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Title: Understanding and Curing Structural Defects in Colloidal GaAs Nanocrystals

Abstract

Nearly three decades since the first report on the synthesis of colloidal GaAs nanocrystals (NCs), the preparation and properties of this material remain highly controversial. Traditional synthetic routes either fail to produce the GaAs phase or result in materials that do not show expected optical properties such as excitonic transitions. In this work, we demonstrate a variety of synthetic routes toward crystalline GaAs NCs. By using a combination of Raman, EXAFS and transient absorption spectroscopies, we conclude that unusual optical properties of 2 colloidal GaAs NCs can be related to the presence of vacancies and lattice disorder. We introduce novel molten salt based annealing approach to alleviate these structural defects and show the emergence of size-dependent excitonic transitions in colloidal GaAs quantum dots.

Authors:
 [1];  [1];  [1];  [1];  [1];  [2]; ORCiD logo [2];  [3];  [4]; ORCiD logo [5]
  1. Department of Chemistry and James Franck Institute, University of Chicago, Chicago, Illinois 60637, United States
  2. Advanced Photon Source, Argonne National Laboratory, Argonne, Illinois 60439, United States
  3. Center for Nanoscale Materials, Argonne National Laboratory, Argonne, Illinois 60439, United States
  4. Center for Nanoscale Materials, Argonne National Laboratory, Argonne, Illinois 60439, United States; Department of Chemistry, Northwestern University, Evanston, Illinois 60208, United States
  5. Department of Chemistry and James Franck Institute, University of Chicago, Chicago, Illinois 60637, United States; Center for Nanoscale Materials, Argonne National Laboratory, Argonne, Illinois 60439, United States
Publication Date:
Research Org.:
Argonne National Lab. (ANL), Argonne, IL (United States)
Sponsoring Org.:
National Science Foundation (NSF); USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22); Air Force Research Laboratory (AFRL) - Air Force Office of Scientific Research (AFOSR); US Department of the Navy, Office of Naval Research (ONR)
OSTI Identifier:
1414429
DOE Contract Number:
AC02-06CH11357
Resource Type:
Journal Article
Resource Relation:
Journal Name: Nano Letters; Journal Volume: 17; Journal Issue: 3
Country of Publication:
United States
Language:
English
Subject:
Colloidal Nanocrystals; Excitonic Transitions; Gallium Arsenide; Lattice Disorder; Molten Salt; Raman Spectroscopy; Transient Absorption

Citation Formats

Srivastava, Vishwas, Liu, Wenyong, Janke, Eric M., Kamysbayev, Vladislav, Filatov, Alexander S., Sun, Cheng-Jun, Lee, Byeongdu, Rajh, Tijana, Schaller, Richard D., and Talapin, Dmitri V. Understanding and Curing Structural Defects in Colloidal GaAs Nanocrystals. United States: N. p., 2017. Web. doi:10.1021/acs.nanolett.7b00481.
Srivastava, Vishwas, Liu, Wenyong, Janke, Eric M., Kamysbayev, Vladislav, Filatov, Alexander S., Sun, Cheng-Jun, Lee, Byeongdu, Rajh, Tijana, Schaller, Richard D., & Talapin, Dmitri V. Understanding and Curing Structural Defects in Colloidal GaAs Nanocrystals. United States. doi:10.1021/acs.nanolett.7b00481.
Srivastava, Vishwas, Liu, Wenyong, Janke, Eric M., Kamysbayev, Vladislav, Filatov, Alexander S., Sun, Cheng-Jun, Lee, Byeongdu, Rajh, Tijana, Schaller, Richard D., and Talapin, Dmitri V. Wed . "Understanding and Curing Structural Defects in Colloidal GaAs Nanocrystals". United States. doi:10.1021/acs.nanolett.7b00481.
@article{osti_1414429,
title = {Understanding and Curing Structural Defects in Colloidal GaAs Nanocrystals},
author = {Srivastava, Vishwas and Liu, Wenyong and Janke, Eric M. and Kamysbayev, Vladislav and Filatov, Alexander S. and Sun, Cheng-Jun and Lee, Byeongdu and Rajh, Tijana and Schaller, Richard D. and Talapin, Dmitri V.},
abstractNote = {Nearly three decades since the first report on the synthesis of colloidal GaAs nanocrystals (NCs), the preparation and properties of this material remain highly controversial. Traditional synthetic routes either fail to produce the GaAs phase or result in materials that do not show expected optical properties such as excitonic transitions. In this work, we demonstrate a variety of synthetic routes toward crystalline GaAs NCs. By using a combination of Raman, EXAFS and transient absorption spectroscopies, we conclude that unusual optical properties of 2 colloidal GaAs NCs can be related to the presence of vacancies and lattice disorder. We introduce novel molten salt based annealing approach to alleviate these structural defects and show the emergence of size-dependent excitonic transitions in colloidal GaAs quantum dots.},
doi = {10.1021/acs.nanolett.7b00481},
journal = {Nano Letters},
number = 3,
volume = 17,
place = {United States},
year = {Wed Feb 22 00:00:00 EST 2017},
month = {Wed Feb 22 00:00:00 EST 2017}
}
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  • In this study, we have developed a general X-ray powder diffraction (XPD) methodology for the simultaneous structural and compositional characterization of inorganic nanomaterials. The approach is validated on colloidal tungsten oxide nanocrystals (WO 3-x NCs), as a model polymorphic nanoscale material system. Rod-shaped WO 3-x NCs with different crystal structure and stoichiometry are comparatively investigated under an inert atmosphere and after prolonged air exposure. An initial structural model for the as-synthesized NCs is preliminarily identified by means of Rietveld analysis against several reference crystal phases, followed by atomic pair distribution function (PDF) refinement of the best-matching candidates (static analysis). Subtlemore » stoichiometry deviations from the corresponding bulk standards are revealed. NCs exposed to air at room temperature are monitored by XPD measurements at scheduled time intervals. The static PDF analysis is complemented with an investigation into the evolution of the WO 3-x NC structure, performed by applying the modulation enhanced diffraction technique to the whole time series of XPD profiles (dynamical analysis). Prolonged contact with ambient air is found to cause an appreciable increase in the static disorder of the O atoms in the WO 3-x NC lattice, rather than a variation in stoichiometry. Finally, the time behavior of such structural change is identified on the basis of multivariate analysis.« less