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

Appavoo, Kannatassen; Liu, Mingzhao

doi:10.1063/1.4868534

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

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Abstract

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:: Appavoo, Kannatassen; Liu, Mingzhao

Publication Date:: Mon Mar 31 00:00:00 EDT 2014

OSTI Identifier:: 22261642

Resource Type:: Journal Article

Journal Name:: Applied Physics Letters

Additional Journal Information:: Journal Volume: 104; Journal Issue: 13; Other Information: (c) 2014 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA); Journal ID: ISSN 0003-6951

Country of Publication:: United States

Language:: English

Subject:: 36 MATERIALS SCIENCE; 77 NANOSCIENCE AND NANOTECHNOLOGY; EXCITED STATES; NANOSTRUCTURES; RECOMBINATION; THERMALIZATION; ULTRAVIOLET RADIATION; ZINC OXIDES

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                    Appavoo, Kannatassen, Liu, Mingzhao, and Sfeir, Matthew Y., E-mail: msfeir@bnl.gov. Role of size and defects in ultrafast broadband emission dynamics of ZnO nanostructures.  United States: N. p., 2014. 
        Web.  doi:10.1063/1.4868534.

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                    Appavoo, Kannatassen, Liu, Mingzhao, & Sfeir, Matthew Y., E-mail: msfeir@bnl.gov. Role of size and defects in ultrafast broadband emission dynamics of ZnO nanostructures.  United States.  https://doi.org/10.1063/1.4868534

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                    Appavoo, Kannatassen, Liu, Mingzhao, and Sfeir, Matthew Y., E-mail: msfeir@bnl.gov. 2014.  
        "Role of size and defects in ultrafast broadband emission dynamics of ZnO nanostructures".  United States.  https://doi.org/10.1063/1.4868534.

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@article{osti_22261642,

  title        = {Role of size and defects in ultrafast broadband emission dynamics of ZnO nanostructures},

  author       = {Appavoo, Kannatassen and Liu, Mingzhao and Sfeir, Matthew Y., E-mail: msfeir@bnl.gov},

  abstractNote = {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.},

  doi          = {10.1063/1.4868534},

  url          = {https://www.osti.gov/biblio/22261642},
  journal      = {Applied Physics Letters},

  issn         = {0003-6951},

  number       = 13,

  volume       = 104,

  place        = {United States},

  year         = {Mon Mar 31 00:00:00 EDT 2014},

  month        = {Mon Mar 31 00:00:00 EDT 2014}

}

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