Journal
NANO LETTERS
Volume 17, Issue 3, Pages 2094-2101Publisher
AMER CHEMICAL SOC
DOI: 10.1021/acs.nanolett.7b00481
Keywords
Gallium arsenide; colloidal nanocrystals; excitonic transitions; lattice disorder; Raman spectroscopy; EXAFS; transient absorption; molten salt
Categories
Funding
- Department of Defense (DOD) Air Force Office of Scientific Research [FA9550-14-1-0367]
- Office of Naval Research [N00014-13-1-0490]
- NSF [DMR-1310398, DMR-1611371]
- II-VI Foundation
- US Department of Energy Basic Energy Sciences
- Canadian Light Source
- U.S. DOE [DE-AC02-06CH11357]
- Direct For Mathematical & Physical Scien
- Division Of Materials Research [1611371] Funding Source: National Science Foundation
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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.
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