的发光是不均匀分布在单纳米线水平。具体而言,近带边发射来自纳米线芯,而缺陷相关的绿色发光源自靠近纳米线侧壁的体积。二维模拟的ZnO纳米线所支持的光波导模式,使我们能够排除波导效应的发光不均匀性的根本原因。因此,我们将这一观察归因于核-壳结构的形成,其中壳的特征在于相对于核的高浓度的发绿光的辐射点缺陷。

英文摘要:

We analyse the morphological, structural and luminescence properties of self-assembled ZnO nanowires grown by chemical vapour transport on Si(001). The examination of nanowire ensembles by scanning electron microscopy reveals that a non-negligible fraction of nanowires merge together forming coalesced aggregates during growth. We show that the coalescence degree can be unambiguously quantified by a statistical analysis of the cross-sectional shape of the nanowires. The examination of the structural properties by X-ray diffraction evidences that the nanowires crystallize in the wurtzite phase, elongate along the c-axis, and are randomly oriented in plane. The luminescence of the ZnO nanowires, investigated by photoluminescence and cathodoluminescence spectroscopies, is characterized by two bands, the nearband-edge emission and the characteristic defect-related green luminescence of ZnO. The cross-correlation of scanning electron micrographs and monochromatic cathodoluminescence intensity maps reveals that: (i) coalescence joints act as a source of non-radiative recombination, and (ii) the luminescence of ZnO nanowires is inhomogeneously distributed at the single nanowire level. Specifically, the near-band-edge emission arises from the nanowire cores, while the defect-related green luminescence originates from the volume close to the nanowire sidewalls. Two-dimensional simulations of the optical guided modes supported by ZnO nanowires allow us to exclude waveguiding effects as the underlying reason for the luminescence inhomogeneities. We thus attribute this observation to the formation of a core-shell structure in which the shell is characterized by a high concentration of green-emitting radiative point defects with respect to the core.

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