Role of photoexcitation and field ionization in the measurement of accurate oxide stoichiometry by laser-assisted atom probe tomography

A. Devaraj, R. Colby, W. P. Hess, D. E. Perea, S. Thevuthasan

Research output: Contribution to journalArticle

70 Citations (Scopus)

Abstract

The addition of pulsed lasers to atom probe tomography (APT) extends its high spatial and mass resolution capability to nonconducting materials, such as oxides. For a prototypical metal oxide, MgO, the measured stoichiometry depends strongly on the laser pulse energy and applied voltage. Very low laser energies (0.02 pJ) and high electric fields yield optimal stoichiometric accuracy. Correlated APT and aberration-corrected transmission electron microscopy (TEM) are used to establish the high density of corner and terrace sites on MgO sample surfaces before and after APT. For MgO, long-lifetime photoexcited holes localized at oxygen corner sites can assist in the creation of oxygen neutrals that may spontaneously desorb either as atomic O or as molecular O2. The observed trends are best explained by the relative field-dependent ionization of photodesorbed O or O2 neutrals. These results emphasize the importance of considering electronic excitations in APT analysis of oxide materials.

Original languageEnglish
Pages (from-to)993-998
Number of pages6
JournalJournal of Physical Chemistry Letters
Volume4
Issue number6
DOIs
Publication statusPublished - 21 Mar 2013
Externally publishedYes

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Keywords

  • aberration-corrected TEM
  • atom probe tomography
  • MgO
  • photoexcitation

ASJC Scopus subject areas

  • Materials Science(all)

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