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Title: Surfaces of colloidal PbSe nanocrystals probed by thin-film positron annihilation spectroscopy

Positron annihilation lifetime spectroscopy and positron-electron momentum density (PEMD) studies on multilayers of PbSe nanocrystals (NCs), supported by transmission electron microscopy, show that positrons are strongly trapped at NC surfaces, where they provide insight into the surface composition and electronic structure of PbSe NCs. Our analysis indicates abundant annihilation of positrons with Se electrons at the NC surfaces and with O electrons of the oleic ligands bound to Pb ad-atoms at the NC surfaces, which demonstrates that positrons can be used as a sensitive probe to investigate the surface physics and chemistry of nanocrystals inside multilayers. Ab initio electronic structure calculations provide detailed insight in the valence and semi-core electron contributions to the positron-electron momentum density of PbSe. Both lifetime and PEMD are found to correlate with changes in the particle morphology characteristic of partial ligand removal.
Authors:
; ; ;  [1] ; ; ;  [2] ;  [3] ;  [4] ;  [3] ;  [1] ;  [5] ;  [6] ; ;  [7] ;  [2] ;  [8]
  1. Department of Radiation, Radionuclides and Reactors, Faculty of Applied Sciences, Delft University of Technology, Mekelweg 15, NL-2629 JB Delft (Netherlands)
  2. Physics Department, Northeastern University, Boston, Massachusetts 02115 (United States)
  3. Department of Chemical Engineering, Faculty of Applied Sciences, Delft University of Technology, Julianalaan 136, NL-2628 BL Delft (Netherlands)
  4. (Netherlands)
  5. (United States)
  6. Kavli Institute of Nanoscience, Faculty of Applied Sciences, Delft University of Technology, Lorentzweg 1, NL-2628 CJ Delft (Netherlands)
  7. Institut für Angewandte Physik und Messtechnik, Universität der Bundeswehr München, Werner-Heisenberg-Weg 39, D-85579 Neubiberg (Germany)
  8. (Poland)
Publication Date:
OSTI Identifier:
22269584
Resource Type:
Journal Article
Resource Relation:
Journal Name: APL Materials; Journal Volume: 1; Journal Issue: 2; Other Information: (c) 2013 Author(s); Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; DENSITY; ELECTRONIC STRUCTURE; ELECTRONS; LEAD SELENIDES; LIGANDS; NANOSTRUCTURES; PARTICLES; POSITRONS; SPECTROSCOPY; SURFACES; THIN FILMS; TRANSMISSION ELECTRON MICROSCOPY