Abstract The growth of high quality ZnO thin films is a hot research topic in the field of optoelectronic materials. In this study, high quality ZnO thin films with a double-layer structure were obtained by sol-gel method. Al-doping induced transition from polycrystals to single crystals in the ZnO thin films was found. The results show that Al-doping improves the c-axis orientation of ZnO thin films. When the Al-doping concentration is higher than 4at%, the frustum of hexagonal pyramid (FHP) shaped ZnO nanostructures are formed on the polycrystalline ZnO thin films surface. As the Al-doping concentration further rises, the areal density of the FHP-shaped nanostructures also gradually increases and the size becomes more uniform. Both SAED patterns and high-resolution TEM images indicate that the FHP-shaped ZnO nanostructures are single crystals. It is of great scientific significance to transform polycrystalline ZnO into single crystal ZnO by Al-doping combined with a simple heat-treatment process. Compared with pure ZnO thin films, the FHP-shaped nanostructures on the surface show better UV emission performance, suggesting these materials are ideal ones for the preparation of ZnO-based UV emitters. The authors propose that the growth mechanism of FHP-shaped ZnO nanostructure is a multi-step solid-solid reaction dominated by surface diffusion of zinc atoms.

中文翻译：

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ZnO薄膜中掺杂诱导从多晶到单晶的转变

摘要 高品质ZnO薄膜的生长是光电材料领域的一个热门研究课题。在这项研究中，通过溶胶-凝胶法获得了具有双层结构的高质量 ZnO 薄膜。发现在 ZnO 薄膜中铝掺杂诱导从多晶到单晶的转变。结果表明，Al掺杂改善了ZnO薄膜的c轴取向。当Al掺杂浓度高于4at%时，在多晶ZnO薄膜表面形成六棱锥（FHP）形ZnO纳米结构的平截头体。随着Al掺杂浓度的进一步升高，FHP形纳米结构的面密度也逐渐增加，尺寸变得更加均匀。SAED 图案和高分辨率 TEM 图像均表明 FHP 形 ZnO 纳米结构是单晶。通过Al掺杂结合简单的热处理工艺将多晶ZnO转化为单晶ZnO具有重要的科学意义。与纯ZnO薄膜相比，表面的FHP形纳米结构表现出更好的紫外发射性能，表明这些材料是制备ZnO基紫外发射体的理想材料。作者提出，FHP 形 ZnO 纳米结构的生长机制是多步固-固反应，以锌原子的表面扩散为主。表明这些材料是制备 ZnO 基紫外线发射器的理想材料。作者提出，FHP 形 ZnO 纳米结构的生长机制是多步固-固反应，以锌原子的表面扩散为主。表明这些材料是制备 ZnO 基紫外线发射器的理想材料。作者提出，FHP 形 ZnO 纳米结构的生长机制是多步固-固反应，以锌原子的表面扩散为主。