Phase separation inside the CdTe - CdSe type II quantum dots revealed by synchrotron X-ray diffraction and scattering
Journal
Journal of Physical Chemistry C
Journal Volume
112
Journal Issue
26
Pages
9617-9622
Date Issued
2008
Author(s)
Abstract
Using synchrotron powder X-ray diffraction (PXRD) and small-angle X-ray scattering (SAXS), we have studied the structures of the two CdSe/CdTe and CdTe/CdSe type II quantum dots (QDs), including the crystalline structure, particle shape and size, as well as phase separation of the two components. The X-ray results suggest that the spherical CdTe/CdSe QDs of the size ∼8 nm, synthesized in a two-step procedure with CdTe nanoparticles (4 nm) as nuclides, have the structure of a CdTe-rich core enclosed by a CdSe shell. On the other hand, the spherical CdSe/CdTe QDs of the size ∼9 nm, synthesized via a similar two-step procedure but with CdSe nanoparticles (∼3 nm) as nuclides, show mainly one-phase structure with a relatively uniform distribution of CdSe and CdTe. The phase separation of the two components CdSe and CdTe inside each of the two QDs, a decisive factor in the photovoltaic applications, is furthermore examined using anomalous SAXS (ASAXS) for a consistent conclusion. For comparison, single-phase nanoparticles CdSe and CdTe are also examined. The correlation between the synthesis procedures and the corresponding structures of the QDs is discussed. © 2008 American Chemical Society.
SDGs
Other Subjects
Atoms; Cadmium compounds; Diffraction; Isomers; Isotopes; Nanoparticles; Nanostructured materials; Nanostructures; Optical waveguides; Particle accelerators; Phase modulation; Phase separation; Quantum electronics; Scattering; Semiconductor quantum dots; Separation; Size separation; Synchrotrons; X ray analysis; X ray diffraction; X ray scattering; CdSe nano-particles; CdTe nanoparticles; Crystalline structures; Particle shape and size; Photovoltaic applications; Small-angle x-ray scattering; Synchrotron powder X-ray diffraction; Synchrotron x-ray diffraction; Two-step procedure; Type II quantum dots; Unifor m distribution; Cadmium alloys
Type
journal article