title: Understanding and Curing Structural Defects in Colloidal GaAs Nanocrystals.
abstract: GaAs is one of the most important semiconductors. However, colloidal GaAs nanocrystals remain largely unexplored because of the difficulties with their synthesis. Traditional synthetic routes either fail to produce pure GaAs phase or result in materials whose optical properties are very different from the behavior expected for quantum dots of direct-gap semiconductors. In this work, we demonstrate a variety of synthetic routes toward crystalline GaAs NCs. By using a combination of Raman, EXAFS, transient absorption, and EPR spectroscopies, we conclude that unusual optical properties of colloidal GaAs NCs can be related to the presence of Ga vacancies and lattice disorder. These defects do not manifest themselves in TEM images and powder X-ray diffraction patterns but are responsible for the lack of absorption features even in apparently crystalline GaAs nanoparticles. We introduce a 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.affiliation: Department of Chemistry and James Franck Institute, University of Chicago , Chicago, Illinois 60637, United States.
authors.forename: Vishwas
authors.initials: V
authors.lastname: Srivastava
authors.affiliation: Department of Chemistry and James Franck Institute, University of Chicago , Chicago, Illinois 60637, United States.
authors.forename: Wenyong
authors.initials: W
authors.lastname: Liu
authors.affiliation: Department of Chemistry and James Franck Institute, University of Chicago , Chicago, Illinois 60637, United States.
authors.forename: Eric M
authors.initials: EM
authors.lastname: Janke
authors.affiliation: Department of Chemistry and James Franck Institute, University of Chicago , Chicago, Illinois 60637, United States.
authors.forename: Vladislav
authors.initials: V
authors.lastname: Kamysbayev
authors.affiliation: Department of Chemistry and James Franck Institute, University of Chicago , Chicago, Illinois 60637, United States.
authors.forename: Alexander S
authors.initials: AS
authors.lastname: Filatov
authors.affiliation: Advanced Photon Source, Argonne National Laboratory , Argonne, Illinois 60439, United States.
authors.forename: Cheng-Jun
authors.initials: CJ
authors.lastname: Sun
authors.affiliation: Advanced Photon Source, Argonne National Laboratory , Argonne, Illinois 60439, United States.
authors.forename: Byeongdu
authors.identifier: 0000-0003-2514-8805
authors.initials: B
authors.lastname: Lee
authors.affiliation: Center for Nanoscale Materials, Argonne National Laboratory , Argonne, Illinois 60439, United States.
authors.forename: Tijana
authors.initials: T
authors.lastname: Rajh
authors.affiliation: Center for Nanoscale Materials, Argonne National Laboratory , Argonne, Illinois 60439, United States.|Department of Chemistry, Northwestern University , Evanston, Illinois 60208, United States.
authors.forename: Richard D
authors.initials: RD
authors.lastname: Schaller
authors.affiliation: 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.
authors.forename: Dmitri V
authors.identifier: 0000-0002-6414-8587
authors.initials: DV
authors.lastname: Talapin
keywords: EXAFS; Gallium arsenide; Raman spectroscopy; colloidal nanocrystals; excitonic transitions; lattice disorder; molten salt; transient absorption