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Title:Structure, electronic levels, and ionic interactions of 1 nanometer silicon particles
Author(s):Mantey, Kevin A.
Director of Research:Nayfeh, Munir H.
Doctoral Committee Chair(s):Clegg, Robert M.
Doctoral Committee Member(s):Nayfeh, Munir H.; Ceperley, David M.; Stack, John D.
Department / Program:Physics
Degree Granting Institution:University of Illinois at Urbana-Champaign
Subject(s):Silicon nanocrystal
Vibrational spectroscopy
Metal ion complex
Abstract:Silicon particles are created via anodic or platinum catalyzed etching of bulk silicon. A peroxide and HF etchant provides uniform surface termination, and results in discrete stable sizes for particles below 3 nm in size. The smallest of these are 1 nm silicon particles, which is amenable to rst principles quan- tum calculations of the structure, electronic levels, and ionic interactions. The vibrational modes of several candidate structures of the 1 nm particles are calculated at the Hartree-Fock level, and compared to previously acquired Raman spectra to determine the structure. The vibrational modes are also compared to the vibrational structure in low temperature photo-luminescence to indicate surface reconstruction bonds play a role in the uorescence. The uorescence mechanism is explored further with calculations of the excited state potential energy surface using time dependent density functional theory, which show radiative traps accessible via direct excitation at the band edge of the ground state geometry. The self-trapped excitons proposed by Lannoo et al. [1, 2] are found to be unstable for the Si29H24 structure, with the outer-well leading to non-radiative recombination via conical intersection of the excited state with the ground state. Absorption measurements indicate the silicon nanoparticles may form charge complexes with iron ions in aque- ous solutions. Calculations including solvation e ects provide a proposed structure for the complex, with a binding energy of 0.49 eV. The binding mechanism is quite general and suggests many other ions could form charge complexes with the silicon particles in aqueous solutions, potentially leading to new applications.
Issue Date:2011-08-25
Rights Information:Copyright 2011 Kevin A. Mantey
Date Available in IDEALS:2011-08-25
Date Deposited:2011-08

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