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      Systematic spatial and stoichiometric screening towards understanding the surface of ultrasmall oxygenated silicon nanocrystal

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      Author
      Niaz, S.
      Zdetsis, A. D.
      Koukaras, E. N.
      Gülseren, O.
      Sadiq, I.
      Date
      2016-11
      Source Title
      Applied Surface Science
      Print ISSN
      0169-4332
      Publisher
      Elsevier
      Volume
      387
      Pages
      771 - 778
      Language
      English
      Type
      Article
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      Abstract
      In most of the realistic ab initio and model calculations which have appeared on the emission of light from silicon nanocrystals, the role of surface oxygen has been usually ignored, underestimated or completely ruled out. We investigate theoretically, by density functional theory (DFT/B3LYP) possible modes of oxygen bonding in hydrogen terminated silicon quantum dots using as a representative case of the Si29 nanocrystal. We have considered Bridge-bonded oxygen (BBO), Doubly-bonded oxygen (DBO), hydroxyl (OH) and Mix of these oxidizing agents. Due to stoichiometry, all comparisons performed are unbiased with respect to composition whereas spatial distribution of oxygen species pointed out drastic change in electronic and cohesive characteristics of nanocrytals. From an overall perspective of this study, it is shown that bridge bonded oxygenated Si nanocrystals accompanied by Mix have higher binding energies and large electronic gap compared to nanocrystals with doubly bonded oxygen atoms. In addition, it is observed that the presence of OH along with BBO, DBO and mixed configurations further lowers electronic gaps and binding energies but trends in same fashion. It is also demonstrated that within same composition, oxidizing constituent, along with their spatial distribution substantially alters binding energy, highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) gap (up to 1.48 eV) and localization of frontier orbitals.
      Keywords
      DFT calculations
      Electronic properties
      Oxygenated dots
      Quantum dots
      Silicon nanocrystals
      Stoichiometry
      Binding energy
      Bins
      Calculations
      Chemical bonds
      Density functional theory
      Electronic properties
      Molecular orbitals
      Optical waveguides
      Oxygen
      Semiconductor quantum dots
      Silicon
      Spatial distribution
      Stoichiometry
      DFT calculation
      Highest occupied molecular orbital
      Hydrogen-terminated silicon
      Lowest unoccupied molecular orbital
      Model calculations
      Oxygenated dots
      Representative case
      Silicon nanocrystals
      Nanocrystals
      Permalink
      http://hdl.handle.net/11693/36876
      Published Version (Please cite this version)
      https://doi.org/10.1016/j.apsusc.2016.06.197
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      • Department of Physics 2149

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