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Title: Nature of the Positron State in CdSe Quantum Dots

Journal Article · · Physical Review Letters
 [1];  [2];  [3];  [2];  [1];  [4];  [4];  [5];  [6];  [6];  [1];  [2];  [7];  [1]
  1. Delft Univ. of Technology (Netherlands). Fundamental Aspects of Materials and Energy. Faculty of Applied Sciences
  2. Univ. of Antwerp (Belgium). Dept. of Physics
  3. Lappeenranta Univ. of Technology (Finland). School of Engineering Science; Northeastern Univ., Boston, MA (United States). Dept. of Physics
  4. Univ. der Bundeswehr München, Neubiberg (Germany). Inst. for Applied Physics and Measurement Technology
  5. Technische Univ. München, Garching (Germany). Physics Dept. Heinz Maier-Leibnitz Zentrum (MLZ)
  6. Univ. of Maine, Orono, ME (United States). Dept. of Physics and Astronomy. Lab. for Surface Science and Technology
  7. Northeastern Univ., Boston, MA (United States). Dept. of Physics
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Previous studies have shown that positron-annihilation spectroscopy is a highly sensitive probe of the electronic structure and surface composition of ligand-capped semiconductor quantum dots (QDs) embedded in thin films. The nature of the associated positron state, however, whether the positron is confined inside the QDs or localized at their surfaces, has so far remained unresolved. Our positron-annihilation lifetime spectroscopy studies of CdSe QDs reveal the presence of a strong lifetime component in the narrow range of 358–371 ps, indicating abundant trapping and annihilation of positrons at the surfaces of the QDs. Furthermore, our ab initio calculations of the positron wave function and lifetime employing a recent formulation of the weighted density approximation demonstrate the presence of a positron surface state and predict positron lifetimes close to experimental values. Our study thus resolves the long-standing question regarding the nature of the positron state in semiconductor QDs and opens the way to extract quantitative information on surface composition and ligand-surface interactions of colloidal semiconductor QDs through highly sensitive positron-annihilation techniques.

Research Organization:
Energy Frontier Research Centers (EFRC) (United States). Center for Complex Materials from First Principles (CCM); Northeastern Univ., Boston, MA (United States); Temple Univ., Philadelphia, PA (United States)
Sponsoring Organization:
USDOE Office of Science (SC), Basic Energy Sciences (BES)
Grant/Contract Number:
FG02-07ER46352; SC0012575; AC02-05CH11231
OSTI ID:
1541347
Alternate ID(s):
OSTI ID: 1462583
Journal Information:
Physical Review Letters, Vol. 121, Issue 5; ISSN 0031-9007
Publisher:
American Physical Society (APS)Copyright Statement
Country of Publication:
United States
Language:
English
Citation Metrics:
Cited by: 4 works
Citation information provided by
Web of Science

References (44)

Hybrid passivated colloidal quantum dot solids journal July 2012
Generalized Gradient Approximation Made Simple journal October 1996
Suppressing Deep Traps in PbS Colloidal Quantum Dots via Facile Iodide Substitutional Doping for Solar Cells with Efficiency >10% journal March 2017
The surface science of nanocrystals journal January 2016
Microscopic Theory of Cation Exchange in CdSe Nanocrystals journal October 2014
Study of colloidal quantum-dot surfaces using an innovative thin-film positron 2D-ACAR method journal December 2005
Measurement of the orthopositronium confinement energy in mesoporous thin films journal May 2010
Comment on the Positron Surface-State Lifetime journal September 1984
Auger electron emission initiated by the creation of valence-band holes in graphene by positron annihilation journal July 2017
Positron Surface States on Clean and Oxidized Al and in Surface Vacancies journal January 1983
Projector augmented-wave method journal December 1994
Efficiency of ab-initio total energy calculations for metals and semiconductors using a plane-wave basis set journal July 1996
Experimental determination of the state-dependent enhancement of the electron-positron momentum density in solids journal September 2010
Defect identification in semiconductors with positron annihilation: Experiment and theory journal November 2013
Quantum Monte Carlo Study of a Positron in an Electron Gas journal November 2011
Direct observation of energy-gap scaling law in CdSe quantum dots with positrons journal July 2002
Unprecedented intensity of a low-energy positron beam
  • Hugenschmidt, C.; Löwe, B.; Mayer, J.
  • Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, Vol. 593, Issue 3 https://doi.org/10.1016/j.nima.2008.05.038
journal August 2008
Impact of Stoichiometry on the Electronic Structure of PbS Quantum Dots journal May 2013
Ligand-surface interactions and surface oxidation of colloidal PbSe quantum dots revealed by thin-film positron annihilation methods journal February 2016
A Closer Look into the Traditional Purification Process of CdSe Semiconductor Quantum Dots journal November 2015
Modification of the conduction band edge energy via hybridization in quantum dots journal November 2012
Experimental Observation of Quantum Confinement in the Conduction Band of CdSe Quantum Dots journal April 2007
Efficient iterative schemes for ab initio total-energy calculations using a plane-wave basis set journal October 1996
Surfaces of colloidal PbSe nanocrystals probed by thin-film positron annihilation spectroscopy journal August 2013
LT10 Program for Solving Basic Problems Connected with Defect Detection journal January 2012
From ultrasoft pseudopotentials to the projector augmented-wave method journal January 1999
Structural and electronic properties of PbSe nanocrystals from first principles journal August 2008
Investigations of epoxy-based adhesives with PLEPS journal October 2008
Positron surface state as a spectroscopic probe for characterizing surfaces of topological insulator materials journal September 2016
Status of the pulsed low energy positron beam system (PLEPS) at the Munich Research Reactor FRM-II journal October 2008
PbSe quantum dots: Finite, off-stoichiometric, and structurally distorted journal June 2010
Non-Local Electron-Positron Enhancement Factors in Solids journal April 1999
Application of the weighted-density approximation to the accurate description of electron-positron correlation effects in materials journal August 2017
Direct evidence of Cd vacancies in CdSe nanoparticles: positron annihilation studies journal August 2011
Self-Healing of CdSe Nanocrystals: First-Principles Calculations journal May 2004
Interaction of positron beams with surfaces, thin films, and interfaces journal July 1988
Positron Annihilation as a Method to Characterize Porous Materials journal August 2006
Measurement of the Positron Surface-State Lifetime for Al journal March 1984
Atomistic Model of Fluorescence Intermittency of Colloidal Quantum Dots journal April 2014
Electron-positron enhancement factors at a metal surface: Aluminum journal November 1991
Auger-Mediated Sticking of Positrons to Surfaces: Evidence for a Single-Step Transition from a Scattering State to a Surface Image Potential Bound State journal June 2010
Ligand-Mediated Modification of the Electronic Structure of CdSe Quantum Dots journal May 2012
Positron annihilation in II-VI compound semiconductors: theory journal October 1994
Nonlocal electron-positron correlations in solids within the weighted density approximation journal November 1998

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