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Effect of doping mechanism on photogenerated carriers behavior in Cu-doped ZnSe/ZnS/L-Cys core-shell quantum dots
摘要： Cu-doped ZnSe/ZnS/L-Cys core–shell QDs are prepared by both nucleation doping and growth doping in an aqueous synthesis method. Transport of photogenerated free charge carriers (FCCs) in these Cu-doped QDs is probed via a combination of surface photovoltaic (SPV), photoacoustic (PA), and electric-field-induced SPV techniques, supplemented by the UV–VIS absorption spectrum and Raman spectrum. The results confirm that the two doping mechanisms result in different doping locations and microelectronic structures of the Cu-doped QDs. The distinctive microelectronic structure of the QDs prepared by nucleation doping, as compared with those prepared by growth doping, results in a number of favorable SPV characteristics. For example, the QDs prepared by nucleation doping exhibit a higher SPV response intensity at 600 nm because of a higher concentration of photogenerated FCCs. The ratio of the strongest SPV response and the strongest PA signal of the QDs prepared by nucleation doping is up to 2.41 times greater than those of the QDs prepared by growth doping. This is because the greater numbers of photogenerated FCCs in the QDs prepared by nucleation doping generate the PV effect rather than the PA effect that is caused by a nonradiative de-excitation process. The position of the shoulder peak of the SPV response at a long wavelength of the QDs prepared by nucleation doping is significantly red-shifted compared with that of the QDs prepared by growth doping, leading to a broader SPV response range in the visible region. The QDs prepared by nucleation doping have a more obvious donor feature than those prepared by growth doping.
关键词： photogenerated carriers,Cu-doped ZnSe/ZnS/L-Cys,quantum dots,photoacoustic,surface photovoltaic,nucleation doping,growth doping
更新于2025-09-11 14:15:04
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Study of indium and antimony incorporation into SnS2 single crystals
摘要： Pure SnS2, 5% In-doped SnS2, 15% In-doped SnS2, 5% Sb-doped SnS2 and 15% Sb-doped SnS2 single crystals are grown in closed sealed quartz ampoule by direct vapour transport technique. The energy dispersive analysis of X-rays analysis of all the five as-grown single crystals showed them to be stoichiometric. The X-ray diffraction analysis showed that all the crystals are single phase possessing a hexagonal structure with (001) preferential orientation. The surface morphology of as-grown single crystals studied by scanning electron microscopy and optical microscopy showed crystal growth is by layer growth mechanism supported by screw dislocation. Selected area electron diffraction showed hexagonal spot pattern confirming the single crystalline nature of the crystals. Optical bandgap of the as-grown crystals determined by UV-Vis-NIR spectroscopy showed that the single crystals possess direct optical bandgap and the value varied between 1.89 and 2.31 eV. The photoluminescence spectra study showed the presence of six peaks. The Raman spectra showed SnS2 type the A1g vibrational mode and shifting in A1g vibrational mode with In and Sb doping. The results are elaborated in details.
关键词： Single crystal growth,Doping,Characterization,Crystal morphology,X-ray diffraction,Crystal structure
更新于2025-09-10 09:29:36