School of Electrical and Electronic Engineering, Nanyang Technological University (NTU), Block S2, Nanyang Avenue, Singapore 639798, Singapore.
Nanoscale Res Lett. 2013 Dec 6;8(1):517. doi: 10.1186/1556-276X-8-517.
We report on efficient ZnO nanocrystal (ZnO-NC) emission in the near-UV region. We show that luminescence from ZnO nanocrystals embedded in a SiO2 matrix can vary significantly as a function of the annealing temperature from 450°C to 700°C. We manage to correlate the emission of the ZnO nanocrystals embedded in SiO2 thin films with transmission electron microscopy images in order to optimize the fabrication process. Emission can be explained using two main contributions, near-band-edge emission (UV range) and defect-related emissions (visible). Both contributions over 500°C are found to be size dependent in intensity due to a decrease of the absorption cross section. For the smallest-size nanocrystals, UV emission can only be accounted for using a blueshifted UV contribution as compared to the ZnO band gap. In order to further optimize the emission properties, we have studied different annealing atmospheres under oxygen and under argon gas. We conclude that a softer annealing temperature at 450°C but with longer annealing time under oxygen is the most preferable scenario in order to improve near-UV emission of the ZnO nanocrystals embedded in an SiO2 matrix.
我们报告了在近紫外区域中氧化锌纳米晶体（ZnO-NC）的高效发光。我们表明，嵌入 SiO2 基质中的 ZnO 纳米晶体的发光可以随着退火温度从 450°C 到 700°C 的变化而显著变化。我们成功地将嵌入 SiO2 薄膜中的 ZnO 纳米晶体的发射与透射电子显微镜图像相关联，以优化制造工艺。发光可以用两个主要贡献来解释，即近带边发射（UV 范围）和与缺陷相关的发射（可见）。由于吸收截面的减小，在 500°C 以上，这两种贡献的强度都呈现出尺寸依赖性。对于最小尺寸的纳米晶体，与 ZnO 带隙相比，只有使用蓝移的 UV 贡献才能解释 UV 发射。为了进一步优化发光性能，我们研究了在氧气和氩气下的不同退火气氛。我们得出的结论是，在 450°C 下进行较软的退火温度，但在氧气下进行更长时间的退火时间，是改善嵌入 SiO2 基质中的 ZnO 纳米晶体近紫外发光的最优选方案。
