University of Illinois Urbana-Champaign

Disordering of small metal particles in a scanning transmission electron microscope

Vanfleet, Richard R.

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Description

Title
Disordering of small metal particles in a scanning transmission electron microscope
Author(s)
Vanfleet, Richard R.
Issue Date
1997
Director of Research (if dissertation) or Advisor (if thesis)
Mochel, J.M.
Department of Study
Physics
Discipline
Physics
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
  • Scanning Transmission Electron Microscope (STEM)
  • platinum
  • palladium
  • rhodium
  • iridium
  • electron scattering in metals
  • diffraction patten
  • thermodynamics
  • small metal particles
Language
en
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.
Type of Resource
text
Permalink
http://hdl.handle.net/2142/30770
Copyright and License Information
© 1997 Richard R. Vanfleet

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