Size-Dependent Fault-Driven Relaxation and Faceting in Zincblende CdSe Colloidal Quantum Dots

Research output: Contribution to journal/Conference contribution in journal/Contribution to newspaperJournal articleResearchpeer-review

DOI

  • Daniele Moscheni, Università dell’Insubria, Italy
  • Federica Bertolotti
  • Laura Piveteau, ETH Zürich, Empa-Swiss Federal Laboratories for Materials Science and Technology, Switzerland
  • Loredana Protesescu, ETH Zürich, Empa-Swiss Federal Laboratories for Materials Science and Technology, Switzerland
  • Dmitry N Dirin, ETH Zürich, Empa-Swiss Federal Laboratories for Materials Science and Technology, Switzerland
  • Maksym V Kovalenko, ETH Zürich, Empa-Swiss Federal Laboratories for Materials Science and Technology, Switzerland
  • Antonio Cervellino, Paul Scherrer Institut, Switzerland
  • Jan Skov Pedersen
  • Norberto Masciocchi, Università dell’Insubria, Italy
  • Antonietta Guagliardi, Consiglio Nazionale delle Ricerche, Italy

Surface chemistry and core defects are known to play a prominent role in governing the photophysical properties of nanocrystalline semiconductors. Nevertheless, investigating them in small nanocrystals remains a complex task. Here, by combining X-ray scattering techniques in the wide- and small-angle regions and using the Debye Scattering Equation (DSE) method of analysis, we unveil a high density of planar defects in oleate-terminated zincblende (ZB) CdSe colloidal quantum dots (QDs) and size-dependent faceting within a square-cuboid morphology. Atomistic models of faulted ZB nanocrystals, based on the probabilistic stacking of CdSe layers in cubic and hexagonal sequences, and data analysis point to the preferential location of faults near the center of nanocrystals. By finely modeling faulting and morphological effects on the X-ray scattering pattern, a relaxation of the Cd-Se bond distance parallel to the stacking direction, up to +3% (2.71 Å) with respect to the reference bulk value (2.63 Å) is detected, at the cubic/hexagonal transitions. The smallest nanocrystals show cubic {100} facets; {111} facets appear above 4 nm and progressively extend at larger sizes. These structural and morphological features likely vary depending on the synthesis conditions; nevertheless, since planar defects are nearly ubiquitous in CdSe QDs, the modeling approach here presented has a general validity. This work also points to the great potential of combining small- and wide-angle X-ray scattering and DSE-modeling techniques in gaining important knowledge on atomic-scale defects of semiconductor nanocrystals, underpinning the comprehension of the impact of structural defectiveness on the exciting properties of these QDs.

Original languageEnglish
JournalACS Nano
Volume12
Issue12
Pages (from-to)12558-12570
Number of pages13
ISSN1936-0851
DOIs
Publication statusPublished - 2018

    Research areas

  • Debye scattering equation, X-ray small- and wide-angle scattering, nanocrystals, quantum dots, stacking faults, wurtzite, zincblende

See relations at Aarhus University Citationformats

ID: 139439641