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Electron Beam Driven Disordering in Small Particles

Published online by Cambridge University Press:  15 February 2011

Richard R. Vanfleet
Affiliation:
Material Research Lab and Physics Department, University of Illinois, Urbana, IL 61801
Jack Mochel
Affiliation:
Material Research Lab and Physics Department, University of Illinois, Urbana, IL 61801
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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. After the electron beam is removed, the particles will recrystallize after minutes or hours. Only particles below a critical size are seen to fully disorder. We have observed this in Platinum, Palladium, Rhodium, and Iridium and based on our model of disordering process believe it is a universal effect. It has also been observed with a Platinum Ruthenium alloy. We discuss the mechanism of this disordering and the structure of the resulting disordering particle for the case of Platinum clusters.

Type
Research Article
Copyright
Copyright © Materials Research Society 1997

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