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Title: Role of size and defects in ultrafast broadband emission dynamics of ZnO nanostructures

As wide bandgap materials are nanostructured for optoelectronics and energy technologies, understanding how size and defects modify the carrier dynamics becomes critical. Here, we examine broadband ultraviolet-visible subpicosecond emission dynamics of prototypical ZnO in bulk, nanowire and nanosphere geometries. Using a high-sensitivity transient emission Kerr-based spectrometer, we probe exciton dynamics in the low fluence regime to determine how defects states impact thermalization and recombination rates. In contrast to steady-state measurements, we transiently identify low-energy emission features that originate from localized excitonic states rather than mid-gap states, characterized by distinct recombination kinetics, and correlate to longer thermalization times. These states are critical for understanding the overall excited state lifetime of materials in this size regime, where crystallinity rather than dimensionality plays a primary role in dictating recombination dynamics.
Authors:
; ;  [1]
  1. Center for Functional Nanomaterials, Brookhaven National Laboratory, Upton, New York 11973 (United States)
Publication Date:
OSTI Identifier:
22261642
Resource Type:
Journal Article
Resource Relation:
Journal Name: Applied Physics Letters; Journal Volume: 104; Journal Issue: 13; Other Information: (c) 2014 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; 77 NANOSCIENCE AND NANOTECHNOLOGY; EXCITED STATES; NANOSTRUCTURES; RECOMBINATION; THERMALIZATION; ULTRAVIOLET RADIATION; ZINC OXIDES