We investigated the effects of surface modification on the defect-related photoluminescence (PL) band in colloidal CdS quantum dots (QDs). A size-selective photoetching process and a surface modification technique with a Cd(OH)₂ layer enabled the preparation of size-controlled CdS QDs with high PL efficiency. The Stokes shift of the defect-related PL band before and after the surface modification was ∼1.0 eV and ∼0.63 eV, respectively. This difference in the Stokes shifts suggests that the origin of the defect-related PL band was changed by the surface modification. Analysis by X-ray photoelectron spectroscopy revealed that the surface of the CdS QDs before and after the surface modification was S rich and Cd rich, respectively. These results suggest that Cd-vacancy acceptors and S-vacancy donors affect PL processes in CdS QDs before and after the surface modification, respectively.

中文翻译：

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表面改性对胶体CdS量子点中与缺陷相关的光致发光的影响†

我们研究了表面改性对胶体CdS量子点（QDs）中与缺陷相关的光致发光（PL）带的影响。Cd（OH）_2的尺寸选择光刻工艺和表面改性技术层使得能够制备具有高PL效率的尺寸受控的CdS QD。表面改性前后与缺陷相关的PL带的斯托克斯位移分别为〜1.0 eV和〜0.63 eV。斯托克斯位移的这种差异表明，与缺陷相关的PL带的起源已通过表面改性而改变。X射线光电子能谱分析表明，表面改性前后CdS量子点的表面分别为富S和富Cd。这些结果表明，Cd-空位受体和S-空位供体分别影响表面修饰前后CdS QDs中的PL过程。