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Disordering of small metal particles in a scanning transmission electron microscope

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PDF 1997_vanfleet.pdf (4MB) Restricted to U of Illinois 1997 Vanfleet PDF
Title: Disordering of small metal particles in a scanning transmission electron microscope
Author(s): Vanfleet, Richard R.
Director of Research: Mochel, J. M.
Department / Program: Physics
Discipline: Physics
Degree: Ph.D.
Genre: Dissertation
Subject(s): Scanning Transmission Electron Microscope (STEM) platinum palladium rhodium iridium electron scattering in metals diffraction patten thermodynamics small metal particles
Abstract: Small metal particles in the range of a few nanometers in diameter are seen to progressively disorder when the 100 keV electron beam of a Scanning Transmission Electron Microscope (STEM) is held stationary on the particle. The diffraction pattern of the individual particle is seen to progress from an initial array of indexable diffraction spots to a mixture of diffraction spots and amorphous-like rings and finally to rings with no persistent diffraction spots. Only particles below a critical size are seen to fully disorder. We have observed this disordering in Platinum, Palladium, Rhodium, and Iridium and have developed a model for the disordering process. In this model, electrons scattering from surface atoms transfer enough energy to break the surface atoms from their binding site. A competing process of disordered atoms rebinding to crystalline sites is also included. Because small particles have large fractions of their atoms on the surface, the beam driven disorder, under certain conditions, is able to propagate into the core of the particle. For Platinum, surface disordering requires energy transfers from the electrons to the Platinum atoms of0.54 eV.
Issue Date: 1997
Genre: Dissertation / Thesis
Type: Text
Language: English
Rights Information: © 1997 Richard R. Vanfleet
Date Available in IDEALS: 2012-04-26
Identifier in Online Catalog: 4048920

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